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¿Donde va mapa? Una revisión y el potencial futuro de atmósfera modificada empaquetado de carne Kenneth W. McMillin

*

Escuela de Animal Sciences, centro agrícola de la Universidad Estatal de Louisiana, Baton Rouge, LA 70803-4210, USA

información del artículo

R e s u m e n

Historia del artículo: 07 De abril de 2008 recibió Recibido en forma revisada el 19 de mayo de 2008 20 De mayo de 2008 aceptado

Envasado en atmósfera modificada (mapa) es el retiro o reemplazo de la atmósfera envolventeIng el producto antes de sellar en materiales de barrera de vapor. Técnicamente diferente, mientras que muchas formas de mapa son también envasado case-ready, donde la carne se corta y empaquetado en una ubicación centralizada para su transporte a y Mostrar en una tienda especializada. La mayoría de las propiedades de la vida útil de la carne es otorgada por el uso del mapa, pero formas anóxicas del mapa sin monóxido de carbono (CO) no proporcionan florecido carne roja color y mapa con el oxígeno (O) 2 puede promover la oxidación de lípidos y pigmentos. Avances en materiales plásticos y equiparment han impulsado avances en el mapa, pero se necesitan otras consideraciones tecnológicas y logísticas para sistemas exitosos del mapa para carne fresca refrigerada. Opciones de mapa actuales de más permeable al aire envuelto de bandejas en máster packs, bajos 2formatos O de envasado al vacío de la película encogido (VP) o mapa con car Bon dióxido (CO) 2y nitrógeno (N) y sus2 derivados de película de barrera pelable y alta O mapa cada2uno tienen ventajas y desventajas. Embalaje de innovaciones tecnológicas e ingenio seguirá proporcionar mapa orientado al consumidor, producto mejora, ambientalmente sensibles y costo eficaciase necesitarán tive, pero continua investigación y desarrollo de los sectores científicos y la industria.  2008 Elsevier Ltd. Todos los derechos reservados.

Palabras clave: Embalaje Atmósfera modificada Case-ready Propiedades de la carne

Contenido 1.

2.

3.

Introducción a la modificada envasado en atmósfera (mapa)...... 44 1.1. Definiciones y descripción de mapa............. 44 1.2. Base histórica para la carne y mapa............ 44 Aplicaciones del mapa para carne........ .................................................................................... 45 2.1. MAPA conceptos de empaquetado de carne enfriada........ 45 2.2. Propiedades de la carne en el mapa. .......................................................................... 48 2.2.1. Pigmento color y presiones parciales................. 48 2.2.2. M e t m y o g l o b i n r e d u c t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 8 2.2.3. Flavor attributes . . . . . . . . . . . ............................................................................... 49 2.2.4. Goteo y capacidad de retención de agua................. 49 2.2.5. Microbiology. . . . . . . . . . . . . . ............................................................................... 50 2.2.6. Cooked meat color . . . . . . . . . ............................................................................... 50 2.3. C o n s i d e r a c i o n e s p a r a l a i m p l e m e n t a c i ó n d e l m a p a . . . . . . . 5 1 2.3.1. Flor y residual o 2 .................................................................................. 51 2.3.2. Gas mixtures. . . . . . . . . . . . . . ............................................................................... 51 2.3.3. M e j o r a e i n g r e d i e n t e s . . . 5 2 2.3.4. O x i d a t i v e s t a b i l i t y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 2.3.5. Requisitos de espacio y opciones de bandeja............ 53 2.3.6. Merchandising y productividad................... 53 2.4. Comparisons of MAP options . . . . . . . . . . . . . .......................................................................... 54 Futuro del mapa. ....................................................................................................... 55 3.1. Packaging innovations y tendencias............ 55 3.1.1. Envasado case-ready o centralizada................. 55 3.1.2. Consideraciones ambientales y renovables... más... 56

* Tel.: + 1 225 578 3438; Fax: + 1 225 578 3279. Dirección de correo [email protected] electrónico: 0309-1740 /$ - ver materia de frente  2008 Elsevier Ltd. Todos los derechos reservados. doi:10.1016/j.meatsci.2008.05.028

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K.W. McMillin / carne ciencia 80 43–65 (2008)

4.

3.1.3. Envases activos........ .................................................................................. 56 3.1.4. C o n s u m e r i n f l u e n c e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 7 3.2. Research and industry needs . . . . . . . . . . ............................................................................. 58 Conclusiones. .......................................................................................................... 60 References . . . . . . . . . . . . . .............................................................................................. 60

vide una base para la especulación de las necesidades de la industria y el consumidor para búsqueda y mejoras en el mapa para carne. 1.1. Definiciones y descripción de mapa Carnes rojas de (frescas) frías crudas será el mayor énfasis de este papel. El actual paquete estándar de las aves de corral en todo el mundo es un exAcondicionamiento de los alimentos sirve para proteger los productos contra catabólico bandeja poliestireno panded retractiladas con Policloruro de vinilo efectos, contener el producto, comunicarse al consumidor como un (PVC) o polyolefin película estirada y calor reducido sobre la bandeja herramienta de marketing y proporcionar a los consumidores con la facilidad de usoyyproducto con (Jenkins & Harrington, 1991). La mayoría del paquete las edades de valor añadido son productos cárnicos en vacío y simple película venience (ñame, Takhistov & Miltz, 2005). La pantalla de carne en materiales plásticos permite evaluación del consumidor del producto en un estado sellado (Eilert, 2005), mientras que allí son varios sistemas de mapa paquete atractivo, higiénico y conveniente (Renerre & Labadie, utilizado para cárnicos y aves de corral (Belcher, 2006; Blakistone, 1993). El empaquetado de alimentos ahora se realiza más allá de lo convencional 1999b, Cap. 10; Jenkins & Harrington, 1991). propiedades de protección y proporciona muchas funciones para el con producto figura (Han, 2005a, Cap. 1). 1.2. Histórico base para carne y mapa Envasado en atmósfera modificada (mapa) consiste en la extracción o sustitución de la atmósfera que rodea el producto antes de Formas más avanzadas de embalaje de carne fueron requeridas como sellado en materiales de barrera de vapor (McMillin, Huang, Ho & Smith, Carnicero de corte y de envasado de carne en papel o papel encerado 1999, Cap. 6). MAPA puede ser envasado al vacío (VP), que rea la demanda por parte del comprador fueron reemplazados por corte de tienda se mueve la mayor parte del aire antes de que el producto se encuentra dentro de lay barrera la presentación de los paquetes en vitrinas de autoservicio refrigerado materiales o formas de reemplazo del gas, donde se extrae el aire por en la década de 1950 (Brody, 2002). Carne refrigerada iluminado casos donde vacío o flushing y reemplazada con otra mezcla de gas antes de los consumidores podrían manejar y seleccionar entre diferentes paquetes reembalaje sellado en materiales de barrera. El ambiente espacios vacíos embalaje necesario que protegía el contenido al mismo tiempo que muestra la y el producto puede cambiar durante el almacenamiento en el mapa, pero hay no características del producto, principalmente color magra y cantidades de grasa, manipulación adicional del medio interno (McMillin durante la visualización del diario. Embalaje varió de empaquetado de la envoltura et al., 1999, Cap. 6) mientras que el envasado en atmósfera controlada para almacenamiento refrigerado a corto plazo y/o por menor Mostrar a barrera pack(CAP) utiliza un monitoreo continuo y control del medio ambiente edades por períodos más largos de almacenamiento refrigerado o pantalla (Kerry et al., para mantener un ambiente estable de gas y otras condiciones tales como 2006). La industria química proporciona plásticos y otros polímeros temperatura y humedad dentro del paquete (Brody, 1989, Chap. formas de materiales para satisfacer los requisitos de empaquetado de estante2). CAP más a menudo se ha utilizado para controlar la maduración y descomposición vida, costo y atractivo para envoltura permeable al aire moisde frutas y verduras (Príncipe, 1989), generalmente en envases más grandes Ture-impermeable carne enfriada empaquetado y barrera packagde paquetes de menor tamaño aunque algunas investigaciones ha sido con Ing para carnes procesadas. Permeable al aire y barrera contra la humedad conductos en envase individuales frutas y hortalizas (Benpelícula de cloruro de polivinilo que estiraría todo claro o ampliado Yehoshua, 1989, Cap. 6). bandejas de poliestireno se desarrollaron para carne fresca cruda (Brody, 2002). Ha sido un cambio de paradigma importante en envases de pasiva a Los consumidores comenzaron a asociar el color rojo brillante del florecido de preactivo (Yam et al., 2005). Envases activos es la incorporación de ser de carne envasado en envases permeable al aire con la frescura de la carnecompuestos específicos en sistemas de envasado para mantener o ampliar causa de que esto era el color de la carne primera vista en pantalla en autocalidad del producto y validez mientras embalaje inteligente o smart casos de carne del servicio (Jenkins & Harrington, 1991). proporciona para la detección del medio ambiente de propiedades o paquete de alimentos Las economías de canal rompiendo en plantas procesadoras y para informar el procesador, minorista o consumidor del estado de envío de cortes primarios en lugar de cadáveres, lados o cuartos el medio ambiente o la comida (Kerry, O'Grady & Hogan, 2006). En activo a tiendas para cortar avances propulsado de porciones por menor empaquetado, las tecnologías activas primarias sobre todo mejoran la en los materiales de envasado al vacío y equipo. Empaquetado de carne protección o la vida útil del producto en respuesta a las interacciones también fue alterada por el aumento de la competencia de tiendas minoristas y del producto, paquete y medio ambiente, aunque packag activa cadenas, requisitos de inocuidad y salubridad del producto Ing puede realizar otras funciones (Brody, Strupinsky & Kline, 2001; UCTS, escasez de carniceros calificados y necesidades para la carne bien surtido Día, 2003, Cap. 9; Yam et al., 2005). Envases activos pueden también encasos con tiempos más largos de operaciones de la tienda (Cole, 1986). La cortevolve la alteración deliberada del medio paquete en un especTing y envasado de carne refrigerada en más permeable al aire ified tiempo o condición a través de la voz pasiva o activa significa, pero abrigo de packaging en tiendas individuales ha sido reemplazada gradualmente por sin las entradas y monitoreo continuo con CAP case-ready o centralizadas operaciones en muchos países desarrollados. (Zhao, pozos & McMillin, 1994). Sistemas de envasado inteligente Envasado case-ready o centralizada es la fabricación y envasadotienen componentes que percibir el medio ambiente y el proceso de la Ing de artículos por menor uso del consumidor en un proceso, almacén, o información y luego permita que la acción proteger el producto por con otro lugar de no-venta centralizado para el transporte y posterior conductos funciones de comunicación (Yam et al., 2005). exhibición en tiendas con mínima o ninguna manipulación del paquete de Este documento constituirá una base para las discusiones y cambios en el paquete individual después del retiro de la caja de envío tecnología para el uso del mapa con carne en el futuro. Fondo (McMillin, 1994). Las estimaciones más recientes son eso envasado case-ready información en el mapa y no-mapa para carne y explicaciones de es de 43% en los mercados europeos del frescos (Belcher, 2006) y el 64% de la MAPA de cárnicos formará un contexto y base para technologpaquetes en casos autoservicio de carnes frescas de Estados Unidos (equipos, 2007). CEN iCal y desarrollaron innovaciones científicos en mapa para carne en y empaquetado de tralized proporciona ventajas de mayor espacio y lapaíses en desarrollo. Innovaciones y tendencias de envasado serán proutilización de recursos de Bor, mejora de la calidad, reducción, de los residuos 1. Introducción a (mapa) de envasado en atmósfera modificada

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facilitación de automatización, mejor uniformidad de cortes y grasaningunos filos, listo sellabilidad, fabricación flexibilidad, environniveles de acabado y control de inventarios mejorada que mejora ganancias propiedades de durabilidad, barrera y permeabilidad mentales, imprimir y (Cole, 1986). Muchos de los sistemas de case-ready mapa incorporanmetal la receptividad de la capa, resistencia al desgarro y a la perforación, y causar sistema economías de costos y efficiencies junto con el Flexibilidad a bajas temperaturas que los hacen adecuados para alimentos desarrollos en materiales de empaque, proceso y equipo embalaje. Las características importantes de plásticos para alimentos aplicahan hecho mapa práctico y económicamente competitiva para carne ciones son temperatura de transición vítrea, punto de fusión cristalina, (Zhao et al., 1994). flexural módulo, resistencia a la tracción, resistencia, resistencia al impacto, al desgarro Mediados del siglo XX fue también el período vacío packflex vida, tasa de transmisión de vapor de agua, O 2 permeabilidad, óptica envejecimiento comenzó para cortes primarios y carnes curadas (Brody, 2002). En propiedades, propiedades de sellado, y fuerza (Jenkins de vinculación alrededor de esta época, empaquetado y corte de carne centralizado fue también & Harrington, 1991). Propiedades de la película plástico de grosor (1 - 2 intento en Europa. En países donde la tierra carne embalaje milésimas de pulgada), claridad de contracción (distorsión de reloj de arena en algunas fue requerido en presencia del cliente, la corte centralizada(haze, brillante), fuerza (desgarro, punción), transmisión O humedad 2 Ting y envasado de cortes de músculo entero no fue ampliamente aceptada. transmisión y la vida útil de los agentes antiniebla son importantes para En otros países, tuvo éxito en empaquetado de carne centralizado materiales del paquete de carne (Smith, 2001). Las características importantes pequeñas tiendas sin espacio para carniceros y vida útil de 6 a 10 días de resinas plásticas para carne embalaje están en la tabla 1. La mayor parte podría lograrse manteniendo la carne a menos de 2  C y en el 80% polímeros utilizados para envasado de alimentos son de baja densidad O:2 20% CO gas. También se usó el caso listo para embalaje en los Estados Unidos por polietileno, polietileno de alta densidad, polipropileno, polytet2 corte y envasado de carne en una película permeable al aire en un cercano rafluoroethylene y poliamida (nylon) (Jan, Zhang & Buffo, Ubicación central para su distribución a tiendas individuales. Éxito de 2005, Cap. 4). Cloruro de polivinilideno poliéster, PVC, cintaEstos sistemas de case-ready fue dependiente de la venta rápida de Rene, poliamida y etileno acetato de vinilo se utilizan también con cada tienda debido a la limitada vida útil y la existencia alimentos (Marsh & Bugusu, 2007). Cada tipo de material de embalaje de múltiples ubicaciones de supermercado cerca de la fabricación central tiene ventajas, desventajas, consumo y problemas de comercialización, y ubicación de embalaje. Otra versión de case-ready se corte medio ambiente consideraciones, y costo (Marsh & Bugusu, de cortes subprimal y primarios en porciones de minoristas que eran reas2007). Embalaje de carne fresca sólo es mínimamente permeable a montadas en una bolsa de barrera y distribuida a la tienda para con se previene la humedad y así la desecación superficial (Faustman & ventional envasado, etiquetado, y precios de el Cassens, 1990), mientras que la permeabilidad de gas varía con la aplica cortes individuales por menor. El éxito limitado de mapa inicial para carne Tion. La base de datos de envasado alimentario irlandés indicó que la poli condujo al aumento de plástico y avances del proceso. Paquete principal conMer tipos destinados como capas contactos frescos refrigerados y congelados c para la colocación de los paquetes envueltos en larcarne fueron poliestireno de 79% y 38% PVC Policloruro de vinilideno, bolsas de barrera de GER o bolsas fueron desarrolladas. Altos2O sistemas con 13% polipropileno y polietileno de 8% (Duffy, abundante, Gilsenan, atmósferas de O y 2dióxido de carbono (CO) superior al ambiente & Gibney, 2006). Una sola capa o tipo de plástico generalmente no 2 niveles previstos de color de la carne roja y la inhibición de deterioro no tiene todas las propiedades necesarias para un paquete de alimentos aplicaTion, así la laminación, capa o coextrusión permite crear laycrecimiento del microorganismo. Éxito y continuación de los muchos venta diferentes formatos de mapa ha sido dependiente del producto, ERS de plástico con las propiedades deseadas (Jenkins & Harrington, paquete y las interacciones del sistema, relaciones de procesadores 1991). A menudo se mejoran las propiedades de sellado y barrera de calor y minoristas y la aceptación del consumidor del merchandising mediante la aplicación de recubrimientos para las superficies de plástico películas (Kirwa formato (Brody, 2002). & Strawbridge, 2003, Cap. 7). MAPA de aplicaciones pueden tener base bandejas termoformadas de PVC no plastificado/polietileno, polietileno tereftalato / 2. Aplicaciones del mapa para carne polietileno, poliestireno/Etileno vinilo alcohol/polietileno, o polietileno tereftalato/Etileno vinilo acetato/polietileno 2.1. Mapa de conceptos de empaquetado de carne refrigerada mientras a menudo se hacen bandejas preformadas base de polietileno tereftalato, polipropileno o Policloruro de vinilo no plastificado / El paquete protege contra efectos catabólico polietileno. Lidding películas suelen ser cloruro de polivinilideno (Yam et al., 2005), que pueden incluir decoloración, off-flavor revestido polipropileno/polietileno, Polyvinylidene cloruro y desarrollo de olor, pérdida de nutrientes, cambios de textura, patógenosrevestido de tereftalato de polietileno/polietileno o poliamida / nicity y otros factores medibles (Skibsted, Bertelsen & Qvist, polietileno. Películas de abrigo de flujo pueden ser de poliamida/polietileno, 1994). Las propiedades de la carne que son importantes en la determinación de poliamida/ionómero, o poliamida/etileno acetato de vinilo/polyethvida útil incluir el agua capacidad vinculante (o tenencia), color, micro ylene (Mullan & McDowell, 2003, Cap. 10). Agentes antiniebla BIAL calidad, estabilidad de lípidos y palatabilidad (Renerre & Labadie, externamente se aplican a la superficie del polímero por dipcoating o 1993; Taylor, 1985, Cap. 4; Zhao et al., 1994). Vida útil es el porpulverización o mezcladas en el polímero para la migración a la superficie. IOD de tiempo entre el embalaje del producto y su uso que la Agentes antivaho bajar la tensión superficial del agua que se condensa propiedades del producto siendo aceptables para el usuario del producto, con en el interior superficie de películas cuando hay una temperatura differen propiedades de la vida útil es el aspecto, textura, flavor, color, y TiAL entre la superficie de la película y el entorno. valor nutritivo (Singh & Singh, 2005, Cap. 3). Las variables que Los agentes utilizados para evitar que se empañen la película son ésteres de glicerol, influencia las propiedades de la vida útil de carne fresca empaquetada son producto poliglicerol éteres, ésteres de sorbitan y sus etoxilados, alcohol UCT, mezcla de gases, paquete y espacios vacíos, embalaje de equipos, etoxilados y Nonil fenoles etoxilados (Osswald, Baur, bordetemperatura de almacenamiento y aditivos (Hotchkiss, 1989). La calidad Mann, Oberbach & Schmachtenberg, 2006). de alimentos envasados está directamente relacionada con el alimento y el empaquetado Opciones de empaquetado de carne enfriada están permeable al aire, bajo materiales atributos (Han, 2005a, Cap. 1) hasta los materiales de embalaje El2vacío, bajo O mapa con gases anóxicos y alta O mapa (Bel2 2 se han desarrollado para mantener las propiedades deseadas de carne Cher, 2006; Brody, 2007; Cole, 1986; Gill & Gill, 2005, Cap. 13; durante el almacenamiento y exhibición. Jenkins & Harrington, 1991; McMillin et al., 1999, Cap. 6; Renerre Materiales utilizados en el acondicionamiento de los alimentos son vidrio, metal,&papel, y 1993). Si bien empaquetado permeable al aire no es un mapa, usar Labadie, plástico (Marsh & Bugusu, 2007). Propiedades de plástico hacerlos de los materiales de embalaje envueltos dentro de paquete principal o bandejamuy adecuado para envasado (Jenkins & Harrington, 1991). manga en sistemas permite esta opción de empaque para ser un compoPlásticos tienen propiedades de baja densidad, resistencia a la fractura, Nent de mapa (McMillin et al., 1999, Cap. 6).

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Table 1 Properties of major packaging resins used for meat and poultry

a

Abbreviation

Water vapor transmission rate, g/ m 2/24 h

O2transmission rate, cc/m 2/24 h

Tensile strength, MPa

Tear strength, g/mL

Impact strength, J/m

Haze, %

Light transmission, %

Heat seal temperature,  C range,  C

Notes

Polyinyl chloride Polyvinylidene chloride Polypropylene High density polyethylene Low density polyethylene Linear low density polyethylene Ionomer

PVC PVdC

1.5–5 0.5–1

8–25 2–4

9–45 55–110

400–700 10–19

180–290 –

1–2 1–5

90 90

135–170 120–150

Moisture impermeable; resistant to chemicals Vapor barrier; high hardness; abrasion resistant

PP HDPE

5–12 7–10

2000–4500 1600–2000

35.8 38.2

340 200–350

43 373

3 3

80 –

93–150 135–155

Clear, readily processed Used for structure

LDPE

10–20

6500–8500

11.6

100–200

375

5–10

65

120–177

Lidding film use; high strength, low cost sealant

LLDPE

15.5–18.5

200

7–135

150–900

200

6–13

–

104–170

Superior hot tack; poor sealing through grease

25–35

6000

24–35

20–40

150

–

–

107–150

Ethylene vinyl acetate Ethylene vinyl alcohol Polyamide (nylon) Polyethylene terephthalate Polystyrene

EVA

40–60

12,500

14–21

40–200

45

2–10

55–75

66–177

EVOH

1000

0.5

8–12

400–600

–

1–2

90

177–205

Metallic salts of acid copolymers of PE; broad heat sealant range 4% improves heat sealability; 8% increases toughness and elasticity Vapor barrier

PA

300–400

50–75

81

15–30

50–60

1.5

88

120–177

PET

15–20

100–150

159

20–100

100

2

88

135–177

PS

70–150

4500–6000

45.1

2–15

59

1

92

121–177

High heat and abrasion resistance, clear, easily thermoformed; printable Polyester from terephthalic acid reaction with ethylene glycol; abrasion and chemical resistant; structure use High impact PS (HIPS) for multilayer sheet extrusion; strong; structure use

a Based upon one mil film; information from Baker and Mead (2000, Chap. 1), Elias (2003), Jenkins and Harrington (1991), Kirwan and Strawbridge (2003, Chap. 7), Mullan and McDowell (2003, Chap. 10), Robertson (2006) . Additional references are Brody and Marsh (1997), Hanlon et al. (1998) and Osswald et al. (2006).

K.W. McMillin / Meat Science80 (2008) 43–65

Packaging resin

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Meat that is cut in the retail store or butchery is usually part of boxed meat systems where primal cuts are fabricated and vacuum packaged at the packing plant and shipped in cardboard boxes to retail distribution centers or individual stores. Distribution centers or retail stores receive the beef primal cuts in VP an average of 22.6 days after carcass fabrication, with a range of 3–83 days ( Voges et al., 2007 ). At the retail outlet, the primal cuts are removed from VP to be further cut, tenderized, trimmed and/or ground before placement onto expanded polystyrene trays and overwrapped with PVC, polyethylene, or polyolefin film before stacking in selfservice refrigerated cases. Chub packages of coarsely or finely ground beef may also be received at retail from the packing plant. The film often has O permeability of 8000 to 12,000 cc per m per2 2 24 h at 1 atmosphere ( Cole, 1986) and moisture vapor transmis2 sion rate of less than 15 g per m per 24 h ( Jenkins & Harrington, 1991). Fresh meat air-permeable packaging in cellophane was replaced by development of PVC stretch film, but the intent is to provide blooming of myoglobin pigments to oxymyoglobin before retail display (Brody, 1989, Chap. 2). PVC film offers the same protection and oxygen permeability as cellophane, but at lower cost, superior sheet flatness, and less wrinkling. Additionally, replacement of the paperboard support tray by an expanded polystyrene tray improved package attractiveness ( Jenkins & Harrington, 1991). Globally, this package is still the most popular form for air-permeable packaging of meat for self-service display. The traditional Styrofoam tray with PVC wrap is offered in both in-store and case-ready systems while most other retail package formats are offered almost exclusively in centralized packaging operations ( Eilert, 2005). MAP for meat requires a barrier of both moisture and gas permeation through packaging materials to maintain a constant package environment during storage. With any type of MAP, removal or changing the normal composition of atmospheric air is necessary (Blakistone, 1999a, Chap. 1 ) and encompasses both aerobic and anaerobic types of packaging for meat. The major gases in dry air by volume at sea level are nitrogen (N , 78%), O (20.99%), argon 2 2 (0.94%) and CO2 (0.03%), but the percentages vary when calculated by weight (Compressed Gas Association, 1981). The VP materials for primal cuts are often a three layer coextrusion of ethyl vinyl actate/polyvinylidene chloride/ethyl vinyl acetate with O permeability of less than 15.5 cc per m per 224 h at 1 2 atmosphere due to the polyvinylidene chloride layer ( Jenkins & Harrington, 1991). The absence of O in2 low O packages usually 2 causes pigments to be in the deoxymyoglobin state and to minimize oxidative deteriorative reactions. Low O 2 vacuum packages for retail cuts are usually vacuum skin packaging (VSP) systems for placing the retail cut in a barrier styrene or polypropylene tray and vacuum sealing barrier films that are heat shrunk to conform to the shape of the product (Belcher, 2006). VSP packaging equipment may use a vacuum to remove atmospheric air or flush the air from the package with gaseous mixtures such as N2 ,CO2 , or mixtures of N2and CO before heat sealing the film layers ( Blakistone, 1999b, 2 Chap. 10). Common construction for the top and bottom package webs is nylon, barrier polymer of polyvinylidene chloride or ethylene vinyl alcohol, tie layer, and ionomer. Nylon provides bulk, toughness and low melting point while the barrier layer prevents vapor permeation and ionomer gives necessary seal characteristics (Jenkins & Harrington, 1991). A variation of VSP is for the lidding film to have outer barrier and inner air-permeable layers so that before retail display, the outer barrier film layer is peeled away from the permeable layer so that air can then contact the meat product and cause a bloomed color ( Belcher, 2006; Buffo & Holley, 2005; Jeyamkondan, Jayas, & Holley, 2000; Renerre & Labadie, 1993 ). Low O 2 MAP has been readily available, but lesser used even though VP is the most cost effective packaging. The development of shrinkable films for use on horizontal form-fill-seal equipment

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eliminates excessive film and wrinkles for these packages ( Eilert, 2005). Low O 2 MAP may be a barrier package with an anoxic atmosphere of N 2 and CO 2 (Gill & Gill, 2005, Chap. 13 ). The N 2 is an inert gas that is not reactive with meat pigments and not absorbed by the meat so it maintains integrity of the package by its presence in the headspace. The CO 2 reacts with meat, changing the properties as noted in the next section. Barrier trays are filled with product and then sealed with barrier lidding film after flushing with the desired gas mixture. The barrier tray is most often preformed off-site from the fabrication and packaging plant, but may be made on form-fill-seal packaging equipment where the web or base film is heated and drawn into the tray mold by a vacuum so product can be placed into the formed film cavity before heat sealing of barrier film to the top edges of the formed tray (Jenkins and Harrington). The product has deoxymygolobin pigment state, which causes a purple meat color unfamiliar to many consumers ( Lynch, Kastner, & Kropf, 1986 ). Nonbarrier overwrapped packages of meat may be enclosed in a barrier pouch sized for each individual overwrapped tray package (tray-in-sleeve configuration) or in a larger barrier film master pack that contains multiple packages in the anoxic gas ( McMillin et al., 1999, Chap. 6 ). When the overwrapped permeable film package is removed from the master pack for retail display, the meat pigments become oxygenated ( Belcher, 2006; Buffo & Holley, 2005, Chap. 14 ). Another variation is the use of anoxic MAP that has an inner air-permeable film and outer barrier film sealed to the barrier tray or bottom web containing the meat. When the outer film is peeled before display, the meat is exposed to O 2 in the atmospheric air and blooms. Because air-permeable films may not allow sufficient O 2 passage for adequate oxymyoglobin formation, microperforated shrink films with additional holes or perforations have been manufactured that promote faster meat blooming after removal of barrier film or removal of overwrapped trays from master packs ( Beggan, Allen, & Butler, 2005 ). Carbon monoxide (CO) has also been used in low O 2retail packaging systems. Meat may be exposed to CO before packaging or CO may also be used to gas flush VSP packages before sealing, but the small amounts of CO are still sufficient to impart a desired red meat color ( Belcher, 2006; Cornforth & Hunt, 2008; Eilert, 2005 ). The majority of fresh meat MAP has been with a high O envi2 ronment (around 80% O 2) that gives sufficient shelf life for processors and retailers with controlled distribution systems ( Eilert, 2005). High O MAP systems use a barrier tray, often polystyrene, 2 polypropylene, or polyethylene, sealed with a clear or printed barrier film ( Belcher, 2006). Another O package variation is to use a 2 non-barrier polystyrene tray that is completely overwrapped by a barrier film ( Belcher, 2006). Headspaces of 25–90% O and 15– 2 80% CO2 may be used ( Blakistone, 1999b, Chap. 10 ), although 80% O2 :20% CO2 is the most common gas mixture ( Belcher, 2006; Eilert, 2005). Packaging becomes active when it performs another desired role other than providing an inert barrier to external conditions and has developed as a series of responses to maintain quality and safety of food ( Rooney, 1995, Chap. 1 ). Examples of active packaging systems are absorbing or scavenging properties for O , 2 CO2 , moisture, ethylene, flavors, taints, UV light; releasing or emitting properties for CO , ethanol, antioxidants, preservatives, fla2 vors, pesticides; removing properties for catalyzing food component removal of lactose and cholesterol; temperature control by insulating materials, self-cooling or self-heating materials, microwave susceptors and modifiers; and microbial control with antimicrobial compounds and UV light ( Church, 1994; Day, 2003, Chap. 9; Kerry et al., 2006 ). Smart or intelligent packages interact with the product and provide information on the condition of the packaged food and may actually respond to changes in the environment (de Kruijf et al., 2002; Rooney, 1995, Chap. 1 ).

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There is a focus to match the package properties to the desired characteristics of the food R ( ooney, 1995, Chap. 1). This has caused development of multiple stage packaging systems for meat (McMillin et al., 1999, Chap. 6 ). The removal of overwrapped airpermeable packages from a master pack, peeling of barrier film from anoxic packages to allow atmospheric air blooming of product, or the physical exchange of gases using gas exchange technologies to replace anoxic distribution gas mixtures with 80% O :20% 2 CO2 for retail display are examples of multiple stage packaging systems that give extended storage and distribution in anoxic MAP while allowing display of meat with oxymyoglobin pigments (McMillin et al., 1999, Chap. 6 ). 2.2. Properties of meat in MAP Packaging influences the extension of raw chilled meat shelf life (Renerre & Labadie, 1993). The properties of meat that are important in determining shelf life include water binding (or holding) capacity, color, microbial quality, lipid stability, and palatability (Renerre & Labadie, 1993; Taylor, 1985, Chap. 4; Zhao et al., 1994). The variables that influence the shelf life properties of packaged fresh meat are the product, gas mixture, package and headspace, packaging equipment, storage temperature, and additives (Hotchkiss, 1989). Deteriorative changes during meat storage are affected by metabolic reactions from biological membrane disruption (Stanley, 1991) and biochemical oxidative processes ( Xiong & Decker, 1995). Deterioration of quality may include discoloration, off-flavor and off-odor development, nutrient loss, texture changes, pathogenicity, and progression of spoilage factors ( Skibsted et al., 1994). The purpose of MAP is to maintain the desired properties of meat for the desired period of storage and display. The use of MAP for meat and the properties of meat in MAP have been previously discussed in other reviews ( Blakistone, 1999b, Chap. 10; Brody, 1989, Chap. 2; Church, 1993, Chap. 10; Doherty, 1996; Finne, 1982; Gill, 1990; Hood, 1984; Hood & Mead, 1993, Chap. 10; Hotchkiss, 1989; Inns, 1987, Chap. 3; McMillin et al., 1999, Chap. 6 ; Renerre & Labadie, 1993; Robertson, 1993; Sebranek, 1986; Seideman & Durland, 1983; Seideman & Durland, 1984; Smith, Ramaswamy, & Simpson, 1990; Stiles, 1991, Chap. 5; Wolfe, 1980; Young, Reviere, & Cole, 1985, Cha 4; Young et al., 1988; Zhao et al., 1994). Centralized meat packaging systems were discussed by Jeyamkondan et al. (2000) and Buffo and Holley (2005, Chap. 14). Raw chilled meat during storage exhibits the chemical reactions of respiration, which is the active absorption of O 2 and release of CO ,2 but meat respiration is not as pronounced as in fresh fruits and vegetables ( Siegel, 2001 ). Postmortem muscle mitochondria continue to metabolize O , but 2 active mitochondrial O2 consumption and CO 2 evolution decrease with postmortem time ( Faustman & Cassens, 1990 ). Mitochondria can influence myoglobin redox stability by O consumption that decreases par2 tial O 2 pressure, reduction of metmyoglobin by mitochondrial electron transport chain reactions, and/or mitochondrial membrane lipid oxidation ( Tang, Faustman, Mancini, Seyfert, & Hunt, 2006). Reduction of metmyoglobin is necessary for maintenance of meat color life and depends upon enzyme systems and NADH reservoirs, which are depleted with postmortem time ( Mancini & Hunt, 2005 ). The oxidation-reduction potential of cytochromes and aromatic amino acid side chains in the meat ( Giddings, 1977) help maintain ferrous pigment forms if meat O 2 tension is low. Heme oxidation is also influenced by the levels and wavelengths of light ( Bertelsen & Skibsted, 1987), amount and types of bacterial growth, pH level, heat exposure, and CO tension at the 2 meat surface. Temperature, package film vapor permeability and gaseous atmospheres also impact the degree and maintenance of bloomed meat color ( Kropf, 1980).

2.2.1. Pigment color and partial pressures Color of prepackaged meat and its stability or discoloration are the most important quality attributes in shelf life ( Renerre & Labadie, 1993). Meat purchasing decisions are influenced more by color than any other quality factors ( Mancini & Hunt, 2005 ), with a strong relationship between color preference and purchase intent by consumers who would discriminate against beef that was not red ( Carpenter, Cornforth, & Whittier, 2001 ). Meat with 20% metmyoglobin is discriminated by consumers ( MacDougall, 1982 ) and is downgraded or rejected for purchase when metmyoglobin levels exceed 40% ( Greene, Hsin, & Zipser, 1971 ). As previously noted, consumers also rate appearance of beef steaks and patties with purple color below those with red color, but above those with brown color ( Carpenter et al., 2001 ). 2+ Deoxymyoglobin is the reduced form of myoglobin (Fe ) that gives purple color in the absence of O when meat is first cut or 2 has been vacuum packaged. Metmyoglobin is the oxidized pigment state of myoglobin, the dominant sarcoplasmic pigment in muscle, and the Fe 3+ results in a brown or gray meat color. Oxymyoglobin is the reduced pigment form (Fe 2+) in which O occupies the ligand 2 position and the perceived color is red (bloomed). Penetration depth of O 2 and the oxymyoglobin layer thickness depend upon meat temperature, O partial pressure, pH, and competition of O 2 2 by other respiratory processes ( Mancini & Hunt, 2005 ). Metmyoglobin forms when pigments are exposed for extended times to light, heat, O ,2microbial growth, or freezing. Carboxymyoglobin is formed when deoxymyoglobin is exposed to CO ( Mancini & Hunt, 2005 ). The reduction of metmyoglobin was increased by 1–5% CO even in the presence of air (Lanier, Carpenter, Toledo, & Reagan, 1978 ). The chemical status of each individual pigment molecule is independent of other pigment molecules, and in the absence of CO, the three states of myoglobin may exist simultaneously in varying amounts in the same muscle dependent on redox conditions. The bright red bloomed color of beef is due to the predominating oxymyoglobin pigment that is easily obtained with greater than 40 torr partial pressure of O 2 (5.25%) in air-permeable PVC packaging ( Rizvi, 1981 ). Oxymyoglobin is formed by O 2 binding to the ferrous heme with high O tension while metmyoglobin is 2 caused by oxidation of heme pigments to a ferric state ( Seideman & Durland, 1984). Deoxymyoglobin dominates in conditions of less than 0.2% O2 , high metmyoglobin reducing activity, and package O 2 2 transmission rates (OTR) of less than 38 cc per 100 m while oxymyoglobin dominates with greater than 13% O , low O consump2 2 tion rates (OCR), high metmyoglobin reducing rates, and OTR of 5038 cc per 100 m . 2Metmyoglobin pigment forms dominate at available oxygen levels of 0.2–13%, high OCR, low metmyoglobin reducing rates, and OTR between 38 and 5038 cc per 100 m ( 2Siegel, 2001). Fresh meat is very susceptible to metmyoglobin formation by low O 2 pressure in the range of 5–10 mm mercury (2.6– 5.3%) (Sebranek & Houser, 2006, Chap. 6). High O 2maintains oxymyoglobin pigments, but may induce other oxidative reactions (McMillin, 1996 ). 2.2.2. Metmyoglobin reduction Muscles of high color stability had high resistance to induced metmyoglobin formation, high nitric oxide reducing ability, high O2 penetration depth, low OCR, low myoglobin content, and low oxidative rancidity with the discoloration differences between muscles related to the proportion of reducing activity and OCR (McKenna et al., 2005 ). This substantiated the strong relationship of meat color stability in different muscles to inherent OCR, metmyoglobin reducing capacity (MRA), and metmyoglobin reductase activity ( Bendall & Taylor, 1972; Eschevarne, Renerre, & Labas, 1990; Hood, 1980; Kropf, 1993; Lanari & Cassens, 1991; Madhavi & Carpenter, 1993; O’Keeffe & Hood, 1982; Reddy & Carpenter,

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1991; Sammel, Hunt, Kropf, Hachmeister, & Johnson, 2002; Seyfert et al., 2006 ). It was concluded that initial metmyoglobin formation was more useful for relating metmyoglobin reducing activity (MRA) to color stability during display than more commonly used absolute and relative calculations based upon nitric-oxide MRA assay (Mancini, Seyfert, & Hunt, 2008). 2.2.3. Flavor attributes Flavor is a very complex attribute of meat palatability (Calkins & Hodgen, 2007), but was the most important factor affecting consumer meat purchase habits and preferences when tenderness was held constant ( Sitz, Calkins, Feuz, Umberger, & Eskridge, 2005). Small changes in flavor sensory ratings greatly influenced overall steak acceptability ( Platter et al., 2003 ). Flavor and odor compounds may originate from lipid and peptide components in muscle or meat ( Spanier, 1992). Palatability characteristics generally influence repeat sales but are not readily discernible by consumers contemplating meat purchases. Steak choices by French consumers were based 46% on appearance/color and 9% on tenderness before tasting and 15% on appearance/color and 42% on tenderness after tasting ( Dransfield, Zamora, & Bayle, 1998 ). Meat texture is governed primarily by the myofibrillar structure and the connective tissue structure (Harris & Shorthose, 1988 ). As muscle fibers swell, less force is needed to shear samples and the density of the meat decreases. Warner–Bratzler shear values of less than 42.87 N and greater than 52.68 N allow classification of tough and tender beef in a sufficiently reliable way to be highly related to consumer tenderness perception ( Destefanis, Brugiapaglia, Barge, & Dal Molin, 2008 ). Oxidation of the myofibrillar proteins has been linked to changes in functionality and quality deterioration of meat ( Xiong, 1996). Increased protein carbonyl content due to protein oxidation had negative effects on meat color and tenderness ( Rowe, Maddock, OLonergan, & Huff-Lonergan, 2004). High O MAP has been shown 2 to be detrimental for tenderness of beef ( Seyfert et al., 2005 ) and pork due to protein cross-linking from oxidative processes ( Lund, Lametsch, Hviid, Jensen, & Skibsted, 2007). The oxidative processes initiated by endogenous or exogenous factors occur because of the components of muscle foods (Kanner, 1994), with pigments, fatty acids, amino acids, and vitamins as the biological compounds most influenced by oxidation-reduction metabolic processes (McMillin, 1996). Oxidation of meat pigments has been linked to other oxidation-reduction reactions in meat through the generation of superoxide anions ( Gotoh & Shikama, 1976), which produce additional free radical compounds that are involved in oxidative reactions ( McMillin, 1996 ). In retail meat bloomed with air, discoloration typically precedes lipid oxidation, so lipid deterioration is not usually an important shelf-life property. However, meat in packages with greater than 21% O may in2 duce oxidative processes and lipid oxidation may be a problem with meat in high O 2 MAP (Jackson, Acuff, Vanderzant, Sharp, & Savell, 1992). Oxidation of lipids has been linked to oxidation of pigments and meat discoloration ( Faustman & Cassens, 1990, 1991; Faustman et al., 1989; Greene, 1969; Govindarajan, Hultin, & Kotula, 1977; Hutchins, Liu, & Watts, 1967; Yin, Faustman, Riesen, & Williams, 1993). Lipid autoxidation causes flavor deterioration and off-odors (Lillard, 1987 ) through a complex process whereby unsaturated fatty acids react with molecular O 2 via free radical mechanisms to form fatty acyl hydroperoxides or peroxides ( Gray, 1978). Factors influencing lipid oxidation include fatty acid composition, prooxidants, enzymes, and heat (Lillard, 1987). Lipid oxidation can be determined by sensory and chemical measurement, with thiobarbituric acid reactive substances (TBARS) a strong objective predictor of the perception of rancidity. Threshold TBARS values of 0.5– 1.0 for fresh ground pork were highly correlated (0.89) to intensity

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of rancid odor by trained sensory panelists ( Tarladgis, Watts, Younathan, & Dugan, 1960 ) and consumer panelists preferred cooked pork patties with TBARS of less than 0.5 compared with patties that had TBARS numbers greater than 1.4Jayasingh ( & Cornforth, 2004). A TBARS value of 2 was considered the limiting threshold for oxidized beef acceptability (Campo et al., 2006). It was postulated that repression of other deteriorative mechanisms in meat by MAP might cause lipid oxidation, normally not a limiting factor of shelf life, to decrease shelf life ( McMillin, 1994). Although earlier studies did not report increased lipid oxidation with elevated O , most 2 more recent studies have indicated that high O 2 increased lipid oxidation, usually in comparison with VP or low O MAP 2 ( Cayuela, Gil, Bañón, & Garrido, 2004; John et al., 2004; John et al., 2005 ). Flavor of ground beef was less desirable and lipid oxidation was higher in high O 2 compared with low O 2 MAP after 6 or 10 days (Jayasingh, Cornforth, Brennand, Carpenter, & Whittier, 2002 ). However, sensory panelists preferred steaks stored in 50% O even 2 though oxidized flavors were detected compared with steaks in other levels of O (20% CO ; 2balance N ), 2which could be a result 2 of adaptation to, or familiarity with, oxidized flavors in meat ( Zakrys et al., 2008). There was a tendency for consumers, while having no preference differences between minced meat in high O stored 2 for 0, 6 or 8 days, to separate into two separate groups, one preferring day 0 and the other group day 8 samples ( Lagerstedt et al., 2007). Various methodologies have been proposed for use on meat to improve color and lipid stability. Antioxidants endogenous to meat are tocopherols, carotenoids, histidine-dipeptides, polyamines, some nucleotides, ascorbic acid, and glutathione, which interact with the cytosolic antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, and ceruloplasmin ( Decker & Mei, 1996). Antioxidant additives include synthetic phenolics, chelators such as phosphates, ascorbate, nitrite, and spice derivatives.Deck( er & Mei, 1996 ). Oxidative stability has been increased by feeding a-tocopherol or vitamin E in animal diets or by adding antioxidants directly to meat (Faustman, Chan, Lynch, & Joo, 1996). Cuts may be dipped in solutions of antioxidant compounds before packaging (Mitsumoto, Arnold, Schaefer, & Cassens, 1993; Mitsumoto, Cassens, Schaefer, Arnold, & Scheller, 1991; Okayama, 1987; Shivas et al., 1984; Yin et al., 1993) or organic acid dips may be combined with MAP packaging for pork and beef ( Cocoma & Cheng, 1988; Manu-Tawiah, Ammann, Sebranek, & Molins, 1991; Huang, Ho, & McMillin, 2005). Hood (1975) described injection of sodium ascorbate into beef cattle to subsequently inhibit metmyoglobin formation. The incorporation of agents with antioxidant properties into meat may be accomplished by feeding vitamin E to livestock ( Arnold, Arp, Scheller, Williams, & Schaefer, 1993a; Arnold, Scheller, Arp, Williams, & Schaefer, 1993b; Buckley & Morrissey, 1992; Lanari, Cassens, Schaefer, & Scheller, 1993; Leedle, Leedle, & Butine, 1993; Mitsumoto et al., 1993 ). At certain levels, however, compounds such as ascorbate may decompose to form hydrogen peroxide, which may bleach meat color and cause subsequent quality deterioration ( Morey, Hansen, & Brown, 1973 ; Ladikos & Lougovois, 1990). Beef cubes immersed in different preservatives before mincing and storage in 70% O :30% CO had lower aerobic 2 2 microorganisms on day 12, but were discolored with lactic acid, were organoleptically unacceptable with potassium sorbate, and had improved color with sodium ascorbate ( Friedrich et al., 2008 ). 2.2.4. Drip and water holding capacity Variations in water holding capacity at a given meat pH and storage temperature have been proposed to be partially due to variations in proteolysis and subsequent shrinkage and movement of water into extracellular spaces ( Huff-Lonergan & Lonergan, 2005). Water binding or water holding capacity is a measure of the ability of meat to hold its own or added water ( Hamm, 1960;

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Offer & Knight, 1988 ) and the amount of bound water affects the appearance of products and their economic value (Offer & Cousins, 1992). Packages of meat containing a pool of fluid surrounding the meat are not desirable to consumers. Consumers also do not like handling meat packages that leak fluids. Drip is composed primarily of sarcoplasmic proteins ( Savage, Warriss, & Jolley, 1990 ) and may be from 2–10% of lean weight ( Offer & Knight, 1988). A major determinant of weepage is the ratio of surface area to volume, with drip loss minimized by decreased exposed surface area and longitudinal, rather than transverse, cutting of muscle fibers. Drip increases occur nonlinearly with storage time. Packaging in polyethylene or in nonshrinking ethylene-Saran composites did not affect drip, but shrinking films reduced drip by 51–68% compared with nonshrinking films ( Zarate & Zaritzky, 1985 ). A likely source of drip is the shrinkage of myofibrils during rigor onset and their expulsion of fluid into extracellular spaces ( Offer & Cousins, 1992) so increased handling and pressure changes on the meat surface may be expected to increase drip losses. VP increased initial weight loss to 5.1% on the second day of storage of pork compared with high O MAP ( Cayuela et al., 2004). Drip loss increased 2 from 1.57% on the first day to 5.64% after 7 days in retail trays of case-ready pork, with the development of drip loss mainly dependent upon the initial amount of drip loss ( Otto et al., 2006 ). 2.2.5. Microbiology The species and population of microorganisms on meat are influenced by animal species, state of health, and handling of live animals; slaughter practices, plant and personnel sanitation, and carcass chilling; fabrication sanitation, type of packaging, storage time, and storage temperature ( Nottingham, 1982, Chap. 2; Grau, 1986). Discoloration, off-odors, and slime production are among the deteriorative factors caused by bacterial growth ( Butler, Bratzler, & Mallman, 1953 ). Aerobic microorganisms like Pseudomonas and Achromobacter are commonly found on meat and reduce the O2tension and increase discoloration of raw meat in ambient air environments (Robach & Costilow, 1961). Bacterial numbers lower 6 than the level of log 10 colony forming units (CFU) associated with spoilage may affect color by reducing the O tension at the meat 2 surface and excreting oxidizing agents (Siegel, 2001). Growth and survival of spoilage and pathogenic microorganisms are affected by MAP ( Blakistone, 1999b, Chap. 10; Farber, 1991). N 2has minimal effects on metabolic reactions in the meat, being lowly soluble in water and lipid ( Church, 1994), but anoxic atmospheres created by use of N 2 and/or other gases will select for anaerobic, aerotolerant lactobacilli ( Thippareddi & Phebus, 2007). Uptake of O 2and CO evolution is due to muscle tissue res2 piration and microorganism growth ( Ingram, 1962), with no difference in CO 2 evolution between aerobically and anaerobically stored pork or between pre-rigor or post-rigor meat ( Enfors & Molin, 1984 ). Increased levels of CO 2 inhibit microbial growth in refrigerated storage, with 20–40% CO used in MAP (Clark & Lentz, 2 1969), and high levels raise the possibility of establishing conditions where pathogenic organisms may survive ( Daniels, Krishnamurthi, & Rizvi, 1985 ). The CO in 2 MAP is absorbed by water and lipid portions of meat until saturation or equilibration is reached (Jakobsen & Bertelsen, 2002 ), with the full preservative effect of CO2 achieved only with excess of CO above saturation levels ( Gill 2 & Penney, 1988). Gram-negative bacteria are generally more sensitive to CO 2 than Gram-positive bacteria ( Church, 1994) because most Gram-positive bacteria are facultative or strict anaerobes (Gill & Tan, 1980 ), but individual bacteria vary in sensitivity to CO2 (Farber, 1991). Levels of 20–60% CO2are required for effectiveness against aerobic spoilage organisms by penetrating membranes and lowering intracellular pH ( Smith et al., 1990 ), but little or no effect is observed with CO above 50–60% ( Gill & Tan, 2 1980).

Lactic acid bacteria increased in pork in O -free 2 atmospheres and were lowest in 100% O 2 MAP after 20 days of storage while Pseudomonas growth was limited in pork loins in VP, 100% CO , 2 1% CO and 99% CO Viana, ( 2 , with higher counts for pork in 100% O2 Gomide, & Vanetti, 2005 ). O 2generally stimulates growth of aerobic bacteria and inhibits growth of strict anaerobic microorganisms, but the sensitivity of anaerobes to O 2 is variable ( Church, 5 1994). Aerobic plate counts increased to 9 x 10 CFU per gram by 10 days of storage, but were not different in low O 2 chub packs compared with high O 2 MAP ( Jayasingh et al., 2002 ). Slight amounts of O 2in nominally anoxic packaging of pork did not influence microbial spoilage (Jeremiah, Gibson, & Arganosa, 1992). Aerobic microbial growth also causes O 2 uptake and CO 2 evolution (Sebranek, 1986). Pseudomonas and Lactobacillus sakei were identified as major spoilage organisms with 60% O MAP (Ercolini, Rus2 so, Torrieri, Masi, & Villani, 2006 ). Predominant microorganisms for ground beef stored in 80% N : 20% CO and 2 2 displayed in 80% O2:20% CO2 or displayed in conventional overwrap air-permeable packaging after VP storage were Pseudomonas, Aeromonas, and Enterobacter, with Yersinia found in high O MAP and Brochothrix, 2 Moraxella, and Lactobacillus in conventional overwrap packaging, indicating that control of storage and display temperatures is critical with MAP ( Ho, Huang, & McMillin, 2003 ). Use of 1% CO, 50% CO2 , and balance air extended ground beef shelf life about 4.5 days ( Gee & Brown, 1978 ). Although shelf life was extended with CO above 0.5% ( Clark, Lentz, & Roth, 1976 ), the growth of pure microbial cultures was variable, with no effect of CO on Pseudomonas aeruginosa , inhibition of E. coli proportional to CO level, lag phase increased for Achromobacter, and the growth rate inhibited and lag time increased for P. fluorescens (Gee & Brown, 1980). Psychrotrophic counts were similar for control and CO-treated beef steaks in VP during 4 weeks, but were lower with CO after 8 weeks in storage B ( rewer, Wu, Field, & Ray, 1994). Packaging materials and methods play a role in controlling the rate of growth with aerobic bacteria having a generation time of about 12 h and being inhibited by CO and 2 anaerobic bacteria having a generation time of about 40 h, with inhibition by O 2 (Siegel, 2001). Pathogen growth was suppressed in high O 2 MAP and CO MAP containing CO 2 while spoilage characteristics developed in ground beef in those packages ( Brooks et al., 2008 ). Additional information about microbiological properties of meat in MAP are available in other reviews ( Blakistone, 1999b, Chap. 10; Farber, 1991; Gill, 1986, Chap. 2; Gill & Gill, 2005, Nychas, Drosinos, & Board, 13; Gill & Newton, 1978; Nottingham, 1982, Chap. 2; Nychas et al., 1998, Chap. 9; Silliker & Wolfe, 1980; Stanbridge & Davies, 1998, Chap. 6; Thippareddi & Phebus, 2007). 2.2.6. Cooked meat color Premature browning of meat during cooking is the attainment of a brown color before a microbiologically safe temperature has been reached (King & Whyte, 2006). Ground beef patties from high O2packaging were prematurely brown compared with those from VP when cooked to 71.1  C regardless of the time in display ( Seyfert, Mancini, & Hunt, 2004 ). Enhanced beef round muscles stored in high O 2and cooked to 71.1  C also exhibited premature browning (Seyfert, Hunt, Mancini, Kropf, & Stroda, 2004b). Steaks stored in 80% O2 developed a brown internal color at temperatures as low as 57  C(John et al., 2005). Loin steaks from 0.4% CO MAP that were cooked to medium degree of doneness (70  ) had the expected pink internal color while steaks from 80% O :20% CO MAP had the low2 2 est a* values and were brown inside at this temperature, posing a safety risk ( Grobbel, Dikeman, Hunt, & Milliken, 2008 ). While premature browning was observed at internal temperatures as low as 49  C for ground beef stored in 80% O 2, the internal color of cooked beef after storage in CO remained somewhat red even after cooking to 79  C(John et al., 2004 ). In injected and non-injected meat, CO

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MAP packaging results in retention of pink meat color after cooking (Mancini, Kropf, Hunt, & Johnson, 2005). Possible explanations for the pink color even when pork from CO MAP was cooked to 82 C  were that carboxymyoglobin resists heat denaturation and the binding of the carbonyl ligand to myoglobin may protect the iron core from oxidation even if the globin moiety is denatured (De Santos, Rojas, Lockhorn, & Brewer, 2007). However, 0.9% CO was lost during air storage in raw ground beef with a half-life of about 3 days and maximum loss of CO during 8 min of cooking at 195 C  was 85% ( Watts, Wolfe, & Brown, 1978 ). The retention of pink internal color after attainment of temperatures ensuring microbiological safety is primarily caused by exposure to nitrogen compounds (Cornforth, 1991) and by high meat pH ( Hunt, Sørheim, & Slinde, 1999; Mendenhall, 1989; Trout, 1989 ). 2.3. Considerations for MAP implementation For successful active packaging, MAP must be viewed as interrelated with other processing, distribution and display components of the entire fresh-meat marketing system rather than as an isolated aspect at the end of the sales chain ( McMillin, 1994). Success of MAP systems requires decisions on high O 2 or low O 2 meat color during transit and display, postmortem age of whole muscle cuts, injected and enhanced products, phosphate types, use of vitamin E, slicing method for bone-in products, bone discoloration, package seal integrity, pre-pricing and dating, freight, cube and tray size issues, and productivity measurements (Smith, 2001). Other considerations of meat for MAP include globin state as raw or cooked, time after harvest, conditions at harvest, temperature of storage, anatomical muscle location, intact or ground, headspace to product volume, exposure to light and heat, anaerobic or aerobic atmosphere, and other conditions (Siegel, 2001). Extension of shelf life with MAP requires matching product and packaging materials through careful selection, proper gas mixes, online analysis of the packaged products, detection of leaker packages, and off-line testing for overall quality control ( Stahl, 2007). A major decision in choosing a MAP system is color of meat desired during transit and subsequent display. The packaging systems that provide meat for retail display with a red color are more highly used because consumers will discriminate against beef that is not red during display ( Carpenter et al., 2001) and will avoid purchasing meat with 20% or more metmyoglobin ( MacDougall, 1982). Even though a limiting value of about 5% O 2 partial pressure is needed to maintain oxymyoglobin ( Ledward, 1970 ), O2higher than 13% will provide predominant oxymyoglobin pigments (Siegel, 2001). This is readily achievable with air-permeable overwrap packaging or high O MAP and use of 0.4% or higher CO in 2 any anaerobic packaging system will produce red carboxymyoglobin ( Cornforth & Hunt, 2008 ). 2.3.1. Blooming and residual O2 Bloom time had no influence on L* values of pork muscles and while there were no differences between muscles, a* and b* (yellowness) values did not increase after 10 min of bloom time (Brewer, Zhu, Bidner, Meisinger, & McKeith, 2001 ). The oxygenation depth increased with time of air exposure before packaging and during display time for ground beef and steaks, but was not related to surface color development or maintenance. Highest redness was achieved after 20 min air exposure for ground beef and 15 min exposure for steaks before overwrap packaging McMillin, Ho, Huang, and Smith (1994a) . Shelf life of PVC wrapped meats is 5–7 days for steaks (Cornforth & Hunt, 2008) and less for ground beef, 3–5 days (Cole, 1986), due to discoloration. A difficulty with re-blooming of meat in overwrap packages after low O MAP storage has been inability to bloom and/or lack 2 of color uniformity ( Beggan et al., 2005 ). Psoas majorand Longissi-

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mus thoracis et lumborum muscles that were initially packed in trays with micro-perforated lidding film in a master bag with N , 2 CO2 , and O2-scavengers bloomed immediately after removal from the master bag and aerobic display, but blooming did not occur with the Semimembranosusor if O 2 scavengers were not used in the master bags (Beggan et al., 2005). Residual O in 2 masterpacks without O 2 scavengers was 1.5–3% and was generally less than 0.5% with O2scavengers, which resulted in improved bloomed color during display after 42 days ( Venturini, Contreras, Sarantópoulos, & Villanueva, 2006 ). O 2 levels of 0.15–2.0% predispose fresh beef products to turn brown ( Mancini & Hunt, 2005) because fresh meat is very susceptible to metmyoglobin formation by low O 2 pressure in the range of 5–10 mm mercury (2.6–5.3%) ( Sebranek & Houser, 2006, Chap. 6). Although meat will absorb low levels of O ( 2Blakistone, 1999b, Chap. 10) in low O 2MAP, packages should contain less than 0.5% O 2 to minimize tissue respiration and maintain optimal reducing conditions (Taylor, 1985, Chap. 4). Ground beef should be stored in low O2MAP with less than 0.1% O for 2 a minimum of 2 days to achieve a purple color ( Sørheim, Westad, Larsen, & Alveike, 2007). It may be necessary to reduce residual O 2 to 500 ppm (0.05%) or lower to inhibit metmyoglobin formation and induce optimal re-blooming upon exposure of meat to air. Various O absorbers or scaveng2 ers have been used to reduce the concentration of O 2 in low O 2 MAP packages (Abe & Kondoh, 1989, Chap. 9). Scavengers could remove 1–1.5% O2 per hour, with greater O absorption at higher rel2 ative humidity ( Klein & Knorr, 1990 ). Beef in retail overwrap trays stored in a low O (CO :N2 ) mother pack with O scavengers for 6 2 2 2 weeks at 0  C had increased redness of six different muscles during 96 h of retail display after removal from low O 2 compared with control steaks without O scavengers that did not bloom after re2 moval from the mother pack ( Isdell, Allen, Doherty, & Butler, 1999). Sufficient O scavenger sachets were needed to reduce O 2 2 to less than 500 ppm within 0.7 h of initial packaging in air-permeable shrinkable film and storage in low O MAP with N so 2that the 2 meat would bloom after removal from MAP ( Tewari, Jeremiah, Jayas, & Holley, 2002 ). After storage in CO masterpacks with O 2 2 scavengers for 42 days at 1  C, Longissimus dorsi in air-permeable packaging had acceptable color during retail display while Gluteus medius had variable discoloration ( Venturini et al., 2006 ). There are several potential disadvantages with use of O absor2 bents. A free flow of gas surrounding the sachet is necessary for full effectiveness. There may be potential package collapse if O is2 absorbed without concurrent CO generation. The growth of anaero2 bic bacteria may be enhanced and there are concerns about the presence and potential misuse of the O absorbent sachets within 2 packages (Smith et al., 1990 ). Cost and type of materials that absorb O 2 are considerations because metal detectors sense ironbased scavengers (Storck, 2008). The 0.5–1% O 2in MAP obtainable by packaging equipment may be reduced by a scavenging polymer coextruded as a layer of the lidding film that is activated by a UV unit on the packager just prior to sealing ( Cutter, 2002). In MAP systems with less than 2% residual O ,2UV light-activated O scav2 enging films can typically reduce O 2 to less than 0.1% in 3 days (Coma, 2008). The rate of O 2removal must be considered in addition to the initial residual O level Smith, 2001) since only mini2 ( mal time of exposure to 0.5–2% O may cause browning. 2 2.3.2. Gas mixtures High O 2MAP may have headspaces of 25–90% O and 2 15–80% CO2 (Blakistone, 1999b, Chap. 10), although 80% O :20% CO 2 is 2 the most common gas mixture ( Belcher, 2006; Eilert, 2005 ). Film characteristics of 1–2 mil thickness, CO , 2transmission of less than 65 cc per m 2 per day, and moisture transmission of less than 645 g per m 2 per day are desirable to maintain gaseous atmospheres (Smith, 2001). Elevated O 2 levels in high O 2 MAP delay

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browning of fresh meats because the surface oxymyoglobin depth is increased (MacDougall & Taylor, 1975.) The thicker layer of surface oxymyoglobin extends display life ( Siegel, 2001). Oxymyoglobin levels of minced M. semimembranosus samples stored for 4 days in 20%, 40%, 60% or 80% 2O were similar, but higher in all MAP packs compared with samples stored in air although at 7 days of storage, the oxymyoglobin content of minced M. semimembranosus samples decreased with decreasing O .2Minced beef stored in 80% O 2 had increased lipid oxidation between days 7 and 10 of storage. At day 10, lipid oxidation was slightly increased with increased O 2 (O’Grady, Monahan, Burke, & Allen, 2000 ). Increased O2increased TBARS during refrigerated storage F ( ormanek et al., 2001). The TBARS of Longissimus dorsiincreased after 6 days of storage and was increased with increased O while a* declined 2 with storage time and was highest with 50% O 2 (Zakrys, Hogan, O’Sullivan, Allan, & Kerry, 2007 ). Minced meat in high O had 2 increased cooking loss, decreased a-tocopherol content, increased protein oxidation, and increased TBARS through 8 days at 4 C,  but TBARS did not exceed the level of 2 ( Lagerstedt et al., 2007 ) suggested as unacceptable (Campo et al., 2006). Use of 1% CO, 50% CO 2 , and balance air extended bloomed red color of ground beef for 6 days compared with discoloration of air-stored samples after 3 days ( Gee & Brown, 1978 ). Psychrotrophic bacteria populations were reduced by 1% CO:24% O :50% 2 CO2 :25% N2, while stable red color was maintained for 29 days in beef loin steaks and ground beef with that gas composition and 1% CO:70% O 2:20% CO :9% N 2 compared with high O 2 2 (70% O2:20% CO2 :10% N Luño, Beltrán, & Roncalés, 1998 ). 2 )( Savell, Smith, Hanna, and Vanderzant (1981) reported that use of 75% O2:25% CO2 gas mixtures for MAP retail cuts could be successful if relatively fresh beef subprimals were used, but MAP was not comparable to PVC for retail steaks if VP subprimals were fabricated 14 or 28 days after arrival. Psychrotrophic microorganism counts of M. longissiumus lumborum increased with fabrication time and redness was increased at 48 h compared with 0.5 or 96 h postmortem, but there was no influence of fabrication time on TBARS or weight retention in conventional air-permeable packaging or high O 2MAP ( McMillin, Huang, Ho, & Smith, 1994b). Desmin degradation was increased for beef steaks at 14 days compared with 7 days in VP, low O MAP CO, and high O MAP ( Grobbel, Dik2 2 eman, Hunt, & Milliken, 2007 ). 2.3.3. Enhancement and ingredients In 2007, 28% of pork in the US was enhanced with added moisture and another 16% had flavor or ingredients added while 10.5% of beef was enhanced with added moisture and an additional 4.5% had flavor or ingredients added ( Crews, 2007). Enhancement has been defined as the addition of non-meat ingredients to raw chilled meat for the purpose of improving its quality, appearance and shelf life ( Brooks, 2005 ). Enhancement improves juiciness and tenderness and increases the weight of saleable product due to the retention of added water ( Sheard & Tali, 2004 ), with no differences in purge or drip losses reported between enhanced and non-enhanced boneless pork chops ( Wright et al., 2005 ). Beef steaks and roasts were more acceptable if enhanced than non-enhanced (Robbins et al., 2003 ). Color and microbiological shelf-life of pork with pH higher than 5.75 and enhanced with sodium acetate were improved compared with other chops ( Livingston, Brewer, Killifer, Bidner, & McKeith, 2004 ). Color of beef stored for 9 days and displayed for 5 days in high O could be stabilized with 2 2.5% potassium lactate, which would replenish NADH via LDH activity (Kim et al., 2006 ). Sodium lactate decreased metmyoglobin formation, which might explain improved color stability of lactate injection-enhanced beef ( Mancini & Ramanathan, 2008 ). Use of enhancement solutions containing CO improved color of pork chops in 80% N :20% CO 2 and VP, while shear force of chops in 2

80% O2:20% CO2 and in air-permeable packaging was less than for chops in anoxic packaging after storage for 4 weeks. All gaseous enhancement solutions containing CO improved pork shelf life in 2 MAP compared with pork enhanced with no gases and air-permeable packaging (Guerra, McMillin, Bidner, Janes, & Persica III, 2007 ). Use of CO in enhancement solutions with ammonium hydroxide and salt increased color stability of triceps brachii in high O MAP 2 and biceps femoris and rectus femoris in low O (100% CO )2during 2 7 days of simulated retail display after 7 weeks of dark storage, but oxidation values of triceps brachii were very high and total plate counts were higher in injected than non-injected steaks (Hamling, Jenschke, & Calkins, 2008). Phosphate types used in enhancement solutions will influence meat characteristics in MAP. Higher levels of phosphates and use of sodium tripolyphosphate (STP) or tetrasodium pyrophosphate (TSP) rather than sodium hexametaphosphate (SHMP) improved water retention and yield in overwrapped beef biceps femoris(Baublits, Pohlman, Brown, & Johnson, 2005a). However, color was not improved with phosphate addition compared with non-enhanced steaks (Baublits, Pohlman, Brown, & Johnson, 2005b ). Chops enhanced with STP and packaged in CO MAP experienced the least amount of purge loss while chops in high O MAP 2 with both STP and STP-SHMP blend had the most purge ( Wicklund et al., 2006). Color striping (two-toning) was less with the STP-SHMP blend than STP at 0.4% enhancement levels, but cook yields were higher with STP ( Wicklund et al., 2006 ). Removing phosphate from enhancement solutions containing potassium chloride, sodium chloride and sodium acetate did not affect color of beef rib steaks in high O2MAP ( Knock et al., 2006a ) while sodium acetate and potassium lactate improved sensory attributes of injection-enhanced beef (Knock et al., 2006b). 2.3.4. Oxidative stability Dietary supplementation of animals with vitamin E increased stability of lipids and color during storage (Gray, Gomaa, & Buckley, 1996). Discoloration and TBARS values in M. Longissimus lumborum and M. triceps brachii from cattle supplemented with vitamin E that were aerobically packaged and displayed for 9 days or in 80% O2:20% CO2 for 13 days were lower compared with muscles from non-supplemented cattle ( Gatellier, Hamelin, Durand, & Renerre, 2001). Supplementation with dietary a-tocopherol did not influence color of pork chops in aerobic packaging or high O 2 MAP, but reduced TBARS in fresh and salted pork ( Phillips et al., 2001). Beef from cattle supplemented with vitamin E in aerobic packaging or MAP with 30%, 70%, or 80% O 2 (balance CO 2) had increased TBARS during refrigerated storage with increased O ,2but rosemary extracts or synthetic antioxidants improved oxidative stability (Formanek et al., 2001). Lamb quality was maintained for 28 days of storage only when lambs were fed 1000 mg per kg dietary vitamin E ( Lauzurica et al., 2005). O2 promotes lipid oxidation in minced beef that has its cell structure disrupted ( Sato & Hegarty, 1971 ). Lipid oxidation in minced M. semimembranosus stored in 40%, 60%, or 80% O 2 was higher than in intact M. semimembranosus. Compared to intact M. semimembranosus, the oxymyoglobin content of minced M. semimembranosuswas lower in 20%, 40% or 60% O2 after 7 days of storage, but there was no color difference between minced and intact M. semimembranosus stored in 80% O 2 (O’Grady et al., 2000 ). Although supplementation of cattle with vitamin E improved lipid and color stability of beef in high O MAP, ground chuck did not 2 have high TBARS accumulation for up to 4 days of display after previous 6 days of storage while color and TBARS of top loin steaks were similar through 8 days of display after storage of 10 days (Stubbs, Morgan, Ray, & Dolezal, 2002). About 57% of products in the fresh meat case in 2004 were boneless even though only 18.6% of whole muscle beef contained

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bone (Kelly, 2006a). Bone marrow color is determined by the oxidative state of hemoglobin on the surface of cut bones Lanari ( et al., 1993), with discoloration from red to brown being problematic in O2 MAP ( Mancini, Hunt, Hachmeister, Kropf, & Johnson, 2004 ). Ascorbic acid treatment at 1.5–2.5% minimized bone discoloration during 5 days of display in high O , with no effect on longissimus 2 discoloration (Mancini et al., 2004 ; Mancini et al., 2006). Use of an enhancement solution of 4% phosphate and 4% NaCl increased redness of bone marrow in high O 2 MAP compared with no enhancement or air-permeable packaging ( Nicolalde, Stetzer, Tucker, McKeith, & Brewer, 2006). Improved bone color is obtained by band saw cutting compared with automated slicing and cleaving equipment and careful cleaning of bone dust from cuts ( Smith, 2001). Freezing of bones caused more darkening and was suggested as a means for investigations on prevention of bone discoloration (Nicolade, Stetzer, Tucker, McKeith, & Brewer, 2005). Meat color is influenced by pre-harvest factors of diet, breed, housing, pre-harvest handling, and glycolytic potential and postharvest factors of chilling rate, antioxidant availability, antimicrobial compounds, package atmospheres, and cooking ( Mancini & Hunt, 2005). Different muscles have differing fiber types and metabolic functions, which result in different ranges of O consump2 tion rates (OCR), pigment reduction, mitochondrial respiration, and total reducing activities ( Seyfert et al., 2006 ). Muscles could be grouped by color stability based upon objective measures of discoloration and biochemical changes during retail display ( McKenna et al., 2005 ). Color stability was highest for Longissimus lumborum followed by semintendinosus, superficial semimembranosus, psoas major, and deep semimembranosusin 20% or 80% O2 with or without 0.4% CO ( Seyfert, Mancini, Hunt, Tang, & Faustman, 2007). 2.3.5. Headspace requirements and tray options Headspace gas must be approximately 1.5–2 times the meat volume (Blakistone, 1999b, Chap. 10) and package collapse is generally thought to be prevented by headspace gas to meat volumes of 2 to 3 ( Gill & Gill, 2005, Chap. 13 ). The CO2solubility profile of each product, temperature, and package combination must be determined to allow the proper initial ratio of solid to gaseous CO2 . There is an optimal ratio of headspace to meat volume for fresh beef and the headspace CO 2varies with different concentrations of CO2in the gaseous mixture and with storage temperatures (Zhao, Wells, & McMillin, 1995 ). Altitude will affect package headspace volumes, as changes in altitude cause changes in headspace pressures (Siegel, 2001). Higher tissue pH and decreased temperatures increase the absorption of CO , 2with size and shape of meat pieces also influencing absorption ( Gill & Penney, 1988 ). The amount of CO 2absorption/evolution with beef after 12 h of storage is about 10.2 mL per kg meat for each 1  C temperature rise with headspace to meat volume ratios from 1.8 to 5.9 ( Zhao et al., 1995). A two-phase MAP system where both solid and gaseous CO2 are added at initial packaging may minimize package collapse with high levels of CO (2 Bush, 1991). The solid CO sublimes to re2 place the gaseous CO2 absorbed by the meat and so the headspace volume in the package is maintained. Increased concentration and reduced headspace may have a stronger influence on development of carboxymyoglobin than availability of CO. While reducing headspace reduces package sizes, there would be less available CO for binding to myoglobin so smaller headspaces and higher CO may decrease package size and maintain or improve color stability of fresh meat in CO (Raines, Hunt, & Daniel, 2007). Headspace is also important in tray and lidding film packaging because product touching the film darkens more quickly. A package has been developed with two coextruded films of a permeable sealant film plus outer barrier film with separation of the double film on the film roll at packaging so the MAP gases travel between the two films. If the

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meat touches the permeable contact film, the gas mixture moves through the film and prevents product discoloration ( Connolly, 2008). Packaging features of tray design, barrier properties, antifog components, antigrease methods, EZ open, reclosability, microwavability, freezability, ovenability, irradiatability, and compartmentalization require careful consideration. Tray design considerations are size and shape, draw depth, draft angle, color, foam or plastic, open cell, soaker pad use, and other considerations (Siegel, 2001). The most common tray colors were 40% white, 229% yellow, and 12% black while 18% of products did not use a tray and foam trays were used for 75% of all packages in the retail meat case (Kelly, 2006b). The average weight of fresh meat packages in the US in 2007 were 0.77 kg for ground beef and turkey, 0.91 kg for pork, and 1.13 kg for chicken ( Crews, 2007). 2.3.6. Merchandising and productivity Consumer selection of sirloin steaks was influenced by eating quality, nominal price, and labeling ( Dransfield et al., 1998 ). Not all MAP packaging systems, particularly those in master packs or other similar formats, allow prepricing and labeling due to technological or net weight restrictions (Smith, 2001). Packages in the CO MAP system must be labeled with a validated open date code at a central location with no further processing or manipulation at retail and with the open date code not exceeding 35 days following the date of packaging for intact muscle cuts and 28 days for ground beef (Sebranek & Houser, 2006, Chap. 6; Tarantino, 2004, 2005 ). This requires a high degree of inventory control and logistical integration between processors and retailers. Freight, cube and tray sizes are issues with MAP (Smith, 2001). The high price of energy requires maximizing weight per space. A maximum of 9000 kg of case-ready MAP can be loaded onto a 16 m truck compared with more than 18,000 kg of boxed beef, which doubles freight costs for MAP. Corrugated boxes of preformed MAP trays do not fit well into the standard pallet configuration in the US (1 m by 1.2 m). There is only about 68% cube efficiency that can be attained with current mixed load tray sizes ( Smith, 2001). Illumination source influences the appearance of fresh meat cuts, with incandescent light sources giving more desired color of all meats, with meat being dark brown or dark red under fluorescent and metal halide sources, and the effects being more pronounced for beef than pork ( Barbut, 2001 ). Detailed information is available on types and intensities of light for meat ( Kropf, 1980). Fresh sausage display life was decreased by 25% with standard fluorescent lighting and while a UV filter extended display life to 12 days, use of a low-UV lamp did not protect against discoloration during display ( Martínez, Cilla, Beltrán, & Roncalés, 2007 ). Productivity is a key to optimizing and pricing of meat in packaging systems so rework and labor are important determinants (Smith, 2001 ). Items such as packaging machine maintenance, gas mixer calibration, methods of denesting preformed trays, sealing time and temperature parameters, and vacuum levels influence the number of trays that can be packaged per time. Operating conditions of flange contamination, worker handling of trays, wiping (and re-wiping) of flanges, and film cutting difficulties on tray sealers due to dull knives or improper knife temperatures will decrease output efficiencies ( Smith, 2001 ). Other determinations by management are film and tray seal compatibility, especially if materials are from different suppliers; compatible sealant layers; sufficient film sealant to flow into tray flange irregularities; evaluation of film barrier properties independent of tray barrier properties; and always keeping some package supply inventory cold ( Smith, 2001). Additionally, quality assurance programs and productivity audits require planning and execution. It is suggested that measurements be made of each package or carefully selected samples

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of packages for gas composition immediately post-packaging and at a designated time period after packaging and for seal integrity to detect leaker packages. Products in MAP should be sampled for temperature, microbiological characteristics, lean to fat ratios for ground products, and cutting or trimming specifications for whole muscle products. Audits should also include in-store sampling as well as in-plant sampling. Minimal equipment for auditing and testing are O and CO analyzer, certified reference gases for 2 2 calibration of analyzers and gas mixers, burst tank for leak detection, and caliper or micrometer for measuring thicknesses of tray flanges, corners of thermoformed drawn trays, bags, and film (Smith, 2001). 2.4. Comparisons of MAP options Package type influences red color perception with meat packaged with film contact perceived as being more red than meat in packages with headspace ( Carpenter et al., 2001 ). In both VP or MAP with inert gaseous atmospheres, meat pigments are retained in the deoxymyoglobin state ( Seideman & Durland, 1984; Brody, 1989, Chap. 2 ). The resultant purplish color is unfamiliar to uneducated consumers ( Lynch et al., 1986 ) so deoxymyoglobin produced in low O 2 MAP (without CO) limits its use for products in retail display (John et al., 2004 ). While temperature and time were the most important factors for retaining beef muscle color and minimizing lipid oxidation during 10 days, the O 2levels from 20% to 80% also affected both meat characteristics, with a stable interval of meat color found between 55% and 80% O2 (Jakobsen & Bertelsen, 2000). Ground beef patties from high O and O -impermeable chubs had bloomed color with 2 2 about the same redness ( Jayasingh et al., 2002 ). Discoloration was more rapid for beef Biceps femoris, semimembranosus, vastus lateralis and rectus femoris at the end of 3 days of display in low O2MAP (80% N :20% CO 2) than after 5 days of display in high O 2 2 (80% O2 :20% CO Seyfert et al., 2004a). After 20 days of storage 2 )( in 100% O2, pork loins were rejected by consumers due to browning while pork stored in VP after 1 h exposure to 1% CO:99% CO 2or 100% CO before VP were still acceptable to consumersViana ( et al., 2005). The O 2 in headspace of air packaging of beef at 5 C de creased from 21% to 0% and CO 2increased from 0% to 25% in 14 days while gas mixtures of 20% O :40 CO : 240% N remained con2 2 stant during 7 days and of 60%O2:20 CO 2remained constant during 14 days ( Ercolini et al., 2006 ). O at 2 80% increased color stability during 7 days of retail display and reduced variability among muscles compared with 20% O ,2but inclusion of 0.4% CO with 20% or 80% O2 did not impact reducing activity, OCR, or color, perhaps due to preferential formation of oxymyoglobin rather than carboxymyoglobin at those oxygen levels (Seyfert et al., 2007 ). Fresh sausages stored in 60% O2 :40% CO 2 had lower bacterial growth, less cooking loss, less shear force, and stable red color compared with sausages in 70% O 2:20% CO 2:10% N 2 or 30% O 2:40% CO 2:30% N 2 (Tremonte et al., 2005). Fresh sausage in VP or low O2with O scav2 engers had low oxidation rates that extended color and odor stability while high O improved color, but only for 8 days and oxidation 2 increased with increased O 2 (Martínez, Djenane, Cilla, Beltrán, & Roncalés, 2006). Steaks remained red for 21 days following 24 h exposure to 0.5% CO and for six weeks when exposed to 100% CO for 1 h before VP (Jayasingh, Cornforth, Carpenter, & Whittier, 2001 ). Color stability of ground beef and loineye steaks was decreased after storage in 0.4% CO (30% CO 2 , balance N2 ) up to 35 days before removal and display in air-permeable packaging compared with immediate display in air-permeable packaging while color life of tenderloin and inside semimembranosus muscles was increased with CO exposure compared with air-permeable packaging. No steaks with acceptable color had spoilage microorganism counts of greater than log

7 CFU ( Hunt et al., 2004 ). Color of master-packed fresh pork was enhanced by 0.4% CO, with no difference in plate counts or lipid oxidation, which might cause a food safety risk for meat in CO MAP under certain conditions ( Wilkinson, Janz, Morel, Purchas, & Hendriks, 2006). Higher acceptance scores were given by consumers and color was lighter for pork treated with 1% CO and then stored for 20 days compared with VP, 100% O 2, and 100% CO2Via( na et al., 2005). Steaks in 0.4% CO within a master bag achieved 21 days of desirable red color compared with steaks in 80% O , 2which had highest TBA values (John et al., 2005). Loin steaks packaged in VP or ultralow O 2with 0.4% CO and balance CO2 ,N,2and/or argon had little or no surface discoloration during display while steaks in 80% O2 :20% CO2 discolored faster than with the other packaging treatments (Grobbel et al., 2008). Enhanced beef longissimus, semitendinosus, and triceps brachii had more off-flavors than non-enhanced steaks. Steaks in high O 2 MAP were less tender and had more-off flavors than in VP or low O MAP with CO while desmin 2 degradation did not vary with packaging type ( Grobbel et al., 2007). Meat in overwrap packaging and high O 2 MAP developed off-odors during display earlier than ground beef in CO, but rosemary extract delayed development of oxidation in beef patties stored and displayed in 80% O 2 or in low O 2 MAP with 0.4% CO and 30% CO2 (Brooks et al., 2008). Pork sausage in 0.4% CO and 99.6% CO2 had redder color in the raw state, more purge, and increased anaerobic growth compared with sausage in O -permeable 2 film (Laury & Sebranek, 2007). While increased levels of CO 2 inhibit microbial growth in refrigerated storage, 20–40% CO is 2 usually used in MAP ( Taylor, 1985, Chap. 4; Clark & Lentz, 1969). Levels below 15% CO do 2 not inhibit microorganism growth satisfactorily while levels above 40% may result in package collapse because the CO 2 is absorbed by the meat tissue ( McMillin et al., 1999, Chap. 6 ). The amount of CO2 absorbed varies from 0 to 1.8 L CO 2 per kg meat depending upon the applied packaging and storage conditions ( Jakobsen & Bertelsen, 2002). The solubility or absorption of CO by2 meat in a gaseous atmosphere of CO 2 will continue until saturation is reached. Unless the CO 2 amount is in excess of the quantity needed for meat saturation, the package will shrink or collapse (Gill & Penney, 1988 ). Dissolution of CO 2 in the meat tissue decreases the initial CO 2 concentration inside the package, which decreases the total gas pressure inside the package and causes flexible packaging materials to shrink or collapse around the product (Zhao et al., 1995 ). The volume of gas may need to be twice the volume of meat for adequate microbial inhibition even though CO 2is dissolved and absorbed into the meat during storage (Sofos, 1994, Chap. 14). VP or MAP with inert gaseous atmospheres can increase shelf life to 7 to 21 days ( Hermansen, 1983). High O 2 MAP with 85% O2:15% CO 2 was effective in inhibiting surface microorganism growth and maintaining bright red color in prepackaged beef for at least 20 days ( Bala, Stringer, & Naumann, 1977 ). Quality life of fresh meat with oxymyoglobin in high O 2 MAP is limited to about 10 to 12 days for ground beef and 12–16 days for whole muscle and display life under retail lights is two to 4 days ( Belcher, 2006). Varying physical compression of meat during different packaging processes complicates comparison of different weight losses due to drip ( Jakobsen & Bertelsen, 2002 ). Drip loss in case-ready pork increased from 1.57% initially to 5.64% after 7 days in retail trays of case-ready pork with amount of drip loss highly dependent on the initial amount of drip loss ( Otto et al., 2006). Descriptions and major characteristics of the retail raw chilled fresh meat package systems currently in use (air-permeable, air-permeable in master packs, VSP, low O 2 MAP, peelable barrier films with VSP and low O 2 MAP, low O 2 MAP with CO, and high O 2 MAP) are in Table 2.

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K.W. McMillin /Meat Science 80 (2008) 43–65 Table 2 Major packaging types and characteristics for fresh retail meat

a

Package

Air-permeable overwrap

Air-permeable overwrap in master pack

Vacuum skin packaging (VSP)

Low O 2with CO and N 2

System description

Air-permeable film overwrap of product on tray; product displayed in package

Gases in headspace

Atmosphere air

Flexible film shrunk around product on a rigid base web; product displayed in package No gas headspace

O2scavengers Meat color in storage Meat color for display

none Red

Barrier bag with single or multiple trays of product in airpermeable packaging; trays removed for retail display Usually CO2and/ or N 2in master pack Recommended Purple

Sometimes Purple

Red

Red

Purple

Whole muscle shelf life, d at 4  C Minced or ground shelf life, d at 4  C Display life, d Drip loss, % Advantages

5–7

10–14

2–3

2–7 8–10 Consumers familiar with packaging; high product visibility; lowest cost; multiple sizes on same equipment Short display life; leaky package if bottom sealed rather than tube sealed at ends

Disadvantages

Peelable VSP or low O 2 w i t h C O2 : N2

Low O 2with CO

High O 2

Thermoformed or preformed trays with lidding film; may be a master pack for product in air-permeable packages

VSP or barrier tray with 2 layer lidding film; outer barrier film peeled from inner permeable film before product display

VSP; may be thermoformed or preformed tray with lidding film; product displayed in package

Thermoformed or preformed tray with lidding film; product displayed in package

CO2 and/or N

No headspace with VSP; CO2 and/or N 2

CO2 and/or N2 ;no headspace with VSP

O2and CO ;2 often 80% O2 :20% CO2

Recommended Purple

Recommended Purple

Recommended Red

None Red

Red

Red

Red

60–90

Purple; red after removal from master pack 30–60

30–45

35

12–16

7–10

45–60

20–40

20–30

28

10–12

2–7 3–5 Storage life extended before display

30–60 2–5 Long storage life before display; high product visibility

15–40 1–5 Long storage life before display

2–7 0–7 Long storage life before display; high product visibility with VSP

28–35 1–7 Long red color stability and no lipid oxidation; high product visibility with VSP

7–16 0–5 Moderate red color stability

Double packaging costs; short display life; reblooming after air exposure may be inconsistent

Display with purple color

Purple display color in MAP; scavengers increase costs; bloom may be inconsistent on exposure to air after removal from MAP; increased cost with master pack

Film peeling at retail store; may be mottling or inconsistent bloomed color after air exposure; short display life; increased package and scavenger costs

Negative image by consumers; concern red products may be spoiled in other factors; scavengers increase costs; cooked meat color may be pink

Lipid oxidation; may be bone darkening or decreased tenderness; headspace required; may be premature browning of cooked meat

2

2

a Information from Belcher (2006), Buffo and Holley (2005, Chap. 14), Cornforth and Hunt (2008), Eilert (2005), Keith (2001), McMillin et al. (1999, Chap. 6), Siegel (2001), Tewari et al. (1999) .

3. Future of MAP 3.1. Packaging innovations and trends Trends in the evolution of food packaging have been convenience and point-of-purchase marketing in the 1960s; weight, source reduction, and energy savings in the 1970s; safety and tamper-evidence in the 1980s; environmental impact in the 1990s; and safety and security in the 2000s ( Han, 2005a, Chap. 1 ). The key to successful packaging is selection of materials and designs that best balance the competing needs of product characteristics, marketing considerations including distribution and consumer needs, environmental and waste management issues, and cost (Marsh & Bugusu, 2007 ). Traceability of products through appropriate identification and tracking, tamper indicators, and convenience are also important to provide cost-effective packaging that meets consumer expectations and industry requirements, provides for food safety, and minimally impacts the environment (Marsh & Bugusu, 2007). Color, price, visible fat and cut were the most important factors underlying purchases of beef steaks while tenderness, flavor and

juiciness were more highly related to eating satisfaction ( Robbins et al., 2003). Appearance scores of top loin steaks and ground beef in the order of red, purple, and brown and red beef by consumers were correlated with likelihood to purchase, but consumer taste scores were not influenced by meat color or packaging type ( Carpenter et al., 2001 ). Even though this consumer preference for bright red beef in traditional overwrap PVC packaging might slow adaption of central packaging in MAP and VSP by processors and retailers (Carpenter et al., 2001), there appears to be an irreversible shift for meat distribution systems to use centralized packaging operations (Buffo & Holley, 2005, Chap. 14). 3.1.1. Case-ready or centralized packaging Centralized packaging of meat and the need for increased consumer convenience are drivers for changes in meat packaging. Costs of package materials and availability of trained labor for meat merchandising are major factors influencing changes to case-ready packaging (Eilert, 2005). The projections for case-ready packaging utilization in the US have not been met, but not because case-ready packaging technologies are insufficient ( Stahl, 2006 ). Tray sealing equipment has evolved to meet the rapid pace of large

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processing plants along with other technologies to test atmospheres in packager chambers before sealing meat in the package. However, many retailers have been reluctant to change the meat department that has contributed to their reputation as a leader in retail quality, selection or customer service. Also, stores with case-ready systems may lose the ability to display products at reduced prices at specific desired times, inventory ordering and management are complex, and there are challenges of predicting demand, marketing, and risk ( Stahl, 2006). Even so, 64% of fresh meat packages in the US were case-ready in 2007 compared with 49% in 2002 (Crews, 2007). The delivered cost of case-ready meat to the store is higher than for boxed beef that will be cut and wrapped by store butchers and any store shrink and out-of-stock items must be managed to improve long-term profitability ( Stahl, 2006). Benefits of case-ready packaging are increased profitability, with average increases of 7% for net margins, 15% for annual growth, and 40% for market penetration, but benefits and reasons to convert to case-ready vary with country ( Vink, 2007). Demand for livestock products in developing countries is growing three times faster than in industrialized countries, but citizens of developing countries still eat two-thirds less meat ( Holmes, 2001). Obesity as a global epidemic is becoming an issue for the meat category as meat consumption increases ( Vink, 2007 ). As more livestock is raised to meet strong worldwide demand for animal protein, primarily through industrial farming methods, there are risks to water, air, and human health (Holmes, 2001). Recycling of plastics is becoming more common, requiring functional barriers in multilayer structures to be used between the recycled plastic and food to prevent food contact by any contaminants in the recycled plastics. It is also necessary to prevent food contact by substances not approved by regulation and to prevent migration of active substances or constituents of active packaging substances from reaching the food (Feigenbaum et al., 2005). It is unlikely that polyolefins and ethyl vinyl acetate would be functional barriers regardless of layer thickness while other polymers like polyethylene terphthalate,, ethylene vinyl alcohol, polyvinyl chloride, and polyvinylidene chloride may serve as functional barriers if the layer is sufficiently thick ( Feigenbaum et al., 2005 ). 3.1.2. Environmental and renewable considerations Any assessment of the environmental impact of food packaging must consider the positive benefits of reduced food waste in the supply chain (Marsh & Bugusu, 2007). While only 31% of the municipal solid waste in the US came from packaging-related materials in 2005, food packaging accounted for almost 2/3 of total packaging waste by volume and food packaging was about 50% by weight of total packaging sales. The waste has initiated social, political, and research interest in several options, including source reduction (thinner gauges of materials, alternate materials, or reusable containers), recycling, composting, combustion or incineration, and landfilling ( Marsh & Bugusu, 2007 ). Alternatives to petroleumbased materials will probably evolve and become more economically competitive ( Eilert, 2005 ). Consumer demand for more environmentally friendly packaging and more natural products will also create increased demand for packaging from biodegradable and renewable resources ( Cutter, 2006). Organic-based materials may be anaerobically degraded while biodegradable polymers from replenishable agricultural feedstocks, animal sources, marine food processing industry wastes, or microbial sources are being developed Marsh ( & Bugusu, 2007). Biopolymer films may be potential replacements for synthetic films in food packaging applications to address strong marketing trends towards more environmentally friendly materials, but hydrophilicty is a central limitation to replacement and fullscale commercial utilization of biodegradable films ( Han, Zhang, & Buffo, 2005, Chap. 4). Materials used for edible films and coatings

are film-forming materials (proteins, polysaccharides, lipids), plasticizers (glycerin, propylene glycol, sorbitol, sucrose, polyethylene glycol, corn syrup, water), functional additives (antioxidants, antimicrobials, nutrients, nutraceuticals, pharmaceuticals, flavors, colors), and other additives (emulsifiers, lipid emulsions) ( Han & Gennadios, 2005, Chap. 15). Bacterial cellulose is another source of biobased packaging (Weber, Haugaard, Festersen, & Bertelsen, 2002). While containment of dry foods or preweighed ingredients is a proposed use of edible films that are compression molded and extruded from vegetable and animal proteins, the films could also be used with conventional packaging to improve food quality, reduce amount and complexity of packaging waste, and make packaging more easily recyclable ( Hernandez-Izquierdo & Krochta, 2008). The antimicrobial activity and film-forming ability of chitosan make it a potential source of bio-based packaging (No, Meyers, Prinyawiwatkul, & Xu, 2007 ). Polylactic acid is a degradable aliphatic polyester that can be produced synthetically or from renewable corn or whey resources and has food packaging applications because of mechanical stability in ambient to chilled temperatures (Holm, Ndoni, & Risbo, 2006). A variety of bio-based materials have been shown to prevent moisture loss, reduce lipid oxidation, improve flavor, retain color, and stabilize microbial characteristics of foods ( Cutter, 2006). 3.1.3. Active packaging Active packaging functions and technologies include moisture control, O 2-permeable films, O scavengers or absorbers, O gener2 2 ators, CO2controllers, odor controllers, flavor enhancement, ethylene removal, antimicrobial agents, and microwave susceptors (Brody et al., 2001; Brody, 2005, Chap. 25) in addition to indicators of specific compounds (de Kruijf et al., 2002) and temperature control packaging (Day, 2003, Chap. 9 ). Antimicrobial packaging is an extremely challenging technology that could extend shelf life and improve food safety in both synthetic polymers and edible films. The market volume for antimicrobial use in polyolefins is projected to increase from 3300 tons in 2006 to 5480 tons in 2012 (Intertechpira, 2007 ). Antimicrobial films may incorporate antimicrobial agents into sachets connected to the packaging for release of the volatile bioactive agent during storage, may directly incorporate the agent into the packaging film, or coat the package with a matrix that is a carrier for the antimicrobial agent (Cooksey, 2001). Sachets include O 2 scavengers, CO2 generators, chlorine dioxide generators while bioactive agents dispersed in the packaging may be O 2 scavenging films, silver ions, triclosan, bacteriocins, spices, essential oils, enzymes, and other additives ( Coma, 2008). Extrusion of the antimicrobial agent into the film results in less product to agent contact than application of the agent to the surface of the film. However, agents bound to the film surface are likely limited to enzymes or other proteins because the molecular structure must be large enough to retain activity on the microorganism cell wall while being bound to the plastic ( Quintavalla & Vicini, 2002). Another approach is the release of active agents onto the surface of the food. Slow migration of the antimicrobial agents to the product surface improves efficiency and helps maintain high concentrations. Packages with headspace require volatile active substances to migrate through the headspace and gaps between the package and food ( Quintavalla & Vicini, 2002 ). Potential antimicrobial agents for use in food packaging systems are organic acids, acid salts, acid anhydrides, parabenzoic acids, alcohol, bacteriocins, fatty acids, fatty acid esters, chelating agents, enzymes, metals, antioxidants, antibiotics, fungicides, sterilizing gases, sanitizing agents, polysaccharides, phenolics, plant volatiles, plant and spice extracts, and probiotics (Cutter, 2006; Han, 2005b, Chap. 6 ). Antimicrobial compounds that have been evaluated in film structures are organic acids and their salts, enzymes, bacteriocins, triclosan, silver zeolites, and fungicides ( Quintavalla & Vicini, 2002 ).

K.W. McMillin /Meat Science 80 (2008) 43–65

Antimicrobial substances are defined as biocidal products under EU Directives, but would be permitted in food packaging only if there was no direct impact on the packaged food quality. This requires that agent migration into food must be incidental rather than intentional, the agent could not provide preservative effect to the food, and the agent could not allow selection of biocide resistance in the microorganisms ( Quintavalla & Vicini, 2002 ). Triclosan at 500 and 1000 mg per kg in LDPE films exhibited antimicrobial activity against pathogenic bacteria in agar diffusion assay, but did not effectively reduce microorganism growth on chicken breasts in VP at 7  C(Vermeiren, Devlieghere, & Debevere, 2002). Bioactive surface coatings on packaging materials might have activity based on migration or release by evaporation into headspace and may be bacteriocins, spices, or essential oilsComa, ( 2008). Examination of four polyethylene films differing in linear, ethylene vinyl acetate, and erucamide content coated with three different bacteriocins showed antimicrobial activity against most of the indicator strains, with antimicrobial agent distribution and roughness of the film related to activity of the packaging (La Storia, Ercolini, Marinello, & Mauriello, 2008 ). Some polymers such as chitosan that exhibit film forming properties also are antimicrobials (No et al., 2007). The microbial growth and drip loss were inhibited and a* value maintained on chilled pork by combining a chitosan coating with spice extracts ( Xia, Kong, Xiong, & Meng, 2007). Antimicrobial agents such as nisin and chlorine dioxide have shown effectiveness against bacteria, but increased technical developments are needed for commercial implementation ( Cooksey, 2005). Fast- and slow-release ClO 2sachets reduced total plate counts by 1–1.5 logs in packages of chicken breasts after 15 days with no off-odor detection by sensory panelists, but the color of chicken next to the ClO 2 was adversely affected ( Ellis, Cooksey, Dawson, Han, & Vergano, 2006 ). Nisin incorporated into polylactic acid had antimicrobial effectiveness against foodborne pathogens. Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enteritidis when evaluated in culture media and liquid foods ( Jin & Zhang, 2008). The same approaches for use of agents to control microorganisms may also be applicable for control of oxidative processes. Rosemary extract was incorporated into PP film so the active film enhanced the stability of myoglobin and beef steaks by inhibition of metmyoglobin and lipid oxidation ( Nerín et al., 2006 ). Many intelligent packaging systems use sensors and indicators, including those for fluorescence-based O 2, gas detection, temperature monitoring, toxic compounds, freshness through monitoring of specific components, package integrity, and identification ( de Kruijf et al., 2002; Kerry et al., 2006; Yam et al., 2005 ). Advances are being made in O2sensors based on fluorescence for remote measurement of headspace gases, sensors on microporous support materials for many different compounds, sensors that operate over wide temperature ranges, integrity indicators that indicate leaks or loss of package integrity, freshness indicators using target metabolite markers and indicators, and diffusion-based and enzymatic timetemperature indicators (Kerry et al., 2006 ). Dry chemicals in packets were proposed to provide a continuous emission of CO 2 in packages ( Benedict, Strange, Palumbo, & Swift, 1975). A CO 2 emitter prepared with NaHCO , citric acid, 3 and a liquid absorber activated by water before package sealing kept CO2at a stable level through 10 days of refrigerated storage for Atlantic cod (Hansen, Mørkøre, Rudi, Olsen, & Eie, 2007 ). Bovine gelatin reduced purge and color deterioration in beef and pork, but was not an effective barrier for lipid oxidation for meat in high O 2 MAP (80% O2:20% CO2 ) or VP at refrigerated temperatures ( Antoniewski, Barringer, Knipe, & Zerby, 2007). A color-changing sensor was accurately related to the package headspace amine concentrations, which are indicators of microbial breakdown products, and also correlated to changes in non-pathogenic microbial popula-

57

tions of fish ( Pacquit et al., 2007). The formation of volatile amines in chicken meat during chilled storage in air packaging, VP, and MAP with 30% CO :5% O 2 was highly related to total microbial 2 counts and sensory taste scores, suggesting that biosensors for the volatiles might be developed to indicate spoilage in chicken (Balamatsia, Patsias, Kontomina, & Savvaidis, 2007 ). However, food pathogen levels were not related to microbial and sensory spoilage traits in ground beef patties in high O MAP and low O MAP 2 2 with 0.4% CO or in chicken in low O2with 0.4% CO because food spoilage is defined collectively by factors such as storage temperature, package atmosphere, light intensity, meat constituents, initial microbial loads, endogenous enzyme activity, and consumer perceptions that have little effect on growth and survivability of food pathogens under controlled conditions ( Brooks, Brashears, & Miller, 2007). The development of improved data generation from devices such as barcode labels, radio frequency identification tags, time-temperature indicators, gas indicators, and biosensors and improved communication of information among multiple devices at multiple locations would improve traceability, tracking and recordkeeping of products through production and supply chains (Yam et al., 2005). 3.1.4. Consumer influences Key drivers for meat packaging are maintaining a supply of meat in display cases and safe food assurance ( Keith, 2001 ). Although there are distinct advantages of storage and display life of meat with CO in VP or low O MAP, consumers have a negative 2 image of CO because CO is a potentially hazardous gas and there is concern that products might appear fresh even though the product might have other spoilage traits ( Cornforth & Hunt, 2008 ). It was recommended to have expiration dates on the label for ground beef in 0.5% CO because color stability was improved, but after five weeks of storage the product could be spoiled by greater than 2 10 6CFU per cm (Jayasingh et al., 2001). Open date codes for products packed in the CO MAP system in the US are 35 days following the date of packaging for intact muscle cuts and 28 days for ground beef (Tarantino, 2004, 2005; Sebranek & Houser, 2006, Chap. 6 ). The declaration of CO for meat as generally recognized as safe (GRAS) in the US has a legal basis ( Boeckman, 2006), but there are still legislative controversies and consumer concerns over the process by which CO was given approval (Bjerklie, 2007). Although Norway had used CO for a number of years and demonstrated the safety for use of CO at 0.3–0.5%, it was decided by EU Parliament committee in 2004 not to allow use of CO for meat ( Sørheim, 2006, Chap. 7). The decision by different governmental agencies in different areas of the world to make different decisions on use of a technology or process has fostered discussion and controversy. The publicized recalls of meat in the US due to food safety concerns may have magnified the attention on approval of CO for meat. Trust is critical for the food sector because it is so complex in risks and benefits that an individual consumer has no choice but to rely upon others to fully control any situation. Trust depends upon two elements, the competence of the trustee and good will ( Meijboom, 2007). While anticipatory trust is based upon a normal pattern of predictive behavior in which the trustee has acted in a trustworthy manner, responsive trust is based not upon predictive behavior, but that the trustee will respond to the expectations that the trustor has of the trustee to respond to the trust placed in the trustee (Meijboom, Visak, & Brom, 2006 ). After seeing and purchasing fresh meat in air-permeable packaging for several decades, the new MAP options have evidently not been fully understood by consumers and they have been left to rely on anticipatory trust because the ‘‘new” MAP packages appeared similar during each shopping trip and the package and products seemed to meet their expectations of price, palatability,

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and integrity. However, consumers rated beef of the same color higher in appearance with PVC, then VSP, and last in MAPCarpen( ter et al., 2001 ). The introduction of CO in low O MAP introduced 2 yet another package type without full information to consumers. Enhancing trustworthiness requires a clear distribution of responsibility (Meijboom et al., 2006). It would seem as if the information to consumers and government officials has not been sufficient in establishing the desired level of trust in the scientific integrity of the many MAP options for meat to dissuade debates in public and governmental regulatory forums and to allow decision making based on scientific data. Wal-Mart Corporation in the US was a major influence in the increased use of case-ready, particularly for enhanced meat in high O2 MAP, because it had no long history in meat sales, but had a logistical system suited to case-ready distribution without long time restrictions ( Stahl, 2006). While it may seem counterintuitive because of inventory management, some Wal-Mart stores in the southeast US are now switching to case-ready PVC overwrap packaging transported in master packs (Gabbett, 2008). It is speculated that the decision to change back to a package more acceptable to consumers is based upon need for public acceptance, but it may also point to a reluctance to continue involvement in public debate over use of MAP, particularly CO in low O packaging, that may de2 ceive consumers about freshness (Gabbett, 2008). Emerging trends that will impact marketing of meat are concern for all aspects of food animal production, continued growth in natural and organic, increased focus on skilled and unskilled labor, ethanol, animal- and food-borne diseases, and growth of niche markets (Graves, 2007). These will also impact meat packaging and the perceptions of consumers about meat and its packaging. In the US, labeling of meat products as natural grew from 22% in 2004 (Kelly, 2006a) to 29% in 2007 with 67% of chicken packages containing a natural claim ( Crews, 2007). It is expected that energy costs will continue to increase, impacting raw material costs for packaging and the transport of packaging and packaged meat (Eilert, 2005). MAP provides too many advantages of cost, shelf life, tamper evidence, product uniformity, label information, and supply chain integration for most industrialized countries to return to in-store cutting and packaging to supply self-service meat cases. Developing countries have opportunities to determine supply chain and packaging formats that fit with retail and consumer desires. However, there is a general lack of cooperation among industry companies and education of the different government, industry, and consumer segments is a major impediment to technological improvements and industry progress ( Stier, Ahmed, & Weinstein, 2002). MAP will continue to be used for meat in the future, most probably with several different MAP formats in use around the world. Mechanistic, logistical, and perception obstacles will require effort and ingenuity to overcome existing package and system difficulties and promote implementation of processing and packaging technologies. 3.2. Research and industry needs Key needs and issues for the industry are an improved understanding of costs, a realization that technology cannot answer questions of consumer acceptance of MAP or case-ready meat, a change from national to regional meat packing, and a need for multiple package styles (Keith, 2001). Successful customer driven supply requires external focus on the target customers, partnering with firms that deliver customer service, creating value by increased responsiveness and efficient differentiation leverage, managing complexity, evaluating costs and eliminating waste, effectively using information technology to synchronize data and product flow, and investing in a customer driven logistic supply

chain ( Poole, 2008). Improved stocking guidelines with identification of core and flexible meat items coupled with simple information systems could ensure that needed meat items are in-stock every day to prevent lost sales with inadequate inventory ( Kelly, 2006a). Fresh meat to a large extent is a commodity and since it is mostly unbranded and unlabeled, consumers must generally base their quality evaluation at the time of purchase on the product appearance (Grunert, Bredahl, & Brunsø, 2004). The two segments of cautious meat lovers and concerned meat consumers constitute 2/3 of the market in Belgium (Verbeke & Vackier, 2004). Consumer reassurance of these two market segments may be gained through quality improvement, labeling, and/or communication. Increased information through labeling, traceability systems, and quality assurance schemes has only minimally increased consumer trust in meat as a safe and wholesome product. Process traceability of the origin and the production method appears most useful and preferred by consumers (Gellynck, Verbeke, & Vermeire, 2006). A difference in packaging approaches by European and US governments is that the EU has regulations where the producer pays a fee and is responsible for disposal of packaging in an environmentally benign manner while post-consumer packaging in the US has no federal, only state and local, government regulations. EU consumers tend to be buffered from concerns about the environmental impacts of packaging. Renewable packaging has received more attention in the US than EU, primarily because advocates of biopolymers have to maneuver through exemption approval processes in the EU ( Demetrakakes, 2008). However, recent rising food prices have promoted the perception that ecologicallyfriendly products and packages cost too much more than traditional products and packages to be practical for many households with children ( Doyle, 2008 ). The changing faces of ecologically friendly packaging require addressing multiple aspects of packaging, including recyclability, simple packaging, reusable, refillable, renewable materials, less materials, less or no plastics, and bulk rather than individual packaging ( Doyle, 2008). Consumer perception is viewed the most significant factor limiting application of new product technologies so there is great need to translate technical information into understandable communication forms so consumers are able to understand more clearly about packaging and products B ( ugusu & Bryant, 2006). Food packaging technologies also require integration with other processing and preservation activities such as freezing, irradiation, pulsed electric fields, high pressure processing, and pulsed light ( Han, 2005a, Chap. 1) so even more technical advances in ovenable trays and films and improved compatibility of packaging with postpackaging processing steps are necessary Belcher, ( 2006). Scientific research is needed in most areas regarding meat packaging- materials, selection of meat and its handling before packaging, meat properties under differing conditions, meat in packaging systems, and integration of the different components of logistic components of the cold chain- as might be surmised from previous sections of this paper. The key research needs for MAP of meat are summarized in Table 3. An example of the inadequacy of current measurements or analytical techniques is that the mass transport through perforated packaging films cannot be describing using conventional permeability equations (Henry’s and Fick’s laws), even though other expressions may be valid ( Del-Valle, Almenar, Lagarón, Catalá, & Gavara, 2003 ). Industry requires improved product consistency, shelf life, acceptable appearance, and cost effectiveness for success of meat in MAP. There are several primary areas for industry improvement (Table 4). Development and use of edible coatings for antioxidant or antimicrobial agent contact with meat surfaces would also limit moisture loss during storage, assist in drip maintenance of products in retail trays, reduce rate of oxidative processes, restrict

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K.W. McMillin /Meat Science 80 (2008) 43–65 Table 3 Research needs for modified atmosphere packaging of meat

a

Research need

Specific information or data requirements

 Characterization of each MAP option

– Biochemical affects on appearance and palatability traits, including postmortem tenderization processes, and interactions with each MAP system – Interactions of meat components with packaging materials, gases, and headspace volumes – Blooming ability and bloomed color stability – Inadequate or imprecise analytical techniques for meat in MAP, particularly with multistage systems – Techniques not sufficiently rapid for continuous process and quality control programs – Expensive or unavailable scanning and digital technologies for analytical or online meat assessment – Creation and reversion of deoxymyoglobin pigments under different conditions of MAP – Formation and stability of carboxymyoglobin under different conditions – Fundamental relationships between metmyoglobin reduction and O consumption processes 2 – Genetic inheritance of color and other meat traits are not well characterized – Improved petroleum and biological polymers have not been examined for use in meat packaging – No reports of microorganism growth, oxidative stability, package gas concentrations, and other shelf life factors for many meat and package interactions – Improved mechanical, thermal, and barrier properties of materials would enhance meat quality and shelf life – Methods, materials, safety evaluations, and risk assessments for meat use have not been reported – Insufficient or unavailable information on many MAP systems creates reliance on inferences for assessments of safety and risk

 Additional and improved methodologies for evaluation of meat and meat products  Pigment chemistry data

 Roles of genetics and quantitative trait loci  Application of active packaging technologies for meat

 Nanotechnologies and nano-scale materials

 Clinical trials on specific product and packaging interactions and components a

Information from Mancini and Hunt (2005), Cornforth and Hunt (2008), McMillin et al. (1999, Chap. 6)

Table 4 Industry improvements desired for modified atmosphere packaging of meat

; and the individuals recognized in the acknowledgements.

a

Industry improvement

Rationale

 Vacuum levels during initial evacuation and in low O2MAP  Residual O2in low O MAP 2  Improved O 2scavengers for low O MAP 2

– Non-uniform products during storage and display from inconsistent equipment and processes

 Minimization of headspace in barrier tray and lidding film MAP

 Stabilization of headspace in barrier tray and lidding film MAP  Packaging materials and technologies

 Consumer trust in meat industry and products

– – – – – – – – – – – – – – –

a Information from Belcher (2006), Bogusu and Bryant (2006), recognized in the acknowledgements.

Non-uniform and excessive residual O contributes to inconsistent product color and other meat traits 2 Small O 2levels after initial packaging not absorbed to sufficiently low levels for color stability More rapid O absorption would decrease time as metmyoglobin before reduction to deoxymyoglobin 2 Useful scavenger life too short for many meat applications Headspace reduces meat visibility and alters consumer perceptions of meat color and product amount per package size Large headspace causes consumer perception of smaller product amount per package Increased transport costs due to weight per package volume restrictions Altitude changes from location of packaging to location of display may cause package deformation Headspace changes may cause package deformation, leakage, and/or contact of lidding film to meat surface Active packaging controls and technologies would enhance shelf life and package display aesthetics Additives and processing aids such as plasticizers would improve bio-based packaging functionality Recycled and waste packaging materials are incompatible with food use Delivery of cost effective active ingredients at appropriate release rates for specific products would enhance meat quality and shelf life Improved communication through media and labeling Traceability control and system logistical improvements Eilert (2005), Mancini and Hunt (2005), Siegel (2001), Smith (2001)

volatile flavor and odor loss or exchange, and reduce surface microbial loads ( Quintavalla & Vicini, 2002 ). A difficulty with antimicrobial and antioxidant agents may be regulatory approval of specific compounds even if delivery systems of product contact or release into headspace are developed, requiring extensive studies of the interactions and optimization of agents and headspace gases. Although not discussed extensively, food safety concerns will continue to impact packaging choices by processors, retailers, and consumers. Calculations of CO exposure level from consumption of CO-packaged meats were based upon US Environmental Protection Agency National Ambient Air Quality Standards for CO inhalation (Cornforth & Hunt, 2008 ), which presumed that the human metabolism of CO would be the same for digestive processes after consumption of meat with CO as the metabolic respiratory and circulatory processes after CO inhalation. Every segment of the cold chain requires examination, including genetic selection of livestock for desired meat traits, production of livestock to produce meat cuts optimally sized to the packages desired by consumers, explanations of cost structures and accurate characterization of meat supply and packaging systems by proces-

, Smith (2008), and the individuals

sors to retailers, and increased communication of food practices from industry to consumers. Consultation with other scientists and industry practitioners with MAP indicated that low O MAP will receive more attention 2 in the immediate future since the major advantage of high O 2 MAP is red color for display, but oxidation of meat components is becoming a greater obstacle to longer shelf life needs and more discriminating consumers. A much higher level of sustainability with specific packaging options is needed by industry, requiring detailed scientific experiments and practical field tests for successful implementation. Internationally, there will be additional use of MAP due to continued competition among companies in global meat markets. The benefits and reasons to select specific packaging systems vary with country ( Vink, 2007 ), which means that only some of the information about a particularly packaging system will be useful and applicable for its implementation in a specific market while additional testing and data will be required in all countries, whether developing or developed. Continuing consumer desires to purchase meat from different species and muscles with red oxymyoglobin pigments coupled

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with industry requirements for shelf life will maintain the need for MAP and research in MAP for meat. 4. Conclusions MAP provides a means to display meat in self-service meat cases in a manner attractive to consumers while providing processors and retailers with advantages of cost, distribution and storage life, and stability of many desired meat properties. Each low O and 2 high O 2system has specific benefits and disadvantages, prompting development of multiple stage packaging systems to provide suitable meat traits until consumer purchase. Integration of meat characteristics with available packaging materials and equipment into current cold chain logistical and information systems has resulted in a sufficiently high state of complexity that has caused uncertainty and confusion among industry, regulatory agency, and consumer segments. Advances in technology will continue to allow industry to address consumer needs for food safety, palatability, cost, environmental concern, and information with MAP in most global meat markets, with increased communication needed among all segments of the meat cold chain. Acknowledgements Appreciation is expressed to J.N. Belcher, J.C. Brooks, D. Cornforth, S. Eilert, M.C. Hunt, D. McDonnell, and O. Sørheim for their comments and suggestions for this manuscript. Approved for publication by the director of the Louisiana Agric Exp Sta as Manuscript No. 2008-230-1647. References Abe, Y., & Kondoh, Y. (1989). Oxygen absorbers. In A. L. Brody (Ed.), Controlled/ modified atmosphere/vacuum packaging of foods (pp. 149–158). Trumbull, Connecticut: Food and Nutrition Press. Antoniewski, M. N., Barringer, S. A., Knipe, C. L., & Zerby, H. N. (2007). Effect of a gelatin coating on the shelf life of fresh meat. Journal of Food Science, 72(6), E382–E387. Arnold, R. N., Arp, S. C., Scheller, K. K., Williams, S. N., & Schaefer, D. M. (1993a). Tissue equilibrium and subcellular distribution of vitamin E relative to myoglobin and lipid oxidation in displayed beef. Journal of Animal Science, 71, 105–118. Arnold, R. N., Scheller, K. K., Arp, S. C., Williams, S. N., & Schaefer, D. M. (1993b). Dietary a-tocopherol acetate enhances beef quality in Holstein and beef breed steers. Journal of Food Science, 58 , 28–33. Baker, A.-M. M., & Mead, J. (2000). Thermoplastics. In C. A. Harper (Ed.), Modern Plastics Handbook(pp. 1.1–1.9). New York: McGraw-Hill. Balamatsia, C. C., Patsias, A., Kontomina, M. G., & Savvaidis, I. N. (2007). Possible role of volatile amines as quality-inidicating metabolies in modified atmosphere packaged chicken fillets: Correlation with microbiological and sensory attributes. Food Chemistry, 104, 1622–1628. Bala, K., Stringer, W. C., & Naumann, H. D. (1977). Effect of spray sanitation treatment and gaseous atmospheres on the stability of pre-packaged fresh beef. Journal of Food Science, 42 (3), 743–746. Barbut, S. (2001). Effect of illumination source on the appearance of fresh meat cuts. Meat Science, 59, 187–191. Baublits, R. T., Pohlman, F. W., Brown, A. H., Jr., & Johnson, Z. B. (2005a). Effects of sodium chloride, phosphate type and concentration, and pump rate on beef biceps femoris quality and sensory characteristics. Meat Science, 71, 205–214. Baublits, R. T., Pohlman, F. W., Brown, A. H., Jr., & Johnson, Z. B. (2005b). Effects of enhancement with varying phosphate types and concentrations, at two different pump rates, on beef biceps femoris instrumental color characteristics. Meat Science, 71, 264–276. Beggan, M., Allen, P., & Butler, F. (2005). The use of micro-perforated lidding film in low-oxygen storage of beef steaks. Journal of Muscle Foods, 16, 103–116. Belcher, J. N. (2006). Industrial packaging developments for the global meat market. Meat Science, 74, 143–148. Bendall, J. R., & Taylor, A. A. (1972). Consumption of oxygen by the muscles of beef animals and related species. II. Consumption of oxygen by post-rigor muscles. Journal of the Science of Food and Agriculture, 23, 707–719. Benedict, R. C., Strange, E. D., Palumbo, S., & Swift, C. E. (1975). Use of in-package controlled atmospheres for extending the shelf life of meat products. Journal of Agricultural and Food Chemistry, 23(6), 1208–1212. Ben-Yehoshua, S. (1989). Individual self-packaging of fruit and vegetables in plastic film. In A. L. Brody (Ed.), Controlled/modified atmosphere/vacuum packaging of foods (pp. 101–117). Trumbull, Connecticut: Food & Nutrition Press.

Bertelsen, G., & Skibsted, L. H. (1987). Photooxidation of oxymyoglobin. Wavelength dependence of quantum yields in relation to light discoloration of meat. Meat Science, 19, 243–251. Bjerklie, S. (2007). MAP stepping on the gas. The MAP debate gets ugly. Meat & Poultry, 53(12), 102. 104. Blakistone, B. A. (1999a). Introduction. In B. A. Blakistone (Ed.), Principles and applications of modified atmosphere packaging of foods (pp. 1–13). Gaithersburg, Maryland: Aspen Publishers. Blakistone, B. A. (1999b). Meats and poultry. In B. A. Blakistone (Ed.), Principles and applications of modified atmosphere packaging of foods (pp. 240–290). Gaithersburg, Maryland: Aspen Publishers. Boeckman, A. M. (2006). Regulatory status of carbon monoxide for meat packaging. In Proceedings 59th reciprocal meat conference (pp. 59–60), 18-21 June 2006, Champaign-Urbana, Illinois, USA. Brewer, M. S., Wu, S., Field, R. A., & Ray, B. (1994). Carbon monoxide effects on color and microbial counts of vacuum-packaged fresh beef steaks in refrigerated storage. Journal of Food Quality, 17, 231–244. Brewer, M. S., Zhu, L. G., Bidner, B., Meisinger, D. J., & McKeith, F. K. (2001). Measuring pork color: Effects of bloom time, muscle, pH and relationship to instrumental parameters. Meat Science, 57, 169–176. Brody, A. L. (1989). Modified atmosphere/vacuum packaging of meat. In A. L. Brody (Ed.), Controlled/modified atmosphere/vacuum packaging of foods (pp. 17–37). Trumbull, Connecticut: Food & Nutrition Press. Brody, A. L. (2002). Meat Packaging: Past, Present and Future. Presentation at 55th reciprocal meat conference, 31 July 2002, East Lansing, Michigan, USA.Accessed 26.02.08. Brody, A. L. (2005). Commercial uses of active food packaging and modified atmosphere packaging systems. In J. H. Han (Ed.), Innovations in food packaging (pp. 457–474). Amsterdam: Elsevier Academic Press. Brody, A. L. (2007). Case-ready packaging for fresh meat. Food Technology, 61(3), 70–72. Brody, A. L., & Marsh, K. E. (1997). The Wiley encyclopedia of packaging technology. New York: John Wiley & Sons. Brody, A. L., Strupinsky, E. R., & Kline, L. R. (2001). Active packaging for food applications. Lancaster: Technomic Publishing. Brooks, J. C. (2005). Tender is the bite. Meat Marketing and Technology, 13 (10), 101–104. Brooks, J. C., Alvarado, M., Stephens, T. P., Kellermeier, J. D., Tittor, A. W., Miller, M. F., et al. (2008). Spoilage and safety characteristics of ground beef packaged in traditional and modified atmosphere packages. Journal of Food Protection, 71(2), 293–301. Brooks, J. C., Brashears, M. M., & Miller, M. F. (2007). Is there a link between food safety and food spoilage? Journal of Animal Science, 85 (Suppl. 1), 137 (Abstr.). Buckley, D. J., & Morrissey, P. A. (1992). Vitamin E and meat quality. Animal production highlights monograph . Basel, Switzerland: Hoffmann-La Roche, Ltd.. Buffo, R. A., & Holley, R. A. (2005). Centralized packaging systems for meats. In J. H. Han (Ed.), Innovations in food packaging (pp. 227–236). Amsterdam: Elsevier Academic Press. Bugusu, B., & Bryant, C. (2006). Defining the future of food packaging. Food Technology, 60(12), 39–42. Bush, P. (1991). Packaging for fresh perceptions. Prepared Foods, 160(4), 104–106. Butler, O. D., Bratzler, L. J., & Mallman, W. L. (1953). The effect of bacteria on the color of prepackaged retail beef cuts. Food Technology, 7, 397–400. Calkins, C. R., & Hodgen, J. M. (2007). A fresh look at meat flavor. Meat Science, 77, 63–80. Campo, M. M., Nute, G. R., Hughes, S. I., Enser, M., Wood, J. D., & Richardson, R. I. (2006). Flavour perception of oxidation in beef. Meat Science, 72, 303–311. Carpenter, C. E., Cornforth, D. P., & Whittier, D. (2001). Consumer preferences for beef color and packaging did not affect eating satisfaction. Meat Science, 57, 359–363. Cayuela, J. M., Gil, M. D., Bañón, S., & Garrido, M. D. (2004). Effect of vacuum and modified atmosphere packaging on the quality of pork loin. European Food Research and Technology, 219 , 316–320. Church, P. N. (1993). Meat products. In R. T. Parry (Ed.), Principles and applications of modified atmosphere packaging of foods (pp. 229–268). New York: Blackie Academic & Professional. Church, N. (1994). Developments in modified-atmosphere packaging and related technologies. Trends in Food Science and Technology, ,5345–352. Clark, D. S., & Lentz, C. P. (1969). The effect of carbon dioxide on the growth of slime producing bacteria on fresh beef. Canadian Institute of Food Science and Technology Journal, 2(2), 72–75. Clark, D. S., Lentz, C. P., & Roth, L. A. (1976). Use of carbon monoxide for extending shelf-life of prepackaged fresh beef. Canadian Institute of Food Science and Technology Journal, 9(3), 114–117. Cocoma, G. J., & Cheng, C. S. (1988). A process for central prepackaging of fresh meat. In Proceedings 34th international congress of meat science and technology (pp. 492–500), 29 August-2 September 1988, Brisbane, Australia. Cole Jr., A. B., (1986). Retail packaging systems for fresh red meat cuts. In Proceedings 39th reciprocal meat conference (pp. 106–111), 8–11 June 1986, Champaign, Illinois, USA. Coma, V. (2008). Bioactive packaging technologies for extended shelf life of meatbased products. Meat Science, 78, 90–103. Compressed Gas Association. (1981). Handbook of compressed gases. New York: Van Nostrand Reinhold.

K.W. McMillin /Meat Science 80 (2008) 43–65 Connolly, K. B. (2008). Meat packaging: On the innovation trail. Food & Beverage Packaging, 72(3), 26–28. Cooksey, K. (2001). Antimicrobial food packaging. Food, Cosmetics and Drug Packaging, 24, 133–137. Cooksey, K. (2005). Effectiveness of antimicrobial food packaging materials. Food Additives and Contaminants, 19(Suppl.), 144–162. Cornforth, D. P. (1991). Methods for identification and prevention of pink color in cooked meats. In Proceedings 44th reciprocal meat conference (pp. 53–56), 9– 12 June 1991, Manhattan, Kansas, USA. Cornforth, D., & Hunt, M. (2008). Low-oxygen packaging of fresh meat with carbon monoxide. Meat quality, microbiology, and safety. AMSA White Paper Series, (number 2) (pp. 1–10). Savoy, Illinois: American Meat Science Association. Crews, J. (2007). A closer look. The 2007 national meat case study sheds new light on retail protein offerings. Meat & Poultry (October), 42. 46, 48, 50, 52. Cutter, C. N. (2002). Microbial control by packaging: A review. Critical Reviews in Food Science and Nutrition, 42(2), 151–161. Cutter, C. N. (2006). Opportunities for bio-based packaging technologies to improve the quality and safety of fresh and further processed muscle foods. Meat Science, 74, 131–142. Daniels, J. A., Krishnamurthi, R., & Rizvi, S. S. H. (1985). A review of effects of carbon dioxide on microbial growth and food quality. Journal of Food Protection, 48(6), 532–537. Day, B. P. F. (2003). Active packaging. In R. Coles, D. McDowell, & M. J. Kirwan (Eds.), Food packaging technology(pp. 282–302). London: Blackwell Publishing. Decker, E. A., & Mei, L. (1996). Antioxidant mechanisms and applications in muscle foods. In Proceedings 49th reciprocal meat conference (pp. 64–72), 9–12 June 1996, Provo, Utah, USA. de Kruijf, N., van Beest, M., Rijk, R., Sipiläinen-Malm Losada, P. P., & De Meulenaer, B. (2002). Active and intelligent packaging: applications and regulatory aspects. Food Additives and Contaminants, 19(Supplement), 144–162. Del-Valle, V., Almenar, E., Lagarón, J. M., Catalá, R., & Gavara, R. (2003). Modelling permeation through porous polymeric films for modified atmosphere packaging. Food Additives and Contaminants, 20(2), 170–179. Demetrakakes, P. (2008). Global sustainability: Europe unifies over packaging waste issues. Food & Beverage Packaging, 72 (3), 20–25. De Santos, F., Rojas, M., Lockhorn, G., & Brewer, M. S. (2007). Effect of carbon monoxide in modified atmosphere packaging, storage time and endpoint cooking temperature on the internal color of enhanced pork. Meat Science, 77, 520–528. Destefanis, G., Brugiapaglia, A., Barge, M. T., & Dal Molin, E. (2008). Relationship between beef consumer tenderness perception and Warner–Bratzler shear force. Meat Science, 78, 153–156. Doherty, A. (1996). Modified atmosphere packaging. Meat International, 6 (2), 34–35. 37. Doyle, M. (2008). Green expectations are changing. Food & Beverage Packaging, 72(2), 10–11. Dransfield, E., Zamora, F., & Bayle, M. (1998). Consumer selection of steaks as influenced by information and price index. Food Quality and Preference, 9 (5), 321–326. Duffy, E., Hearty, A. P., Gilsenan, M. B., & Gibney, M. J. (2006). Estimation of exposure to food packaging materials. 1: Development of a food-packaging database. Food Additives and Contaminants, 23(6), 623–633. Eilert, S. J. (2005). New packaging technologies for the 21st century. Meat Science, 71, 122–127. Elias, H-G. (2003). An introduction to plastics (2nd ed.). Weinheim: Wiley-VCH (pp. 239–290). Ellis, M., Cooksey, K., Dawson, P., Han, I., & Vergano, P. (2006). Quality of fresh chicken breasts using a combination of modified atmosphere packaging and chlorine dioxide sachets. Journal of Food Protection, 69(8), 1991–1996. Enfors, S.-O., & Molin, G. (1984). Carbon dioxide evolution of refrigerated meat. Meat Science, 10, 197–206. Ercolini, D., Russo, F., Torrieri, E., Masi, P., & Villani, F. (2006). Changes in the spoilage-related microbiota of beef during refrigerated storage under different packaging conditions. Applied and Environmental Microbiology, 72(7), 4371–4663. Eschevarne, C., Renerre, M., & Labas, R. (1990). Metmyoglobin reductase activity in bovine muscles. Meat Science, 27, 161–172. Farber, J. M. (1991). Microbiological aspects of modified-atmosphere packaging technology – A review. Journal of Food Protection, 54(1), 58–70. Faustman, C., & Cassens, R. G. (1990). The biochemical basis for discoloration in fresh meat: A review. Journal of Muscle Foods, 1, 217–243. Faustman, C., & Cassens, R. G. (1991). The effect of cattle breed and muscle type on cisocoloration and various biochemical parameters in fresh beef. Journal of Animal Science, 69, 184–193. Faustman, C., Cassens, R. G., Schaefer, D. M., Buege, D. R., Williams, S. N., & Scheller, K. K. (1989). Improvement of pigment and lipid stability in Holstein steer beef by dietary supplementation with vitamin E. Journal of Food Science, 54 , 858–865. Faustman, C., Chan, W. K. M., Lynch, M. P., & Joo, S. T. (1996). Strategies for increasing oxidative stability of (fresh) meat color. In Proceedings 49th reciprocal meat conference (pp. 73–79), 9–12 June 1996, Provo, Utah, USA. Feigenbaum, A., Dole, P., Aucejo, S., Dainelli, D., De La Cruz Garcia, C., Hankemeier, T., et al. (2005). Functional barriers: Properties and evaluation. Food Additives and Contaminants, 22(10), 980–987. Finne, G. (1982). Modified- and controlled-atmosphere storage of muscle foods. Food Technology, 36(2), 128–133.

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Formanek, Z., Kerry, J. P., Higgins, F. M., Buckley, D. J., Morrissey, P. A., & Farkas, J. (2001). Addition of synthetic and natural antioxidants to a-tocopherol acetate supplemented beef patties: effects of antioxidants and packaging on lipid oxidation. Meat Science, 58, 337–341. Friedrich, L., Siró, I., Dalmadi, I., Horváth, K., Ágoston, R., & Balla, C. (2008). Influence of various preservatives on the quality of minced beef under modified atmosphere at chilled storage. Meat Science, 79, 332–343. Gabbett, J. (2008). Off the MAP. Meatingplace, February, 51–52, p. 54. Gatellier, P., Hamelin, C., Durand, Y., & Renerre, M. (2001). Effect of a dietary vitamin E supplementation on colour stability and lipid oxidation of air- and modified atmosphere-packaged beef. Meat Science, 59, 133–140. Gee & Brown, W. D. (1978). Extension of shelf life in refrigerated ground beef stored under an atmosphere containing carbon dioxide and carbon monoxide. Journal of Agricultural and Food Chemistry, 26(1), 274–276. Gee, D. L., & Brown, W. D. (1980). The effect of carbon monoxide on bacterial growth. Meat Science, 5, 215–222. Gellynck, X., Verbeke, W., & Vermeire, B. (2006). Pathways to increase consumer trust in meat as a safe and wholesome food. Meat Science, 74, 161–171. Giddings, G. G. (1977). The basis of color in muscle foods. Journal of Food Science, 42 , 288–294. Gill, C. O. (1986). The control of microbial spoilage in fresh meats. In A. M. Pearson & T. R. Dutson (Eds.). Advances in meat research (Vol. 2, pp. 49–88). Westport, Connecticut: AVI Publishing Company. Gill, C. O. (1990). Controlled atmosphere packaging of meat. Food Control, 1, 74–78. Gill, A. O., & Gill, C. O. (2005). Preservative packaging for fresh meats, poultry, and fin fish. In J. H. Han (Ed.), Innovations in food packaging (pp. 204–226). Amsterdam: Elsevier Academic Press. Gill, C. O., & Newton, K. G. (1978). The ecology of bacterial spoilage of fresh meat at chill temperatures. Meat Science, 2, 207–217. Gill, C. O., & Penney, N. (1988). The effect of the initial gas volume ot meat weight ratio on the storage life of chilled beef packaged under carbon dioxide. Meat Science, 22, 53–63. Gill, C. O., & Tan, K. H. (1980). Effect of carbon dioxide on growth of meat spoilage bacteria. Applied and Environmental Microbiology, 39 , 317–319. Gotoh, T., & Shikama, K. (1976). Generation of the superoxide radical during autoxidation of oxymyoglobin. Journal of Biochemistry, 80, 376–399. Govindarajan, S., Hultin, H. O., & Kotula, A. W. (1977). Myoglobin oxidation in ground beef: Mechanistic studies. Journal of Food Science, 42 , 571–577. p. 582. Grau, F. H. (1986). Microbial ecology of meat and poultry. In A. M. Pearson & T. R. Dutson (Eds.). Advances in meat research (Vol. 2, pp. 1–47). Westport, Connecticut: AVI Publishing Company. Graves, M. H. (2007). Emerging trends in 2007. National Meat Association Marketing Trends, February 5, 2007. Gray, J. I. (1978). Measurement of lipid oxidation. A review. Journal of the American Oil Chemists Society, 55, 539–546. Gray, J. I., Gomaa, E. A., & Buckley, D. J. (1996). Oxidative quality and shelf life of meats. Meat Science, 43, S111–S123. Greene, B. E. (1969). Lipid oxidation and pigment changes in raw beef. Journal of Food Science, 34 , 110–113. Greene, B. E., Hsin, I.-M., & Zipser, M. W. (1971). Retardation of oxidative color changes in raw ground beef. Journal of Food Science, 36 , 940–942. Grobbel, J. P., Dikeman, M. E., Hunt, M. C., & Milliken, G. A. (2008). Effects of packaging atmospheres on beef instrumental tenderness, fresh color stability, and internal cooked color. Journal of Animal Science, 86, 1191–1199. Grobbel, J. P., Dikeman, M. E., Hunt, M. C., & Milliken, G. A. (2007). Different packaging environments alter tenderness and sensory traits from nonenhanced and injection-enhanced beef. In Proceedings 53rd international congress of meat science and technology (pp. 527–528), 5–10 August 2007, Beijing, China. Grunert, K. G., Bredahl, L., & Brunsø, K. (2004). Consumer perception of meat quality and implications for product development in the meat sector – A review. Meat Science, 66, 259–272. Guerra, M. O., McMillin, K. W., Bidner, T. D., Janes, M. E., & Persica III, M. A. (2007). Carbonated or gaseous enhancement solutions improve injected pork properties in modified atmosphere packaging. In Proceedings 53rd international congress of meat science and technology (pp. 523–524), 5–10 August 2007, Beijing, China. Hamling, A. E., Jenschke, B. E., & Calkins, C. R. (2008). Effects of dark storage and retail display on beef chuck and round muscles enhanced with ammonium, hydroxide, salt, and carbon monoxide. Journal of Animal Science, 86, 972–981. Hamm, R. (1960). Biochemistry of meat hydration. Advances in Food Research, 10, 355–463. Han, J. H. (2005a). New technologies in food packaging: Overview. In J. H. Han (Ed.), Innovations in food packaging (pp. 3–11). Amsterdam: Elsevier Academic Press. Han, J. H. (2005b). Antimicrobial packaging systems. In J. H. Han (Ed.), Innovations in food packaging (pp. 80–107). Amsterdam: Elsevier Academic Press. Han, J. H., & Gennadios, A. (2005). Edible films and coatings: A review. In J. H. Han (Ed.), Innovations in food packaging (pp. 240–262). Amsterdam: Elsevier Academic Press. Hanlon, J. F., Kelsey, R. J., & Forcino, H. E. (1998). Handbook of package engineering (3rd ed.). Lancaster: Technomic Publishing. Hansen, A. Å., Mørkøre, T., Rudi, K., Olsen, E., & Eie, T. (2007). Quality changes during refrigerated storage of MA-packaged pre-rigor fillets of farmed Atlantic cod (Gadus morhua L) using traditional MAP, CO2 emitter, and vacuum. Journal of Food Science, 72 (9), M423–M430.

62

K.W. McMillin/ Meat Science 80 (2008) 43–65

Han, J. H., Zhang, Y., & Buffo, R. (2005). Surface chemistry of food, packaging and biopolymer materials. In J. H. Han (Ed.), Innovations in food packaging (pp. 45–57). Amsterdam: Elsevier Academic Press. Harris, P. V., & Shorthose, W. R. (1988). Meat texture. In R. Lawrie (Ed.). Developments in meat science(Vol. 4). London: Elsevier Applied Science. Hermansen, P. (1983). Comparison of modified atmosphere versus vacuum packaging to extend the shelf life of retail fresh meat cuts. In Proceedings 35th reciprocal meat conference (pp. 60–64), 12–15 June 1983, Fargo, North Dakota, USA. Hernandez-Izquierdo, V. M., & Krochta, J. M. (2008). Thermoplastic processing of proteins for film formation – A review. Journal of Food Science, 73 (2), R30–R39. Ho, C.-P., Huang, N.-Y., & McMillin, K. W. (2003). Microflora and color of ground beef in gase exchange modified atmosphere packaging with abusive display temperatures. Journal of Food Science, 68 (5), 1771–1776. Holmes, K. (2001). Carnivorous cravings: Charting the world’s protein shift. EarthTrends, July. Accessed 08.03.08. Holm, V. K., Ndoni, S., & Risbo, J. (2006). The stability of poly(lactic acid) packaging films as influenced by humidity and temperature. Journal of Food Science, 71 (2), E40–E44. Hood, D. E. (1975). Pre-slaughter injection of sodium ascorbate as a method of inhibiting metmyoglobin formation in fresh beef. Journal of Science of Food and Agriculture, 26, 85–90. Hood, D. E. (1980). Factors affecting the rate of metmyoglobin accumulation in prepackaged beef. Meat Science, 4, 247–265. Hood, T. (1984). The chemistry of vacuum and gas packaging of meat. In A. J. Bailey (Ed.), Recent advances in the chemistry of meat (pp. 213–230). London: Burlington House (Royal Society of Chemistry). Hood, D. E., & Mead, G. C. (1993). Modified atmosphere storage of fresh meat and poultry. In R. T. Parry (Ed.), Principles and applications of modified atmosphere packaging of foods (pp. 269–298). New York: Blackie Academic & Professional. Hotchkiss, J. H. (1989). Advances in and aspects of modified atmosphere packaging in fresh red meats. In Proceedings 42nd reciprocal meat conference (pp. 31–33), 11–14 June 1989, Guelph, Canada. Huang, N-Y., Ho, C-P., & McMillin, K. W. (2005). Retail shelf-life of pork dipped in organic acid before modified atmosphere or vacuum packaging. Journal of Food Science, 70(8), M382–M387. Huff-Lonergan, E., & Lonergan, S. M. (2005). Mechanisms of water-holding capacity of meat: The role of postmortem biochemical and structural changes. Meat Science, 71, 194–204. Hunt, M. C., Mancini, R. A., Hachmeister, K. A., Kropf, D. H., Merriman, M., DelDuca, G., et al. (2004). Carbon monoxide in modified atmosphere packaging affects color, shelf life, and microorganisms of beef steaks and ground beef. Journal of Food Science, 69 (1), FCT45–FCT52. Hunt, M. C., Sørheim, O., & Slinde, E. (1999). Color and heat denaturation of myoglobin forms in ground beef. Journal of Food Science, 64 (5), 847–851. Hutchins, B. K., Liu, T. H. P., & Watts, B. M. (1967). Effects of additives and refrigeration on reducing activity, metmyoglobin and malonaldehyde of raw ground beef. Journal of Food Science, 32 , 214–217. Ingram, M. (1962). Microbiological principles in prepacking meat. Journal of Applied Bacteriology, 25, 259. Inns, R. (1987). Modified atmosphere packaging. In F. A. Paine (Ed.), Modern processing, packaging and distribution systems for food (pp. 36–51). Glasgow: Blackie. Intertechpira. (2007). The future for global markets for antimicrobials in plastics – Strategic forecast to 2012. Leatherhead, Surrey, United Kingdom: Intertechpira. Isdell, E., Allen, P., Doherty, A. M., & Butler, F. (1999). Colour stability of six beef muscles stored in a modifed atmosphere mother pack system with oxygen scavengers. International Journal of Food Science and Technology, 34, 71–80. Jackson, T. C., Acuff, G. R., Vanderzant, C., Sharp, T. R., & Savell, J. W. (1992). Identification and evaluation of volatile compounds of vacuum and modified atmosphere packaged beef strip loins. Meat Science, 31, 175–190. Jakobsen, M., & Bertelsen, G. (2000). Colour stability and lipid oxidation of fresh beef. Development of a response surface model for predicting the effects of temperature, storage time, and modified atmosphere composition. Meat Science, 54, 49–57. Jakobsen, M., & Bertelsen, G. (2002). The use of CO2 in packaging of fresh red meats and its effect on chemical quality changes in the meat: A review. Journal of Muscle Foods, 13, 143–168. Jan, J. H., Zhang, Y., & Buffo, R. (2005). Surface chemistry of food, packaging and biopolymer materials. In J. H. Han (Ed.), Innovations in food packaging (pp. 45–59). Amsterdam: Elsevier Academic Press. Jayasingh, P., & Cornforth, D. P. (2004). Comparison of antioxidant effects of milk mineral, butylated hydroxytoluene and sodium tripolyphosphate in raw and cooked ground pork. Meat Science, 66, 83–89. Jayasingh, P., Cornforth, D. P., Brennand, C. P., Carpenter, C. E., & Whittier, D. R. (2002). Sensory evaluation of ground beef stored in high-oxygen modified atmosphere packaging. Journal of Food Science, 67 (9), 3493–3496. Jayasingh, P., Cornforth, D. P., Carpenter, C. E., & Whittier, D. (2001). Evaluation of carbon monoxide treatment in modified atmosphere packaging or vacuum packaging to increase color stability of fresh beef. Meat Science, 59, 317–324. Jenkins, W. A., & Harrington, J. P. (1991). Packaging foods with plastics. Lancaster: Technomic Publishing Company. Jeremiah, L. E., Gibson, L. L., & Arganosa, G. C. (1992). The influence of CO2 level on the storage life of chilled pork stored at C. Journal of Muscle Foods, 3 , 1.5  263–281.

Jeyamkondan, W., Jayas, D. S., & Holley, R. A. (2000). Review of centralized packaging systems for distribution of retail-ready meat. Journal of Food Protection, 63, 796–804. Jin, T., & Zhang, H. (2008). Biodegradable polylactic acid polymer with nisin for use in antimicrobial food packaging. Journal of Food Science, 73 (3), M127–M134. John, L., Cornforth, D., Carpenter, C. E., Sorheim, O., Pettee, B. C., & Whittier, D. R. (2004). Comparisons of color and thiobarbituric acid values of cooked hamburger patties after storage of fresh beef chubs in modified atmospheres. Journal of Food Science, 69 (8), C608–C614. John, L., Cornforth, D., Carpenter, C. E., Sorheim, O., Pettee, B. C., & Whittier, D. R. (2005). Color and thiobarbituric acid values of cooked top sirloin steaks packaged in modified atmospheres of 80% oxygen, or 0.4% carbon monoxide, or vacuum. Meat Science, 69, 441–449. Kanner, J. (1994). Oxidative processes in meat and meat products: Quality implications. Meat Science, 36, 169–189. Keith, H. (2001). The realization of case ready packaging technology overview of an emerging market. In Meat industry research conference, 15-17 October 2001, Chicago, Illinois, USA. Accessed on 09.03.08. Kelly, J. (2006a). National meat case study. In Proceedings 59th reciprocal meat conference (pp. 55–57), 18–21 June 2006, Champaign-Urbana, Illinois, USA. Kelly, J. (2006b). National meat case study. Presentation at 59th reciprocal meat conference, 21 June 2006, Champaign, Urbana, Illinois, USA. Accessed 19.05.08. Kerry, J. P., O’Grady, M. N., & Hogan, S. A. (2006). Past, current and potential utilization of active and intelligent packaging systems for meat and musclebased products: A review. Meat Science, 74, 113–130. Kim, Y. H., Hunt, M. C., Mancini, R. A., Seyfert, M., Loughin, T. M., Kropf, D. H., et al. (2006). Mechanism for lactate-color stabilization in injection-enhanced beef. Journal of Agricultural and Food Chemistry, 54, 7856–7862. King, N. J., & Whyte, R. (2006). Does it look cooked? A review of factors that influence cooked meat color. Journal of Food Science, 71 (4), R31–R40. Kirwan, M. J., & Strawbridge, J. W. (2003). Plastics in food packaging. In R. Coles, D. McDowell, & M. J. Kirwan (Eds.), Food packaging technology (pp. 174–240). London: Blackwell Publishing. Klein, T., & Knorr, D. (1990). Oxygen absorption properties of powdered iron. Journal of Food Science, 55, 869–870. Knock, R. C., Seyfert, M., Hunt, M. C., Dikeman, M. E., Mancini, R. A., Unruh, J. A., et al. (2006a). Effects of potassium lactate, sodium chloride, sodium tripolyphosphate, and sodium acetate on colour, colour stability, and oxidative properties of injection-enhanced beef rib steaks. Meat Science, 74, 312–318. Knock, R. C., Seyfert, M., Hunt, M. C., Dikeman, M. E., Mancini, R. A., Unruh, J. A., et al. (2006b). Effects of potassium lactate, sodium chloride, and sodium acetate on surface shininess/gloss and sensory properties of injection-enhanced beef striploin steaks. Meat Science, 74, 319–326. Kropf, D. H. (1980). Effects of retail display conditions on meat color. In Proceedings 33rd reciprocal meat conference (pp. 15–32), 22–25 June 1980, West Lafayette, Indiana, USA. Kropf, D. H. (1993). Color stability. Meat Focus International, 2(6), 269–275. Ladikos, D., & Lougovois, V. (1990). Lipid oxidation in muscle foods: A review. Food Chemistry, 35(4), 295–314. Lagerstedt, Å, Edblad, U., Wretström, S., Enfält, L., Johansson, L., & Lundström, K. (2007). Minced meat packed in high-oxygen modified atmosphere- effects on sensory quality and oxidation products. In Proceedings 53rd international congress of meat science and technology (pp. 515–516), 5–10 August 2007, Beijing, China. Lanari, M. C., & Cassens, R. G. (1991). Mitochondrial activity and beef muscle color stability. Journal of Food Science, 56 (6), 1476–1479. Lanari, M. C., Cassens, R. G., Schaefer, D. M., & Scheller, K. K. (1993). Dietary vitamin E enhances color and display life of frozen beef from Holstein steers. Journal of Food Science, 58 , 701–704. Lanier, T. C., Carpenter, J. A., Toledo, R. T., & Reagan, J. O. (1978). Metmyoglobin reduction in beef as affected by aerobic, anaerobic and carbon monoxide containing environments. Journal of Food Science, 43 , 1788–1792, 1796. La Storia, A., Ercolini, D., Marinello, F., & Mauriello, G. (2008). Characterization of baceriocin-coated antimicrobial polyethylene films by atomic force microscopy. Journal of Food Science, 73 (4), T48–T54. Laury, A., & Sebranek, J. G. (2007). Use of carbon monoxide combined with carbon dioxide for modified atmosphere packaging of pre- and postrigor fresh pork sausage to improve shelf life. Journal of Food Protection, 70(4), 937–942. Lauzurica, S., de la Fuente, J., Díaz, M. T., Álvarez, I., Pérez, C., & Cañeque, V. (2005). Effect of dietary supplementation of vitamin E on characteristics of lamb meat packed under modified atmosphere. Meat Science, 70, 639–646. Ledward, D. A. (1970). Metmyoglobin formation in beef stored in carbon dioxide enriched and oxygen depleted atmospheres. Journal of Food Science, 35 , 33–37. Leedle, R. A., Leedle, J. A. Z., & Butine, M. D. (1993). Vitamin E is not degraded by ruminal microorganisms: Assessment with ruminal contents from a steer fed a high-concentrate diet. Journal of Animal Science, 71, 3442–3450. Lillard, D. A. (1987). Oxidative deterioration in meat, poultry, and fish. In A. J. St. Angelo & M. E. Bailey (Eds.), Warmed-over flavor of meat (pp. 41–67). Orlando, Florida: Academic Press. Livingston, M., Brewer, M. S., Killifer, J., Bidner, B., & McKeith, F. (2004). Shelf life characteristics of enhanced modified atmosphere packaged pork. Meat Science, 68, 115–122.

K.W. McMillin /Meat Science 80 (2008) 43–65 Lund, M. N., Lametsch, R., Hviid, M. S., Jensen, O. N., & Skibsted, L. H. (2007). Highoxygen packaging atmosphere influences protein oxidation and tenderness of porcine longissimus dorsi during chill storage. Meat Science, 77, 295–303. Luño, M., Beltrán, J. A., & Roncalés, P. (1998). Shelf-life extension and colour stabilization of beef packaged in a low O 2 atmosphere containing CO: Loin steaks and ground meat. Meat Science, 48(1), 75–84. Lynch, N. M., Kastner, C. L., & Kropf, D. H. (1986). Consumer acceptance of vacuum packaged ground beef as influrneced by product color and educational materials. Journal of Food Science, 51 , 253–255. 272. MacDougall, D. B. (1982). Changes in the colour and opacity of meat. Food Chemistry, 9, 75–88. MacDougall, D. B., & Taylor, A. A. (1975). Colour retention in fresh meat stored in oxygen- a commercial scale trial. Journal of Food Technology, 10, 339–347. Madhavi, D. L., & Carpenter, C. E. (1993). Aging and processing affect color, metmyoglobin reductase and oxygen consumption of beef muscles. Journal of Food Science, 58 , 939–942. 947. Mancini, R. A., & Hunt, M. C. (2005). Current research in meat color. Meat Science, 71 , 100–121. Mancini, R. A., Hunt, M. C., Hachmeister, K. A., Kropf, D. H., & Johnson, D. E. (2004). Ascorbic acid minimizes lumbar vertebrae discoloration. Meat Science, 68 , 339–345. Mancini, R. A., Kropf, D. H., Hunt, M. C., & Johnson, D. E. (2005). Effects of endpoint temperature, pH, and storage time on cooked internal color reversion of pork longissimus chops. Journal of Muscle Foods, 16(1), 16–26. Mancini, R. A., & Ramanathan, R. (2008). Sodium lactate influences myoglobin redox stability in vitro. Meat Science, 78, 529–532. Mancini, R. A., Seyfert, M., & Hunt, M. C. (2008). Effects of data expression, sample location, and oxygen partial pressure on initial nitric oxide metmyoglobin formation and metmyoglobin-reducing-activity measurement in beef muscle. Meat Science, 79, 244–251. Manu-Tawiah, W., Ammann, L. L., Sebranek, J. G., & Molins, R. A. (1991). Extending the color stability and shelf life of fresh meat. Food Technology, 45 (3), 94. 96–98, 100–102. Marsh, K., & Bugusu, B. (2007). Food packaging – Roles, materials, and environmental issues. Food Science, 72 (3), R39–R55. Martínez, L., Cilla, I., Beltrán, J. A., & Roncalés, P. (2007). Effect of illumination on the display life of fresh pork sausages packaged in modified atmosphere. Influence of the addition of rosemary, ascorbic acid and black pepper. Meat Science, 75, 443–450. Martínez, L., Djenane, D., Cilla, I., Beltrán, J. A., & Roncalés, P. (2006). Effect of varying oxygen concentrations on the shelf-life of fresh pork sausages packaged in modified atmosphere. Food Chemistry, 94, 219–225. McKenna, D. R., Mies, P. D., Baird, B. E., Pfeiffer, K. D., Ellenbracht, J. W., & Savell, J. W. (2005). Biochemical and physical factors affecting discoloration characteristics of 19 bovine muscles. Meat Science, 70, 665–682. McMillin, K. W. (1994). Gas-exchange systems for fresh meat in modified atmosphere packaging. In A. L. Brody (Ed.), Modified atmosphere food packaging (pp. 85–102). Herndon, Virginia: Institute of Packaging Professionals. McMillin, K. W. (1996). Initiation of oxidative processes in muscle foods. In Proceedings 49th reciprocal meat conference (pp. 53–64), 9–12 June 1996, Provo, Utah, USA. McMillin, K. W., Ho, C. P., Huang, N. Y., & Smith, B. S. (1994a). Beef color with increased postmortem fabrication and air exposure times. In Proceedings 40th international congress of meat science and technology (W-3.16 pp. 1–4), 28 August-2 September 1994, The Hague, Netherlands. McMillin, K. W., Huang, N. Y., Ho, C. P., & Smith, B. S. (1994b). Beef traits with differing fabrication times and gases in modified atmosphere packaging. In Proceedings 40th international congress of meat science and technology (S-VIIA.10 pp. 1–6), 28 August-2 September 1994, The Hague, Netherlands. McMillin, K. W., Huang, N. Y., Ho, C. P., & Smith, B. S. (1999). Quality and shelf-life of meat in case-ready modified atmosphere packaging. In Y. L. Xiong, F. Shahidi, & C. T. Ho (Eds.), Quality attributes in muscle foods (pp. 73–93). New York: ACS Symposium Series, Plenum Publishing Corporation. Meijboom, F. L. B. (2007). Trust, food, and health. Questions of trust at the interface between food and health. Journal of Agricultural and Environmental Ethics, 20 , 231–245. Meijboom, F. L. B., Visak, T., & Brom, F. W. A. (2006). From trust to trustworthiness: Why information is not enough in the food sector. Journal of Agricultural and Environmental Ethics, 19, 427–442. Mendenhall, VT. (1989). Effect of pH and total pigment concentration on the internal color of cooked ground beef patties. Journal of Food Science, 54 (1), 1–2. Mitsumoto, M., Arnold, R. N., Schaefer, D. M., & Cassens, R. G. (1993). Dietary versus postmortem supplementation of vitamin E on pigment and lipid stability in ground beef. Journal of Animal Science, 71, 1812–1816. Mitsumoto, M., Cassens, R. G., Schaefer, D. M., Arnold, R. N., & Scheller, K. K. (1991). Improvement of color and lipid stability in beef longissimus with dietary vitamin E and vitamin C dip treatment. Journal of Food Science, 56 , 1489–1492. Morey, K. S., Hansen, S. P., & Brown, W. D. (1973). Reaction of hydrogen peroxide with myoglobins. Journal of Food Science , 1104–1107. Mullan, M., & McDowell, D. (2003). Modified atmosphere packaging. In R. Coles, D. McDowell, & M. J. Kirwan (Eds.), Food packaging technology (pp. 303–339). London: Blackwell Publishing. Nerín, C., Tovar, L., Djenane, D., Camo, J., Salafranca, J., & Beltrán, Pedro Roncalés. (2006). Stabilization of beef meat by a new active packaging containing natural antioxidants. Journal of Agricultural and Food Chemistry, 54, 7840–7846.

63

Nicolade, C., Stetzer, A. J., Tucker, E. M., McKeith, F. K., & Brewer, M. S. (2005). Development of a model system to mimic beef bone discoloration. Journal of Food Science, 70 (9), C575–C580. Nicolalde, C., Stetzer, A. J., Tucker, E., McKeith, F. K., & Brewer, M. S. (2006). Effect of freezing, exposure to enhancement solution and modified atmosphere on pork bone discoloration. Journal of Muscle Foods, 17, 428–442. No, H. K., Meyers, S. P., Prinyawiwatkul, W., & Xu, Z. (2007). Applications of chitosan for improvement of quality and shelf life of foods: A review. Journal of Food Science, 72(5), R87–R100. Nottingham, P. M. (1982). Microbiology of carcass meats. In M. H. Brown (Ed.), Meat microbiology (pp. 13–65). London: Applied Science Publishers. Nychas, G. J. E., Drosinos, E. H., & Board, R. G. (1998). Chemical changes in stored meat. In A. Davies & R. Board (Eds.), The microbiology of meat and poultry (pp. 288–326). London: Blackie Academic & Professional. Offer, G., & Knight, P., 1988. The structural basis of water-holding in meat. Part 1: General principles and water uptake in meat processing and Part 2: Drip losses. In Lawrie, R. (Ed.). Developments in Meat Science-4. Offer, G., & Cousins, T. (1992). The mechanism of drip production: Formation of two compartments of extracellular space in muscle post mortem. Journal of the Science of Food and Agriculture, 58, 107–116. O’Grady, M. N., Monahan, F. J., Burke, R. M., & Allen, P. (2000). The effect of oxygen level and exogenous a-tocopherol on the oxidative stability of minced beef in modified atmosphere packs. Meat Science, 55, 39–45. Okayama, T. (1987). Effect of modified gas atmosphere packaging after dip treatment on myoglobin and lipid oxidation of beef steaks. Meat Science, 19, 179–185. O’Keeffe, M., & Hood, D. E. (1982). Biochemical factors influencing metmyoglobin formation on beef from muscles of differing colour stability. Meat Science, 7, 209–228. Osswald, T. A., Baur, E., Brinkmann, S., Oberbach, K., & Schmachtenberg, E. (2006). International plastics handbook . Munich: Hanser Publishers (pp. 507–699, 708). Otto, G., Roehe, R., Looft, H., Thoelking, L., Henning, M., Plastow, G. S., et al. (2006). Drip loss of case-ready meat and of premium cuts and their associations with earlier measured sample drip loss, meat quality and carcass traits in pigs. Meat Science, 72, 680–687. Pacquit, A., Frisby, J., Diamond, D., Lau, K. T., Farrell, A., Quilty, B., et al. (2007). Development of a smart packaging for the monitoring of fish spoilage. Food Chemistry, 102, 466–470. Phillips, A. L., Faustman, C., Lynch, M. P., Govoni, K. E., Hoagland, T. A., & Zinn, S. A. (2001). Effect of dietary a-tocopherol supplementation on color and lipid stability in pork. Meat Science, 58, 389–393. Platter, W. J., Tatum, J. D., Belk, K. E., Chapman, P. L., Scanga, J. A., & Smith, G. C. (2003). Relationships of consumer sensory ratings, marbling score, and shear force value to consumer acceptance of beef strip loin steaks. Journal of Animal Science, 81(11), 2741–2750. Poole, C. (2008). The seven dimensions of customer driven supply. SupplyChainStandard electronic newsletter. Accessed 04.01.08. Prince, T. A. (1989). Modified atmosphere packaging of horticultural commodities. In A. L. Brody (Ed.), Controlled/modified atmosphere/vacuum packaging of foods (pp. 67–100). Trumbull, Connecticut: Food & Nutrition Press. Quintavalla, S., & Vicini, L. (2002). Antimicrobial food packaging in meat industry. Meat Science, 62, 373–380. Raines, C. R., Hunt, M. C., & Daniel, M. J. (2007). Carbon monoxide headspace activity of modified atmosphere packaged beef steaks. In Proceedings 53rd international congress of meat science and technology (pp. 521–522), 5–10 August 2007, Beijing, China. Reddy, I. M., & Carpenter, C. E. (1991). Determination of metmyoglobin reductase activity in bovine skeletal muscles. Journal of Food Science, 56 , 1161–1164. Renerre, M., & Labadie, J. (1993). Fresh red meat packaging and meat quality. In Proceedings 39th international congress of meat science and technology (pp. 361–387), 1–6 August 1993, Calgary, Canada. Rizvi, S. S. H. (1981). Requirements for foods packaged in polymeric films. Critical Reviews in Food Science and Nutrition, 14(2), 111–134. Robach, D. L., & Costilow, R. N. (1961). Role of bacteria in the oxidation of myoglobin. Applied Microbiology, 9, 529–533. Robbins, K., Jensen, J., Ryan, K. J., Homco-Ryan, C., McKeith, F. K., & Brewer, M. S. (2003). Consumer attitudes towards beef and acceptability of enhanced beef. Meat Science, 65, 721–729. Robertson, G. (1993). Food packaging principles and practice . New York: Marcel Dekker (pp. 431–469). Robertson, G. L. (2006). Food packaging principles and practice(2nd ed.). Boca Raton: Taylor & Francis (pp. 9–42). Rooney, M. L. (1995). Overview of active food packaging. In M. L. Rooney (Ed.),Active food packaging (pp. 1–37). London: Blackie Academic & Professional. Rowe, L. J., Maddock, K. R., OLonergan, S. M., & Huff-Lonergan, E. (2004). Influence of early postmortem protein oxidation on beef quality. Journal of Animal Science, 82, 785–793. Sammel, L. M., Hunt, M. C., Kropf, D. H., Hachmeister, K. A., & Johnson, D. E. (2002). Comparison of assays for metmyoglobin reducing ability in beef inside and outside Semimembranosus muscle. Journal of Food Science, 67 (3), 978–984. Sato, K., & Hegarty, G. R. (1971). Warmed over flavor in cooked meats. Journal of Food Science, 36 , 1098–1102. Savage, A. W. J., Warriss, P. D., & Jolley, P. D. (1990). The amount and composition of the proteins in drip from stored pig meat. Meat Science, 27, 289–303.

64

K.W. McMillin / Meat Science 80 (2008) 43–65

Savell, J. W., Smith, G. C., Hanna, M. O., & Vanderzant, C. (1981). Packaging of beef loin steaks in 75% O2plus 25% CO 2. I. Physical and sensory properties. Journal of Food Protection, 44, 923–927. Sebranek, J. G. (1986). ‘‘Meat is dynamic’ – Factors in controlled atmosphere packs. National Provisioner, 194(19), 10–16. Sebranek, J. G., & Houser, T. A. (2006). Use of CO for red meats: Current research and recent regulatory approvals. In W. S. Otwell, H. G. Kristinsson, & M. O. Balaban (Eds.), Modified atmosphere processing and packaging of fish(pp. 87–101). Ames, Iowa: Blackwell Publishing. Seideman, S. C., & Durland, P. R. (1983). Vacuum packaging of fresh beef: A review. Journal of Food Quality, 6, 29–47. Seideman, S. C., & Durland, P. R. (1984). The utilization of modified atmosphere gas packaging for fresh meat: A review. Journal of Food Quality, 6, 239–255. Seyfert, M., Hunt, M. C., Mancini, R. A., Hachmeister, K. A., Kropf, D. H., & Unruh, J. A. (2004a). Accelerated chilling and modified atmosphere packaging affect colour and colour stability of injection-enhanced beef round muscles. Meat Science, 68, 209–219. Seyfert, M., Hunt, M. C., Mancini, R. A., Hachmeister, K. A., Kropf, D. H., Unruh, J. A., et al. (2005). Beef quadriceps hot boning and modified-atmosphere packaging influence properties of inection-enhanced beef round muscles. Journal of Animal Science, 83, 686–693. Seyfert, M., Hunt, M. C., Mancini, R. A., Kropf, D. H., & Stroda, S. L. (2004b). Internal premature browning in cooked steaks form enhanced beef round muscles packaged in high-oxygen and ultra-low oxygen modified atmospheres. Journal of Food Science, 69 (2), FCT142–FCT146. Seyfert, M., Mancini, R. A., & Hunt, M. C. (2004). Internation premature browning in cooked ground beef patties from high-oxygen modified-atmosphere packaging. Journal of Food Science, 69 (9), C721–C725. Seyfert, M., Mancini, R. A., Hunt, M. C., Tang, J., & Faustman, C. (2007). Influence of carbon monoxide in package atmospheres containing oxygen on colour, reducing activity, and oxygen consumption of five bovine muscles. Meat Science, 75, 432–442. Seyfert, M., Mancini, R. A., Hunt, M. C., Tang, J., Faustman, C., & Garcia, M. (2006). Color stability, reducing activity, and cytochrome c oxidase activity of five bovine muscles. Journal of Agricultural and Food Chemistry, 54, 8919–8925. Sheard, P. R., & Tali, A. (2004). Injection of salt, tripolyphosphate and bicarbonate marinade solutions to improve the yield and tenderness of cooked pork loin. Meat Science, 68, 305–311. Shivas, S. D., Kropf, D. H., Hunt, M. C., Kastner, C. L., Kendall, J. L. A., & Dayton, A. D. (1984). Effects of ascorbic acid on display life of ground beef. Journal of Food Protection, 47, 11–15. Siegel, D. G. (2001). Case ready concepts- packaging technologies. Western science research update conference on technologies for improving the quality and safety of case- ready products, Annual meeting of national meat association, 22 February 2001. Las Vegas, Nevada, USA. Accessed 26.02.08. Silliker, J. H., & Wolfe, S. K. (1980). Microbiologcial safety considerations in controlled-atmosphere storage of meats. Food Technology, 34(3), 59–63. Singh, R. K., & Singh, N. (2005). Quality of packaged foods. In J. H. Han (Ed.), Innovations in food packaging (pp. 24–44). Amsterdam: Elsevier Academic Press. Sitz, B. M., Calkins, C. R., Feuz, D. M., Umberger, W. J., & Eskridge, K. M. (2005). Consumer sensory acceptance and value of domestic, Canadian, and Australian grass-fed beef steaks. Journal of Animal Science, 83(12), 2863–2868. Skibsted, L. H., Bertelsen, G., & Qvist, S. (1994). Quality changes during storage of meat and slightly preserved meat products. In Proceedings 40th international congress of meat science and technology (S-II.MP1 pp. 1–10). 28 August-2 September 1994, The Hague, Netherlands. Smith, P. (2008). Industry mainstay. The National Provisioner, 122(3), 106, 108, 112. Smith, B. S. (2001). The maturation of case-ready technology- operational challenges. In Meat industry research conference (pp. 117–118), 15–17 October 2001, Chicago, Illinois, USA. Smith, J. P., Ramaswamy, H. S., & Simpson, B. K. (1990). Developments in food packaging technology. Part II. Storage aspects. Trends in Food Science and Technology, 1(5), 111–118. Sofos, J. N. (1994). Microbial growth and its control in meat, poultry and fish. In A. M. Pearson & T. R. Dutson (Eds.). Advances in meat research (Vol. 9, pp. 359–403). London: Blackie Academic and Professional. Sørheim, O. (2006). Prospects for utilization of carbon monoxide in the muscle food industry. In W. S. Otwell, H. G. Kristinsson, & M. O. Balaban (Eds.), Modified atmosphere processing and packaging of fish (pp. 103–115). Ames, Iowa: Blackwell Publishing. Sørheim, O., Westad, F., Larsen, H., & Alveike, O. (2007). Critical factors for the colour of ground beef packaged in low oxygen atmospheres. In Proceedings 53rd international congress of meat science and technology (pp. 519–520), 5–10 August 2007, Beijing, China. Spanier, A. M. (1992). Current approaches to the study of meat flavor quality. Developments in Food Science, 29 , 695–709. Stahl, N. Z. (2006). The soft side of case-ready packaging. Meat Processing, 45(4), 41–44. Stahl, N. Z. (2007). New packaging formats drive new products. Meat Processing, 46(5), 40–42. 44. Stanbridge, L. H., & Davies, A. R. (1998). The microbiology of chill-stored meat. In A. Davies & R. Board (Eds.), The microbiology of meat and poultry (pp. 174–219). London: Blackie Academic & Professional. Stanley, D. W. (1991). Biological membrane deterioration and associated quality losses in food tissues. Critical Reviews in Food Science and Nutrition, 30 , 487–553.

Stier, R. F., Ahmed, M. S., & Weinstein, H. (2002). Contraints to HACCP implementation in developing countries. Food Safety Magazine, April–May, 36–40. Stiles, M. E. (1991). Modified atmosphere packaging of meat, poultry and their products. In B. Ooraikul & M. E. Stiles (Eds.), Modified atmosphere packaging of food (pp. 118–147). Chichester, England: Ellis Horwood Limited. Storck, A. B. (2008). Scavenger hunt. Meatingplace, 16(3), 62. 64. Stubbs, R. L., Morgan, J. B., Ray, F. K., & Dolezal, H. G. (2002). Effect of supplemental vitamin E on the color and case-life of top loin steaks and ground chuck patties in modified atmosphere case-ready retail packaging systems. Meat Science, 61, 1–5. Tang, J., Faustman, C., Mancini, R. A., Seyfert, M., & Hunt, M. C. (2006). The effects of freeze-thaw and sonication on mitochondrial oxygen consumption, electron transport chain-linked metmyoglobin reduction, lipid oxidation, and oxymyoglobin oxidation. Meat Science, 74, 510–515. Tarantino, L. M. (2004). Agency response letter GRAS Notice No. GRN 000143. U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition Office of Food Additive Safety, Washington, DC, July 29. Tarantino, L. M. (2005). Agency response letter GRAS Notice No. GRN 000167. U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition Office of Food Additive Safety, Washington, DC, September 29. Tarladgis, B. G., Watts, B. M., Younathan, M. T., & Dugan, L., Jr. (1960). A distillation method for the quantitative determination of malonaldehyde in rancid foods. Journal of the American Oil Chemists Society, 37(1), 44–48. Taylor, A. A. (1985). Packaging fresh meat. In R. Lawrie (Ed.). Developments in meat science(Vol. 3, pp. 89–113). London: Elsevier Applied Science. Tewari, G., Jayas, D. S., & Holley, R. A. (1999). Centralized packaging of retail meat cuts: A review. Journal of Food Protection, 62, 418–425. Tewari, G., Jeremiah, L. E., Jayas, D. S., & Holley, R. A. (2002). Improved use of oxygen scavengers to stabilize the colour of retail-ready meat cuts stored in modified atmospheres. International Journal of Food Science and Technology, 37 , 199–207. Thippareddi, H., & Phebus, R. K. (2007). Modified atmosphere packaging (MAP): Microbial control and quality. Pork Information Gateway Factsheet, 12-05-07, 1-5. Tremonte, P., Sorrentino, E., Succi, M., Reale, A., Maiorano, G., & Coppola, R. (2005). Shelf life of fresh sausages stored under modified atmospheres. Journal of Food Protection, 68(12), 2686–2692. Trout, G. R. (1989). Variation in myoglobin denaturation and color of cooked beef, pork, and turkey meat as influenced by pH, sodium chloride, sodium tripolyphosphate, and cooking temperature. Journal of Food Science, 54 (3), 536–540. 544. Venturini, A. C., Contreras, C. J. C., Sarantópoulos, C. I. G. L., & Villanueva, N. D. M. (2006). The effects of residual oxygen on the storage life of retail-ready fresh beef steaks masterpackaged under a CO 2 atmosphere. Journal of Food Science, 71(7), S560–S566. Verbeke, W., & Vackier, Isabelle. (2004). Profile and effects of consumer involvement in fresh meat. Meat Science, 67, 159–168. Vermeiren, L., Devlieghere, F., & Debevere, J. (2002). Effectiveness of some recent antimicrobial packaging concepts. Food Additives and Contaminants, 19(Supplement), 163–171. Viana, E. S., Gomide, L. A. M., & Vanetti, M. C. D. (2005). Effect of modified atmospheres on microbiological, color and sensory properties of refrigerated pork. Meat Science, 71, 696–705. Vink, R. (2007). Packaging the market for case-ready packaging. Meat International, 17(4), 20–22. Voges, K. L., Mason, C. L., Brooks, J. C., Delmore, R. J., Griffin, D. B., Hale, D. S., et al. (2007). National beef tenderness survey–2006: Assessment of Warner–Bratzler shear and sensory panel ratings for beef from US retail and foodservice establishments. Meat Science, 77, 357–364. Watts, D. A., Wolfe, S. K., & Brown, W. D. (1978). Fate of [ 14 C] carbon monoxide in cooked or stroed ground beef samples. Journal of Agricultural and Food Chemistry, 26(1), 210–214. Weber, C. J., Haugaard, V., Festersen, R., & Bertelsen, G. (2002). Production and applications of biobased packaging materials for the food industry. Food Additives and Contaminants, 19(Suppl.), 172–177. Wicklund, R. A., Paulson, D. D., Tucker, E. M., Stetzer, A. J., DeSantos, F., Rojas, M., et al. (2006). Effect of carbon monoxide and high oxygen modified atmosphere packaging and phosphate-enhanced, case-ready pork chops. Meat Science, 74, 704–709. Wilkinson, B. H. P., Janz, J. A. M., Morel, P. C. H., Purchas, R. W., & Hendriks, W. H. (2006). The effect of modified atmosphere packaging with carbon monoxide on the storage quality of master-packaged fres pork. Meat Science, 73, 605–610. Wolfe, S. K. (1980). Use of CO- and CO 2-enriched atmospheres for meats, fish, and produce. Food Technology, 34(3), 55–58. 63. Wright, L. I., Scanga, J. A., Belk, K. E., Engle, T. E., Tatum, J. D., Person, R. C., et al. (2005). Benchmarking value in the pork supply chain: Characterization of US pork in the retail marketplace. Meat Science, 71, 451–463. Xia, X., Kong, B., Xiong, Y. L., & Meng, X. (2007). Extending the shelf-life of chilled pork by combination of chitosan coating with spice extracts. In Proceedings 53rd international congress of meat science and technology (pp. 457–458), 5– 10 August 2007, Beijing, China. Xiong, Y. L. (1996). Impacts of oxidation on muscle protein functionality. In Proceedings 49th reciprocal meat conference (pp. 79–86), 9–12 June 1996, Provo, Utah, USA. Xiong, Y. L., & Decker, E. A. (1995). Alterations in muscle protein functionality by oxidative and antioxidative processes. Journal of Muscle Foods, 6, 139–160.

K.W. McMillin /Meat Science 80 (2008) 43–65 Yam, K. L., Takhistov, P. T., & Miltz, J. (2005). Intelligent packaging: Concepts and applications. Journal of Food Science, 70 (1), R1–R10. Yin, M. C., Faustman, C., Riesen, J. W., & Williams, S. N. (1993). a-Tocopherol and ascorbate delay oxymyoglobin and phospholipid oxidation in vitro. Journal of Food Science, 58 , 1273–1276. 1281. Young, L. L., Reviere, R. D., & Cole, A. B. (1988). Fresh red meats: A place to apply modified atmospheres. Food Technology, 42(9), 65–66. 68. Zakrys, P. I., Hogan, S. A., O’Sullivan, M. G., Allan, P., & Kerry, J. P. (2007). Effects of oxygen concentration on the quality of beef steak packed under modified atmosphere. In Proceedings 53rd international congress of meat science and technology (pp. 525–526), 5–10 August 2007, Beijing, China.

65

Zakrys, P. I., Hogan, S. A., O’Sullivan, M. G., Allen, P., & Kerry, J. P. (in press). Effects of oxygen concentration on the sensory evaluation and quality indicators of beef muscle packed under modified atmosphere. Meat Science, doi:10.016/ j.meatsci.2007.10.030. Zarate, J. R., & Zaritzky, N. E. (1985). Production of weep in packaged refrigerated beef. Journal of Food Science, 50 , 155–159. 191. Zhao, Y., Wells, J. H., & McMillin, K. W. (1994). Applications of dynamic modified atmosphere packaing systems for fresh red meats: A review. Journal of Muscle Foods, 5, 299–328. Zhao, Y., Wells, J. H., & McMillin, K. W. (1995). Dynamic changes of headspace gases in CO2and N packaged fresh beef. Journal of Food Science, 60 , 571–575. 591. 2