Safety of Goat Milk Products

Safety of Goat Milk Products

Young W. Park Georgia Small Ruminant Research & Extension Center Fort Valley State University, Fort Valley, GA Introduction Producing high quality raw milk is of paramount importance for successful production, processing, and marketing of milk and its manufactured products. Milk and its products must be safe to consume, free of pathogenic bacteria, antibiotic, insecticide, and herbicide compounds. They should have good and no objectionable flavor, be free of spoilage bacteria, and contain legal minimum amounts of all nutrients. All standards and regulations pertaining to production, manufacturing, and marketing of milk and dairy products in the U.S. are described in the publication of the federal government (FDA: Food and Drug Administration), which is called the Grade “A” Pasteurized Milk Ordinance (PMO). The PMO has been developed and evolved from earlier publications from the US Surgeon General (US Public Health Service), and contains great details about the requirements of sanitary facilities, equipment, and practices for the production of safe and quality cow milk. It also describes definitions of nutritional standards including inspection requirements and score cards, and states in section 1-I that “Goat milk is the lacteal secretion, free from colostrum, obtained by the complete milking of healthy goats, and shall comply with all the requirements of this ordinance. The word ‘milk’ shall be interpreted to include goat milk”. In the European Union, similar standards are enforced such as Codex or IDF (International Dairy Federation) regulations. Further information on the PMO and other regulations regarding goat milk can be found in the PMO 2011. Quality of milk can be determined by parameters evaluating suitability of raw milk for consumption, processing the milk for dairy products, and health status of individual animals producing the milk. In this perspective, milk quality may be evaluated through measuring total bacteria count or the presence of specific types of bacteria, and somatic cell count (SCC) or numbers of leukocytes per milliliter of milk. Differential somatic cell count by using flow cytometry procedure can be used for the evaluation of udder health and leukocyte cell types in milk. Numerous studies, mostly on cow milk, have demonstrated that an increase in SCC causes a decrease in milk yield and affects milk composition, which results in reduced cheese making suitability. However, the effect

of SCC on milk yield, composition, and cheese making ability has not been well-studied in goat and sheep milk which are mainly used for cheese manufacture. Composition and yield of milk are influenced by many factors, which have direct effects on the quality of milk and its processed products. Diet, breed, parity, stage of lactation, type of birth, disease, estrus, diurnal, monthly, seasonal variations, and environmental temperature significantly contribute to changes in SCC in goat and sheep milk. These factors may explain 48% of SCC variance. The purpose of this chapter is to review and delineate the key issues involved in milk quality standards and quality control, production and processing of quality milk and its products in relation to human consumption, well-being, and nutrition.

Production of Quality Goat Milk

Basic principles to produce quality milk

Production of high quality raw milk is the prerequisite for successful manufacture and marketing of milk and dairy products. Production of high quality milk products for all dairy species largely depends on workers at the farm and dairy processing plants, product distributors, and retail outlets. Quality milk production must start at the farm level, because flavor and quality of the milk cannot be improved later in the processing stages. The general principle of quality dairy production is that the better the raw milk, the better the processed products The fresh milk drawn from the mammary glands is highly perishable, and its quality is easily deteriorated or negatively affected by many factors such as feeding, handling of animals prior and during milking, handling of the milk during and after milking, cooling, transportation, pasteurization, processing, packaging, and processing utensils, etc. A clean environment in the milking parlor and milking barn is just as important as the composition of the raw milk. Milk can be rapidly degraded because it is a highly desirable environment and nutritious medium for bacterial growth. Good quality milk should not have too numerous basic bacterial flora and also should not contain harmful pathogens or microorganisms likely to damage the cultured dairy products. In addition, it Page 243

Safety of Goat Milk Products

should be free of foreign substances such as antibiotics, antiseptics, or pesticide residues. At least five major parameters are routinely monitored by various regulatory and government agencies at commercial milk production farms and processing plants in order to safeguard quality milk production. These parameters include: (i) nutritional constituents in milk, (ii) somatic cell counts as related to mastitis, (iii) bacteria counts as related to sanitary practices, (iv) adulteration and pesticide residue contents, and (v) flavor, taste, appearance and temperature. Freshly produced goat milk can have off-flavors. These off-flavors in raw goat milk may be caused by the feeds, weeds, forages, chemicals, building materials, colostrum, estrus, mastitic milk, filthy utensils and strainer, unclean milking equipment, slow cooling, odors from bucks, barn and/or milk room. Feeding odorous feeds, such as pasture containing garlic, less than 2 hours before milking is not recommended. Short-chain free fatty acids, such as butyric, capric, caproic, and caprylic acids are considered to cause goaty and rancid flavors. These short-chain fatty acids can be generated by lipase (an enzyme that breaks down fats) in goat milk due to improper milking procedures and cooling. The production of good quality goat milk can be achieved only through good management practices of the entire farm system. Therefore, the production of high quality goat milk requires the recommended milking practices in a daily routine, maintain functioning and sanitary equipment, have healthy animals, and use recommended detergent, acid and sanitizers for cleaning and milking equipment.

Regulatory standards for quality milk There are at least four important requirements for Grade “A” milk quality. Those are: i) safe to drink, ii) good flavor, iii) relatively free from spoilage bacteria and somatic or body cells, and iv) composition. In addition to these requirements, PMO requirements for SCC must be met to produce Grade “A” milk. It must be stressed that good flavor of raw goat milk comes from clean, healthy, properly managed dairy goat herds. The ideal flavor is slightly sweet and slightly salty with complete absence of strong odors and flavors. Oxidized flavor is attributed to churning of milk in high pipelines in milking parlors, elbows in pipelines, nutritional imbalances of the dairy animals, or exposure of the bottled milk to light. All milk, especially goat milk, can develop rancid, off- or goaty-flavor when the milk fat is partially disintegrated by lipase enzyme action. Proper rapid cooling after milking, pasteurization, and protec-

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tion of the milk from sun and UV light can prevent the milk from the off-flavors. All Grade “A” pasteurized milk and milk products must be produced, processed, and pasteurized to conform with the specific PMO codes. Standard milk composition for the fluid milk market refers to the levels of major nutrients such as fat, protein, lactose, and minerals. The 2011 PMO states regarding goat milk that “Goat milk sold in retail packages shall contain not less than 2½ percent milk fat and not less than 7½ percent milk solids not fat.” Regulatory standards for production of quality raw and pasteurized milk can be set by local and state level regulatory agencies, based on FDA PMO codes and regulations. An example of regulatory standards for the chemical, bacteriological, and temperatures, and the sanitation requirements by the Colorado Department of Health (1980) is shown in Table 1. In addition, the quality control guidelines for microbiological standards in dairy foods are also presented in Table 2. These regulations and guidelines on cow milk may be applied to goat milk. There are many laboratory testing procedures to control contamination with water, dirt, antibiotics, off-flavors, thermoduric (surviving pasteurization), psychrotrophic and coliform bacteria, etc. These milk quality parameters include but are not limited to physico-chemical and enzymatic indices as well as specific milk components, including specific gravity, freezing point, Soxhlet-Henkel (SH) value, titratable acidity, redox potential, electrical conductivity, and enzyme levels (i.e., alkaline phosphatases, lipoprotein lipases and proteinases) of the milk. In addition to visual inspections by the tank truck driver upon loading milk from farms, daily laboratory tests are performed for nutritional contents and whether the delivered milk at the processing plant meets physical and bacterial requirements. Each truck load is sampled and tested for seven criteria before it can be unloaded, which are: 1. Visual color and physical condition (normal), 2. Flavor (absence of off-flavors), 3. Temperature (below 5°C), 4. Dirt and sediment score (low), 5. Cryoscopic check on water contamination (-0.530 to –0.550°C), 6. Freedom of antibiotics, and 7. Somatic cell count (below 1.5 million for goat milk, below 400,000 for cow milk). A state inspector and a veterinarian visit dairy farms at least once a year to review facilities, milking conditions using a detailed 100 point score card, and the health of the dairy animals and their udders, respectively. A federal inspector may also visit the farm each year. In addition, most milk processing companies provide incentive payments

Safety of Goat Milk Products Table 1. Chemical, Bateriological, and Temperature Standards.a Grade A raw milk for pasteurization Temperature

Cooled to 45°F (7°C) or less within 2 hours after milking, provided that the blend temperature after the first and subsequent milkings does not exceed 50°F (10°C).

Bacterial limits

Individual producer milk not to exceed 100,000 per ml prior to commingling with other producer milk. Not to exceed 300,000 per ml as commingled milk prior to pasteurization.

Antibiotics

Individual producer milk: No detectable zone with the Bacillus subtilies method or equivalent. Commingled milk: No detectable zone by the Sarcina lutea Cylinder Plate Method or equivalent.

Somatic cell count

Individual producer milk. Not to exceed 1,500,000 per ml.

Grade A pasteurized milk and milk products Temperature

Cooled to 45°F (7°C) or less and maintained thereat.

Bacterial limits

20,000 per ml.*

Coliform

Not to exceed 10 per ml: Provided that , in the case of bulk milk transport tank shipments, shall not exceed 100 per ml.

Phosphatase

Less than 1 microgram per ml by the Scharer Rapid Method or equivalent.

Antibiotics

No detectable zone by the Sarcina lutea Cylinder Plate Method or equivalent

*Not applicable to cultured products. Data from Colorado Department of Health. 1980. Colorado Grade A Pasteurized Fluid Milk and Milk Products Regulations, Denver, CO. a

to producers for meeting or exceeding minimum nutrient contents and bacterial standards, or deductions in payment for failing to meet these requirements.

Raw vs. Pasteurized Milk Products in Food Safety Perspectives

Raw milk

Raw milk of major dairy species such as cows, goats and sheep milk contains some major pathogens including

Staphylococcus aureus, Salmonella, Listeria monocytogenes and E. coli. It is practically impossible to eliminate pathogenic bacteria from raw milk. Microbiological contaminations in raw milk can be originated from the milking animal itself, the farm and milking personnel, the environment, water supply, and milking equipment, etc. There have been numerous incidences of the outbreak of foodborne illnesses due to consumption of raw milk which was contaminated with different types of harmful pathogens. Somatic cell counts (SCC) is the degree of glandular irritation or infection in mammary gland, where the

Table 2. Quality control guidelines for microbiological standards in dairy foods. Product Standard plate Coliform Psychrotrophic Yeast Staphycount SPC after 5 days and lococci at 70°F (21°C) mold

Salmonella

Raw milk- Bulk tankers