Article

Ultraviolet-C light effect on physicochemical, bioactive, microbiological, and sensorial characteristics of carrot (Daucus carota) beverages ´ ndez-Carranza1, Irving Israel Ruiz-Lo ´ pez1, Paola Herna ´ ngel Guerrero-Beltra ´A ´ n3, Francisco Manuel Pacheco-Aguirre2, Jose 4 4 ´ vila-Sosa and Carlos Enrique Ochoa-Velasco ´l A Rau

Abstract The aim of this research was to evaluate the effect of ultraviolet-C light on physicochemical, bioactive, microbial, and sensory characteristics of carrot beverages. Beverages were formulated with different concentrations of carrot juice (60, 80, and 100% [v/v]) and treated with ultraviolet-C light at different flow rates (0, 0.5, 3.9, and 7.9 mL s1) and times (5, 10, 15, 20, and 30 min), equivalent to ultraviolet-C dosages of 13.2, 26.4, 39.6, 52.8, and 79.2 J cm2. Total soluble solids, pH, and titratable acidity were not affected by the ultravioletC light treatment. Ultraviolet-C light significantly affected (p < 0.05) color parameters of pure juice; however, at low concentration of juice, total color change was slightly affected (
E ¼ 2.0  0.7). Phenolic compounds (4.1  0.1, 5.2  0.2, and 8.6  0.3 mg of GAE 100 mL1 of beverage with 60, 80, and 100% of juice, respectively) and antioxidant capacity (6.1  0.4, 8.5  0.4, and 9.4  0.3 mg of Trolox 100 mL1 of beverage with 60, 80, and 100% of juice, respectively) of carrot beverages were not affected by ultraviolet-C light treatment. Microbial kinetics showed that mesophiles were mostly reduced at high flow rates in carrot beverages with 60% of juice. Maximum logarithmic reductions for mesophiles and total coliforms were 3.2  0.1 and 2.6  0.1, respectively, after 30 min of ultraviolet-C light processing. Beverages were well accepted (6–7) by judges who did not perceive the difference between untreated and Ultraviolet-C light treated beverages.

Keywords Ultraviolet-C light, carrot beverage, bioactive compound, microbial load Date received: 5 June 2015; accepted: 11 January 2016

INTRODUCTION Carrot is an important vegetable for human diet, and its consumption is increasing due to its characteristic taste and flavor related to non-volatile (free sugars, phosphates, nitrogenous compounds, and organic acids) and volatile compounds (terpenes and sesquiterpenes) (Howard et al., 1995; Simon, 1985). Moreover, it is a source of dietary fiber and bioactive compounds such as phenolic acids (chlorogenic, caffeic, p-hydroxybenzoic, ferulic, and cinnamic acids, among others phenolic compounds), Food Science and Technology International 22(6) 536–546 ! The Author(s) 2016 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1082013216631646 fst.sagepub.com

carotenoids (b-carotene, lycopene, and lutein), vitamins (A and C), and minerals (Alasalvar et al., 2005;

1

Food Engineering, Chemical Engineering Department, ´rita Universidad Auto ´ noma de Puebla, Ciudad Beneme Universitaria, Puebla, Mexico 2 ´rita Universidad Chemical Engineering Department, Beneme ´noma de Puebla, Ciudad Universitaria, Puebla, Mexico Aute 3 Chemical, Food and Environmental Engineering Department, ´ricas, Puebla, Cholula, Mexico Universidad de las Ame 4 ´rita Biochemistry-Food Department, Beneme Universidad ´ noma de Puebla, Ciudad Universitaria, Puebla, Mexico Auto Corresponding author: Carlos Enrique Ochoa-Velasco, Biochemistry-Food Department, ´rita Universidad Auto ´ noma de Puebla, Ciudad Beneme Universitaria, Av. San Claudio y 18 Sur., Puebla, Pue., Mexico. Email: [email protected]

´ndez-Carranza et al. Herna Sun et al., 2009) that may help to human health. Some of these compounds are anticarcinogenic, antiulcer, antiaging, and antioxidants that may improve the immune system (Leja et al., 2013; Sant’Ana et al., 1998). The main problem of carrot and its products (like juice) is the high microbial count because they are covered with soil during their growth. Carrot juice is a low acid food (pH 6.0), which could be easily contaminated with microorganisms; therefore, severe thermal treatments are required that may affect desirable characteristics of these beverages (Park et al., 2002). One of the most important products of fruits and vegetables are juices and nectars; these beverages have high nutritional value (natural or enriched) related to vitamins, pigments, and minerals (Cassano et al., 2003). According to the Association of the Industry of Juices and Nectars (2014), juice and nectar production in 2013 was over 11,000 million of liters, being orange, apple, pineapple, and peach the main fruits used. Several countries consume vegetal beverages with different concentration of juice formulated with flavorings, organic acids, colorants, essences, and water (CODEX, 1964) that increase the demand of juice and nectar production. Currently, food trends are focused on high-quality products (nutritious, fresh-like, safe, natural, organic, and free from artificial additives) with minimal processing or ready-to-eat products (Koutchma, 2009). Moreover, consumers demand products with functional characteristics, such as beneficial microorganisms, antioxidant properties, free from toxical compounds, among others (Welti-Chanes et al., 2009). Ultraviolet-C (UV-C) light treatment is a non-thermal technology commonly used for disinfection of water, air, and surfaces (Koutchma et al., 2004). Food and Drug Administration (FDA) (2001a) approved UV-C light as a cold pasteurization process, advising that treatments should reach at least 5 log reduction of a pathogen capable to grow in food products. Ultraviolet process, as a physical treatment, does not generate chemical residues in foods (Guerrero-Beltra´n and Barbosa-Ca´novas, 2004; Koutchma, 2008). UV-C light has been used in juices mainly to inactivate microorganisms (pathogens, spoilages, or native flora) and to evaluate its effect on some physicochemical characteristics (soluble solids, pH, acidity, and color) and functional compounds (phenols, pigments, vitamins, and antioxidant capacity). Nevertheless, there are few studies that evaluated the stability and shelf-life of UV-C light treated products (Guevara et al., 2012; Keyser et al., 2008; Ochoa-Velasco and GuerreroBeltra´n, 2013; Ochoa-Velasco et al., 2014; Pala and Toklucu, 2011; Torkamani and Niakousari, 2011). Some researchers indicated that UV-C light has a potential application in juices and nectars industries due to the low cost of processing (Bintsis et al., 2000;

Guerrero-Beltra´n and Barbosa-Ca´novas, 2004). Consequently, different authors have designed and validated the equipment efficacy in order to accomplish some targets: to reduce energy requirements, achieve adequate logarithmic microbial reductions, and avoid food damage. Until now, there are no reports about the effect of UV-C light on carrot beverages; therefore, the aim of this research was to evaluate the effect of UV-C light on quality parameters of carrot beverages with different concentrations of juice.

MATERIALS AND METHODS Carrot beverages Carrots were acquired in a local market in Puebla (Mexico) and selected free from physical and microbial damages. Carrots were washed with distilled water and sanitized for 10 min with hypochlorite sodium (100 ppm) solution (FDA, 2001b). Carrot juice (0.5 L for each kg of carrot) was extracted using an electrodomestic food processor (Turmix, Switzerland), and then juice was sieved (0.5 mm of mesh size). Beverages were prepared using different carrot juice concentrations (60, 80, and 100% [v/v]); sucrose and citric acid were added to adjust total soluble solids (TSS) and pH similar to carrot juice (100%). Beverages were divided in two batches (replicate of UV-C treatment) and stored at 4 C until used (8–10 h). UV-C light equipment Annular UV-C light equipment used in this study was designed and assembled at the Benemerita Universidad Autonoma de Puebla (BUAP), Puebla, Mexico. Contrary to the observed in others UV-C light designs in which juice cooling is performed in a double wall glass vessel before processing, in our equipment lamps and treatment tubes are immersed in a cold water bath (5 C); therefore, the beverage is treated at constant low temperature. The equipment was made of stainless steel and consisted in (a) receiving tank, (b) Master Flex peristaltic pump (Vernon, Illinois, USA), (c) three UV-C lamps immersed in a (d) recirculating water bath, and a (e) refrigeration system (Figure 1). UV-C lamps (254 nm; 12 W UV-C output) were acquired from TodoAgua (SLP, Mexico) and provide a nominal dose of 0.044 W cm2. UV-C lamp was inserted in a quartz sleeve of 29.3 cm and 2.3 cm of length and external diameter, respectively, and an outer stainless steel sleeve of 29.5 and 4.8 cm of length and internal diameter, respectively. The volume of each lamp was 0.4 L. Lamp intensity was measured on surface (similar to the carrot beverage treatment) using a light meter digital radiometer (model DT-1309 with an interface RS-232, London, UK). UV-C light doses treatment were 537

Food Science and Technology International 22(6) where Lo*, ao*, and bo* are color parameters of the untreated carrot beverages; L*, a*, and b* are color parameters after 30 min of treatment. Phenolic compounds

Figure 1. Annular UV-C light equipment designed and assembled (a) receiving tank, (b) peristaltic pump, (c) three UV-C lamps immersed in a (d) recirculating water bath, and a (e) refrigeration system at the Benemerita Universidad Autonoma de Puebla, Mexico.

calculated according to the next equation

F¼It

ð1Þ 2

where F is the UV-C irradiation doses (J cm ), I is the lamp intensity (W cm2), and t is the processing time (min or s). UV-C light processing Carrot beverages (1.5 L) were processed for 30 min at different flow rates (0.5, 3.9, and 7.9 mL s1). Samples were collected at 5, 10, 15, 20, and 30 min of processing equivalent to dosages of 13.2, 26.4, 39.6, 52.8, and 79.2 J cm2, respectively. After processing, beverages were immediately analyzed in physiochemical, antioxidants, and microbiological characteristics. Untreated beverages were used as control. The process was performed in duplicate and each analysis in triplicate. TSS, pH, and acidity TSS, pH, and titratable acidity were analyzed according to the 932.12, 981.12, and 942.15 methods (AOAC, 2000), respectively. Color Hunter L*, a*, and b* scale color parameters of beverages were evaluated, using a Colorflex M 6405 (HunterLab, Reston, Virginia, USA) colorimeter in reflectance mode. In order to evaluate the effect of the UV-C light treatment on color carrot beverages, total color change (
E) was calculated using the next equation

qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi  2  2  2
E ¼ L  L0 þ a  a0 þ b  b0 538

ð2Þ

Total phenolic compounds were analyzed according to Gao et al. (2000) methodology with modifications. One milliliter of Folin and Ciocalteu reagent (Sigma– Aldrich Inc., Toluca, Mexico) was mixed with 1 mL of carrot beverage, and after 3 min, 1 mL of 0.5% Na2CO3 (Sigma–Aldrich Inc., Toluca, Mexico) was added. The mixture was stored for 30 min in darkness at room temperature. Phenolic compounds were evaluated using an UV-Vis Jenway spectrophotometer model 6405 (Staffordshire, UK) at 765 nm. Total phenolic compounds were calculated as Gallic acid (Sigma– Aldrich Inc., Toluca, Mexico) equivalents (GAE) per 100 mL of juice using the following standard curve

GAE Abs  b ¼  100 100 mL m

ð3Þ

where Abs is the absorbance of sample, b is the intercept, and m is the slope (mL GAE1) of the linear regression. The equation of Gallic acid standard curve was Abs ¼ 0.0327 (mL mg GAE1)  (mg GAE mL1) 0.1238 (R2 ¼ 0.994). Antioxidant capacity Two milliliters of DPPH (2,2-diphenyl-1-picrylhidrazyl) radical (0.004% in ethanol) were mixed with 2 mL of carrot beverage. The mixture was stored for 30 min at room temperature in darkness. The absorbance was measured at 517 nm using a UV-Vis spectrophotometer. The antioxidant capacity was calculated as Trolox equivalents (6-hydroxy-2,5,7,8 tetramethylchroman-2-carboxylic acid) per 100 mL of juice using the following standard curve

mg Trolox Abs  b ¼  100 100 mL m

ð4Þ

where Abs is the absorbance, b is the intercept, and m is the slope (mL mg Trolox1) of the linear regression. The equation of Trolox standard curve was Abs ¼4.809 (mL Trolox1)  (mg Trolox mL1) 4.5113 (R2 ¼ 0.991). Microbial counts Microbial count was evaluated as follows: 10 mL of beverage were diluted with 90 mL of peptone water (BD Bioxon, Mexico City, Mexico). Serial dilutions were performed. One milliliter of the adequate dilution

´ndez-Carranza et al. Herna of juice was placed in Petri dishes and mixed with about 15 mL of standard plate count and VRBA agars (BD Bioxon) for counting mesophiles and total coliforms (pour plate technique), respectively. Petri dishes were incubated at 35  2 C for 24–48 h before counting microorganisms as colony forming units per milliliter (CFU mL1). Microbial reduction Microbial reduction was evaluated by plotting log Nt  N1 (Nt is the microbial count [CFU mL1] at a 0 given time, and No is the initial microbial count [CFU mL1]) versus treatment time (t). Microbial reduction was analyzed using the first-order (equation (5)), Duv (equation (6)), and Weibull (equation (7)) models



 Nt ¼ kt ¼ kF log N0 Duv ¼ 

1 k

 Nt log ¼ btn N0

ð5Þ

ð6Þ



Weibull parameters. Analysis of variance was performed by Minitab 15 software (Minitab Inc., PA, USA, 2008). Differences between treatment means were analyzed by the Tukey’s comparison test (p < 0.05).

RESULTS AND DISCUSSION TSS, pH, and acidity Initial TSS, pH, and acidity of carrot juice were 7.3  0.03%, 6.1  0.1, and 0.09  0.01% (citric acid), respectively. TSS, pH, and acidity at the end of UV-C light treatments were 7.3  0.3%, 6.2  0.1, and 0.09  0.02%, respectively. No significant changes (p > 0.05) were obtained between treated and untreated carrot juices. Similar results were observed in carrot beverages with 80% (6.9  0.2 to 6.6  0.1, 6.5  0.0 to 6.5  0.0, and 0.06  0.01 to 0.06  0.02 for TSS, pH, and acidity, respectively), and 60% of juice (5.8  0.1 to 5.9  0.1, 6.3  0.0 to 6.3  0.1, and 0.06  0.00 to 0.06  0.01 for TSS, pH, and acidity, respectively). Several researchers pointed out that UV-C light (254 nm) does not affect physicochemical characteristics of different fruit juices (Caminiti et al., 2012; Noci et al., 2008; Tran and Farid, 2004).

ð7Þ

where k (slope, m) is the inactivation rate constant (min1 or cm2 J1), and F is the UV-C doses (J cm2). Duv is the decimal reduction time (min or s) required to inactivate 90% of the microorganisms at constant UV-C dosage. The b (inactivation rate) and n (resistance of microorganisms to the treatment) are the parameters of the Weibull model. If n is equal to 1 the Weibull model becomes a first-order model, if n is lower than 1 (concave curves) the microorganisms become more resistant to the UV-C treatment having the ability to adapt to applied treatment, and if n is higher than 1 (convex curves), the microorganisms become more sensitive (increasingly the damaged) to the UV-C treatment. Sensorial evaluation UV-C light treated and untreated carrot beverages were sensorial evaluated using an affective hedonic scale of 9 points according to Larmond (1987), where 9 means ‘‘like extremely’’ and 1 ‘‘dislike extremely.’’ Ten milliliters of carrot beverages were given to 80 untrained judges to evaluate their aroma, color, flavor, and overall acceptability. Statistical analysis Microsoft Excel Program (Microsoft Inc. Redmond, WA) was used to calculate the first-order, Duv, and

Color Table 1 shows the L*, a*, and b* color parameters of UV-C light treated and untreated carrot beverages. In beverage with 60% of carrot juice there were not significant (p > 0.05) changes in color parameters due to UV-C light treatment at any flow rate. However, increasing the carrot juice concentration increased the effect of UV-C light, especially in a* and b* color parameters. It is important to note that color parameters decreased indicating a reduction in lightness, red, and yellow colors. Total color change (
E) was calculated to observe the effect of UV-C light on color of carrot beverages, which indicates the magnitude of color difference between untreated and UV-C light treated carrot beverages. The average of total color changes was 2.0  0.7, 2.4  1.4, and 5.9  2.1 in UV-C light treated (30 min) carrot beverages with 60, 80, and 100% of juice, respectively. Lee and Coates (2003) informed that total color changes higher than 2 are visually noticeable. Higher change in color carrot beverage (100%) is related to higher content of carotenoids (b-carotene, a-carotene) and xanthophylls (the main pigments of carrots), pigments that are extremely susceptible to degradation due to different factors such as temperature, radiation, and oxygen (Britton, 1992; Leja et al., 2013). It was also observed that lower flow rates may affect more color changes of carrot beverages, and this could be because lower flow rates of UV-C light processing may cause higher residence time of 539

540

5.2  0.1 4.2  0.5

beverages in the system; therefore, more photodegradation may affect conjugated bonds of organic molecules (Koutchma, 2009; Pala and Toklucu, 2013). GuerreroBeltra´n et al. (2009) pointed out that higher flow rates reduced color changes in grape juice. Phenolic compounds and antioxidant capacity

Average  standard deviation. Different letters within the same column for each juice concentration indicate significant difference (p < 0.05).

a

39.9  0.3b 40.6  0.2b 30

40.1  0.2b

16.1  0.1b

15.3  0.1b

15.0  0.1b

39.7  0.1b

38.6  0.4b

39.0  0.3b

8.2  0.1

1.4  0.1

0 0 0 42.4  0.1a 41.7  0.3a 44.7  0.1a 18.7  0.1a 17.7  0.1a 41.6  0.1a 41.6  0.2a 43.2  0.3a 100

0

36.4  0.3a 37.1  0.5a 30

36.5  2.3a

22.0  0.0a

0

4.0  0.5 1.9  0.3 35.0  0.0b 33.2  0.2b 36.7  0.1b 12.4  0.0b 10.5  0.0b

0 35.9  0.1a 35.6  0.2a 35.0  0.2a 13.4  0.1a 12.8  0.0a 11.9  0.2a 36.8  0.4a 36.4  0.2a

34.2  1.6a

80

36.5  1.3a 0

30

60

0

36.4  0.3a

12.2  0.1a

1.2  0.2 2.4  0.6

0

0 0

2.5  1.1 32.2  1.0a

32.9  0.7a 33.0  1.3a

33.7  0.2a 32.3  0.2a

32.5  0.4a 12.1  1.1a

12.0  0.5a 11.8  0.1a

11.1  1.1a

36.3  0.3a 36.6  0.2a

10.6  0.4a 36.5  0.4a 35.8  1.2a

11.3  0.3a

0

7.9 3.9 0.5 0.5 7.9 3.9 0.5 7.9 3.9 0.5 (mL s1) Time (min) Juice (%)

a L

Color parameters

Table 1. Color parameters of carrot beverages treated with UV-C light at different flow ratea

b

3.9

7.9


E

Food Science and Technology International 22(6)

Figure 2 illustrates the amounts of phenolic compounds (a) and antioxidant capacity (b) of UV-C light treated and untreated carrot beverages. As observed, phenolic compounds increased from 4.1  0.1 mg of GAE 100 mL1 in beverage with 60% of carrot juice to 8.6  0.3 mg of GAE 100 mL1 in carrot juice (100%). UV-C light treatment did not have a significant effect (p > 0.05) on phenolic compounds of carrot juice at the three flow rates. UV-C light effect on phenolic compounds in liquid foods has not been clarified. Noci et al. (2008) reported that UV-C light negatively affected the phenolic compounds content in apple juice, reducing 29% of them compared to fresh apple juice. Other researchers have reported that phenolic compounds were not affected by UV-C light treatment (Caminiti et al., 2012; Ochoa-Velasco and GuerreroBeltra´n, 2013). Falguera et al. (2014) reported that UV-C light may increase phenolic compounds of different pear juices; they pointed out that UV-C light might break complex phenolic polymers releasing simple phenolic compounds that can interact mostly with Folin and Ciocalteu reagent. Antioxidant capacity (Figure 2(b)) was higher in 100% carrot juice than in beverages, and it varied from 6.1  0.4 to 9.4  0.3 mg of Trolox 100 mL1 (53.4–85.0% of inhibition of DPPHþ radical). Values obtained in this study were similar to those obtained by Wootton-Beard et al. (2011); they reported inhibition of DPPH radical of 57.8 and 82.2% for two different organic carrot juices. UV-C light treatment did not significantly affect (p > 0.05) the antioxidant capacity of carrot beverages at the three flow rates. Results in this study were similar to those reported by other researchers (Noci et al., 2008; Pala and Toklucu, 2011). Microbiological reduction The initial microbial counts in carrot beverages were (2.98  0.30)  105 (5.47 log) and (1.42  0.18)  105 (5.15 log) CFU mL1 for mesophiles and total coliforms, respectively. Figure 3 shows the log reduction of mesophiles (a) and total coliforms (b) using the firstorder and Weibull models of carrot beverages treated with UV-C light. As observed, increasing processing time increases mesophiles and total coliforms reductions (Figure 3). Juice concentration significantly affected (p < 0.05) log reduction of microorganisms in

´ndez-Carranza et al. Herna

Figure 2. Phenolic compounds (a) and antioxidant capacity (b) of carrot beverages untreated and treated with UV-C light. Bars in treatments indicate standard deviations.

carrot beverages. Maximum mesophiles reduction (3.2 log CFU mL1) was observed at low juice concentration (60%) and the highest flow rate (7.9 mL s1) for 30 min of UV-C light treatment. The major reduction (2.6 log CFU mL1) for total coliforms (Figure 3(b)) was observed in beverages with 60 and 80% of carrot juice at a flow rate of 3.9 mL s1 after 30 min. It is well known that UV-C irradiation is absorbed by the DNA of microorganisms causing a cross-linking between neighboring thymine and cytosine in the same DNA strand, inhibiting the cell replication and transcription, causing death (Guerrero-Beltra´n and Barbosa-Ca´novas, 2004). The efficacy of UV-C light on liquid foods is related to their color, lightness, turbidity, UV-C light

transmittance, and types of microorganisms in their composition (Guerrero-Beltra´n and Barbosa-Ca´novas, 2004). Pala and Toklucu (2011) reported maximum log reductions of 0.79 and 0.2 for mesophiles and molds and yeasts, respectively, in pomegranate juice, treated at a dosage of 12.6 J mL1. At the same dosage, in grape juice, log reductions were 3.59 and 2.89 for total count and molds plus yeasts, respectively (Pala and Toklucu, 2013). Ochoa-Velasco and Guerrero-Beltra´n (2013) reported 1.76 log reductions for mesophiles in pitaya (Stenocereus griseus) juice treated at 1.026 kJ m2. At the same treatment conditions, the maximum reduction in coconut milk was 4.1 log for both Escherichia coli and Salmonella typhimurium (Ochoa-Velasco et al., 2014). 541

Food Science and Technology International 22(6)

Figure 3. Microbial reduction of mesophiles (a) at 7.9 mL s1 and total coliforms (b) at 3.9 mL s1 of carrot beverages treated with UV-C light during 30 min at different juice concentration (60 ¨, 80 #, and 100% ~). Points in figures mean real data, continuous and discontinuous lines show tendency with first-order and Weibull models, respectively. Bars in treatments indicate standard deviations.

Inactivation kinetics Microbial inactivation parameters for mesophiles and total coliforms in carrot beverages treated with UV-C light are shown in Tables 2 and 3, respectively. These kinetic parameters can be used to evaluate the time required for reach the 5 log reduction demanded by FDA (2001a) and to evaluate the possible effect of UV-C light on microorganisms. In general, first-order kinetics modeling showed adequate fitting of experimental data of microbial inactivation with UV-C light. Although some curves did not fit well with the first-order model, Duv values varied from 9.9  0.2 to 542

16.8  0.7 and from 11.4  0.0 to 20.9  2.7 minutes, for mesophiles (Table 2) and total coliforms (Table 3), respectively. It is important to note that in both types of microorganisms, the flow rate significantly affected (p < 0.05) the time to reduce one logarithmic cycle. In general, the higher the flow rates reduced the time (Duv) to inactivate 90% of microorganisms. Mesophiles and coliforms inactivation kinetics showed differences probably because gram-negative bacteria are less sensitive to UV-C light treatment (Rowan et al., 1999); therefore, low variation in juice concentration or flow rate may greatly affect microbial load. As observed in tables and

´ndez-Carranza et al. Herna Table 2. Kinetic parameters of the mesophiles reduction in carrot beverages treated with UV-C lighta Flow rate (mL s1)

Concentration (%)

0.5

60 80 100 60 80 100 60 80 100

3.9

7.9

First-order model b

Weibull model c

k

Duv

0.059  0.0a 0.067  0.0a 0.061  0.0a 0.088  0.0bc 0.064  0.0a 0.091  0.0bc 0.101  0.0bc 0.089  0.1bc 0.073  0.0ab

16.8  0.7a 14.8  1.4a 16.3  0.1a 11.5  0.8bc 15.7  1.3a 10.9  0.0bc 9.9  0.2c 11.3  0.7bc 13.7  0.9ab

2d

MSE

be

ne

R2c

MSE

0.98 0.98 0.89 0.97 0.95 0.94 0.97 0.88 0.92

0.03 0.01 0.07 0.04 0.02 0.07 0.06 0.06 0.07

0.03  0.0c 0.05  0.0c 0.01  0.0c 0.09  0.0c 0.03  0.0c 0.32  0.1ab 0.31  0.0ab 0.40  0.1a 0.12  0.1bc

1.20  0.2b 1.14  0.2bc 1.74  0.1a 1.00  0.1bcd 1.31  0.1ab 0.65  0.1cd 0.69  0.0cd 0.58  0.1d 0.89  0.2bcd

0.99 0.98 0.98 0.97 0.97 0.97 0.99 0.97 0.92

0.01 0.01 0.03 0.04 0.02 0.03 0.02 0.06 0.06

R

MSE: mean square of error. a Average  standard deviation. Different letters within the same column for each juice concentration indicate significant difference (p < 0.05). b Slope (min1). c Time of decimal reduction (min). d Correlation coefficient. e Weibull parameters.

Table 3. Kinetic parameters of total coliforms reduction in carrot beverages treated with UV-C lighta Flow rate (mL s1)

Concentration (%)

0.5

60 80 100 60 80 100 60 80 100

3.9

7.9

First-order model

Weibull model

kb

Duv

0.066  0.0c 0.047  0.0a 0.059  0.0abc 0.087  0.0d 0.052  0.0ab 0.063  0.0bc 0.068  0.0c 0.064  0.0bc 0.070  0.0c

15.1  1.2cd 20.9  1.7a 17.0  1.6ab 11.4  0.0d 19.1  1.2ab 15.9  0.3bc 14.7  0.7cd 15.7  0.1bc 14.2  0.3cd

c

R2d

MSE

be

ne

R2c

MSE

0.89 0.79 0.40 0.99 0.94 0.72 0.94 0.97 0.83

0.06 0.17 0.11 0.01 0.02 0.23 0.24 0.02 0.15

0.01  0.0c 0.19  0.1b 0.51  0.1a 0.11  0.0bc 0.09  0.0bc 0.41  0.0a 0.05  0.0bc 0.05  0.0bc 0.40  0.0a

1.72  0.3a 0.55  0.1cd 0.30  0.0d 0.92  0.0bc 0.84  0.1bcd 0.48  0.0d 1.07  0.1b 1.04  0.0bc 0.51  0.0cd

0.99 0.91 0.96 0.99 0.95 0.84 0.94 0.97 0.91

0.01 0.02 0.02 0.01 0.02 0.12 0.04 0.02 0.07

MSE: mean square of error. a Average  standard deviation. Different letters within the same column for each juice concentration indicate significant difference (p < 0.05). b Slope (min1). c Time of decimal reduction (min). d Correlation coefficient. e Weibull parameters.

figures, some microbial inactivations were not fitted with first-order models; therefore, the use of Weibull model to fit non-log linear curves was necessary. Weibull model fit adequately (R2 > 0.84) with experimental data. Moreover, for mesophiles in carrot beverage with 60% of juice exist a dependence of flow rate in Weibull parameters. Meaning that, increasing the flow rate increased the inactivation rate (b) (corroborated

the Duv values) and decreased the n parameter. Chen and Hoover (2004) stated that increasing the flow rate, microorganisms become more resistant to the treatment. Similar results were observed in a study performed by Ochoa-Velasco et al. (2014) in coconut milk. They reported that increasing the flow rate in the UV-C light system increased the b and decreased the n values ( 0.05) between fresh and UV-C light processed beverages. The scores obtained for all beverages tests were 6–7 that means: ‘‘I like slightly’’ (6) and ‘‘I like moderately’’ (7) for all sensorial attributes (Table 4). There were no significant differences (p > 0.05) within the juice concentrations (60, 80, and 100% [v/v]). Some of the sensorial characteristics of beverages such as color, flavor, and overall acceptability showed no significant reduction due to the UV-C light treatment compared to untreated beverages. Similar results, regarding sensorial attributes, were reported by Donahue et al. (2004) for apple cider, and Pala and Toklucu (2013) for orange juice for UV-C light treated and untreated products. Caminiti et al. (2012) did not find significant differences (hedonic scale) between apple juice untreated and UV-C light treated using low dosages of irradiation (5.3–10.6 J m2). However, increasing the UV-C light dosage significantly decreased the acceptability by judges compared to fresh juice. It could be possible that the good acceptability of carrot beverages obtained in this study were because the flow system was immersed in a cooling water bath.

CONCLUSIONS UV-C light treatment showed an adequate performance to process carrot beverages. Minimum quality change although high dosage applied was observed in treated beverages. TSS, pH, and titratable acidity of beverages were not affected by the UV-C light. The color parameters were barely affected by the UV-C light at low juice concentration. High flow rate slightly affected color 544

parameters. UV-C light did not affect phenolic compounds and antioxidant capacity within all concentrations and flow rates. Microbial kinetics showed that mesophiles (3.2  0.1 log reduction) and total coliforms (2.6  0.1 log reductions) were more affected at low juice concentration and higher flow rates. Weibull kinetics models showed an adequate fitting with experimental data. Carrot beverages were well accepted by judges; they did not observed differences between untreated and UV-C light treated beverages. Although the five log reduction demanded by FDA was not reached, UV-C light is a promissory technology that could be used in combination with other technologies in order to improve the microbiological inactivation. DECLARATION OF CONFLICTING INTERESTS The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

FUNDING The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was part of the Project Number DITCo2014-13 supported by the Beneme´rita Universidad Auto´noma de Puebla (BUAP), Puebla, Mexico.

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