thermal and pulsed electric fields pasteurization of apple juice

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Information about thermal and pulsed electric fields pasteurization of apple juice
Food

Published on June 29, 2014

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Thermal and pulsed electric fields pasteurization of apple juice: Effects on physicochemical properties and flavour compounds S.F. Aguilar-Rosas a , M.L. Ballinas-Casarrubias a , G.V. Nevarez-Moorillon a , O. Martin-Belloso b , E. Ortega-Rivas a,* a Food and Chemical Engineering Programme, Autonomous University of Chihuahua, University Campus I, Chihuahua, Chih. 31170, Mexico b Department of Food Science and Technology, University of Lleida, Av. Alcalde Rovira Roure 177, 25198 Lleida, Spain Received 6 September 2006; received in revised form 14 December 2006; accepted 15 December 2006 Available online 11 January 2007 Abstract Apple juice, extracted from golden delicious fruits, was pasteurized using a pulsed electric field (PEF) treatment and compared with a conventional high temperature-short time (HTST) method. The PEF treatment was carried out using a PEF laboratory unit, set with a bipolar pulse (4 ls wide), an intensity of 35 kV/cm, and a frequency of 1200 pulses per second (pps). The thermal pasteurization was performed at 90 °C for 30 s with an adapted laboratory set-up. Effects of variables of both treatments on pH, total acidity, phenolics content, and volatile compounds were investigated. While minimal variability was observed in pH and no significant changes were detected in acidity, phenolics content and volatile compounds concentration showed statistical significant differences between treatments. In general, these measured variables were less affected by the PEF treatment than by the thermal pasteurization. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Apple juice; Thermal pasteurization; High voltage pulsed electric fields (PEF); High temperature-short time (HTST) pasteurization; Sensory attributes 1. Introduction Apple juice has been traditionally pasteurized by ther- mal means. Both batch and continuous methods are used in apple juice pasteurization and the treatment may be car- ried out before or after packing the product in the con- tainer. In batch pasteurization, individual volumes are treated in jacketed stainless steel vessels. The jacket may be used both for heating (with steam or hot water) and cooling (with chilled water or brine). Continuous pasteuri- zation may be carried out by passing the juice through plate heat exchangers, which usually comprise the stages of pre-heating, heating, holding and cooling. Currently, high temperature-short time (HTST) pasteurization is a commonly used method for heat treatment of apple juice. In HTST pasteurization, the temperature used is 76.6– 87.7 °C for a holding time between 25 and 30 s (Moyer & Aitken, 1980). Thermal pasteurization is quite efficient in preventing microbial spoilage of apple juice but the applied heat may also cause undesirable biochemical and nutritious changes which may affect overall quality of the final prod- uct. Alternative methods of pasteurization that do not include direct heat have been investigated in order to obtain a product safe for consumption, but with sensory attributes similar to the untreated juice. High voltage pulsed electric fields (PEF) treatment is a promising non- thermal processing method that may radically change liquid food preservation technology. Treating liquid foods with PEF may inactivate micro-organisms and enzymes with only a small increase in temperature, simultaneously providing consumers with safe, nutritious, and fresh-like 0260-8774/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2006.12.011 * Corresponding author. Tel./fax: +52 614 4241868. E-mail address: eortegar@uach.mx (E. Ortega-Rivas). www.elsevier.com/locate/jfoodeng Journal of Food Engineering 83 (2007) 41–46

quality foods. PEF treatment is conducted at ambient tem- perature for a short time (in microseconds), and energy lost due to heating of foods is minimized (Jeyamkondan, Jayas, & Holley, 1999). In terms of microbial safety and energy efficiency, a study of PEF inactivation demonstrated that, for achieving a seven log reduction in survivability of Saccharomyces cerevisiae in apple juice, PEF utilized less than 10% of the electric energy for heat treatment (Qin, Zhang, Barb- osa-Ca´novas, Swanson, & Pedrow, 1994). It has also been reported (Mittal, 1998) that a PEF low energy pulser with an instant-charge-reversal pulse waveform was successfully used in apple cider treatment. The consumed energy was as low as 5.76 J/ml at 20 °C, compared with the 50 kJ/kg nor- mally required in conventional thermal processing. Micro- bial inactivation, coupled with quality retention, has also been reported for apple juice pasteurization using non- thermal methods of preservation (Ortega-Rivas, Za´rate- Rodrı´guez, & Barbosa-Ca´novas, 1998). A comparison of ultrafiltration (UF) and PEF in apple juice pasteurization reported six log reductions in survivability of total aerobic micro-organisms using the indigenous flora of the juice (Ortega-Rivas et al., 1998). In terms of quality aspects, sol- uble solids, pH and acidity were reported practically impaired by both techniques. Colour, however, suffered changes such as browning for UF and fading for PEF (Ort- ega-Rivas et al., 1998; Za´rate-Rodrı´guez, Ortega-Rivas, & Barbosa-Ca´novas, 2000). Flavour components in apple juice are numerous, and flavour identification is considered quite complex due to the aromatic nature of apples. Eight odour-active volatiles have been, however, identified as the most important con- tributors for the aroma–flavour authenticity of apple juice (Cunningham, Acree, Barnard, Butts, & Braell, 1986). Apparently, there are not reported studies of PEF effects on volatile compounds in apple juice. Several reports have appeared for orange juice (Jia, Zhang, & Min, 1999; Yeom, Streaker, Zhang, & Min, 2000) focusing on effects of PEF on quality aspects. The PEF-treated juice was compared with juice pasteurized by heat at 94.6 °C for 30 s. The juice treated by PEF retained greater amounts of vitamin C and some representative flavour compounds, than the juice pas- teurized by heat during storage at 4 °C. In terms of specific flavour compounds, it was found that 40% of decanal was lost by heat treatment at 90 °C for 3 min while no loss was observed by PEF treatment at 30 kV/cm, either at 240 or 480 ls (Jia et al., 1999). Octanal showed a loss of 9.9% for the heat treatment and 0% for any of the two PEF treatments. Some compounds suffered losses for the PEF treatments, but always in less proportion than the heat pas- teurized juice. For example, 5.1% and 9.7% of ethyl buty- rate were lost for the 240 ls and 480 ls treatments, respectively, but 22.4% was lost in the thermal process (Jia et al., 1999). As discussed above, PEF has been challenged against many spoiling micro-organisms in apple juice, with encour- aging results. Also, pertaining quality, there are studies looking at effects on physicochemical properties and some sensory attributes, with results also being promising. For example, Evrendilek et al. (2000) reported no apparent changes in physical and chemical properties directly caused by PEF treatment in apple juice and cider, while Barbosa- Canovas, Pothakamury, Palou, and Swanson (1998) found that pH and vitamin C concentration were not significantly affected by PEF treatment of fresh apple juice and apple juice reconstituted from concentrate. There is, however, a dearth of information in the literature related to actual effects of PEF on composition of volatile chemical com- pounds responsible for odour and flavour of apple juice. There are neither many direct comparisons of PEF and HTST treatments, in terms of quality attributes in general. This paper presents an investigation of a direct comparison of PEF and HTST in pasteurization of apple juice, focused on retention of volatile compounds, which have been iden- tified as responsible for its characteristic aroma and tasteful flavour. 2. Materials and methods Freshly squeezed apple juice, from golden delicious apple variety, was extracted with a domestic juice extrac- tor. The juice was pre-filtered across a bag filter and stored at 4 °C prior to treatment. For conventional heat treatment, an experimental set-up was constructed (Fig. 1). As can be observed, it consisted of sanitary containers to hold heating and cooling fluids, coils for juice passage, a centrifugal sanitary pump to circulate the juice, and thermocouples to record the temperature. A pasteurization temperature of 90 °C was tested for a holding time of 30 s, which was virtually the maximum range suggested in the literature (Moyer & Aitken, 1980). Also, it was sufficient to achieve pasteurization conditions using Lactobacillus brevis and S. cerevisiae, common spoil- age micro-organisms in apple juice, as contaminating spe- cies. As shown in Fig. 2, inoculates of L. brevis and S. cerevisiae, expressed in colony forming units per millilitre (cfu/ml) were properly reduced. A high voltage pulsed electric field unit, designed and constructed at Ohio State University (Columbus, OH, USA) was used for the PEF treatment. As shown in Fig. 3, this test apparatus consists of a high voltage power Feed Pre-heating Holding Cooling Product Fig. 1. Experimental set-up used for heat pasteurization of apple juice. 42 S.F. Aguilar-Rosas et al. / Journal of Food Engineering 83 (2007) 41–46

supply, a high voltage pulse generator, a series of treatment chambers, and sample cooling and delivery devices. Fol- lowing recommendations in the literature (Heinz, Toepfl, & Knorr, 2003), a 4 ls bipolar pulse with an electric field strength of 35 kV/cm was chosen to destroy the same spoil- age micro-organisms mentioned above and select the appropriate frequency for further treatment. Such microbes were inoculated and inactivated using the previ- ously mentioned conditions at different repetition rates. Using 1200 pps, 6.3 and 4.2 log reduction cycles were achieved for the bacterium and yeast, respectively (Fig. 4), which were considered appropriate so this fre- quency was used for experimentation. The pH was measured by direct reading at 25 °C in an Orion Benchtop pH/ISE-meter Model 420 A (Orion Research Inc., Boston MA, USA). Acidity was measured by titration with 0.1 N NaOH to a pH end-point of 8.2, the result being expressed as g malic acid/l of sample (AOAC, 1998). Total phenol content was determined by the Folin–Cio- calteu method (Singleton & Rossi, 1965), reading samples in a HP 845 A UV/visible spectrophotometer (Hewlett– Packard Inc., Palo Alto, CA, USA) at 760 nm. Samples were centrifuged at 2000g (4 °C for 5 min) and diluted by a factor of 10 with distilled water. Results were expressed as mg of gallic acid/l of juice. The flavour compounds in the headspace of the apple juice were analysed by solid-phase microextraction (SPME) and gas chromatography (Buchholz & Pawliszyn, 1994). Samples of 10 ml of apple juice were transferred into 30 ml vials. The SPME fibre coated with 100 lm poly- dimethylsiloxane was inserted into the headspace of the juice and heated at 50 °C for 30 min. The SPME sample was removed from the sample vial and inserted into a gas chromatograph (GC) injection port, and held for 4 min at 250 °C to desorb the flavour compounds absorbed on the SPME coating. The desorbed flavour compounds were separated using an Agilent 5973 Network GC/MS equip- ment (Agilent Technologies, Palo Alto, CA, USA) equipped with a capillary column of 0.25 mm internal diameter Â30 m length, and coated with 0.25 lm thick diphenylpolysiloxane. Helium was the carrying gas at a rate of 1.5 ml/min. The GC oven temperature was pro- grammed from 40 to 250 °C at 20 °C/min and held 10 min at the final temperature. At the end of the experi- mental run, volatiles were qualified using the library in the program of the instrument. After identification of vol- atile compounds, calibration curves were derived for every one using the authentic volatiles. The presence of the main volatiles reported to be present in apple juice were con- firmed by comparing the retention times of gas chromato- graphic peaks to those of authentic compounds. The results were interpreted using simple analyses of variance (ANOVAS). For the volatile compounds, a Stu- 0 1 2 3 4 5 6 7 8 9 L. brevis S. cerevisiae Microbial Inactivation by HTST Method log(cfu/ml) Initial count Final count Fig. 2. Inactivation of Lactobacillus brevis and Saccharomyces cerevisiae by HTST pasteurization (90 °C for 30 s). High voltage power supply High voltage pulse generator Water bath Treatment chambers HV GND T1T2 Feed Product Fig. 3. Diagram of pulsed electric field treatment operation. 0 1 2 3 4 5 6 7 8 9 0 400 800 1200 1600 Pulses per second of PEF treatment log(cfu/ml) L. brevis S. cerevisiae Fig. 4. Inactivation of Lactobacillus brevis and Saccharomyces cerevisiae by PEF pasteurization (pulse frequency at 35 kV/cm). S.F. Aguilar-Rosas et al. / Journal of Food Engineering 83 (2007) 41–46 43

dent t-test for independent samples was used. Means were differentiated by Tukey’s tests. Significance of differences was defined at p < 0.05. The tests were performed in tripli- cate. The statistic system SAS Version 8 (SAS Institute Inc., Cary, NC, USA) was used for actual calculations. 3. Results and discussion An ANOVA for pH determinations showed statistical significant difference (F = 130.40, p = 0.0001) between the untreated apple juice and both the HTST-pasteurized and the PEF-treated samples, as illustrated in Fig. 5. However, by inspecting such figure, it can be observed that such dif- ferences may be considered negligible for practical pur- poses, since the measured pH in the three samples, only vary between 3.8 and 3.9. The observed small discrepancies could be, possibly, attributed to experimental error. These findings agree with an investigation by Heinz et al. (2003) who reported that PEF-pasteurized apple juice did not show practical difference in pH. On the other hand, Charles-Rodrı´guez (2002) found that thermally-treated apple juice presented an increase in pH directly related with temperature, reaching a value of 4.01 at the extreme pas- teurization conditions of 85 °C and 27 s. This author also reported that PEF-pasteurized juice did not show variabil- ity in pH at different electric field strengths and frequencies. It is known that maintaining pH on low values prevent pathogenic microbial growth in fruit juices, so PEF treat- ment gives, apparently, more stability to pH in apple juice than HTST pasteurization. In terms of acidity, no significant statistical difference was observed for any of the treatments (F = 0.94, p = 0.4404), as shown in Fig. 6. These results are in agree- ment with the study of Heinz et al. (2003) already men- tioned, who also reported no significant changes in acidity of PEF-pasteurized apple juice. Ortega-Rivas et al. (1998) presented results of a comparison of UF and PEF in some physicochemical properties of apple juice, finding that acidity did not present significant variability. Acidity in apple juice is an important sensory attribute associated with its characteristic flavour and astringency. Apparently, PEF-pasteurized apple juice do not affect acid- ity, so this important feature remains practically intact with the consequently advantage in overall quality of the product. Considering the results previously discussed, apparently, PEF maintained the physicochemical properties of the ori- ginal juice, while HTST affected the pH and in a less extent the acidity of the juice, as shown in Figs. 5 and 6. Apart from the experimental error that may have caused some discrepancies in readings, the changes observed in the ther- mal method could be attributed to the evaporative effect of organic acids as a function of temperature increase. Contents of total phenol compounds presented variabil- ity for the two compared pasteurization methods. The ANOVA in this case indicated statistical significant differ- ence (F = 44.4, p = 0.0003) between both treatments and the control (Fig. 7). A Tukey test confirmed the difference of means for the three samples. It can be observed in Fig. 7, however, that the HTST treatment caused a considerable 3.74 3.76 3.78 3.8 3.82 3.84 3.86 3.88 3.9 3.92 3.94 Untreated PEF HTST Treatment pH Fig. 5. Effect of treatment method on pH of pasteurized apple juice. 0.31 0.315 0.32 0.325 0.33 0.335 0.34 0.345 0.35 0.355 Untreated PEF HTST Treatment gmalicacid/litre Fig. 6. Effect of treatment method on acidity of pasteurized apple juice. 0 20 40 60 80 100 120 Untreated PEF HTST Treatment ppmofgallicacid Fig. 7. Effect of treatment method on total phenol compounds of pasteurized apple juice. 44 S.F. Aguilar-Rosas et al. / Journal of Food Engineering 83 (2007) 41–46

lost of phenols (32.2%) when compared with the PEF treat- ment, which only caused a 14.49% reduction. These results agree with Spanos and Wrolstad (1992), who reported that total phenol concentration is reduced up to 50% in apple juice pasteurized thermally at 80 °C for 15 min. Gardner, White, McPhail, and Duthie (2000) observed also consider- able losses in phenolics in apple juice pasteurized by ther- mal means. Phenol compounds are secondary metabolites in plants known to play an important role in colour and flavour development in fruit juices and wine. Phenols are important constituents of pear, grapes and apple and may be categorized into two groups: phenolic acids and flavonoids (Spanos & Wrolstad, 1992). The combined odour–flavour characteristics in apple and apple products are due in part to phenol compounds. Phenols are also used as indicators of physiological state and potential damage in quality of fruit products (Blanco, Fraga, & Mangas, 2001). Phenol compounds are, thus, important biochemical sub- stances in apple juice. Their lost or decrease in concentra- tion will, therefore, impair seriously apple juice sensory attributes. PEF treatment with minimal losses (Fig. 7) would represent an obvious advantage over HTST pasteur- ization, in terms of concentration of these chemicals in apple juice. As previously stated, the flavour of apple juice consists of many chemical compounds, but the literature indicates 8–23 compounds most responsible for the odour–flavour attribute (Ko¨nig & Schreier, 1999; Rao, Acree, Cooley, & Ennis, 1987). Eight volatile compounds were properly iden- tified in the apple juice, fresh and processed by any of the treatments, in this work. Table 1 compares the percentage in concentration decrease for those mentioned volatiles in the pasteurization methods investigated. All volatile con- centrations showed statistical significant differences for both treatments, as compared with the untreated sample, by a Student t-test for independent samples (p < 0.05, n = 3). In all compounds, and particularly in one (ethyl acetate), the decrease was considerable higher for the HTST treatment than for the PEF method (Table 1). Some of the volatiles in the PEF treatment were almost retained. Hexanal and hexyl acetate were only lost in 7% and 8.4%, respectively. It is worth to mention (Table 1) that acetic acid was completely lost in HTST treatment. To the extent of the literature survey of this work, there are not reported studies of PEF effects on volatiles in apple juice. As previously discussed, several reports have appeared for orange juice (Jia et al., 1999; Yeom et al., 2000) focusing on effects of PEF on quality aspects. Although orange juice and apple juice are different prod- ucts, the studies mentioned for orange juice, along with the results of this work, may be indicative of a definite evaporative effect of thermal pasteurization methods in fruit juice pasteurization in general. Thus, in a very broad way, it may be considered that non-thermal pasteurization techniques will represent a better choice for processing of fruit juices in general, and apple juice in particular. Vola- tile chemical compounds responsible for colour and fla- vour of fruit juices are retained in a highest ratio, when compared with fresh untreated samples, by the use of non-thermal pasteurization techniques such as high volt- age pulsed electric fields. PEF pasteurization of apple juice may be, therefore, considered a feasible alternative for fruit processors, in order to obtain a premium quality product. 4. Conclusions PEF, a thermal preservation technique to pasteurize apple juice, proved to be efficient in microbial inactivation, as well as in preserving some quality attributes. Conven- tional HTST pasteurization, on the other hand, produced significant losses in phenolic compounds and in volatiles responsible for flavour. PEF-treated juice retained better most of the volatile compounds responsible for colour and flavour of the apple juice. Further studies on the chem- istry of flavour components, to try to preserve them even better, are advisable. It is also recommended to use sensory evaluation to define quality differences of apple juice trea- ted by non-conventional methods. The use of PEF as an alternative to heat pasteurization of apple juice may be considered a strategically important action to obtain a sen- sory impaired product, highly competitive in global markets. Acknowledgements An experimental part of this project was carried out at the Department of Food Technology of University of Lleida, Spain. The authors wish to express their gratitude for the assistance provided by technical and academic staff. Funding for the project was provided by the Na- tional Council of Science and Technology (CONACyT, Me´xico). References AOAC (1998). Official methods of analysis (16th ed.). Arlington, VA, USA: Association of Official Analytical Chemists. Barbosa-Canovas, G. V., Pothakamury, U. R., Palou, E., & Swanson, B. G. (1998). Biological effects and applications of pulsed electric fields for the preservation of foods. In G. V. Barbosa-Canovas, U. R. Table 1 Percentage of volatiles losses, compared with untreated sample, in apple juice treated by two methods Compound Loss percentage for PEF Loss percentage for HTST Acetic acid 39.792 ± 20.84 100 Hexanal 7.042 ± 9.32 62.348 ± 5.35 Butyl hexanoate 18.108 ± 7.72 36.273 ± 24.86 Ethyl acetate 77.458 ± 29.23 67.126 ± 39.33 Ethyl butyrate 60.190 ± 17.80 88.398 ± 12.46 Methyl butyrate 30.081 ± 31.37 51.200 ± 19.56 Hexyl acetate 8.408 ± 16.12 22.910 ± 21.99 1-Hexanal 14.101 ± 7.65 69.307 ± 5.62 Differences by a Student t-test for independent samples (p < 0.05, n = 3). S.F. Aguilar-Rosas et al. / Journal of Food Engineering 83 (2007) 41–46 45

Pothakamury, E. Palou & B. G. Swanson (Eds.), Nonthermal Preservation of Foods (pp. 73–112). New York: Marcel Dekker Inc. Blanco, G. D., Fraga, P. M., & Mangas, A. J. (2001). Capillary liquid chromatographic determination of neutral phenolic compounds in apple juice. Analytica Chimica Acta, 426, 111–117. Buchholz, K. D., & Pawliszyn, J. (1994). Optimization of solid-phase microextraction conditions for determination of phenols. Analytical Chemistry, 66, 160–167. Charles-Rodrı´guez, A.V. (2002). Comparison of thermal processing and pulsed electric fields in apple juice pasteurisation (106 p.). MSc thesis, Chihuahua, Mexico: Autonomous University of Chihuahua, Post- graduate Programme in Food Science and Technology (in Spanish). Cunningham, D. G., Acree, T. E., Barnard, J., Butts, R. M., & Braell, P. A. (1986). Charm analysis of apple volatiles. Food Chemistry, 19, 137–147. Evrendilek, G. A., Jin, Z. T., Ruhlman, K. T., Qin, X., Zhang, Q. H., & Richter, E. R. (2000). Microbial safety and shelf life of apple juice and cider processed by bench and pilot scale PEF systems. Innovative Food Science & Emerging Technologies, 1, 77–86. Gardner, P. T., White, T. A. C., McPhail, D. B., & Duthie, G. G. (2000). The relative contributions of vitamin C, carotenoids and phenolics to the antioxidant potential of fruit juices. Food Chemistry, 68, 471–474. Heinz, V., Toepfl, S., & Knorr, D. (2003). Impact of temperature on lethality and energy efficiency of apple juice pasteurization by pulsed electric fields treatment. Innovative Food Science & Emerging Technol- ogies, 4, 167–175. Jeyamkondan, S., Jayas, D. S., & Holley, R. A. (1999). Pulsed electric field processing of foods: a review. Journal of Food Protection, 62, 1088–1096. Jia, M., Zhang, Q. H., & Min, D. B. (1999). Pulsed electric field processing effects on flavor compounds and microorganisms of orange juice. Food Chemistry, 65, 445–451. Ko¨nig, T., & Schreier, P. (1999). Application of multivariate statistical methods to extend the authenticity control of flavour constituents of apple juice. Zeitschrift fur Lebensmittel-Untersuchung und-Forschung A, 208, 130–133. Mittal, G.S. (1998), A new approach to enhance efficiency of PEF treatments, IFT Annual Meeting, Atlanta, GA, USA, June 1998. Moyer, J. C., & Aitken, H. C. (1980). Apple juice. In P. E. Nelson & D. K. Tressler (Eds.), Fruit and Vegetable Juice Processing Technology (pp. 212–267). Westport, CT, USA: AVI Publishing Co. Ortega-Rivas, E., Za´rate-Rodrı´guez, E., & Barbosa-Ca´novas, G. V. (1998). Apple juice pasteurization using ultrafiltration and pulsed electric fields. Food and Bioproducts Processing, 76(C4), 193–198. Qin, B., Zhang, Q., Barbosa-Ca´novas, G. V., Swanson, B. G., & Pedrow, P. D. (1994). Inactivation of microorganisms by pulsed electric fields of different voltage waveforms. IEEE Transactions on Dielectric Electric Insulation, 1, 1047–1050. Rao, M. A., Acree, T. E., Cooley, H. J., & Ennis, R. W. (1987). Clarification of apple juice by hollow fiber ultrafiltration: fluxes and retention of odor-active volatiles. Journal of Food Science, 52, 375–377. Singleton, V. L., & Rossi, J. A. (1965). Colorimetry of total phenolics with phosphomolybdic–phosphotungstig acid reagents. American Journal of Enology and Viticulture, 16, 144–158. Spanos, G. A., & Wrolstad, R. E. (1992). Phenolic of apple, pear and white grape juices and their changes with processing and storage – a review. Journal of Agriculture and Food Chemistry, 40, 1478–1487. Yeom, H. W., Streaker, C. B., Zhang, Q. H., & Min, D. B. (2000). Effects of pulsed electric fields on the quality of orange juice and comparison with heat pasteurization. Journal of Agricultural and Food Chemistry, 48, 4597–4605. Za´rate-Rodrı´guez, E., Ortega-Rivas, E., & Barbosa-Ca´novas, G. V. (2000). Quality changes in apple juice as related to nonthermal processing. Journal of Food Quality, 23, 337–349. 46 S.F. Aguilar-Rosas et al. / Journal of Food Engineering 83 (2007) 41–46

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