Research – Apple Juice Preservation Using Combined Nonthermal Processing and Antimicrobial Packaging.

Journal of Food Protection

This study investigated the effectiveness of pulsed electric fields (PEF) treatment (19, 23, 30 kV/cm), pulsed UV light (PL) treatment (5 to 50 s; 1.04 J/cm 2 /s), and antimicrobial packaging (AP) treatment, either individually or combined, in inactivating bacteria and in maintaining the quality of fruit juices. Apple juice samples, inoculated with Escherichia coli K12 or native mold and yeast (M&Y), were treated by a bench scale PEF and/or PL processing systems and stored in glass jars with antimicrobial caps containing 10 µl of carvacrol (AP). The reduction in microbial populations and the physicochemical properties of juice samples were determined after treatments and during storage at 10°C. The treatments included PL (5 to 50 s; 1.04 J/cm 2 /s ), PEF (19, 23, 30 kV/cm), PEF followed by PL (PEF+PL), PL followed by PEF (PL+PEF), and PEF+PL+AP. PEF treatments from 19 to 30 kV/cm (PEF19, PEF23, PEF30) achieved E. coli reduction by 2.0, 2.6 and 4.0 log CFU/ml, respectively; PL treatments for 10 to 50 seconds (PL10, PL20, PL30, PL40, PL50) achieved E. coli reduction by 0.45, 0.67, 0.76, 2.3, and 4.0 log CFU/ml, respectively. There were no significant (p>0.05) differences between the combined PL20+PEF19 and PEF19+PL20 treatments; both treatments reduced E. coli K12 populations to non-detectable levels (> 5 log reduction) after 7 days. Both PEF+PL and PEF+PL+AP treatments achieved over 5 log reduction of M&Y; however, juice samples subject to PEF+PL+AP treatment had lower M&Y counts (2.9 log) than samples subject to PEF+PL treatment (3.9 log) after 7 days. There were no significant (p > 0.05) differences in pH, acidity, total soluble solid contents among all samples after treatments. Increased PL treatment times reduced color a*, b* values, total phenolics and carotenoid contents. This study provides valuable information to juice processors for consideration and design of nonthermal pasteurization of juice products.

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