Effects of ultraviolet-C treatment in Teflon®-coil on microbial populations and physico-chemical characteristics of watermelon juice

The efficacy of UVC radiation for inactivation of bacteria (aerobic, coliform) and yeast/mold in watermelon juice using helix Teflon (R)-coil was investigated. Changes in microbial load, pH, degrees brix, color (L*, a*, and b*), lycopene, and phenolics in juice, after UVC treatment were evaluated for 37 days of storage at 5 +/- 1 degrees C. Microbial inactivation was dependent on the UVC intensity between 2.7 and 37.5 J/mL. UVC treatment inactivated all (2.6 log CFU/mL) coliform bacteria. UVC (37.5 J/mL) reduced total aerobes and yeast/mold by 1.47 and 0.99 log CFU/mL, respectively. The microbial load in treated juice remained lower than 6.0 log CFU/mL until the 31st day of storage. UVC treatment resulted in no-significant effects on pH, degrees brix, color change, lycopene, and phenolics, the values of which remained consistent with those of a control until 25th day of storage. UVC treated juice had lower b* (yellowness) and higher a* (redness) colors than untreated juice. Industrial relevance: Watermelon juice is a potential health food and strategies to increase its shelf-life with minimal or no damage to nutritional components are crucial for obtaining more commercial benefits. Our study suggests that a Teflon (R)-coil UVC system can be effectively used as a non-thermal method for microbial inactivation in watermelon juice and to improve the product shelf-life with no significant effects on different physico-chemical and nutritional characteristics. (C) 2013 Elsevier Ltd. All rights reserved.