(177k) Design and Characterization of a UVC-Coiled Tube Reactor and Continuous Flow Microwave System for Pasteurization of Juices

Pasteurization is one of the most preferred preserving methods in the industry for liquid foods, such as milk, sauces and juices, however these last ones are one of the most susceptible to cook-flavor development, and vitamin loses, among other damages related to thermal treatments. Recently, some emerging technologies as have been studied to prevent these unfavorable changes; however, design and characterization of new equipment has become of great importance, especially for combined treatments. In this work, the inactivation of Saccharomyces cerevisiae inoculated in pomegranate juice was studied in individual and combined treatments of short wave ultraviolet (UVC, 254 nm) light and/or a continuous flow microwave (MW) system (1000 W energy output). To characterize the systems, temperature profiles were evaluated at different flow rates between 150 and 1000 mL/min, with temperature rises over 88.8 °C and 30.6 °C, respectively. The obtained data were fitted to a dynamic model that might be useful for further analysis of deactivation during the time-varying temperature process. Two different flow rates (400 and 800 mL/min) with temperature increments of 53 °C and 35 °C, respectively, were studied to determine the effectiveness of the combined treatment at mild temperatures. Juice was treated at these flow rates and residence-time distributions (RTD) were determined in order to describe the flow pattern of the system. The inoculated juice was processed three times through tested systems; individual treatments did not have a significant effect (p>0.05), demonstrating that the inactivation occurs due to the combined treatments and not only due to the thermal treatment corresponding to MW. Combined treatments at 800 mL/min showed a lower inactivation of S. cerevisiae compared with 400 mL/min treatments, where more than four log-cycle reductions were achieved.