Thermal treatment constitutes the most extensively available method for the inactivation of microorganisms in fruit juices to achieve the required 5-log reduction in number of the most resistant pathogens but causes substantial changes in their flavor and nutritional quality. Minimal processing of fruits may include many novel technologies aimed to minimize these changes and to improve shelf life. Short-wave ultraviolet light (UV-C) has shown to be an alternative for reducing different microorganisms in a variety of foods. The objective of this work was to evaluate and characterize the effect of UV-C light on the survival of Escherichia coli, Listeria innocua; Saccharomyces cerevisiae, a yeast cocktail (S. cerevisiae, Candida parapsilosis, Pichia anomala, Zygosaccharomyces bailii and Zygosaccharomyces rouxii) and a mixture of four E. coli strains in apple juice applied in a continuous flow system. Evaluated systems were filtered natural apple juice; a commercial apple juice and acidified peptone water. Five hundred mL- inoculated systems were recirculated through the UV-C annular reactor (1 L/min; 28°C) during 15 minutes (dose 14 kJ/m~2). UV-C efficiency was highly dependent on media nature. The use of this technology to reduce microbial populations in apple juice led to curves with upward concavity. A Weibullian model was successfully fitted to experimental data. E. coli proved to be the specie most sensitive to treatment with UVC, followed by L. innocua and S.cerevisiae. E. coli reached 5 decimal reductions required by the FDA for emerging technologies in the clarified juice and 4.7 reductions in the case of natural apple juice. E. coli ATCC 35218 and its cocktail were more sensitive than S. cerevisiae KE162 and the cocktail of yeasts. This study gives useful quantitative information regarding the effect of UV-C to effectively reduce the number of the microorganisms assayed in different media. Further work is needed to increase its efficiency.
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