Effect of UV-C light on Lactobacillus rhamnosus, Salmonella Typhimurium, and Saccharomyces cerevisiae kinetics in inoculated coconut water: Survival and residual effect

The aim of this study was to evaluate the effect of UV-C light on Lactobacillus rhamnosus, Salmonella Typhimurium, and Saccharomyces cerevisiae inoculated in coconut water and its residual effect during storage. Coconut water was inoculated with Lactobacillus rhamnosus, Salmonella Typhimurium, and Saccharomyces cerevisiae and then treated for up to 10 min with ultraviolet-C (UV-C) light at different flow rates (0.5-8.0 mL s−1). One processing condition (10 min at a flow rate of 8 mL s−1) was selected to evaluate the residual effect of UV-C light on microbial growth in coconut water stored at 5 or 25 °C. Beta function and exponential-delay model were used to fit the kinetics of growing or death of microorganisms inoculated in coconut water. After 10 min of treatment, 3.1-7.79 log microbial reductions were observed for the studied microorganisms. However, for L. rhamnosus (maximum growth of 1.12 ± 0.01 log cycles after 12 h of storage), and S. cerevisiae (a growing of around 0.8 ± 0.1 log cycles was observed after 24 h), an UV-C light residual effect was observed, no refrigeration may be required for the storage of coconut water. The proposed models revealed an adequate fitting (R2 > 0.723) of experimental data and provided information about the microorganism sensitivity to UV-C light.