Characterization of microbial inactivation in clear and turbid juices processed by short-wave ultraviolet light

Abstract

The aim of this study was to analyze the inactivation of a wide spectrum of microorganisms in clear as well as turbid juices processed by ultraviolet light (UV-C: 0–1720 mJ/cm2 ). A biodosimetry assay was used to determine the equivalent UVreduction dose (3.1 mJ/cm2 ). UV-C effectiveness increased in melon (3.2 and 4.4 log-reductions of Saccharomyces cerevisiae and Escherichia coli) and orange-tangerine juices (4.7 log-reductions of E. coli) compared to carrot (2.7, 2.9, and 4.2 log-reductions of S. cerevisiae, Candida parapsilosis and Pseudomonas fluorescens), orange (1.7, 2.0, 2.9 and 4.0 log-reductions of S. cerevisiae, Zygosaccharomyces bailii, Listeria innocua, and E. coli), and orange-carrot juices (2.5, 2.5 and 2.9 log-reductions of S. cerevisiae, P. fluorescens, and E. coli). The Coroller model allowed a better fit compared to the Weibull and modified Gompertz models. UV-C effectiveness in clear juices was related to low absorbance at 254 nm, color, and turbidity; whereas, in the turbid juices, it was also linked to the presence of particle aggregates. Practical applications Short-wave ultraviolet light (UV-C) is a promising preservation technology to partially or totally replace traditional thermal treatments, which severely alter product quality. The present study allowed to interpret how physicochemical properties of clear and turbid juices affected the inactivation of a wide spectrum of microorganisms processed by short-wave ultraviolet light (UV-C, up to 1,720 mJ/cm2 ). UV-C effectiveness was related to high UV-C transmittance, low absorbance, and turbidity in clear juices. Whereas, in the turbid ones, other parameters such as the presence of particle aggregates stemmed the disinfection process. Moreover, the optical properties of the juices were used in the estimation of UV dose distribution. Mathematical modeling revealed differences in microbial sensitivities and the existence of subpopulations with different resistance to UV-C treatment. These results suggest that UV-C light represents a promissory alternative for the processing of a variety of juices and blends with significant differences in their physicochemical characteristics.