Effect of germicidal short wavelength ultraviolet light on the polyphenols, vitamins, and microbial inactivation in a highly opaque apple juice.

The aim of this investigation was to study the efficacy of UV‐C light emitting diode (LED) system operating at 263 nm for the inactivation of Listeria monocytogenes and Escherichia coli O157:H7. UV‐C irradiation was applied to stirred 5 ml samples, using a collimated beam LED system operating at a 263 nm wavelength. UV irradiation doses ranging from 0 to 160 mJ/cm2 were also delivered to apple juice (AJ) and polyphenols and vitamins were profiled. Liquid chromatography–mass spectrometry (LC–MS/MS) analysis was conducted to assess the stability of polyphenols or vitamins in UV‐C exposed AJ. The polyphenol and vitamin results demonstrated that UV‐C irradiation in AJs at relevant commercial UV doses induced significant reductions in the concentrations of selected polyphenols and vitamins, p <.05. Ascorbic acid was reduced to 32%, at 160 mJ/cm2 whereas 17% reduction was observed at 40 mJ/cm2. Riboflavin was observed to be relatively stable. Epicatechin and chlorogenic were significantly reduced at high exposure doses. In contrast, minor changes were observed at 40 mJ/cm2. Results show that UV‐C irradiation effectively inactivated pathogenic microbes in AJ. Inactivation levels of all organisms were proportional to UV‐C dose. The log reduction kinetics of microorganisms followed log‐linear and with higher R2 (>0.95). The decimal reduction dose (D10) values of 4.16 and 3.84 mJ/cm2 were obtained from the inactivation of E. coli and L. monocytogenes in AJ. The results from this study imply that adequate log reduction of pathogens is achievable in AJ and suggests significant potential for UV‐C treatment of other opaque liquid foods. [ABSTRACT FROM AUTHOR]