Investigation of antimicrobial activity of Ultraviolet B radiation and its potential to generate fructose-mediated reactive oxygen species in coconut water

Abstract

We evaluated the potential antimicrobial activity and inactivation kinetics, photo-reactivation potential and ability to generate reactive oxygen species (ROS) and consequent ascorbic acid degradation in fructose enriched coconut water. UV-B caused 4.5 ± 0.19 log inactivation in E. coli K12 at 0.45 J/cm2 and inactivation kinetics followed Weibull model, compared to log-linear 4 ± 0.05 log reduction at 0.2 J/cm2 dose of UV-C. A lower extent of UV-A (360 nm) induced photo-reactivation was observed in UV-B treated samples compared to UV-C. UV-B mediated microbial inactivation was largely caused by DNA damage and impaired metabolic activity of E. coli. UV-B treatment did not cause membrane damage, or thiol oxidation. Compared to UV-C, UV-B produced lower concentration of ROS from fructose. At a dose required for 4 log reduction of E. coli K12 by UV-B, only 8% ascorbic acid degraded. These results show that UV-B is an attractive alternative to UV-C treatment. Industrial relevanceUV-C irradiation is a cost-effective measure to ensure food safety. However, for fructose-rich products fruit juices, UV-C exposure to photo-sensitive compounds like fructose generates reactive oxygen species that can deteriorate the quality of fructose-rich products. In this context, UV-B provides comparable, albeit slower, antimicrobial effect but provokes milder fructose mediated oxidative stress than UV-C. This study highlights the potential for using UV-B as an alternative to UV-C light treatment for liquid foods.