Effect of ultraviolet-C light-emitting diode irradiation on inactivation of white colony-forming yeast in kimchi seasoning

Abstract

The presence of white colony-forming yeasts (WCFYs) in raw materials negatively affects the quality of kimchi. Accordingly, disinfection processes to effectively control spoilage yeasts, including WCFYs, are crucial for extending the shelf life of kimchi. However, conventional disinfection procedures could result in undesirable changes in the nutritional attributes or sensory characteristics of the food. Therefore, in this study, we investigated whether ultraviolet-C light-emitting diode (UVC-LED) treatment combined with an impeller system could inactivate Candida sake and Kazachstania servazzii cells without causing significant variations in the physicochemical characteristics of kimchi seasoning. UVC-LED at 1680 mJ/cm2 combined with the impeller system at 70 and 140 rotations per min (rpm) reduced the number of C. sake cells in kimchi seasoning by 2.29 and 2.79 log10 CFU/g, respectively, whereas the reduction in the number of K. servazzii cells was observed to be < 2 log10 CFU/g. After UVC-LED irradiation up to 1680 mJ/cm2, the changes in titratable acidity, pH, viscosity, and volatile compounds of the kimchi seasoning remained mostly constant (p > 0.05). We observed that the efficacy of UVC-LED treatment increased as the impeller rotation speed increased. K. servazzii was more resistant to UVC-LED irradiation than C. sake. These experimental results demonstrate that UVC-LED treatment may be a practical alternative to the limited disinfection approaches for high-quality kimchi production.