Effects of ZnO Nanoparticles and Microwave Heating on the Sterilization and Product Quality of Vacuum-Packaged Caixin

Abstract

BACKGROUND: The sterilization of vacuum-packaged Caixin (Brassica chinensis L.), which is a green-leafy vegetable and also a low-acid food, remains a difficult problem. In this study, effects of ZnO nanoparticles and microwave heating on the sterilization and product quality of vacuum-packaged Caixin were investigated. RESULTS: Addition of ZnO nanoparticle suspension at 0.01–0.02 g kg-1 reduced the number of bacterial colonies. The antibacterial activity was enhanced with the increased amount of ZnO nanoparticles. Microwave heating (915 and 2450 MHz) was used to sterilize Caixin samples. Samples had good product quality (better greenness, chroma and hue angle values, lower browning index and acceptable texture) and the lowest total colony number under the microwave heating condition of 400 W150 s (2450 MHz). CONCLUSION: The best sterilization condition was observed under 2450 MHz microwave (400W 150 s) heating combined with 0.02 g kg-1 ZnO nanoparticle addition, which led to a total colony number of <1 log CFUg-1 in Caixin samples within 7 days.