Combined treatment of ε-polylysine and thermosonication to inactivate Bacillus cereus and their application in pasteurized milk

Abstract

At present, most liquid milk products use high-temperature short-time heat treatment (HTST). However, HTST treatment cannot completely inactivate the bacteria in milk, which seriously affects the quality, safety, and shelf life of the product. Therefore, exploring the combined use of HTST and other technologies is of great importance to the production of high-quality pasteurized milk. In this study, we compared thermosonication (TS), ε-Polylysine (ε-PL), ε- PL combined with TS (ε-PL-TS), and HTST to inactivate B. cereus in pasteurized milk. Based on this comparison, we further discussed the inactivation ability and potential mechanism of ε-PL-TS treatment on B. cereus. The experimental result indicated that ε-PL-TS treatment had an obvious inactivation impact on B. cereus. The cell architecture was damaged by ε-PL-TS treatment, causing the leakage of proteins and DNA from the cell. ε-PL-TS treatment caused metabolic disorders by reducing the activities of key enzymes such as succinate dehydrogenase (SDH) (72.5%), malate dehydrogenase (MDH) (70.5%), and ATPase (80.3%). Meanwhile, the activity of CAT and POD decreased by 42.5% and 48.7%, respectively, suggesting that oxidative stress may be involved in the bactericidal mechanism. In addition, the combined treatment effectively inhibits microbial proliferation of pasteurized milk during storage at 4 °C. Therefore, ε-PL-TS treatment can be used as a potential new inactivated microorganism technology that is helpful to obtain high-quality pasteurized milk with a long shelf life.