Effect of Ultrasonic Treatment on the Bactericidal Effect of Escherichia coli and Staphylococcus aureus in Goat Milk

Abstract

The bactericidal effect of ultrasonic treatment on Escherichia coli and Staphylococcus aureus in fresh goat milk were studied in this paper, which provided reference for the non-thermal sterilization method and product development of goat milk. Based on a single factor experiment, the Box-Behnken experimental design was used to study the effects of ultrasonic power, temperature and time on the sterilization effect of Escherichia coli and Staphylococcus aureus in goat milk, and the sterilization logarithm of E. coli and S. aureus was taken as response value, the ultrasonic processing conditions were optimized through response surface analysis, and also studied the destruction of bacterial cells of the two strains by ultrasonic and pasteurization treatment and the changes of colony numbers during storage period. The results showed that the optimal conditions were ultrasonic power 530 W, temperature 60 ℃, and time 30 min. Under these conditions, the sterilization logarithms values for E. coli and S. aureus were 7.55 and 6.53. Compared with pasteurization, ultrasonic treatment had grater sterilization effect that could destroy the cell surface structure of E. coli and S. aureus to a greater extent, and extended the storage period of goat milk from 14 d to 21 d after pasteurization, and the quality requirements still met national standards.