Bactericidal Effect of Combined Slightly Acidic Electrolyzed Water and Ultrasonic Treatment against Escherichia coli on Fresh-Cut Lettuce

Abstract

This study aimed to investigate the bactericidal effect and dynamics of slightly acidic electrolyzed water (SAEW) combined with ultrasonic (US) treatment on Escherichia coli on fresh-cut lettuce. Fresh-cut lettuce was treated with SAEW-US under different conditions of solid/liquid ratio (1:5, 1:10 and 1:15 (g/mL)) and temperature (25, 35 and 45 ℃). The colony number of E. coli on lettuce was determined by the plate counting method, and the synergistic effect of combined treatment with SAEW and US on reducing the colony number of E. coli was determined and kinetically analyzed. The sublethal damage of SAEW-US treated E. coli was detected by flow cytometry and the double-layer culture counting method. The results showed that the efficacy of SAEW-US treatment in killing E. coli was significantly better than that of SAEW treatment (p < 0.05), and increased with treatment time, solid/liquid ratio and temperature. SAEW-US treatment had a synergistic effect on killing E. coli, and the sterilization process followed a first-order kinetic model. Moreover, SAEW-US treatment reduced the rate of sublethal damage of E. coli. The results of this study will provide a theoretical basis for the sterilization of fresh agricultural products.

Keywords

• slightly acidic electrolyzed water; ultrasonic; combined treatment; escherichia coli bactericidal kinetics; synergistic effect