Study on the inhibitory mechanism of epigallocatechin gallate against foodborne pathogens and its application

ObjectiveThe bacteriostatic mechanism of epigallocatechin gallate (EGCG) against Staphylococcus aureus (S. aureus) and Salmonella typhimurium (S. typhimurium) and the elimination effect of S. aureus and S. typhimurium in purple yam chip were studied.MethodsThe bacteriostatic effect of EGCG in vitro was determined by microbroth gradient dilution method, and the bacteriostatic mechanism of EGCG was further determined by potassium ion determination, PI staining, OD260 nm value, OD280 nm value and cell morphology observation. Finally, the clearance rate of S. aureus and S. typhimurium in purple yam chip was studied by EGCG combined with pasteurization.ResultsThe minimum inhibitory concentration (MIC) of EGCG for S. aureus and S. typhimurium was 0.512 mg/mL and 0.256 mg/mL, and the minimum bactericidal concentration was 1.024 mg/mL and 0.512 mg/mL, respectively. After MIC and 2MIC treatment, the K+ concentration of S. aureus increased to 2.26 mg/L and 2.39 mg/L, respectively, while after MIC and 2MIC treatment, the K+ concentration of S. typhimurium increased to 1.79 mg/L and 1.84 mg/L, respectively. All strains were higher than those without EGCG treatment. EGCG could destroy the cell membranes of S. aureus and S. typhimurium, promote the increase of membrane permeability, and then appear the phenomenon of cell contents leakage and cell shrinkage, resulting in bacterial death. The clearance rate of S. aureus and S. typhimurium in purple yam chip was 100% after treatment with EGCG at MIC combined with pasteurization.ConclusionEGCG has antibacterial effect on foodborne pathogens in vitro, and can be used as a natural antibacterial preservative in food.