Antibacterial mechanism of ultrasound combined with sodium hypochlorite and their application in pakchoi (Brassica campestris L. ssp. chinensis)

BACKGROUND In order to prolong the storage and inhibit microorganisms of pakchoi, the antibacterial activity and mechanism of ultrasound combined with sodium hypochlorite (NaClO-US), the efficiency of NaClO-US in reducing Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa as well as preserving quality of pakchoi were investigated. RESULTS Ultrasound treatment could significantly reduce the usage of NaClO solution from 800 ppm to 500 ppm. NaClO-US decreased the counts of E. coli, S. aureus and P. aeruginosa, which disrupted the bacterial cell membrane with cytoplasmic leakage. In addition, NaClO-US significantly increased cell membrane permeability, while cell membrane integrity decreased, the secondary structure of bacterial proteins showed several obvious changes, such as the increase of random coil content, as well as the decrease of alpha-helix content. The bacterial counts, E. coli, S. aureus and P. aeruginosa population in pakchoi treated with NaClO-US reduced by 1.89, 1.40, 1.60, 1.72 log CFU g(-1), respectively compared to control sample after storage for 15 days. NaClO-US resulted in minimum chlorophyll depletion, flavor and sensory deterioration. CONCLUSION NaClO-US solution treatment inhibited microorganisms and prolonged storage of pakchoi. (c) 2022 Society of Chemical Industry.