Plasma-activated water and microbubble as postharvest technology: Effects on Escherichia coli O157:H7 reduction, functional and storage quality of romaine lettuce

Abstract

This study aimed to compare the plasma-activated water (PAW) and plasma-activated microbubble water (PAMBW) with commercial sodium hypochlorite (SH) for postharvest processing of fresh-cut romaine lettuce. The PAW and PAMBW properties showed that PAMBW produced higher content and more effective reactive oxygen and nitrogen species than PAW. PAMBW treatment recorded a 4.6 log10 CFU/g Escherichia coli (E. coli) O157:H7 reduction on lettuce compared to a 3.2 log10 CFU/g reduction by SH. Field emission scanning electron microscopy (FE-SEM) and qRT-PCR revealed that the reactive species generated by PAMBW treatment damaged the E. coli O157:H7 cell membranes and significantly (P < 0.05) increased ipfA gene expression. The sensory analysis revealed that the PAMBW treatment exhibited better overall visual quality, edge and surface browning, texture, and odor than SH and control. The PAMBW reduced total color difference (ΔE), declined polyphenol oxidase and peroxidase activities, and kept total phenolics, ascorbic acid, and chlorophyll content, along with a decrease in the respiration rate of lettuce during storage compared to SH. Thus, PAMBW treatment enhanced the safety and kept storage quality parameters of lettuce during storage.