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Inactivation kinetics of Escherichia coli O157:H7 and Salmonella Typhimurium on organic carrot (Daucus carota L.) treated with low concentration electrolyzed water combined with short-time heat treatment

Liu, Qin, Jin, Xiaoxuan, Feng, Xiao, Yang, Hongshun, Fu, Caili
Food control 2019 v.106 pp. 106702
Daucus carota, Escherichia coli O157, Salmonella Typhimurium, Weibull statistics, atomic force microscopy, bacteria, carrots, cell membranes, chlorine, disinfection, electrolyzed water, heat, heat treatment, organic foods, reactive oxygen species, sensory properties, storage temperature, synergism
In the present study, the synergistic disinfection efficacy of low concentration electrolyzed water (LcEW) (free available chlorine, 4 mg/L) combined with brief heat enhancement was evaluated and the bactericidal mechanism was investigated by atomic force microscopy (AFM). The inactivation kinetics of Escherichia coli O157:H7 and Salmonella Typhimurium on organic carrot were fitted with Weibull model to evaluate the synergistic effects. LcEW is effective at inactivating E. coli O157:H7 and S. Typhimurium on organic carrots, and the efficacy is dependent on the temperature. The combined treatment with LcEW at 80 °C resulted in decimal reduction time (TR) of 7.42 and 3.27 s for E. coli O157:H7 and S. Typhimurium, respectively. The reactive oxygen species generated from LcEW were responsible for the microbial inactivation. In addition, AFM observation of E. coli O157:H7 and S. Typhimurium revealed morphological alterations in the bacterial cell structure, which illustrated the damage of cell membrane injury and intracellular component leakage. Quality attributes of carrot treated with LcEW and short-time heating (70 °C, 1 min) were not significantly different from controls. Compared to the control group, the combined treatment exhibited significantly (P < 0.05) greater inhibition of naturally occurring microbiota on organic carrots during storage at 4 °C. Consequently, the application of LcEW combined with short-time heat improved safety of organic carrot, without negatively affecting the sensory properties, which can be explored by the organic industry.