Inactivation of Escherichia coli O157: H7, Salmonella Typhimurium and Listeria monocytogenes in apple juice at different pH levels by gaseous ozone treatment.

Aims We investigated the effect of ozone treatment of apple juice at different pH levels for inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes. Methods and Results Apple juice (pH 3·0, 4·0 and 5·0) inoculated with the three pathogens were treated with gaseous ozone (3·0 l min−1 flow rate and 2·0-3·0 g m−3) for up to 4 min. Ozone treatment (4 min) of pH 3·0 apple juice resulted in >5·36 log CFU ml−1 reduction of E. coli O157:H7. Ozone treatment of pH 4·0 and 5·0 apple juice for 4 min reduced this pathogen by 5·12 log CFU ml−1 and 1·86 log CFU ml−1 respectively. The combination of low pH and ozone showed a great antimicrobial effect in apple juice. Salm. Typhimurium and L. monocytogenes showed a reduction trend similar to E. coli O157:H7. There were no significant changes of colour values when apple juice was treated with ozone, except for b values. Among all ozone treated samples, the browning index was lower than that of nontreated samples and there were no significant differences in total phenolic contents. Conclusions In conclusion, ozone treatment of low pH apple juice was significantly effective in inactivation of foodborne pathogens while maintaining acceptable apple juice quality. Significance and Impact of the Study The antimicrobial effect of ozone treatment on foodborne pathogens in apple juice can be reinforced by lowering the pH of apple juice. [ABSTRACT FROM AUTHOR]