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Inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in apple juice at different pH levels by gaseous ozone treatment
- Song, W.‐J., Shin, J.‐Y., Ryu, S., Kang, D.‐H.
- Journal of applied microbiology 2015 v.119 no.2 pp. 465-474
- Escherichia coli O157, Listeria monocytogenes, Salmonella Typhimurium, anti-infective properties, apple juice, color, food pathogens, juice quality, ozonation, ozone, pH
- 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.