Combination effect of ozone and heat treatments for the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes in apple juice.

We investigated the combination effect of ozone and heat treatments in apple juice for the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes. Apple juices inoculated with the three pathogens were treated with gaseous ozone and heat simultaneously for up to 1 min. Gaseous ozone treatment was progressed at a flow rate of 3.0 l/min with a concentration of 2.0-3.0 g/m³ and heat treatment was performed at temperatures of 25, 45, 50, and 55 °C. Populations of surviving pathogens decreased in all samples as treatment temperature increased from 25 to 55 °C. Heat treatment alone (25, 45, 50 and 55 °C) resulted in 0.20, 0.37, 2.16 and 2.54 log CFU/ml reductions of E. coli O157:H7, respectively, in apple juice. Combination treatment of ozone and heat for 1 min reduced this pathogen by 1.50 and 1.60 log CFU/ml, respectively, at 25 and 45 °C, and below the detection limit (1 log CFU/ml) at 50 and 55 °C. We found a synergistic effect in the inactivation of pathogens in apple juice treated with ozone and heated at 50 °C. The reduction trend of S. Typhimurium and L. monocytogenes in apple juice was similar to that of E. coli O157:H7. There were no significant changes of Hunter color values when apple juices were treated with heat only and the combination of ozone and heat. Residual ozone was measured following ozone treatment. In all ozone treated samples, the concentration of residual ozone was reduced to under acceptable levels (<0.4 mg/l). In conclusion, the combination treatment of ozone and heat was significantly effective in the inactivation of foodborne pathogens while maintaining acceptable apple juice quality.

Sung HJ ，Song WJ ，Kim KP ，Ryu S ，Kang DH ... -  《-》

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

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. 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. In conclusion, ozone treatment of low pH apple juice was significantly effective in inactivation of foodborne pathogens while maintaining acceptable apple juice quality. The antimicrobial effect of ozone treatment on foodborne pathogens in apple juice can be reinforced by lowering the pH of apple juice.

Song WJ ，Shin JY ，Ryu S ，Kang DH ... -  《-》

Inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium in apple juices with different soluble solids content by combining ozone treatment with mild heat.

This study evaluated the combined effects of ozone and heat treatment to inactivate Escherichia coli O157:H7 and Salmonella Typhimurium in three types of apple juice of different soluble solids content. Three types of apple juice (18, 36, 72 °Brix) inoculated with pathogens were subjected to ozone (3·0 l min(-1) flow rate and 2·0-3·0 g m(-3) concentration) and heat treatment (25, 45, 50 and 55°C) simultaneously for 20, 40 and 60 s. Initial populations of pathogens in inoculated apple juice were approximately 10(5)-10(6) CFU ml(-1). Heat treatment alone (25, 45, 50 and 55°C) for 1 min reduced populations of E. coli O157:H7 by 0 to 4·75 log CFU ml(-1) in three types of apple juice. The combination of ozone and heat treatment for 1 min at 25 and 45°C reduced E. coli O157:H7 by 0·93-3·87 log CFU ml(-1) and below the detection limit (>1 log CFU ml(-1)) at 50 and 55°C. A similar tendency was observed for S. Typhimurium. In several instances, results showed a synergistic effect of ozone and heat treatment. Colour values were not changed during ozone and heat treatment. These results show that the combination of ozone and heat treatment can be used as a potential inactivation intervention for E. coli O157:H7 and S. Typhimurium in apple juice. The combination of ozone treatment and mild heat can be used as an alternative intervention for pasteurization of varying soluble solids content apple juice in food industries.

Song WJ ，Sung HJ ，Kang DH 《-》

Inactivation of Escherichia coli O157:H7, Salmonella typhimurium and Listeria monocytogenes in apple juice with gaseous ozone.

This research was initiated to assess the efficacy of gaseous ozone for inactivation Escherichia coli O157:H7, Salmonella typhimurium and Listeria monocytogenes in apple juice. Juice samples with solids content of 18, 36, and 72 °Brix inoculated with a culture cocktail of three foodborne pathogens were treated with gaseous ozone at a flow rate of 3.0 L/min and an ozone generation rate of 0.10, 0.90, 3.51, and 5.57 g/h for 0.5, 1, 5, and 10 min, respectively. The inactivation kinetics of gaseous ozone on foodborne pathogens conformed to the Weibull model. The time required to achieve a 5 log reduction (t(5d)) was estimated using the parameters of the Weibull model. The t(5d) increased with increasing solids content of apple juice. The ozone generation rate did not impart a significant effect (p > 0.05) on t(5d). Gaseous ozone is effective at inactivating foodborne pathogens in apple juice but the efficacy is dependent on the solids content of the juice sample.

Choi MR ，Liu Q ，Lee SY ，Jin JH ，Ryu S ，Kang DH ... -  《-》

Survival of Escherichia coli O157:H7 and Salmonella in apple cider and orange juice as affected by ozone and treatment temperature.

Williams RC ，Sumner SS ，Golden DA 《JOURNAL OF FOOD PROTECTION》