Inactivation kinetics of Yersinia enterocolitica by citric and lactic acid at different temperatures

Inactivation of Yersinia enterocolitica by citric (1-20% w/v) and lactic (0.3-4.0% v/v) acids at different temperatures (4, 20, 40 °C) has been investigated. Inactivation effect of citric and lactic acids was dependent on time and temperature of exposure and acid concentration. Survival curves of Y. enterocolitica suspended in citric acid solutions at 4 and 20 °C displayed a shoulder followed by an exponential inactivation, but at 40 °C a shoulder was not observed. At all temperatures investigated, survival curves of Y. enterocolitica suspended in lactic acid solutions were linear or slightly concave upwards. A mathematical model based on the Weibull distribution accurately described the kinetics of inactivation of Y. enterocolitica by both acids. The influence of the citric acid concentration on Y. enterocolitica resistance was independent of the treatment temperature. However for lactic acid, the influence of the acid concentration on microbial inactivation depended on the temperature. At any temperature investigated, lactic acid was significantly more effective than citric acid.