Assessment of recommended thermal inactivation parameters for fruit juices

Abstract

The aim of this study was to evaluate the efficacy of recommended and recalculated thermal process parameters to achieve mandatory 5-log reduction of shiga toxin-producing Escherichia coli (STEC), Salmonella, and Listeria monocytogenes in fruit juices in the United States. Logarithms of published D-values of pathogens were plotted against temperatures (°C) to recalculate the pasteurization parameters for apple, orange and all studied fruit juices. Fruit juices were inoculated with non-adapted cells grown in TSB without glucose and acid adapted strains grown in TSB containing 1% glucose and TSB with adjusted pH to 5.0 with 1 N HCl. Microcapillary tubes with inoculated apple and orange juice were heat treated in water bath at 71 ± 1 °C for 6, 12, 36, and 48 ± 1 s. Acid adaptation increased the heat resistance of STEC, Salmonella, and L. monocytogenes. Different acid adaptation procedures affected thermal tolerance responses of tested strains. A 5-log reduction of Salmonella and STEC at 71.1 °C was achieved with minimum heat treatment for 6 s in apple juice and 6 to 12 ± 1 s in orange juice. Data presented in this study suggests that current recommended pasteurization parameters failed to reduce viable acid adapted L. monocytogenes by 5-log.