Survival of Listeria innocua in thermally processed orange juice as affected by vanillin addition

Presence of Listeria monocytogenes could seriously affect the safety of fruit juices. Addition of natural antimicrobials may be an alternative to enhance microbial inactivation in fruit juice thermal preservation. The response of L. innocua, surrogate for L. monocytogenes, to combined treatments involving moderate temperatures (57–61 °C) and addition of different levels of vanillin (0–1100 ppm) was assessed to find the most effective inactivation treatment in orange juice. The presence of vanillin greatly increased the bactericidal effect of the mild heat treatment. This effect considerably depended on the amount of added vanillin when working at the lowest temperature (57 °C), while at higher temperatures (60 or 61 °C) the increase in vanillin concentration did not produce a clear change in the response. Nonlinear semilogarithmic survival curves were successfully fitted using a modified version of Gompertz model and by the Weibullian model.