Response surface analysis of the effects of Capsicum extract, temperature and pH on the growth and inactivation of Listeria monocytogenes

A surface response analysis was carried out using the Box-Behnken method in order to determine the effects and interactions of pH (4.5, 5.5, 6.5), temperature (2, 7, 12 °C) and Capsicum extract concentration (0%, 5%, 10%) on the growth kinetics of Listeria monocytogenes Scott A in trypticase soy broth. Survival ratio quadratic models (log N/N0) were obtained for the combination of variables, valid only in the specified ranges. Temperature showed no effect on the bacterial inactivation; however both the extract concentration (5%) and pH value (4.5) had a relevant effect on the microbial counts. The models were validated on acidified milk inoculated with L. monocytogenes. According to their evaluation, it may be possible to use the models in order to obtain reasonable initial estimates of the impact of the Capsicum extract, as well as storage conditions, over the growth of L. monocytogenes after 4 and 8 days of storage.