Modeling the combined effects of enterocins A and B, lactate, and EDTA on the growth of Salmonella at different temperatures

The effects of enterocins A and B (produced by Enterococcus faecium CTC492), lactate, and ethylenedi-aminetetraacetic acid (EDTA) on the growth of Salmonella were modeled together with temperature using the response surface methodology. Six serovars of Salmonella enterica were inoculated (ca. 10(3) cells/ail) in brain-heart infusion broth with different levels of the studied factors and then incubated at different temperatures. The results showed that while Salmonella growth was affected by all the factors, temperature was the most important factor influencing the time to detection of the pathogen. All factors, including temperature, showed significant two-way interactions. The presence of enterocins A and B, lactate, and EDTA had an inhibitory effect that was enhanced at suboptimal temperatures for growth, thus delaying the time to detection. Moderate-low concentrations of lactate and EDTA increased the inhibitory effect of enterocins A and B. The effectiveness of these bacteriocins was not further enhanced by high concentrations of lactate (> 3.6%) or EDTA (> 200 mg/l). The mathematical model obtained from these analyses provides a useful toot to assess the effects of natural antimicrobials and their interactions with other growth-related factors on the growth response of Salmonella. The results can be applied to determine the most effective combination of hurdles to be used in the preservation of food products.