Development and evaluation of a model predicting the survival of Escherichia coli O157 : H7 NCTC 12900 in homemade eggplant salad at various temperatures, pHs, and oregano essential oil concentrations

Homemade eggplant salad, a traditional Greek appetizer, was inoculated Kith Escherichia coli O157:H7 NCTC 12900 supplemented with different concentrat ions of oregano essential oil (0.0, 0.7, 1.4, and 2.1% [vol/wt]) and stored at different temperatures (0, 5, 10, and 15 degrees C), The product's pH n as adjusted to 4.0, 4.5, or 5.0 with lemon juice. For each combination of t he environmental factors, the bacterial counts were modeled, using the Bara nyi model, as a function of time to estimate the kinetic parameters of the pathogen, A reduction of more than 1 log unit in E. coli O157:H7 counts was observed in all cases, and the death rate depended on the pH, the storage temperature, and the essential oil concentration. Separate quadratic models were developed with natural logarithms of the shoulder period and death ra te as estimated by the growth model, as a function of temperature, pH, and oregano essential oil concentrations. These were further used to predict th e population of E. coil O157:H7 NCTC 12900 from other inoculated eggplant s alads at random conditions of temperature, pH, and oregano oil concentratio n. The predicted values were compared with viable-count measurements for va lidation.