Modeling the survival of Escherichia coli O157 : H7 in uncooked, semidry, fermented sausage

The data collected from studies to monitor inactivation of Escherichia coli O157:H7 in uncooked fermented salami were used to develop models to descri be survival of the organism. Three models were developed that included diff erent variables to best describe E. coli O157:H7 reduction. Model A include d the variables water activity (a,), pH, time, and quadratic variables pH a nd time. Model B separated the processing stages into fermentation and dryi ng. The fermentation included the variables pH and temperature x time (ttar ea) and interaction between the two variables. The drying stage was modeled using the variables time and a, and interaction between the two. Model C l ooked at variables a, and the time at pH 5.3 to achieve a 2-D log reduction of E. coli O157:H7 and the interaction between the variables. The variable s selected for inclusion in all the models were significant at the P < 0.00 01 level. The predicted values for all models correlated well to the observ ed values with R-2 Of 0.888, 0.828, 0.836, and 0.818 for models A, B-ferm, B-drying and C, respectively. The models were validated using data from a t rial not used to develop the model. In general the predicted reduction in E . coli O157:H7 count in uncooked fermented salami was greater than for the observed E. coli O157:H7 log reductions for all models, but the relation be tween the two was linear. The results demonstrate that modeling can be a us eful tool in assessing manufacturing practices for uncooked fermented salam i processes.