Predicting Survival of Salmonella in Low-Water Activity Foods: An Analysis of Literature Data

Factors such as temperature, water activity (a(w)), substrate, culture media, serotype, and strain influence the survival of Salmonella in low-a(w) foods. Predictive models for Salmonella survival in low-a(w) foods at temperatures ranging from 21 to 80 degrees C and water activities below 0.6 were previously developed. Literature data on survival of Salmonella in low-a(w) foods were analyzed in the present study to validate these predictive models and to determine global influencing factors. The results showed the Weibull model provided suitable fits to the data in 75% of the curves as compared with the log-linear model. The secondary models predicting the time required for log-decimal reduction (log delta) and shape factor (log beta) values were useful in predicting the survival of Salmonella in low-a(w) foods. Statistical analysis indicated overall fail-safe secondary models, with 88% of the residuals in the acceptable and safe zones (<0.5 log CFU) and a 59% correlation coefficient (R-2 = 0.35). A high variability in log delta-values and log beta-values was observed, emphasizing the importance of experimental design. Factors of significant influence on the times required for first log-decimal reduction included temperature, a(w), product, and serotype. Log beta-values were significantly influenced by serotype, the type of inoculum (wet or dry), and whether the recovery media was selective or not. The results of this analysis provide a general overview of survival kinetics of Salmonella in low-a(w) foods and its influencing factors.