Modelling the effect of osmotic adaptation and temperature on the non-thermal inactivation of Salmonella spp. on brioche-type products

摘要

Salmonella spp. is known to survive in intermediate- and low-moisture foods. Bakery products such as cream filled brioche (a(w) 0.82-0.84), depending mainly on the a(w) of the fillings and the baking they receive for food preservation, may support survival of the pathogen. The study aimed to model the inactivation of osmotically adapted and non-adapted Salmonella in cream-fillings (praline and biscuit) and cream-filled brioche at different storage temperatures. All matrices were inoculated with ca. 6.0 log CFU/g of osmotically adapted and non adapted five-strain cocktail of Salmonella (Typhimurium, Agona, Reading, and Enteritidis) and stored aerobically in 120 mL screw-capped containers at 15, 20, and 30 degrees C. Adaptation of Salmonella was induced in cream-fillings (praline and biscuit) with a(w) adjusted to 0.88, by adding sterile water to each of the original fillings (a(w) 0.78-0.83) and incubating at 37 degrees C for 1 h. Survival of Salmonella was assessed at regular time intervals throughout storage using thin layer agar method to enhance the recovery of injured cells (n = 4). Inactivation curves were fitted best with the Weibull model using the freeware GInaFit tool and the estimated delta and beta values were used to calculate the time for 4D reduction-t(4D). Results showed that inactivation of Salmonella increased with temperature, while osmotic adaptation enhanced its survival in a food matrix-related manner. Higher survival rates of adapted cells were observed in cream-fillings (t(4D): 79.9 +/- 27.1 days on biscuit and 150.3 +/- 19.6 days on praline) compared to brioche (t(4D): 61.3 +/- 0.9 days on biscuit and 52.5 +/- 4.6 days on praline) at 20 degrees C. Secondary (linear) modelling of t(4D) showed that the survival of Salmonella was affected by temperature and osmotic adaptation. Model simulation of pathogen inactivation in independent trials on cream-fillings agreed well with observed data. In conclusion, the present data could be used as a means to identify areas for improving the performance of existing models quantifying the survival of Salmonella in bakery confectionary products with intermediate a(w).