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

Salmonella spp. is known to survive in intermediate- and low-moisture foods. Bakery products such as cream-filled brioche (a 0.82-0.84), depending mainly on the a 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 °C. Adaptation of Salmonella was induced in cream-fillings (praline and biscuit) with a adjusted to 0.88, by adding sterile water to each of the original fillings (a 0.78-0.83) and incubating at 37 °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 δ and β values were used to calculate the time for 4D reduction-t. 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: 79.9 ± 27.1 days on biscuit and 150.3 ± 19.6 days on praline) compared to brioche (t: 61.3 ± 0.9 days on biscuit and 52.5 ± 4.6 days on praline) at 20 °C. Secondary (linear) modelling of t 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.