Application of a predictive microbiological model for estimation of Salmonella behavior throughout the manufacturing process of salami in environmental conditions of small-scale Brazilian manufacturers

Abstract

The microbiological quality of fermented products such as salami are highly dependent on the interaction of environmental conditions during its fabrication. These effects may be predicted by mathematical modeling, and this approach has been adopted in several occasions. The aim of this study was to validate the Gamma concept model to predict Salmonella behavior during salami manufacturing in environmental conditions found in small scale Brazilian manufacturer. Furthermore, we simulated the growth and inactivation of Salmonella in salami considering a Brazilian scenario of contamination level of pork. Salami pieces were elaborated with a cocktail of five strains of Salmonella and subjected to maturation. For the fitted model construction, temperatures of 30°C during fermentation and 20°C during drying were used; while 25°C (fermentation) and 18°C (drying) were used in the validation study. Water activity (a_w) and pH were analyzed and Salmonella enumerated during maturation for fitting the curves. Salmonella isolates recovered at the end of the maturation were subjected to macrorestriction profiling (PFGE). The parameters obtained in the fitted Gamma concept model (μ_opt, δ1, δ2, α) were used to predict the bacteria behaviour in the validation study. During the maturation, Salmonella concentration decreased from 7.086 to 3.368 log₁₀ cfu/g (after 941 horas), and from 7.751 to 2.749 log₁₀ cfu/g (after 1121.5 horas) in the fitted model and validation study, respectively. The a_w was determinant for starting the microbial inactivation in the fitted model. Strains belonging to all PFGE-profiles inoculated in the salami pieces were detected in the end of the maturation. Regarding the simulation in a Brazilian scenario of pork contamination, the model predicted, in the upper 95% confidence interval, zero log₁₀ cfu/g of Salmonella after 670 h of maturation. The results indicate that the Gamma concept model provide a robust alternative to predict the concentration of Salmonella in salami considering the characteristics of production adopted in small industries in Brazil. The model predicted that in a scenario of higher environmental temperatures (30°C fermentation/ 20°C drying) Salmonella absence can be achieved after 15 days.