The Impact of Water and Product Composition on Pathogen Survival and Inactivation

Salmonella is known to persist for long periods in desiccated environments and food products. Additionally, its enhanced resistance to lethal treatments in low-moisture foods is a well-known challenge in designing, validating, and operating pathogen reduction processes for these types of products. In general, Salmonella thermal resistance is known to increase with decreasing water activity; however, the interactions between water content, other product components, product structure, and dynamic process conditions are complex and heretofore rarely reported. The purpose of this presentation is to summarize the state-of-knowledge related to pathogen survival and inactivation in low water activity food products, and the resulting impacts on process validation. Field survey data will illustrate the differential persistence of Salmonella in various components of real-world processing systems (e.g., tree nuts). Laboratory-scale data will demonstrate the significant impact of product characteristics (e.g., water activity, composition, structure) on resulting inactivation kinetics of multiple low-moisture products (e.g., nut, cereal, and fruit products). Lastly, pilot-scale data will show how processing conditions (e.g., humidity and air velocity) can significantly reduce the impact of product water activity on the inactivation of Salmonella during thermal processes.