Determination of thermal inactivation kinetics of Salmonella and a surrogate in dairy powders

​Spray drying dairy powders serves as an intrinsic hurdle (directly related to the food product) by reducing the water activity levels, which prevents and controls microbial growth. However, spray drying is not considered a kill-step and contamination of products with Salmonella may result in outbreaks and consumer illnesses that have been observed in spray dried dairy powders (LiCari & Potter, 1970; Park et al., 2004). Thermal pasteurization of dairy powders is effective against foodborne pathogens, but some, such as Salmonella, have exhibited increased thermal resistance when residing in a low-water activity food. Therefore, changes to thermal resistance of Salmonella- contaminated dairy powders in relation to changes in water activity must be investigated. Thermal inactivation kinetics will be determined of Salmonella spp. in at least two different dairy powders that will be equilibrated to three different water activity levels. Furthermore, Enterococcus faecium will be evaluated as a potential non-pathogenic microorganism to be used as a surrogate for Salmonella to validate thermal pasteurization procedures without exposing processing facilities to pathogenic microorganisms. Methods for determining the kill-ratio of Salmonella to E. faecium based on product, water activity, and treatment will be developed to provide members of the dairy industry with information and tools to increase dairy powder safety.​