Effect of Water Activity on Thermal Inactivation of Salmonella in Ground Turkey

Many factors, such as fat content and pH, are known to affect thermal inactivation of pathogens in meat products, and a few studies have suggested that the humidity of the cooking environment also affects thermal inactivation. However, the effect of process humidity has not been previously isolated from the effect of water activity on Salmonella inactivation. Therefore, the objective of this study was to directly test the effect of meat water activity on thermal inactivation of Salmonella. Ground turkey was dried to achieve water activities of 0.95 to 0.99, inoculated with an 8-strain Salmonella cocktail, and heated isothermally (60 °C) in a water bath. The rate of thermal inactivation of Salmonella decreased 64% (P< 0.01) when decreasing meat water activity from 0.99 to 0.95. Inclusion of water activity improved the accuracy of a 1st-order/Arrhenius-type inactivation model from 1.94 log10 to 0.8 log10 (colony-forming units [CFU]/g).