A Thermal Process Lethality Model for Low Water Activity Food

Science-based verification of pathogen-reduction processes is an increasingly necessary action for regulatory or customer compliance and is a relatively new initiative for baked goods. Direct measure of reduction potential that uses appropriate surrogate microorganisms is effective but becomes cost prohibitive when evaluating multiple food formulas or operational conditions. Thermal predictive models are available and provide valuable tools for foods with a single key changing variable such as temperature; however, a model applied to baked goods must accommodate at least two changing variables, water activity and food temperature, to avoid erroneous results. A single surface response equation (r2 = 0.755) was created from laboratory thermal death time measurements of one formula of grain-based breakfast cereal sampled across three points (start, middle, end) of a baking process. Four additional grain-based food formulas were sampled from the entrance and exit of ovens to verify the original equation and permitted expanded application to cookies and crackers (r2 = 0.756). The surface response equation was combined with exposure time to generate a process inactivation model for low water activity foods. Process lethality estimated by use of the model with commercial production data was comparable to results obtained with direct measure using surrogate organism tested with the same conditions and equipment.