Modelling the thermal inactivation of Salmonella typhimurium using bioluminescence data

Inactivation of micro-organisms by heat is a traditional food processing technique used to reduce or eliminate the microbial load in foods thus preventing bacterial associated disease and food spoilage. Models of thermal death kinetics are routinely used to predict the amount of heat required but such models are limited by the acquisition of accurate thermal death data for bacteria in situ and in complex microflora. In vivo bioluminescence from lux recombinant bacteria is an important alternative to traditional plate counts for examining bacterial injury and stress but the thermal instability of luciferase has appeared to preclude its application in heating studies. We have developed a procedure which overcomes the thermal instability of luciferase and demonstrate that computer generated models of the thermal injury of Salmonella typhimurium show equivalence between bioluminescence and viable count data.