PREDICTIVE MODELING OF INACTIVATION OF LISTERIA SPP. IN BOVINE-MILK DURING HIGH-TEMPERATURE SHORT-TIME PASTEURIZATION

A linear model was derived to describe the thermal inactivation of Lis teria innocua in bovine whole milk in a high-temperature short-time pi lot scale pasteurizer. Integrated lethal effect, or pasteurization eff ect (PE), was obtained by converting times at different temperatures i n the various sections of the pasteurizer to the equivalent time at th e reference temperature (72 degrees C). PE was then related by a simpl e linear function to the log(10) of the % viable counts with a power t ransformation of the PE values to improve the linear fit. R-2 values f or the five L. innocua trials varied from 0.728 to 0.974. Validation o f this model with Listeria monocytogenes confirmed that L. monocytogen es was more heat sensitive. Inter-trial variation was incorporated int o the model using the @RISK(TM) simulation software. Output from simul ations confirmed that pasteurization at the IDF standard conditions of 72 degrees C for 15 sec can ensure at least an 11-log reduction of L. monocytogenes. The results showed that L. innocua may be used as a mo del microorganism to assess the thermal inactivation of L. monocytogen es, since its heat resistance is at least equal to or greater than tha t of the pathogenic species. (C) 1998 Elsevier Science B.V.