PREDICTIVE MODEL DESCRIBING THE EFFECT OF PROLONGED HEATING AT 70-TO-80-DEGREES-C AND INCUBATION AT REFRIGERATION TEMPERATURES ON GROWTH AND TOXIGENESIS BY NONPROTEOLYTIC CLOSTRIDIUM-BOTULINUM

There is growing interest in the food industry in the use of long heat treatments in the range of 70 to 90 degrees C to produce minimally pr ocessed foods that have an extended shelf life at refrigeration temper atures. The risk of growth and toxin production by nonproteolytic Clos tridium botulinum in these foods is of concern. The effect of heat tre atments at 70, 75, 80, 85, and 90 degrees C combined with refrigerated storage for 90 days on growth from 10(6) spores of nonproteolytic C. botulinum (types B, E, and F) in an anaerobic meat medium was studied. The following heat treatments prevented growth and toxin production d uring 90 days provided that the storage temperature was-no higher than 12 degrees C: 75 degrees C for greater than or equal to 1,072 min, 80 degrees C for greater than or equal to 230 min, 85 degrees C for grea ter than or equal to 36 min, and 90 degrees C for greater than or equa l to 10 min. Following heating at 70 degrees C for 2,545 min and stora ge at 12 degrees C, growth was first observed after 22 days. A factori al experimental design allowed a predictive model to be developed that described the incubation time required before the first sample showed growth as a function of heating temperature (70 to 80 degrees C), per iod of heat treatment (up to 2,545 min), and incubation temperature (5 to 25 degrees C). Predictions from the model provided a valid descrip tion of the data used to generate the model, and agreed with observati ons made previously.