There is growing interest in the food industry in the use of long heat treatments in the range of 70 to 90°C to produce minimally processed foods that have an extended shelf life at refrigeration temperatures. The risk of growth and toxin production by nonproteolytic Clostridium botulinum in these foods is of concern. The effect of heat treatments at 70, 75, 80, 85, and 90°C combined with refrigerated storage for 90 days on growth from 106 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 during 90 days provided that the storage temperature was no higher than l2°C: 75°C for ≥1,072 min, 80°C for ≥230 min, 85°C for ≥36 min, and 90°C for ≥10 min. Following heating at 70°C for 2,545 min and storage at 12°C, growth was first observed after 22 days. A factorial 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°C), period of heat treatment (up to 2,545 min), and incubation temperature (5 to 25°C). Predictions from the model provided a valid description of the data used to generate the model, and agreed with observations made previously.

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