1 National Food Institute, Technical University of Denmark2 Division of Food Microbiology, National Food Institute, Technical University of Denmark3 Division of Industrial Food Research, National Food Institute, Technical University of Denmark
Growth potential of Clostridium perfringens in heated (75°C) ready-to-eat foods kept at temperatures between 20°C and 65°C was evaluated. It was examined at which temperatures the foods could be kept, without increasing the level of C. perfringens with more than 1 log cfu/g, over a period of three hours with varying characteristics such as pH, NaCl and cooling constant. Theoretical cooling constants were estimated at different locations in a small and large food (meatball and liver paste) using a variety of realistic heat transfer coefficients (5-500 W∙m-2∙K-1) in a simulation software. Based on this, time/temperature profiles were simulated and the growth of C. perfringens was predicted using Combase Perfringens Predictor. Growth was predicted at pH 6 or 6.5 in combination with 0 – 3 % NaCl at temperatures between 20 and 65°C. Cooling constants varied between 0.2 h-1 and 19 h-1 and differed significantly within the food – especially in the large food type – indicating that it is not sufficient to evaluate growth of C. perfringens in the centre of the food. Moreover, it was found that keeping ready to-eat-foods at temperatures above 52°C, having NaCl ≥3.0 % or pH ≤ 5.5 ensured that growth of C. perfringens was below 1 log cfu/g during a three-hour-storage regardless of the other parameters. For ready-to-eat foods where this is not the case, two tables (pH = 6.0 and pH = 6.5) was created showing which temperatures the foods can be kept at, dependent on the cooling constant.
2013 Congress of the Danish Microbiological Society, 2013