POPULATION DISTRIBUTION OF HEAT RISE CURVES AS A SIGNIFICANT VARIABLE IN HEAT STERILIZATION PROCESS CALCULATIONS

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Abstract
ABSTRACT— Sterilization levels found in inoculated test packs are commonly in disagreement with predicted values. This study was made to determine if predicted sterilization values would be closer to actual test values if the population distribution of the slope indices from a sample of heat rise curves were used instead of the traditional slowest or mean single value of slope index in the sterilization calculations. A computer was programmed to calculate from the basic equations of thermal death times and heat penetration, the amount of sterilization achieved at designated time intervals in a population of food packages. Means and standard deviations of slope indices from both real and postulated heat penetration tests were fed into the computer together with specified processing conditions. Predicted spoilage levels were very close to those obtained from actual inoculated test packs. From input of postulated heat penetration values, it was demonstrated that the larger the standard deviation, the greater the error will be if only a single value of the slope index is used. Manual procedures are given for an accurate determination of the minimum process time required for sterilization. Methods are also given for data expansion to show a curve illustrating the complete relationship between process time and food sterility.

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