Growth of Clostridium perfringens from spore inocula in cooked cured beef: development of a predictive model |
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Authors: | V. K. Juneja J. S. Novak H. M. Marks D. E. Gombas |
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Affiliation: | a US Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA;b US Department of Agriculture, Food Safety Inspection Service, 14th and Independence S.W., Washington, DC 20250, USA;c Nat. Food Processors Assn., 1350 I St. N. W. Ste. 300, Washington, DC 20005, USA |
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Abstract: | The objective of this study was to develop a model to predict the growth of C. perfringens from spores at temperatures applicable to the cooling of cooked cured meat products. C. perfringens growth from spores was not observed at a temperature of 12 °C for up to 3 weeks. The two parameters: germination, outgrowth, and lag (GOL) time and exponential growth rate, EGR, were determined using a function derived from mechanistic and stochastic considerations and the observed relative growths at specified times. A general model to predict the amount of relative growth for arbitrary temperature was determined by fitting the exponential growth rates to a square root Ratkowsky function, and assuming a constant ratio of GOL and generation times. The predicted relative growth is sensitive to the value of this ratio. A closed form equation was developed that can be used to estimate the relative growth for a general cooling scenario and determine a standard error of the estimate. The equation depends upon microbiological assumptions of the effect of history of the GOL times for gradual changes in temperature. Applying multivariate statistical procedures, a confidence interval was computed on the prediction of the amount of growth for a given temperature. The model predicts, for example, a relative growth of 3.17 with an upper 95% confidence limit of 8.50 when cooling the product from 51 to 11 °C in 8 h, assuming a log linear decline in temperature with time. |
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Keywords: | Cooling Clostridium perfringens Cooked cured meat Temperature Spore growth |
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