NUMERICAL ANALYSIS OF THE GROWTH OF CLOSTRIDIUM PERFRINGENS IN COOKED BEEF UNDER ISOTHERMAL AND DYNAMIC CONDITIONS1

Abstract

ABSTRACT The main objective of this study was to develop a numerical technique to solve a set of biologically‐based differential equations used to describe the growth behaviors of bacteria under isothermal conditions in food systems. A 4th‐order Runge‐Kutta method was incorporated to a computer program to solve these equations covering the entire range of bacterial growth, including lag, exponential, and stationary phases. The differential growth models were tested using the spores of Clostridium perfringens inoculated to ground beef and incubated under various isothermal conditions between 17–50C. Results of numerical analysis showed that the differential equations could accurately describe the growth of C. perfringens in cooked ground beef under isothermal conditions. The differential equations were also used to estimate the growth of C. perfringens in cooked ground beef under four different dynamic temperature profiles: 2‐square waves, exponential and linear cooling. In combination with a secondary kinetic model, the growth of C. perfringens in cooked ground beef under dynamic conditions was accurately estimated. Results showed the differences between the estimated and experimentally observed growth curves under dynamic conditions were generally less than 0.5 log (CFU/g). The methodology developed in this study can be a new approach for the food industry, food retailers and consumers, and regulatory agencies to predict and estimate the bacterial growth in cooked meat products under dynamic temperature abuse and deviation conditions.