A numerical algorithm for calculating microbial survival curves during thermal processing

Assuming that the targeted microorganism’s isothermal survival curves follow the Weibullian pattern, which describes a large number of microbial isothermal survival curves, a simple numerical algorithm was developed to calculate the momentary survival ratio during non-isothermal thermal processes. The algorithm is based on a mathematical expression derived from a non-isothermal survival rate model proposed in the literature.Simulations indicated that the proposed algorithm generated the same results as those obtained from other non-isothermal models found in the literature. However, compared to the published models, the proposed algorithm has two advantages. One is that the calculation speed is very fast because only simple algebraic operations are involved, and the other is that it can be programmed very easily in different computer languages and spreadsheets. In addition, the algorithm provides an effective way to estimate changes of microbial survival ratio with time from product temperatures that are either directly measured during thermal processing or predicted by proper heat transfer models. Thus, the algorithm can also be easily incorporated into control systems of commercial thermal process equipment.