Linear and Non-Linear Kinetics in the Synthesis and Degradation of Acrylamide in Foods and Model Systems

Isothermal acrylamide formation in foods and asparagine-glucose model systems has ubiquitous features. On a time scale of about 60 min, at temperatures in the approximate range of 120−160

Microbial survival curves - The reality of flat shoulders and absolute thermal death times

Occasionally, experimental survival curves of micro-organisms exposed to a lethal agent have a flat region and traditionally it has been interpreted as evidence of the existence of a “shoulder”. However, if the survival curve is considered the cumulative distribution of lethal events, which reflects a spectrum of resistances, or sensitivities, then when the distribution\u27s mean, or mode, is large relative to its spread, a region resembling a “shoulder” will be observed irrespective of whether the distribution is symmetric or skewed. Computer simulated survival curves generated with the Fermi and Weibull distributions as models demonstrate that the shape of the survival curve alone is, therefore, insufficient to confirm any specific inactivation mechanisms at the cellular and molecular level, although it can refute the existence of some. Microbial mortality has also been assumed to be a process following an exponential decay and hence that a certain degree of survival is inevitable. It is not inconceivable, however, that there can be an absolute thermal death time if the survivors are being progressively weakened by a prolonged exposure to the lethal agent. This testable possibility is demonstrated with simulated survival curves generated with two mathematical models

Advanced quantitative microbiology for food and biosystems: Models for predicting growth and inactivation

Presenting a novel view of the quantitative modeling of microbial growth and inactivation patterns in food, water, and biosystems, Advanced Quantitative Microbiology for Foods and Biosystems: Models for Predicting Growth and Inactivation describes new models for estimating microbial growth and survival. The author covers traditional and alternative models, thermal and non-thermal preservation, water disinfection, microbial dose response curves, interpretation of irregular count records, and how to estimate the frequencies of future outbursts. He focuses primarily on the mathematical forms of the proposed alternative models and on the rationale for their introduction as substitutes to those currently in use. The book provides examples of how some of the methods can be implemented to follow or predict microbial growth and inactivation patterns, in real time, with free programs posted on the web, written in MS ExcelÒ, and examples of how microbial survival parameters can be derived directly from non-isothermal inactivation data and then used to predict the efficacy of other non-isothermal heat treatments. Featuring numerous illustrations, equations, tables, and figures, the book elucidates a new approach that resolves several outstanding issues in microbial modeling and eliminates inconsistencies often found in current methods