The time-temperature tolerance theory behind thermal kinetic models for shelf-life prediction of common foods

Abstract

Time-Temperature Tolerance (TTT) is an efficient and intuitive method of shelf-life prediction or logistics stability evaluation, but specific for frozen foods, while other thermal kinetic models for chemical reactions and microbial growth are complicated for users and widely used in common foods. In this paper, one common law deduced from TTT theory is that the equivalent conversion ratio (ECR) of the elapsed times for one isothermal interval between different temperatures is only related to the temperatures and equal to the ratio of corresponding shelf-lives. The law was demonstrated by 1-order chemical kinetic model and Gompertz model for chemical reaction and microbial growth. Besides, Crimson seedless fresh grape and Mackerel also proved the constancy of the ECRs between fixed temperatures. With the corresponding ECRs of key quality indicator among relevant temperatures, effect of any time-temperature history can be accumulated into one isothermal one equivalently and the remaining shelf life would be easily predicted, which is the theory of TTT. As a results, the quality following the chemical reaction and microbial growth obey the TTT theory, and the TTT theory can be used to predict the shelf-lives of most foods with developed time-temperature monitoring technologies.