Time-temperature profiles of chilled ready-to-eat foods in school catering and probabilistic analysis of Listeria monocytogenes growth.

The purpose of this study was to evaluate the chill chain in school catering by monitoring time-temperature profiles. Chilled ready-to-eat foods have been chosen as subject of this study because of their high risk due to their production, storage and distribution steps, separated in time, followed by consumption without any further thermal treatment. In order to integrate the effects of storage duration and storage temperature, a quantitative criterion, namely "TTE" or "Time-Temperature Equivalent", was proposed. To illustrate the sanitary consequences of the recorded thermal history, Listeria monocytogenes growth was predicted based on reference growth curves in chilled ready-to-eat food products. The study of five centralised kitchens and 11 school-lunch canteens demonstrated in general a satisfactory maintenance of the chill chain. However, the coincidence of extended storage duration (due to weekends) and temperature abuse was observed and could lead to a significant microbial development.