Isothermal calorimetry approach to evaluate shelf life of foods

Isothermal calorimetry (IC) traces were obtained at three temperatures for industrial whole-eggs, fresh milk and carrot convenience-salads to assess their durability when stored at various temperatures. According to the nature of the degradation process (microbial, metabolic (aerobic, or anaerobic), enzymatic), the order of magnitude of the exothermic signal recorded changed. The present work mainly aimed at determining the onset time of the calorimetric signal which was related to the stability (i.e. safe shelf life) of the food investigated. The higher the storage temperature, the earlier was the onset of the calorimetric signal: the temperature effect on the stability time could be, therefore, determined. This piece of information was used to choose time–temperature–integrators suitable for the products considered. Stability times for the three products were also evaluated with other approaches (microbial plate counts, pH variation, development of turbidity). The comparison between the results of these traditional techniques and the calorimetric monitoring supported the reliability of the latter, which offers some peculiar advantages, like better temperature control, continuous follow up, easier mathematical description, overall energy balance of the degradation process.