UNCERTAINTY OF MICROBIAL SHELF-LIFE ESTIMATIONS FOR REFRIGERATED FOODS DUE TO THE EXPERIMENTAL VARIABILITY OF THE MODEL PARAMETERS

The uncertainty of shelf-life estimations for refrigerated foods exposed to changing temperature was quantified by considering the contribution of the experimental variability of the model parameters. Assuming the real distribution of the parameters can be replaced by an unknown empirical distribution, this uncertainty was analyzed by a bootstrap methodology. Independent sets of heat transfer and microbial growth parameters were chosen randomly from experimental values. Shelf-life values were estimated for each set, with the variability evaluated using an SD value. The procedure was repeated 10 times to obtain 10 shelf-life SDs. The variation coefficient of these SDs is an absolute measurement of shelf-life variability. At the recommended variation coefficient of 0.1, a sample size of 25 was found acceptable. The shelf-life variability estimated was similar (+/- 1 day) for surimi in cardboard and expanded polystyrene containers with different shelf life and temperature profiles. The method is applicable to other predictions of food stability.