Analysis of the microbial growth in 60Co γ-irradiated foods by calorimetry

Using a heat conduction calorimeter equipped with 24 sample units the heat evolutions from growing 60Co γ-irradiated bioburden of black pepper seeds and frozen beef were detected in the form of growth thermograms. 60Co γ-irradiation affected the growth pattern in which a dose-dependent reduction of the growth rate constant was observed together with the retardation in growth, indicating a combination of bactericidal and bacteriostatic effects. We successfully determined the minimal inactivation doses for the two food samples using the relationship between the irradiation dose and the retardation in growth tα, or the growth rate constant μ obtained from the growth thermograms. These results strongly suggested the possibility of calorimetry as measure of predictive microbiology in food irradiation. (author)