Modelling the effect of gamma irradiation on the inactivation and growth kinetics of psychrotrophic bacteria in squid rings during refrigerated storage. Shelf-life predictions

Abstract

Psychrotrophic bacteria behaviour, when gamma irradiation is applied with shelf-life extension purposes to a fresh squid product, was modelled. In this regard, the effect of gamma irradiation at 0, 1.8, 3.3 and 5.8 kGy on psychrotrophic microorganisms in vacuum-packed squid (Illex argentinus) rings was analysed during storage at 4-5 °C. First-order kinetics satisfactorily described the radio-induced inactivation of the initial psychrotrophs population. The growth of surviving bacteria during storage was fitted to two empirical models: modified Gompertz model and a polynomial expression dependent on irradiation dose and storage time. In turn, the influence of irradiation dose on kinetic parameters of Gompertz model was described by second order polynomials. Both proposed models satisfactorily described the behaviour of psychrotrophs as affected by gamma irradiation, allowing accurate shelf-life predictions for doses up to 5.3 kGy. Considering the predictions accuracy, complete Gompertz model was preferred and model validation was done for irradiation at 4.8 kGy.