E-beam irradiation affects the maximum specific growth rate of Bacillus cereus

Summary When conventional preservative treatments are applied, such as heat or acid, the maximum specific growth rate (μmax) of survivors is the same as that of untreated cells. However, when new nonthermal technology is applied, the effects of it on the kinetics of the microorganism can be unpredictable. In this sense, Cabeza et al. (2010) reported longer doubling times after irradiating with accelerated electron beam. The aim of this work was to study the effect of electron beam irradiation on the μmax of Bacillus cereus and compare it with a conventional inactivation treatment (heat). To prove this, μmax was estimated in ham at 12 °C and in TSB at 22 °C after 0, 2, 3 or 4 log reduction by irradiation; likewise, μmax was estimated in whole milk at 12 °C and in TSB at 22 °C after the same log reduction using heat treatments. Our findings show that irradiation affected the μmax of survivor cells. Irradiation intensity was inversely proportional to μmax, such that greater intensity was associated with lower μmax. At the same time, growth temperature had an effect on the decrease in μmax: the radiation‐induced reductions in μmax were greater at 12 °C than at 22 °C. In summary, E‐beam irradiation decreases the μmax of B. cereus, while heat treatment does not. This suggests that the shelf life of irradiated foods must be longer than that of heat‐preserved foods after the application of a similar inactivation treatment.