Abstract

When conventional preservative treatments are applied, such as heat or acid, the maximum specific growth rate (mu max) 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 mu max of Bacillus cereus and compare it with a conventional inactivation treatment (heat). To prove this, mu max was estimated in ham at 12 degrees C and in TSB at 22 degrees C after 0, 2, 3 or 4 log reduction by irradiation; likewise, mu max was estimated in whole milk at 12 degrees C and in TSB at 22 degrees C after the same log reduction using heat treatments. Our findings show that irradiation affected the mu max of survivor cells. Irradiation intensity was inversely proportional to mu max, such that greater intensity was associated with lower mu max. At the same time, growth temperature had an effect on the decrease in mu max: the radiation-induced reductions in mu max were greater at 12 degrees C than at 22 degrees C. In summary, E-beam irradiation decreases the mu max 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.