The effect of electron beam irradiation, combined with acetic acid, on the survival and recovery of Escherichia coli and Lactobacillus curvatus

The preservation of food by ionising radiation may lead to undesirable sensory changes within the food. These changes can be reduced by combining irradiation with other treatments, for example the addition of organic acids. Late exponential phase cultures of Escherichia coli and Lactobacillus curvatus were irradiated, in a liquid medium, at doses of 0-1.8 kilograys (kGy), in the presence of acetic acid (0-2%) at pH 4.6. A synergistic effect occurred when E. coli was irradiated in the presence of acetic acid (0.02-1.0%) at all doses used (0.145-1.1 kGy). There is evidence to suggest that membrane disruption occurred in the cells as a result of the combined treatments and this may account, to some extent, for the synergism observed. The addition of acetic acid up to a concentration of 2.0% had no effect upon the radiation survival or upon the subsequent growth of L. curvatus. (C) 1997 Elsevier Science B.V.