Impact of environmental water activity on E. faecium thermoresistance and possibility of regeneration of heat-damaged cells in pasteurised canned meat

Production of high-quality tinned meat requires optimisation of sterilisation and pasteurisation processes. Changes in conditions during heating (a w , pH) affect thermoresistance of microorganisms and the possibility of their regeneration following the heating process. Inactivation models of microorganisms used in practice do not take into account these factors. The aim of this study was to determine the influence of the decreasing water activity of the medium during heating and recovery on the thermoresistance of Enterococcus faecium and determine z aw (the distance of a w from a wopt = 1 which leads to a tenfold reduction in D value) and z′ aw (the distance of a w from a′ w of the recovery medium which leads to a tenfold reduction in D value) parameters. The performed experiments revealed that Enterococcus faecium PCM 1859 thermoresistance increased during heating in the environment characterised by reduced a w . Statistically significant differences occurred when aw was reduced to the value of <0.97. The impact of a w on the Enterococcus faecium PCM 1859 thermoresistance was characterised by the following coefficients: z aw = 0.14−0.28, z′ aw = 0.18−0.44.