RADIATION SENSITIVITY OF LISTERIA-MONOCYTOGENES ON BEEF AS AFFECTED BY TEMPERATURE

Longissimus dorsi from beef was inoculated with Listeria monocytogenes and the effect of gamma irradiation on the survival of this pathogen at -60 to +15 degrees C was determined. Radiation D-values were determ ined for inactivation of L. monocytogenes at 5 degrees C intervals fro m -20 to 5 degrees C. These data were used to develop an equation to p redict the response to gamma radiation within that range. An abrupt in crease in resistance oc occurred at -5 degrees C. The radiation D-valu e was 0.45 kGy at 0 degrees C, 0.77 kGy at -5 degrees C and 1.21 kGy a t -20 degrees C. A straight line was obtained when the log(10) of the D-values from -5 to -20 degrees C was plotted vs the reciprocal of the absolute temperature. This led us to calculate a value analogous to t he Arrhenius activation energy for inactivation of L. monocytogenes by gamma radiation.