LETHALITY OF HEAT TO LISTERIA-MONOCYTOGENES SCOTT-A - D-VALUE AND Z-VALUE DETERMINATIONS IN GROUND-BEEF AND TURKEY

D-Values and z-values for Listeria monocytogenes strain Scott A were determined in lean (2.0% fat) and fatty (30.5%) ground beef inoculated with approximately 10(7) cells/g. Inoculated ground meat was sealed in glass thermal death time tubes which were completely immersed in a circulating water bath and held at prescribed temperatures for predetermined lengths of time. Survival was determined by enumeration on Columbia CNA agar base containing 1% sodium pyruvate with a CNA + 4% horse blood overlay (CBNA) and on Listeria Plating Medium (LPM). D-values for L. monocytogenes in lean and fatty ground beef at 125-degrees were 81.3 and 71.1 min, respectively, as enumerated on CBNA plus pyruvate. D-values at 135-degrees-F were 2.6 and 5.8 min in lean and fatty beef. At 145-degrees-F, D-values were determined to be 0.6 and 1.2 min. D-values calculated from LPM recovery data from fatty ground beef at 125-degrees-F were 56.1 and 34.5 min, respectively. D-values at 135-degrees-F were 2.4 and 4.6 min in lean and fatty beef. At 145-degrees-F a D-value of 0.5 min was calculated in lean beef and a D-value of 1.1 min was determined in fatty beef. The z-values determined in lean beef and fatty beef using CBNA recovery data were 9.3 and 11.4-degrees-F, respectively. The z-value in lean beef using LPM recovery data was 9.8-degrees-F. The z-value in fatty beef using LPM recovery data was 13.2-degrees-F. A D-value for ground turkey meat at 160-degrees-F could not be determined under the conditions of this study. Problems encountered are discussed.