Thermal inactivation of Listeria monocytogenes and Yersinia enterocoliticain minced beef under laboratory conditions and in sous-vide prepared minced and solid beef cooked in a commercial retort

D-values were obtained for Listeria monocytogenes and Yersinia enterocoliti ca at 50, 55 and 60 degrees C in vacuum-packed minced beef samples heated i n a laboratory water-bath. The experiment was repeated using vacutainers, w hich allowed heating of the beef to the desired temperature before inoculat ion. D-values of between 0.15 and 36.1 min were obtained for L. monocytogen es. Pre-heating the beef samples significantly affected (P < 0.05) the D-60 value only. D-values for Y. enterocolitica ranged from 0.55 to 21.2 min an d all the D-values were significantly different (P < 0.05) after pre-heatin g. In general, the D-values obtained for core inoculated solid beef samples were significantly higher (P < 0.05) than those generated in minced beef w hen heated in a Barriquand Steriflow commercial retort.