Clostridium tyrobutyricum: Heat resistance of vegetative cells

Under conditions of cheese manufacture, the vegetative cells of five strain s of Clostridium tyrobutyricum were tested for heat resistance. Simulating processing conditions, the cultures were exposed to sterile skim milk, whic h was slowly stirred at 30, 42, 45, 48 and 51 degrees C. For the respective temperatures the D-values ((X) over bar G) obtained were 323,5, 44,4, 17,2 , 7,1 and 4,0 min. The resulting z-value was 8,5 degrees C and the Q(10)-va lue 15,2. The inactivation of the cells was due to the combination of heat and incorporated oxygen. The results indicate that the vegetative cells of C. tyrobutyricum cannot survive the heat treatment in the range of 52 to 58 degrees C applied in the manufacture of hard-cheeses from raw milk. Howeve r, in the manufacture of semi-hard cheese from raw milk, the lower scalding temperatures are not sufficient for the inactivation of the vegetative cel ls of C. tyrobutyricum.