Death and injury of Staphytococcus aureus during thermal treatment of milk.

Staphylococcus aureus isolated from milk and grown in milk was heated in milk. The phenomena of death as well as injury was investigated in the range of 50 to 75 degrees C. The D60 value (decimal reduction time on salt-free medium) was 0.87 min, the D'60 value (decimal reduction time in salt-containing medium) was 0.62 min. Cultures were injured as soon as heating started. This initial thermal shock increased with increasing temperature. At 50-60 degrees C injury was more rapid than death. At greater than 60 degrees C death became faster than injury and the two processes coincided at 70 degrees C. The Z value was 9.46 degrees C and the Z' value was 9.93 degrees C.