Aliquots (100 ml) of spore suspensions of NCTC8239 at an initial OD600 w6 were transferred into 5 ml BHI tubes with 50 mM AK. Tubes were heat treated (80 C, 10 min) to activate C. perfringens spores and then transferred to a water bath at 55 C. After 15 , 30 and 60 min of incubation, aliquots (1 ml) were heat treated (80–90 C, 10–20 min) and cooled in an ice-water bath.