Measurement of Heat Resistance Parameters for Spores Isolated from Canned Products

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Abstract
: Spores of Bacillus subtilis, B. cereus, B. megaterium and B. pumilus were isolated from canned products. Heat resistance parameters were determined for these spores in distilled water and in different juices and brines. D values for B. subtilis, B. cereus, B. megaterium and B. pumilus suspended in distilled water were 1·5, 0·8, 1·6, and 1·5 min at 212°F. The D value for B. stearothermophilus in water was 3μ4 min at 248°F. Both D and Z values were reduced when spores of B. megaterium were heated in orange and mango juices. Similarly, spores of B. stearothermophilus were destroyed in okra brine faster than in water. Sodium chloride increased the thermal resistance of B. megaterium spores and this effect was independent of NaCl concentration of 2–15%. Pectin also conferred some protection against heat inactivation of spores of B. megaterium but sucrose had no effect.