Sporicidal action of ozone and hydrogen peroxide: a comparative study

Elimination of contaminating spores on packaging materials and food-contact surfaces remains a challenge to the food industry. Hydrogen peroxide and chlorine are the most commonly used sanitizers to eliminate these contaminants, and ozone was recommended recently as an alternative. Hence, we compared the sporicidal action of ozone and hydrogen peroxide against selected foodborne spores of Bacillus spp. Under identical treatment conditions, 11 mug/ml aqueous ozone decreased spore counts by 1.3 to 6.1 log(10) cfu/ml depending upon the bacterial species tested. Hydrogen peroxide (10%, w/w), produced only 0.32 to 1.6 log(10) cfu/ml reductions in spore counts. Thus, hydrogen peroxide, at similar to 10,000-fold higher concentration, was less effective than ozone against Bacillus spores. Resistance of spores to ozone was highest for Bacillus stearothermophilus and lowest for B. cereus. Therefore, spores of B. stearothermophilus are suitable for testing the efficacy of sanitization by ozone. Electron microscopic study of ozone-treated B. subtilis spores suggests the outer spore coat layers as a probable site of action of ozone. (C) 2001 Elsevier Science B.V. All rights reserved.