Ozone is a strong oxidant and potent disinfecting agent. Even though it is new for the US, it has been utilized in European countries for a long time. Ozone use may have many advantages in the food industry. There are numerous application areas of ozone in food industry such as food surface hygiene, sanitation of food plant equipment and reuse of waste water. While the destruction of bacteria by ozone has been studied extensively, relatively little information is available on the effect of various food components on the bactericidal activity of ozone. In this study, it was aimed to compare the ozone-induced destruction of a sporeformer, a Gram-positive bacterium, and a Gram-negative bacterium in the presence of fat, protein, and carbohydrate sources. The efficacy of ozone to reduce bacterial populations in food components was evaluated using sterile Class C buffer, whipping cream, and 1% solutions of locust bean gum, soluble starch, and sodium caseinate. These substrates were inoculated with spores of Bacillus stearothermophilus or vegetative cells of Escherichia coli or Staphylococcus aureus and ozonated at 0.4 ppm for 10 min. In general. it has been recorded that the starch provided little or no protective effects compared to the buffer control. The locust bean gum provided an intermediate level of protection, while the caseinate and whipping cream provided the greatest levels of protection to the bacterial populations. (C) 2003 Elsevier Ltd. All rights reserved.