Bactericidal properties of ozone and its potential application as a terminal disinfectant

The efficacy of ozone as a terminal disinfectant was evaluated under labora tory conditions. Different microorganisms of importance to the food industr y were inoculated onto stainless steel squares and incubated at various tem peratures and relative humidities for up to 4 h. Survival of microorganism from these controls was compared with identically incubated squares exposed to ozone. Exposure of the contaminated surfaces to ozone (2 ppm for 3 h) r esulted in a reduction in microbial viability that ranged, depending on org anism type, from 7.56 to 2.41 log values. For all the microorganisms tested , this loss in viability was significantly greater (P < 0.05) than that obs erved in the absence of ozone. Gram-negative bacteria were more sensitive t o ozone than gram-positive organisms; bacteria were more sensitive than the yeast strain tested. Exposure to ozone (2 ppm for 4 h) in the presence of ultra-high temperature (UHT) milk resulted in a reduction in bacterial viab ility that ranged from 5.64 to 1.65 log values. In most cases, this reducti on was significantly less (P < 0.05) than that achieved in the absence of o rganic material, although still significantly greater (P < 0.05) than that observed in the absence of ozone. The presence of a meat-based broth reduce d the effectiveness of ozone to a greater extent, although the number of su rviving gram-negative organisms was still significantly less (P < 0.05) tha n in the absence of ozone. Less than 1 log unit of yeast cells was destroye d when exposed to ozone in the presence of UHT milk or meat-based broth. Re sults of this investigation suggest that if applied after adequate cleaning ozone could be used as an effective disinfectant.