Effects of ozone treatments on microbial quality and some chemical properties of lettuce, spinach, and parsley

• Washing vegetables with chlorine was the most effective treatment against E. coli.
• Aqueous ozone was as effective as chlorine in L. innocua inactivation.
• No deleterious effects were observed after aqueous treatments of the oxidants tested.
• Ozone gas treatment significantly reduced the numbers of both microorganisms tested.
• Some important bioactive compounds of parsley were detrimentally affected by ozone gas.

The effects of distilled, ozonated (12 mg L−1) and chlorinated (100 mg L−1) water treatments on inactivation of Escherichia coli and Listeria innocua inoculated on lettuce, spinach, and parsley and on some chemical characteristics (chlorophyll a, chlorophyll b, ascorbic acid, and total phenolic contents and antioxidant activity) of these vegetables were investigated. Chlorine and ozone washes resulted in average log reductions (±standard error) of 2.9 ± 0.1 and 2.0 ± 0.3 for E. coli in the vegetables tested, respectively, while the efficiency of ozone (2.2 ± 0.1 log) was very close to that of chlorine (2.3 ± 0.1 log) on L. innocua. Aqueous ozone did not cause any detrimental effects on the chemical characteristics of the vegetables. The effect of gaseous ozone treatment (950 μL L−1, 20 min) on microbial inactivation and the chemical characteristics of parsley were also determined. This treatment resulted in 1.0–1.5 log reductions in the numbers of both microorganisms but caused significant losses in important bioactive compounds of parsley. Ascorbic acid and total phenolic contents and antioxidant activity in ozone-treated samples were 40.1, 14.4, and 41.0%, respectively, less than the control samples.