Antimicrobial efficacy gaseous ozone on berries and baby leaf vegetables

Ozone, the triatomic form of oxygen,is a strong broad-spectrum antimicrobial agent widely used for improving food safety; it rapidly auto-decomposes to oxygen and does not leaveresidues. However, its antimicrobial efficacy against microorganisms contaminating foods is greatly reduced as it promptly reacts with food organic matter, and consequently, its concentration decreases. In the last years, following the consumers'demand for RTE foods, fruits and vegetables are usually manipulated, processed and cold stored for some days before being ready for consumption. Thus, in comparison with fresh fruits and vegetables, RTE produces lead to a new matter of safety concerns with a greater frequency of foodborne illnesses. Aim of this work was to evaluate the impact of gaseous ozone treatments on microorganisms contaminating berries and baby leaf vegetables. In the case of berries, ozone was applied at 2000 nL L-1 for 5 min, or with continuous fumigation at 300 nL L-1 evaluating the effect on yeast and mold population, the microflora mainly responsible for fruit decay, during seven days of cold storage. As concerns baby leaf vegetables, ozoneation was constant (at 500nL L-1) for seven days but maintaining leaves at 4°C and 10°C, evaluating its effect on Pseudomonadaceae, bacterial population responsible for browning of leaves, as well as on total mesophilyc bacteria. Ozone caused a significant reduction of fungal contaminants on treated berries, during the conservation as compared with untreated fruits, in both application mode 2000 nL L-1 for 5min or in continuous fumigation at 300 nL L-1. The storage of baby leaves under 500 nL L-1of ozone did not significantly affect the concentration of bacterial cells in any of the storage times evaluated at both 4°C and 10°C. In conclusion, this study underlines as gaseous ozone can improve microbial quality of fruits and vegetables but the impact of its efficacy depends on both target microflora and treated vegetable. In the light of these results the control of undesired microorganisms contaminating fruits and vegetables needs to be evaluated case by case