Ozone treatments of post harvested wine grapes: Impact on fermentative yeasts and wine chemical properties

Ozone represents a potent antimicrobial compound that is already proposed as a possible sanitizing agent, especially for surface decontamination of fruits and vegetables. The main objective of this study was to evaluate the effect of ozone, either in aqueous or gaseous form, on wine grape mycobiota and its impact during spontaneous and inoculated fermentations. Gaseous (32 ± 1 μL/L, 12 and 24 h) and aqueous (5 ± 0.25 mg/L, 6 and 12 min) ozone were tested as sanitizing treatments. A multiphasic approach was used employing culture-dependent (traditional plate counts) and -independent techniques, based on DNA and RNA amplification (PCR-denaturing gradient gel electrophoresis [DGGE] and reverse transcription PCR [RT-PCR]-DGGE), respectively. Microbiological analysis data highlighted a reduction of > 0.5 Log CFU/mL of the total yeasts present on grape berry surfaces after ozone treatments, mainly due to the reduction of apiculate yeasts. The chemical analysis of the wines, produced from the treated grapes, showed higher acetic acid content in the untreated spontaneous fermentations (0.52 g/L) compared to the treated (ranged from 0.16 to 0.38 g/L), while all fermentation-inoculated wines contained higher amounts of pleasant volatile compounds.