Impact of Different Winemaking Operations on the Concentration of Dissolved Oxygen in Wines

Abstract

In order to assess the impact of prefermentation alterations of oxidative conditions in Chardonnay juice, 25 small-scale fermentations were carried out. Treatments varied in oxidative aerations or deficits and five different yeast strains were used. The oxidative conditions of the juice were altered at various points in the fermentation to determine optimal processing conditions. The treatments ranged from aeration or sparging with nitrogen prefermentation to aerations at a specific time point in the fermentation or postfermentation or receiving no intentional oxygen introduction. These treatments were intended to mimic realistic production practices in winemaking. Dissolved oxygen readings of the various conditions indicated negligible impact of oxygen introduction or mixing to the juice. Dissolved oxygen readings ranged from 0.05 to 0.12 mg/L and did not stabilize efficiently. Several factors could have influenced this observation, including enzymatic activity of the juice or sensitivity of the instrumentation. The yeast strains used included three MET10-932 Phyterra strains (P1Y0, P2Y3, and P7Y9) and two strains that contained the wild type MET10 gene (CY3079 and EC1118). Preliminary results indicated a significant difference in the fermentation rate of P7Y9 from all other strains used, with P7Y9 taking an average 10 days longer than all other strains to complete primary fermentation. An additional benefit of this research was the examination of the MET10-932 yeast strains that have proven in a laboratory setting to be low in producing H2S. As Chardonnay juice has historically produced H2S in primary fermentation, application of the yeast strains proved to be effective in determining fermentation capabilities of these newly identified strains. Significant differences among treatments within the same strain were not observed in any of the strains in the context of fermentation rates. This practical application is useful in aiding industry decisions in prefermentation processing treatments.