Non-Saccharomyces yeast for lowering wine alcohol levels: partial aeration versus standard conditions

Non-Saccharomyces yeasts have been suggested for use in wine production for lowering alcohol content. In this study, 23 non-Saccharomyces yeasts were investigated in laboratory-scale trials using previously frozen grape must. Both aerated and standard fermentation conditions were investigated and the fermentations were co-inoculated with a commercial Saccharomyces cerevisiae reference yeast strain. Sugar consumed for percentage alcohol formed was calculated from sugar and alcohol measurements. The non-Saccharomyces yeasts showed greater variability in sugar consumption compared with the S. cerevisiae reference yeast. Two of the yeast strains (Starmerella bacillaris and Wickerhamomyces anomalus) consumed more sugar than the S. cerevisiae reference yeast under the same conditions. These two strains were subsequently used in a small-scale wine production trial following a similar aeration and standard fermentation strategy. The wine production trials using aeration compared with the standard strategy showed shorter fermentation times, increased biomass formation and more sugar utilized for alcohol produced, but reduced wine quality. The same yeasts under standard fermentation conditions also showed increased use of sugar, but neutral or positive effects on wine quality. The S. bacillaris strain showed the most potential for use in wine production for lowering alcohol content. Aeration is not necessary to achieve lower alcohol levels using the Starmerellabacillaris and Wickerhamomyces anomalus yeasts, decreasing the risk of unwanted oxidation of wine.

Automated summary

Non-Saccharomyces yeasts, specifically Starmerella bacillaris and Wickerhamomyces anomalus, show potential in wine production for lowering alcohol content. Fermentation with aeration results in shorter fermentation times, increased biomass formation, and higher sugar utilization for alcohol production, but lower wine quality. Under standard fermentation conditions, these yeasts also increase sugar use with neutral or positive effects on wine quality.