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.

Effect of alcoholic and acetous fermentations on the phenolic acids of Kei-apple (Dovyalis caffra L.) fruit.

BACKGROUND: The Kei apple is a tree found on the African continent. Limited information exists on the effect of alcoholic and acetous fermentation on the phytochemicals of Kei apple. The fruit has increased concentrations of l-malic, ascorbic, and phenolic acids among other compounds. Juice was co-inoculated with Schizosaccharomyces pombe (Sp) and Saccharomyces cerevisiae (Sc) to induce alcoholic fermentation (AF). Acetous fermentation followed AF, using an acetic acid bacteria (AAB) consortium. RESULTS: Saccharomyces cerevisiae + Sp wines and vinegars had the highest pH. Total acidity, soluble solids and l-malic acid decreased during AF and acetous fermentation, and was highest in Sc wines and vinegars. Volatile acidity (VA) concentration was highest in Sp vinegars but was not significantly different from Sc and Sc + Sp vinegars. Gallic acid was highest in Sp wines and vinegars, whereas syringic acid was highest in Sc wines and vinegars. The Sc + Sp wines were highest in caffeic, p-coumaric, and protocatechuic acids. Schizosaccharomyces pombe vinegars were highest in caffeic and p-coumaric acids. Highest concentrations of ferulic and sinapic acids were found in Sp and Sc wines, respectively. Chlorogenic acid was most abundant phenolic acid in both wines and vinegars. CONCLUSION: Saccharomyces cerevisiae + Sp and Sc fermentation had a positive effect on most phenolic acids; Sc + AAB had an increased effect on syringic and chlorogenic acids, whereas Sp + AAB resulted in an increase in gallic, caffeic, and p-coumaric acids. The AAB selected had minimal performance with respect to VA production in comparison to commercial vinegars. Acetic acid bacteria selection for acetous fermentation should therefore be reconsidered and the decrease of certain phenolic acids during acetous fermentation needs to be investigated. © 2021 Society of Chemical Industry.