Effect of Isomixing on Grape Must Fermentations of ATF1-Overexpressing Wine Yeast Strains

Speeding up grape must fermentation would be of great economic benefit. We subjected Saccharomyces cerevisiae VIN13 and two recombinant VIN13-strains expressingATF1alleles under two different promoters (eitherPGK1orHXT7) to four styles of grape must fermentations; we then assessed the effect of constantly stirring a must fermentation (isomixing). The four different fermentation setups were as follows:isomixed, closedin an ANKOM Rf Gas productions system;isomixed, openin a stirred tall tube cylinder;static, closedconstituting a conventional fermentation in a wine bottle equipped with an airlock and static; andstatic, openin a tall tube cylinder (without stirring). We report on major fermentation parameters and the volatile aroma compositions generated in the finished wines. The primary fermentations of the strains subjected to constant stirring finished after 7 days, whereas the static fermentations reached dryness after 19 days. The wines derived from isomixed fermentations produced approximately 0.7% less ethanol compared to the unstirred fermentations. The speed that the isomixed fermentation took to reach completion may provide an alternative to static fermentations in the preparation of base wines for sparkling wine production. The observed increase of volatiles of isomixed fermentations merits further investigation.