Impact of Yeasts Present during Prefermentation Cold Maceration of Pinot noir Grapes on Wine Volatile Aromas

Yeasts isolated from a prefermentation cold maceration (at 8 to 9 degrees C) of Vitis vinifera L. cv. Pinot noir grapes were evaluated for beta-glucosidase activity. Among the 13 distinct yeast isolates investigated, five had beta-glucosidase activity. Sequence analysis of the D1/D2 domain of the 26S rDNA gene confirmed the identity of these yeasts as Metschnikowia pulcherrima, Hanseniaspora uvarum, Lachancea thermotolerans, and two isolates of Saccharomyces cerevisiae. The beta-glucosidase activity of these yeast isolates was further investigated at different sugar concentrations and temperatures before the isolates were used in the production of Pinot noir wines. Pinot noir grapes sterilized by high hydrostatic pressure were inoculated with the individual yeast species or a mixture of all yeast species. A seven day prefermentation cold maceration (9 degrees C) was then performed, followed by alcoholic fermentation conducted by S. cerevisiae RC212 at 27 degrees C. Pinot noir grapes were also cold-macerated without the addition of any yeast, while fermentations were also undertaken with no cold maceration. Solid-phase microextraction-gas chromatography-mass spectrometry analysis of the wines indicated that the presence of the different yeast species during the prefermentation cold-maceration altered the volatile aroma composition of the wines. These yeasts altered the concentrations of ethyl esters, branch-chained esters, higher alcohols, and some monoterpenes in the wines.