Definitive Evidence for the Actual Contribution of Yeast in the Transformation of Neutral Precursors of Grape Aromas

Abstract

Experiments were designed to demonstrate the actual contribution of yeast in the formation of the primary aroma during the vinification of neutral grapes. Ruché was chosen as the model wine to study because of its unique fragrance. A yeast strain specific for Ruché was selected using a new and rapid isolation method for red wines. The results of this study can be summarized as follows: Skins from nonaromatic white or red grapes apparently contain most of the primary aroma compounds that are revealed in the must only after contact with yeast cells under defined conditions. Similar results were obtained with the pulp and seeds fractions; however, the olfactory notes, although well characterized, differed from those obtained with skins alone. Clarification, filtration, and centrifugation of the pulp and seed fractions or sonification of the skins produce different and well-characterized olfaction notes during the contact with yeast. The primary aroma of nonaromatic white and red grapes contained in the skins can be revealed within 24-48 h of yeast contact in a synthetic nutrient medium (SNM). The primary aroma precursors extracted from the skins with methanol, water-saturated butanol, or aqueous buffer at pH 3.2, concentrated and eluted from a C18 resin column, can be transformed to the free form wine aroma markers within 6 h of contact with yeast cells in SNM. By contrast, prolonged maceration of the skins in aqueous alcoholic buffer at pH 3.2 or 1.1, at 50 or 70 degrees C did not release primary odors typical of wine. The individual primary aroma compounds, identified by GC-MS analysis in Ruché wine samples or in Ruché skin-yeast-SNM samples, could not explain the complexity of the typical Ruché wine odor. Only odors common to many wine varieties were identified by GC-olfactometry analysis.

Autochthonous fermentation starters for the industrial production of Negroamaro wines

“…These strains were selected to be further characterized. Their main oenological and technological properties and the results of quantitative analysis of the main chemical compounds present in musts fermented by each one of them are shown in Tables 1 and 2, respectively. Several studies [9,17,47,54] have emphasized the existence of a diVerential contribution among selected strains of S. cerevisiae in determining the Xavour and taste of wines, and that yeasts make an important contribution during fermentation to the expression of the character of the grape variety. Indeed, the microfermentation tests made it possible to evaluate, at the same time, the main technological properties that aVect the progress of the fermentation [45] and also oenological and aromatic properties that inXuence the quality of wines [52].…”

Molecular and Technological Characterization ofSaccharomyces cerevisiaeStrains Isolated from Natural Fermentation of Susumaniello Grape Must in Apulia, Southern Italy

“…Numerous compounds, produced by yeast during the fermentation process, determine the organoleptic quality of the final wine [29, 49–53]. The level of these substances allows to differentiate at the strain level different yeasts species [54].…”

Effects of seven yeast strains on the volatile composition of Palomino wines

“…Delfini et al. (2001) reported experiments to demonstrate the actual contribution of yeast to the formation of the primary aroma during the vinification of neutral grapes, such as Ruché.…”