| Abstract
| - Experiments were designed to demonstrate the actual contribution of yeast in the formation of theprimary aroma during the vinification of neutral grapes. Ruché was chosen as the model wine tostudy because of its unique fragrance. A yeast strain specific for Ruché was selected using a newand 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 aromacompounds 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 andwell-characterized olfaction notes during the contact with yeast. The primary aroma of nonaromaticwhite and red grapes contained in the skins can be revealed within 24−48 h of yeast contact in asynthetic nutrient medium (SNM). The primary aroma precursors extracted from the skins withmethanol, water-saturated butanol, or aqueous buffer at pH 3.2, concentrated and eluted from aC18 resin column, can be transformed to the free form wine aroma markers within 6 h of contactwith yeast cells in SNM. By contrast, prolonged maceration of the skins in aqueous alcoholic bufferat pH 3.2 or 1.1, at 50 or 70 °C did not release primary odors typical of wine. The individual primaryaroma 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 commonto many wine varieties were identified by GC−olfactometry analysis. Keywords: Selected yeast; primary aroma; wine variety
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