Influence of indigenous strains of Saccharomyces on the biochemical composition of wine from Voskehat (Kharji) autochthonous grape variety of the Vayots Dzor region, Armenia

Аннотация

Background: Armenia’s winemaking traditions go back centuries, as it is one of the oldest viticultural regions in the world. In winemaking, spontaneous fermentation using indigenous yeasts from autochthonous grape varieties is practiced obtaining unique types of wine, which is also typical of traditional Armenian wines. However, today the wine industry strives for technological standardization, while still emphasizing the value of traditional winemaking styles to preserve the unique bouquets of Armenian wines.

Objective: The aim of this study was to isolate and characterize indigenous Saccharomyces yeast from Voskehat grape must and analyze its effect on the formation of bioactive compounds that determine the functional health potential of white wine from Voskehat grape.

Methods: The grapes were hand-picked in the vineyards of Aghavnadzor village, Vayots Dzor region of Armenia, at the end of September, when they reached full technical maturity. Physicochemical analyses of grapes and wine were carried out by OIV (International Organization of Vine) methods. Organic acids were separated and identified by liquid chromatography. Metabolic characteristics (glucose consumption, ethanol and organic acid production) were determined by laboratory fermentations of grape must. Residual sugar, density, ethanol concentration, titratable and volatile acidity, pH and volatile compounds were determined from 0.9-liter fermentation batches. 

Results: Twenty-eight isolates were obtained from Voskehat grape must. Eighteen representative strains selected from all colony morphotypes were subjected to species identification by sequencing. The autochthonous yeast strains Saccharomyces cerevisiae MDC-9852 and S. bayanus MDC-9862 were selected based on their physiological and biochemical characteristics. The parameters used to evaluate the strains were related to growth (growth kinetics) and metabolism (glucose, sucrose, ethanol and glycerol consumption). Technological characterization of the yeast was carried out in the same Voskehat grape must from which the yeast was isolated. Physicochemical parameters of the autochthonous strains and the commercial reference strain S. cerevisiae VR-44 in terms of alcohol content, residual sugar, volatile acids, free and total sulfur dioxide are almost identical and are within the permissible limits. Samples fermented with S. bayanus MDC-9862 and S. cerevisiae MDC-9852 strains are characterized by a higher content of tartaric acid 1.89 and 1.99 g/l and lactic acid 3.13 and 3.51 g/l, respectively, which have a positive effect on the quality and taste of wine.  

Conclusions: The studied yeast strains are characterized as effective in the process of making white wines. The aldehyde and acetal content indicators are noteworthy. The highest aldehyde values ​​of 85.18 and 81.40 mg/l were recorded in the yeast strains S. bayanus MDC- 9862 and S. cerevisiae MDC- 9852, respectively, so it can be assumed that they can be effective in the production of sherry wines. Wine from the Voskehat grape variety fermented with the yeast strains S. bayanus MDC-9862 and S. cerevisiae MDC-9852 has a high functional potential due to the good level of biologically active organic acids.

Keywords: Voskehat grape, autochthonous yeast, Saccharomyces strains, fermentation, organic acids, wine quality.