Metabolic activity stimulation of the wine yeasts by polyphenols extracted from red grapes

Abstract

Two aqueous of 1% tartaric and citric acid solutions were used for polyphenols extraction from red grapes. The effect of polyphenols of the Saccharomyces cerevisiae var. ellipsoideus strain asa model organism was investigated. Yeast was cultivated in aerobic and facultative anaerobic conditions on grape must medium enriched with different concentrations of polyphenol extracts in variable ratios. Yeasts growth kinetics was evaluated by direct counting of the cells. Cells multiplication was monitored at different moments using kinetic parameters, like number of generations, rate of multiplication and generation time. Cell viability and stability in time were estimated through microscopic observation of cell suspended in methylene blue, used as redox indicator. Results showed that polyphenols from red grapes stimulated the cell multiplication and metabolic activity and decreased the intracellular oxidation with positive effects on cell stability and viability. The maximum of fermentation intensity was reached for concentrations of polyphenols of 0,77 mg/mL extract in tartaric acid and 0,62 mg/mL extract in citric acid, at levels of 98.42% and 92.37% respectively.