ORGANIC ACIDS CONCENTRATION IN WINE STOCKS AFTER Saccharomyces cerevisiae FERMENTATION

97 Organic acids play an important role in wine biotechnology because of the taste im par ted by the concentration, of the different organic acids. Organic acids in wine include tartaric, malic, citric, lactic, acetic, succinic and others. Concentration of organic acids varies depending on different factors such as temperature, pH, concentration of oxygen and carbon dioxide. Wine taste depends mainly on the ratio of tartaric acid to malic one. If the ratio of these acids is about 2 or less, the wine will not be harmonious and will have a sour aftertaste. On the contrary, wine stock with the best flavor and bouquet will be obtained at a ratio of tartaric to malic acid equal coefficient 3 and more. Some organic acids have their own specific taste and aroma. For example citric acid gives freshness to wine, succinic acid has salty-bitter taste, and malic acid gives the taste of green apples. However, malic acid may exhibit different flavours depending on the concentrations of ethanol, tannic acids, sugar, aromatic and mineral substances. Making quantitative changes in the ratio of these compounds makes it possible to achieve the tastes of different harmonious acidity [1, 2]. Buffering also plays an important role in formation of taste that results mostly from potassium ions in malic acid and, to a lesser extent, from small ions of Ca, Mg, and Na. In sparkling wines, acidic harmony is controlled by concentrations of sugar and carbon dioxide, but in dry wines it is controlled by concentrations of organic acids [3, 4]. Interaction of organic acids and alcohol, with their degradation products (example of tartaric acid degradation) play an important role in forming of organoleptic properties of wine stocks, which is very important in wine biotechnology. Organic acids commence to be accumulated in the grapes at the moment when grapes begin to accumulate and concentrate sugar. At the moment of reduced accumulation of organic acids, titratable acidity decreases sharply [5, 6]. During fermentation of grape must with high titratable acidity, decreasing acidity indicates the completion of fermentation. The amount of tartaric and malic acids decrease, however the amount of citric and succinic acids increase, which is natural. Lactic acid is formed, which is impossible to find in the ripe grapes. Wine stocks at a high pH have a sour taste. Therefore, strict adherence to deadlines in harvesting grapes will be a key to successful formation of optimal concentration of organic UDC 634.8:632.93:661.74:663.2