Biochemical processes during secondary fermentation of apple juice and storage of sparkling wines
Apple sparkling wines are characterized not only by the foamy and sparkling properties common to all wines of this type, but also by freshness and lightness of taste, which are the result of a harmonious combination of the taste qualities of fruit juice and its fermentation products against the background of low alcohol content and low oxidation. The aim of the study was to change the main physical and chemical parameters and the number of yeast cells during fermentation - deaeration and fermentation of apple juice and wine. The objects of research were winter varieties of apples Idared, Jonathan, Renet Simirenko, Florina, apple wine materials and finished wine. The chemical composition and quality of fruits and wine materials were determined according to generally accepted methods in winemaking. It has been established that during the day, the decrease in the R potential during deaeration of the fermentation mixture for apple cider occurs within the range of 8-20 mV, and the higher the initial potential, the more effective its reduction. In the first 3-5 days, a decrease in the R potential by an average of 50-71 mV was observed in all samples. Then the potential basically remained at this level without changes. Studies have shown that when fermenting natural fermented juice with freshly introduced wine yeast, the number of cells after 2 days increases by more than 2.7 times, and after 5 days - almost 4.5 times, reaching 31 million/ml. The most intensive reproduction of yeast is observed on the 2nd-3rd day of fermentation. At the same time, there is a sharp decrease of ammonia nitrogen, amine nitrogen and oxygen in the content. A decrease in the content of oxygen and peroxides, in turn, is accompanied by a significant decrease in the R potential of the fermenting must. After 5 days of fermentation, the number of yeast cells increases by 4.4 times with the full use of nitrogen nutrition, especially ammonia nitrogen, as well as oxygen. The increase in the initial alcohol content of the fermented juice to 8.5% vol. reduces the rate of yeast growth.