The basic principle of winemaking is the fermentation of yeast and lactic acid bacteria. Yeast plays a major role. It can be said that without yeast, there is no wine. High quality, highly active yeast is one of the most important factors in the production of good wine.
Traditional home winemaking uses wild yeast attached to the surface of the grape skins for fermentation. Due to differences in variety and quantity, such as incomplete fermentation, flavor and texture, the quality of the wine produced fluctuates greatly and is difficult to control. The use of special quality yeasts in winemaking ensures the absolute superiority of yeast varieties and quantities and yeast colonies, effectively inhibits the reproduction of other impurities, and has advantages in terms of alcohol and sulfur dioxide resistance, thus ensuring the stability and reliability of wine quality.
Winemaking temperature and time: The yeast fermentation temperature of wine is about 15-30 degrees wine, the best temperature is 21 degrees, generally should be controlled at 18-26 degrees. In the early stages of winemaking, the yeast is still growing, so the temperature can be controlled at the lower limit. During vigorous fermentation, the temperature should not be too high because of the large amount of heat released.
In the middle and later stages of fermentation, the control temperature can be increased, which facilitates the maceration and dissolution of the active ingredients in the skins. Low temperature fermentation allows for more fruit flavor, higher wine precision and longer fermentation time.
The fermentation time is usually around 5-7 days, in many cases up to 12 days.
Daily processing: The pomace is pressed and the syrup is stirred every morning and evening to make the fermentation reaction even and complete.
Fermentation process.
On the first day of processing and filling the grapes, the fermentation vat should be kept 1/4 full to prevent rising during the fermentation process and the vat opening should be closed. During 24 hours, the yeast is in the growth phase and the optimal temperature is 21°C.
On the 2nd to 3rd day, the yeast is in the reproduction stage and gradually enters into the vigorous fermentation stage, foam appears on the surface of the syrup and gas escapes from the fermentation barrel. When the leather residue floats, you can smell the wine. Stir and press the leather residue 2-3 times a day to make it ferment evenly. At this time, the temperature should be controlled at 18-20 degrees.
On the 4th-5th day, the operation will be the same as on the 3rd day. The fermentation reaction will gradually ease, the wine will increase in flavor and the sweetness of the syrup will gradually decrease. Additional sugar can be added as appropriate and the temperature can be controlled at 22-26°C. On days 6-7, the procedure is the same as above. As time passes, the color of the syrup gradually becomes lighter and more clarified, and the alcohol content gradually increases. When the alcohol content increases to a certain level (more than 13%-15% alcohol), most of the yeast no longer survive, yeast fermentation stops and the wine is initially formed.
