The need to stop fermentation until all the sugar has been converted into alcohol or the wine has reached its maximum strength (natural reasons for stopping) is often caused by the desire to speed up the preparation process or maintain the current characteristics of the drink (sweetness and strength). In home winemaking, there are three methods for stopping fermentation, suitable for any type of wine (grape, apple, cherry, etc.):
1. Fixing with alcohol
The simplest and most effective method for long-term storage of wine. Wine yeast stops working at a strength above 14-16% (some artificially bred strains are active at an alcohol concentration of up to 18%, but these are isolated cases).
To stop fermentation, you need to remove the wine from the sediment and fix it with alcohol (preferably grape distillate) or vodka to a concentration of 16%. If the initial sugar content of the raw material is unknown, it will not be possible to calculate the natural strength obtained by fermentation. In this case, add 10-15% alcohol by volume of wine.
Disadvantages: the wine becomes very strong, the taste changes, vodka can give an unpleasant smell.
2. Stopping fermentation with cold
The only method that does not affect the aroma, taste, sweetness and strength of the wine. At temperatures below 10°C, yeast fungi enter a state of suspended animation (hibernation) and precipitate at the bottom.
To stop the fermentation, the wine should be transferred to a cold room with a temperature of 2-10°C (necessarily above zero) and left for 3-5 days until the fermentation stops completely, sedimentation and at least partial clarification of the must. Then remove the wine from the sediment and store at a temperature not exceeding 16°C.
Disadvantage: there is no guarantee that all yeast will be filtered out with sediment. When the temperature rises, fermentation may resume. To prevent this, sulfuric anhydrite (3-4 grams per 10 liters) or sorbic acid (according to the instructions) is added to the wine. But the use of preservatives is not the best solution for home winemaking.
3. Heat treatment
Wine yeast is killed at temperatures above 40°C. To stop fermentation, it is enough to heat the wine above the survival point of the yeast.
During classical heat treatment, the wine removed from the sediment is heated to 55-70 ° C (pasteurized) in order to destroy not only yeast, but also other harmful organisms (molds, viruses, etc.) that can survive in more extreme conditions. The stronger the drink, the lower the temperature. Then the wine is pasteurized for 10-20 minutes, cooled to 10-16°C without air (difficult to implement at home), poured into storage containers and sealed.
Disadvantages: during heat treatment, the taste and aroma of the wine deteriorate. To prevent re-infection, it is necessary to protect the wine from contact with the external environment during cooling; without this, the pasteurization efficiency decreases.