Fruit wine is a general term for wine brewed from fruits. In the brewing process of fruit wine, due to the difference of fruit types, mainly the pre-treatment of fruits, the technological process is also slightly different. This article mainly takes grapes as an example to summarize the basic production process as follows.
1. Raw materials
The raw materials for the production of fruit wine are wine grapes and fruits, and the characteristics of the wine produced by the different types of raw materials are also different. Good wine must be produced from good wine grapes. It is very important to choose good grape varieties and high-quality raw materials for wine production.
The selected grapes are required to meet the requirements: good maturity, complete and fresh fruit grains, no rot, no disease, no phytotoxicity, no impurities, and no pollution.
Crushing is the destemming (or partial destemming) of grape berries by pressing them to facilitate the flow of juice. In the process of breaking, it must be done:
After the grapes enter the factory, they should be crushed in time to ensure the freshness of the raw materials;
Try to avoid crushing the core and crushing the fruit stalk;
Grapes and grape juice must not be in contact with iron, copper and other metals;
Sulfur dioxide is added correctly at the same time as the grape must is in the tank so that the fermentation can go smoothly.
Pressing is to squeeze out the juice or wine in the grape berries or pomace to dry the pomace, so as to improve the utilization of raw materials as much as possible. In the production of red wine, the fermented pomace is pressed. In the production of white wine, the grapes are pressed with or without destemming and then fermented. During the pressing process, in order to avoid extruding the undesirable substances contained in the peel, fruit stem and fruit seeds themselves, it is required that the pressing should be carried out slowly, and the pressure should be gradually increased and not too high.
Fermentation is the key process of turning grapes into wine under the action of yeast, and it is the main process control point in the fermentation process.
4.1 Adjust the sugar content of raw materials
Make the alcohol content of the product after fermentation meet the predetermined requirement. Alcohol in wine is produced by the conversion of sugar, so the content of sugar in grape raw materials determines the alcohol content produced by fermentation. Generally, 1.7 g of sugar can be fermented to produce 1 g of alcohol. Therefore, to obtain 12% (V/V) alcohol by fermentation, the sugar content of grape raw materials should be 204 g/L.
4.2 Add active dry yeast and sulfur dioxide
The addition of active dry yeast and sulfur dioxide makes the alcoholic fermentation smooth. After the grape fermentation substrate is treated with an appropriate amount of sulfur dioxide, the fermentation can also be triggered without the addition of artificial yeast alcohol. However, adding the highly active yeast artificially selected into the fermentation substrate can trigger the alcoholic fermentation earlier. Kill wild yeast, ensure the normal and smooth fermentation of fine cultured yeast, increase the fruity aroma of wine, and ensure the quality of fermented wine is stable and consistent.
4.3 Control fermentation temperature and time
A certain amount of heat is generated during the alcoholic fermentation, and as the fermentation progresses, the released heat increases continuously. For every 1 g of alcohol produced, the temperature rises by about 2.5°C. If the fermentation temperature is too high, it will lead to poor texture of the wine, and it is not good for the growth and reproduction of yeast, and it is easy to cause the suspension of fermentation.
Usually white wine is fermented at a temperature of 18-22°C for about 15 days. The fermentation temperature of red wine is controlled at 25-30 ℃, and the time is about 7 days. During the fermentation process, cooling measures are generally taken, such as spraying, interlayer cooling, etc.
When the sugar content reaches about 1%, or when the specific gravity drops below 1000, the fermentation ends.
During the red wine fermentation process, the grape juice must be circulated regularly to increase the pigment content and chroma of the red wine, which is an important link in the red wine fermentation cycle.