Fermentation is an essential link in the process of winemaking, which plays a role of "linking the preceding with the following". The process is not simple. This article will briefly introduce the fermentation process of red and some basic points for attention. First, understand the concept of wine fermentation. The Fermentation process of wine includes alcohol Fermentation and Malolactic Fermentation (" MLF "). Alcoholic fermentation is the process by which sugars in grapes are converted into alcohol and carbon dioxide by yeast in a wine fermentation tank. Malate-lactic acid fermentation occurs at the end of alcoholic fermentation, where lactic acid bacteria convert the sharp malic acid into a milder lactic acid.

The fermentation process of red wine. Most grapes used in red wine are de-stalked and crushed before fermentation, but some winemakers choose to use whole clusters of uncrushed grapes for fermentation, use whole clusters of uncrushed grapes, or add a small portion for slight flavor.

Stalk and Crushed Grape Fermentation After stalking and crushing, grapes are transferred to wine fermentation tank. Fermentation containers can be stainless steel, cement, or oak barrels, and are usually large in volume with an open-top to allow the winemaker to control the cap during fermentation. Cap is floating on the liquid surface in the process of fermentation, a thick layer of pulp and peel, if no wine cap, allow its natural development, then the lower level of spirit and its contact will be limited, is not conducive to fully extraction material color, fragrance, and tannins, so in the process of fermentation, the control of cap is very important. 

The methods of controlling the liquor cap mainly include the following three: 

① Punching Down As the name suggests, it presses the liquor cap into the liquor. Traditionally, the method involves manually pushing the cap down with a paddled stick, but the high concentration of carbon dioxide above the fermenter poses a hazard to workers. Today, mechanical paddles can also achieve the same effect, have been widely used.

② Pumping Over the fermented grape juice from the bottom to the top of the fermenting tank and pouring the wine cap through. 

③ Rack and Return: The juice from the fermented grapes is drained into another wine fermentation tank, leaving only the cap, and the juice is pumped back onto the cap.

The result is a more supple, fresh-fruity wine made by fermentation of whole, unbroken bunches of grapes. However, the necessary precondition for fermentation is that the grape stalks need to be completely ripe, otherwise, the wine will carry the bitter taste of the fruit stalks. The whole bunch of grapes fermentation methods mainly have the following three: 

① carbon dioxide impregnation method: the whole bunch of grapes without broken into the wine fermentation tank, into which the injection of carbon dioxide to remove all oxygen, so that, without the intervention of yeast, the fruit will naturally produce alcohol (that is, "fruit fermentation"). When the alcohol level reaches 2%, the skins begin to crack and the juice begins to flow out. The pressing usually begins at this point. The juice separated from the skins is then transferred to an aerobic environment and yeast is added for a traditional alcoholic fermentation.

② Half carbon dioxide impregnation method: this method does not need to inject carbon dioxide into the wine fermentation tank. 

The weight of the tank at the top of the grape will be at the bottom of the grapes are crushed and broken at the bottom of the grapes from grape juice, under the influence of ambient yeasts, this part of the grape juice to ferment and produce carbon dioxide, cut off from the rest of the complete grapes was carbon dioxide oxygen, started in the fruit fermentation, then gradually split skin and outflow of grape juice, squeezing usually, at this time also, Then yeast was added to make alcoholic fermentation of grape juice. 

③ The whole bunch of grapes will be mixed with the broken grapes: after the fermentation begins, the whole bunch of grapes will be added to the broken grapes, and the grapes will be soaked in it and isolated from oxygen, and then the fermentation will begin. After the pressure cap is passed during fermentation, the whole grape will gradually break up. In all three of the whole bunch fermentation methods, in-fruit fermentation, such as cherry liqueur, banana, bubble gum, and cinnamon, gives the wine its distinctive flavor. In addition, CO² immersion method and half CO² dipping method, because the grape juice and rind of short contact time, main is the surface layer of the skin pigment extract and aromatic substances, and almost won't extract contain deep in the skin more tannins, so into the wine usually supple, tannin content is low, with fragrant and fresh fruit.