Brewing technology of dry white wine:
1) Grape harvesting
White grapes are easy to be oxidized, so care must be taken to keep the fruit intact when harvesting, so as not to affect the quality.
2) Crushing and juicing
The harvested grapes must be juiced as soon as possible. White grapes usually go through the peeling process first, and sometimes the stems are removed. In order not to squeeze out tannins and oils from grape skins, stems and seeds, the pressure must be moderate and even when pressing, and the grape residue should be turned properly.
3) Low-temperature soaking before fermentation
Grape skins are rich in flavor molecules, and traditional white wine brewing is directly juiced, so as to avoid releasing substances in skins as much as possible, and most flavor molecules stored in skins cannot be dissolved in wine. Recently, it was found that a short soaking process before fermentation can enhance the original fresh fruit aroma of grape varieties, and at the same time make the taste of white wine more rich and round. However, in order to avoid releasing too many polyphenols such as tannins, the process of skin soaking must be carried out briefly at low temperature before fermentation, and the degree of skin breaking should be moderate.
4) clear juice fermentation
white wine needs clear juice fermentation, and it takes about one day to clarify by traditional precipitation method; Centrifugal separator is more convenient, but the power is too strong. Yeast is often removed together and artificial yeast needs to be added. Traditional white wine is fermented in oak barrels. In the fermentation process, the smell of woody and vanilla in oak barrels will dissolve into the wine to make the wine more abundant. Generally light white wine is not suitable for this method. In stainless steel tank fermentation, white wine fermentation must be slow to retain the original flavor of grapes and make the fermented flavor more delicate. In order to slow down the fermentation, the temperature must be controlled between 18℃ and 2℃.
5) Aging
Yeast that died after fermentation in oak barrels will be deposited at the bottom of the barrels, and the winemakers will regularly stir to mix the yeast with the wine. This method can make the wine more round. Because the wall of the barrel will permeate a little air, the white wine cultured in the barrel is golden in color and more mature in flavor.
After white wine is fermented, it needs lactic acid fermentation and other procedures to make the wine more stable. Because white wine is fragile, lactic acid fermentation must be carried out in a sealed stainless steel tank, which will weaken the fresh bouquet and sour taste of white wine. Some white wines with fresh fruit aroma and high acidity will deliberately inhibit lactic acid fermentation by adding sulfur dioxide or low temperature treatment.
6) clarification before bottling
before bottling, white wine sometimes contains impurities such as dead yeast and grape chips, which must be removed. Common methods are barrel changing, filtration, centrifugal separator and bentonite filtration, etc. After all the processes are finished, we can bottle the wine. After bottling, the dry wine has changed from grapes to wine.