Where does the alcohol in wine come from, do you know?

The alcohol we feel in our mouth is an important yardstick for judging a wine’s sense of balance. It appears in a crucial stage of winemaking-alcohol fermentation. This article will introduce you to the alcohol fermentation of red wine.

Wine is an alcoholic beverage, but the grapes used to make wine are non-alcoholic! So there must be some change in the brewing process to produce alcohol. This involves the process of alcohol fermentation.

For red wine, the alcohol fermentation is carried out at the same time as the maceration. In fact, when the tannins and pigments are released from the grape skins into the grape juice, the yeast in the grape juice begins to digest the sugar. Yeast is a microorganism whose function is to convert sugar into alcohol under suitable temperature conditions. The reason why we are able to taste good wine is thanks to these little creatures that are invisible to the naked eye.  

Yeast plays a leading role in the alcohol fermentation process. However, whether in the winery or at some tasting meetings, if you want to fully understand the winemaker’s introduction to a wine, you should understand the two sources of yeast.

There are two sources of yeast: natural yeast that comes with grapes and artificially cultivated yeast. Natural yeast is inherently present in grape skins. Many winemakers choose to use artificially cultivated yeast during the alcohol fermentation process. There are about 200 kinds of yeast in the world, and they have different effects on the taste of wine. Therefore, selecting high-quality yeast and controlling its dosage is one of the important tasks of the brewer. This is why some winemakers can proudly say that the wines he makes are definitely not achieved by using natural yeast alone. In fact, this is also a major test for the winemaker. It is necessary to make the grapes have sufficient natural yeast to ensure the smooth progress of the fermentation process, and this work must start at the grape planting stage. In addition, compared with artificially cultivated yeast, the influence of natural yeast on wine taste is more elusive. Fortunately, some artificial yeasts cultivated through strict management are of very high quality and can be used to brew great wines!

Because the alcohol in wine is converted from the sugar in the grapes under the action of yeast, in addition to the sugar content of the grape itself, which affects the alcohol content of the wine, the winemaking process also determines the level of alcohol content of the wine. For example, the year is a very important factor. Generally speaking, the drier and hotter the year, the higher the sugar content of grapes, and the higher the degree of conversion into alcohol. For example, Bordeaux’s 2003, 2005 and 2009 are very obvious examples. Sunshine and temperature also have an important effect on alcohol. For example, wines from regions such as Napa Valley or South Australia with sunny and hot climates tend to have much higher alcohol content than wines from cooler European regions. In the winemaking process, the factors that affect the alcohol content of wine include delaying the time of grape harvest in order to obtain grapes with higher sugar content, shortening the aging time in oak barrels, adding sugar before fermentation, interrupting the fermentation process, and so on.

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