Wine, a world renowned beverage, is known for its character and it is yeast that plays a very important role in determining its character. Not only that, but it also helps to speed up fermentation. It can be rightly said that making wine is next to impossible without yeast. Dried yeast is commonly added for making wines, but some fruits also contain natural yeast. However, the question that arises is that why yeast is so essential for making wine.
Before delving any further, it is crucial to understand what yeast is. Yeast consists of micro organisms. Among these, saccharomyces cerevisiae species is used for fermenting alcoholic drinks. The process of fermentation is carried out when these micro organisms form carbon dioxide from the natural sugar present in fruit, thus forming alcohol. In simple words, winemaking is an art which basically involves the skill to manage and control the yeast.
Commonly winemakers make use of cultured yeast, which is selected as per the character they want their wine to have. However, before they can use the yeast, it is important to remove any natural yeast by introducing sulphur dioxide in controlled amount. After this the next process is to bring the yeast to life and it is done by using warm water, having a temperature of around 40°C, to dissolve it. Then it is left for fifteen minutes during which it multiplies. Once this is done, it is ready to be introduced in the grape juice, also called must.
After adding yeast, it takes some days for the process of fermentation to start. The temperature also starts to rise as yeast continues to consume sugar. This is where the winemaker uses his skills as he is required to intervene, in order to ensure that fermentation takes place at a controlled speed. This becomes even more important when producing white wines, which are considered to be very delicate. This is also done to add complex character and flavour to the wine, as slower fermentation lasts longer. If the wine is allowed to ferment quickly and that too at high temperature, then not only the flavours will get removed through carbon dioxide, but even yeast will be burned sooner.
Another crucial step of wine making is to taste it regularly while it is fermenting, as it helps to avoid the production of any undesired flavours. After the yeast serves its purpose, it settles at the vessel’s bottom and forms what is called lees or dead cells of yeast. The flavour of wine gets enhanced dramatically as it is allowed to sit on lees. However, it can also generate a bad flavour or hydrogen sulphide in the wine. Again, it is the skills of the winemaker that come into play here, as any negligence can lead to poor wine.
Due to the role played by yeast in making wine, there is a variety of yeast available these days, allowing the wine makers to choose the best one as per the style or type of wine they want to produce.