The fermentation process involved in wine making is the chemical reaction that occurs when turning grape juice into an alcoholic beverage. Much consideration should be taken when considering the exact speed and extent of the fermentation process prior to beginning, in order to protect the integrity of the final product. A seasoned winemaker will have a plan of action in place prior to beginning the process.Yeast interacts with sugars in the juice during the fermentation process and creates ethanol, also known as ethyl alcohol. It also creates carbon dioxide as a by-product.The temperature and speed of the fermentation as mentioned before, is of great importance in the fermentation process. Great care should be taken to avoid risk of stuck fermentation. When stuck fermentation occurs it can delay the process anywhere from 5 to 15 days.
Stuck fermentation can be caused by countless influences. It can happen due to incomplete nutrients that are needed in order for the yeast to complete its fermentation. Another cause could be low temperature, or drastic temperature changes which cause the yeast to stop early. And finally the percentage of alcohol could have grown too high as a result of the type of yeast selected to be used in the fermentation process.
The majority of fermentation is done in stainless steel tanks, open wooden vats, inside wine barrels, or inside the wine bottle itself as seen in the production of many types of sparkling wines.
Distinctions are made between the types of yeast that are used in the fermentation process. Ambient yeasts are the natural yeasts that are in the grapes themselves. Cultured yeasts are specifically isolated and implanted for winemaking. The most common types of yeast that is found in winemaking include: Candida, Klöckera/Hanseniaspora, Metschnikowiaceae
Pichia and Zygosaccharomyces.
High quality and special flavored wines can be produced with the use of wild yeasts. However, using these yeasts can sometimes prove to be unpredictable during the fermentation process. The most common genus of yeast used in winemaking are part of the sugar yeast species also known as Saccharomyces cerevisiae. This variety contains an abundance of hundreds strains of yeast.
When it comes to the fermentation process temperature is one of the key factors in producing a quality product. The process of fermentation creates a great deal of residual heat. Wine is generally fermented between 64-68 degrees. However, some winemakers use higher heats in order to expose the complexity of the wine.
For instance, red wine is generally fermented at higher temperatures of up to 85 degrees. As stated before, great care must be taken throughout the entire fermentation process from the type of yeast selected to the temperature used. Using a temperature that is too high can cause some wines flavor to boil away.
Every winemaker has their own secrets when it comes to the fermentation process. Many rely on handed down recipes and processes passed down from family or friends. However, the process of winemaking and proper execution of the fermentation process is something that comes with great practice, patience, and time.