Amber True
 
November 21, 2017 | De Tierra Blog | Amber True

Fermentation

After harvest ends, some may wonder what happens next in the winemaking process. The grapes are taken to the winery to be processed, destemmed, and then crushed. Thus, marking the beginning of the winemaking process?  

 

When the grapes reach the winery they are put through a crusher-destemmer. A destemmer is a machine that cuts the stems off the grape clusters in order to avoid heavier tannins and bitterness in the wine. Though, some wineries cherish the stems because they can contribute more complex flavor in the wine, De Tierra does not use this process. Then the grapes are crushed to expose the juice inside which begins the fermentation process.

 

Red wines get their color from the skins of the grapes. They are crushed and then fermented with the skins in contact with the juice, in order to extract more color. On the other hand, white wines often are not crushed, but are pressed immediately. This is to separate the juice from grape skins to avoid color contamination. White grapes can be pressed whole cluster with the stems to contribute more tannic structure to the wine, or they can be destemmed before they are pressed.

 

After crush, the juice is exposed and yeast are then free to start turning the sugars into alcohol. Sugar is food for yeast and is essential in the winemaking process. There are a few other essentials that yeast need to survive, like oxygen, nitrogen, and some vitamins and minerals. Winemakers need to pay close attention to the juice during fermentation. If the yeast run low on food, they might produce bad smells that could ruin the wine if not fixed. During the beginning of the fermentation process, also known as primary fermentation, yeast multiply rapidly, and are very active due to the nutrients available. Bubbles will start to form on top of the fermentation bin and the wine will start to look alive and foamy. Primary fermentation, which is the most active part of fermentation will only last about three to five days, and will produce around 70% of the alcohol in the wine. The secondary fermentation process is a slower one, taking up to two weeks for the rest of the sugars to be turned into alcohol. Secondary fermentation takes longer due to increasing alcohol levels, which causes oxygen and nitrogen to become limited and nutrients to run low. Without ample food and nutrients, yeast begin to slow down and eventually die off.

 

Temperature is an important factor during the fermentation process for both red and white wine. Red wines should be fermented between 70 and 80 degrees Fahrenheit; color and tannins are better extracted at a higher temperature. White wines should be fermented between 45 and 60 degrees Fahrenheit in order to not extract color and tannins and create a fruitier wine.  Should the temperature get too warm, the flavors in the wine could taste cooked and the yeast will die off too soon. The opposite effect happens if the wine gets too cold during fermentation; the yeast will go dormant and stop fermenting.   

 

After fermentation ends, the wine needs to be clarified. Clarifying will rid the wine of dead yeast cells and other particles that could make the wine hazy. Clarification is done by transferring, also known as racking, the wine into another container such as an oak barrel or a stainless steel tank. Fining agents can be added that will adhere to particles and wines can be run through a filtration system. De Tierra’s wine is always vegan, meaning that there is no use of animal products to fine and clarify our wines. Animal products, such as egg whites, can be a method used to fine and clarify wines. De Tierra uses bentonite, clay made from volcanic ash, to clarify our wines. Bentonite rids the wine of haziness by bonding with particles, such as tartrates. Tartrates are tartaric acid crystals that form in a wine when there is excess acid. Cold stabilization is another way to dispose of tartrates and will prevent them from forming into crystals once the wine has been bottled. Cold stabilization is done by cooling down the wine to about 30 degrees Fahrenheit for a day or so, forcing the excess tartaric acid to form into crystals. The crystals can then be pulled out with a fining agent. Additionally, our wines are run through a filtration system to filter out smaller particles, making the wine clear.  

 

Once the wine is fined and filtered, it can be bottled or aged in barrels or tanks. White wines that don’t need aging will be bottled and released shortly onto the market; while red wines usually need some type of aging in oak barrels. Whites ‘14-’17 are drinking well now, while comparatively reds ‘11-’15 are ready for consumption. Keep this in mind next time you grab a bottle at the supermarket or your local wine shop. Cheers!

 

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