Secondary fermentation (wine)

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Secondary fermentation is a crucial process in the production of certain types of wine, most notably in the creation of sparkling wine and some still wines to enhance complexity. This process follows the initial fermentation where yeast converts sugars in the grape juice into alcohol and carbon dioxide (CO2). Secondary fermentation involves a second addition of yeast and sometimes sugar to the wine, leading to further fermentation within a closed environment. This article delves into the methods, purposes, and outcomes of secondary fermentation in winemaking.

Overview

Secondary fermentation is distinguished from the primary fermentation by its timing and purpose. While primary fermentation's goal is to transform grape juice into an alcoholic beverage, secondary fermentation serves to refine the wine's character, add carbonation, or both. This process can occur in sealed bottles, as in the traditional method for making Champagne, or in large pressurized tanks, known as the Charmat method, used for producing some sparkling wines and Prosecco.

Methods

Traditional Method

The traditional method, or méthode traditionnelle, involves adding a mixture of sugar and yeast, known as the liqueur de tirage, to the wine after the primary fermentation and bottling. The bottles are then sealed, usually with a crown cap, and left to ferment for a second time. This secondary fermentation generates additional alcohol and carbon dioxide, which dissolves into the wine, creating the bubbles characteristic of sparkling wine. After fermentation, the wine ages on the dead yeast cells, or lees, which contributes to its complexity and texture.

Charmat Method

In the Charmat method, the secondary fermentation takes place in large, sealed, pressurized tanks rather than individual bottles. This method is faster and less labor-intensive than the traditional method, making it more cost-effective for producing large quantities of sparkling wine. The wine is later transferred to bottles under pressure to maintain the carbonation.

Purposes and Outcomes

Secondary fermentation can serve various purposes, depending on the type of wine being produced:

• Carbonation: In sparkling wines, the primary purpose is to introduce carbonation, creating the effervescence that these wines are known for.
• Complexity and Flavor: The process of aging on the lees during secondary fermentation can add complexity, body, and flavors to the wine, due to the autolysis of yeast cells.
• Alcohol Content: Although the increase in alcohol content is minimal, secondary fermentation does slightly raise the overall alcohol level of the wine.

Considerations

Secondary fermentation requires careful control of temperature, pressure, and timing to achieve the desired outcome. The process can vary significantly in duration, from a few months to several years, depending on the winemaker's goals. Additionally, the process of removing the dead yeast cells, known as disgorgement, is a critical step in the traditional method, requiring skill and precision.

Conclusion

Secondary fermentation is a vital step in the production of sparkling wines and contributes to the complexity of some still wines. Through careful management of this process, winemakers can craft wines with desired levels of effervescence, flavor, and texture, showcasing the art and science of winemaking.