Autolysis (alcohol fermentation)

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Autolysis in the context of alcohol fermentation refers to the self-digestion or self-destruction of yeast cells by their own enzymes. This process occurs when yeast cells die and their cellular components are broken down, releasing various compounds into the surrounding medium. Autolysis is a significant process in the production of certain alcoholic beverages, particularly in the aging of wine and beer.

Process

During alcohol fermentation, yeast cells convert sugars into ethanol and carbon dioxide. Once the fermentation process is complete, the yeast cells begin to die off. As the cells die, their membranes break down, and the enzymes within the cells start to degrade the cell's own proteins, lipids, and other components. This breakdown releases a variety of compounds, including amino acids, peptides, fatty acids, and nucleotides, into the surrounding liquid.

Impact on Alcoholic Beverages

Autolysis can have both positive and negative effects on the quality of alcoholic beverages:

Wine

In winemaking, autolysis is an important part of the aging process, particularly in the production of sparkling wine such as Champagne. The breakdown of yeast cells releases mannoproteins and other compounds that can enhance the mouthfeel, complexity, and stability of the wine. The process of aging wine on the lees (dead yeast cells) is known as sur lie aging and can contribute to desirable flavors and textures.

Beer

In brewing, autolysis can also play a role, although it is generally less desirable than in winemaking. The release of certain compounds during autolysis can lead to off-flavors, such as a meaty or rubbery taste, which are considered undesirable in most beer styles. Brewers often take steps to minimize autolysis by removing yeast from the beer as soon as fermentation is complete.

Prevention and Control

To control autolysis, winemakers and brewers can manage the conditions under which yeast cells are stored post-fermentation. This includes controlling temperature, pH, and oxygen levels. In winemaking, the process of riddling and disgorging is used to remove dead yeast cells from sparkling wine, while in brewing, techniques such as cold crashing and filtration are employed.

See Also

• Fermentation
• Yeast
• Wine aging
• Beer brewing
• Lees (fermentation)

References

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