Microorganisms play a crucial role in the fermentation process of ice wines and noble rot-affected grapes.
Ice Wines
Ice wines are made from grapes that have been frozen while still on the vine. This freezing process concentrates the sugars in the grapes, resulting in a sweet and flavorful wine. Microorganisms, specifically yeast, are responsible for fermenting the sugars in the grapes into alcohol. Here’s how microorganisms contribute to the fermentation of ice wines:
- Yeast: Saccharomyces cerevisiae is the most common yeast used in winemaking, including ice wines. Yeast metabolizes the sugars in the grapes, converting them into alcohol and carbon dioxide. This fermentation process is essential for producing wine.
- Flavor development: During fermentation, yeast also produces various flavor compounds that contribute to the unique taste of ice wines. These compounds can include fruity esters, spicy phenols, and floral terpenes.
- Preservation: The alcohol produced by yeast during fermentation acts as a natural preservative, helping to extend the shelf life of ice wines.
Noble Rot-Affected Grapes
Noble rot, also known as botrytis cinerea, is a fungus that affects grapes and is commonly used in the production of sweet wines like Sauternes. This fungus pierces the skin of the grape, causing water to evaporate and sugars to concentrate. Microorganisms, including yeast and bacteria, play a significant role in the fermentation of noble rot-affected grapes:
- Yeast: Just like in ice wines, yeast is crucial for fermenting the sugars in noble rot-affected grapes. The concentrated sugars from noble rot produce a luscious sweetness in the wine that is balanced by the fermentation process.
- Bacteria: While yeast is the primary microorganism involved in fermentation, bacteria also play a role in the process. Acetic acid bacteria, for example, can convert alcohol into acetic acid, contributing to the complexity of flavors in the wine.
- Flavor complexity: The interaction between yeast, bacteria, and the unique compounds produced by noble rot results in wines with complex flavors. These wines often exhibit notes of honey, apricot, and botrytized characters that are highly sought after by wine enthusiasts.