Fermentation is the process by which yeast converts grape sugar into alcohol and carbon dioxide, transforming juice into wine. Alcoholic fermentation is the primary step; a second, malolactic fermentation softens acidity. Temperature, yeast strain (native or inoculated) and vessel all shape the result. A secondary fermentation in a sealed vessel traps CO2 to make sparkling wine. Fermentation is the heart of winemaking.
WHY IT MATTERS FOR COLLECTORS
How fermentation is handled — native versus cultured yeast, warm or cool, in oak or steel — defines a wine's character. Native-yeast, low-intervention fermentation is central to the natural-wine ethos and to terroir expression.
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