Wine fermentation

Wine fermentation is yeast on Must. Glucose and fructose become ethanol and carbon dioxide. What remains — acid, residual sugar, phenolics, aroma — is the drink. The shared idea is Fermentation. Bread’s ferment is timed against gluten ¹. Cheese cultures work lactose. Wine fermentation works on grape sugar.

Inoculated Saccharomyces and spontaneous ferments are both used; they are not interchangeable recipes. Yeast dose and temperature depend on the strain, must, vessel, and cellar protocol.

Alcohol is also an extraction solvent #

As sugar falls, alcohol rises, and tannin extraction from skins increases ². That is why red cap management during the ferment is Extraction, not a separate magic. Whites that were pressed off skins before yeast started skip that solvent trick on purpose.

Malolactic fermentation is bacteria on malic acid, often after the yeast is done. Do not call both “the ferment” as if they were one organism.

An AVA names where the grapes grew; it does not name the yeast ³.

What to notice #

Look: bubbles, a rising cap of skins in a red, the liquid looking less like juice. Smell: fruit into yeast into wine — vinegar as the main note is a problem. Taste sweetness disappearing; warmth of alcohol appearing; Acidity still holding the line so the wine does not taste flat.

When bubbling ceases, you have a dry (or stuck) ferment, not automatically a stable wine. Stability, sulfur, and aging are later pages. Return to Wine.