Y

YEAST

A micro-organism that converts sugar into alcohol in a process known as alcoholic fermentation. Present naturally in the vineyard, harvested grapes will begin to ferment naturally, primarily if they are crushed to break the skins and expose the sugar-rich juice inside to the yeasts that reside on the grape skins. Some winemakers prefer to add cultured yeasts rather than rely on the action of wild yeasts. This gives greater control over the fermentation, but some argue it may intrinsically alter the style or quality of the wine, as a single strain might not produce the same flavors as the multiple strains present in the vineyard.

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YIELD

The yield is the amount of wine produced in a vineyard or estate and is usually expressed in hectoliters per hectare. Yields vary according to the type of vine—some are heavy croppers, some yield less—and also with climate and soil. The winemaker may influence yields by performing a green harvest to reduce them. Low yields are associated with increased quality.