Mustjuice

Mustjuice is a term used in viticulture and enology to denote the unfermented grape juice that forms the must when grapes are crushed. The must includes the liquid and suspended solids, and must juice specifically refers to the liquid portion that will be fermented into wine. Winemakers typically divide the must into free-run juice and press juice; free-run juice is usually lighter in tannins, while press juice is richer and more astringent.

Mustjuice contains fermentable sugars, organic acids, minerals, amino acids, and aromatic compounds from the grape. Sugar content, measured as must weight or Brix, determines potential alcohol after fermentation. Temperature, pH, and the duration of skin contact during maceration influence the chemical profile of mustjuice and the resulting wine.

After harvest and crushing, mustjuice is cooled and may be adjusted with additives before fermentation begins. Yeast inoculation or spontaneous fermentation then converts sugars to alcohol. The quality and characteristics of mustjuice depend on grape variety, vintage conditions, and vineyard practices, and they guide decisions on fermentation temperature, duration, and juice handling.

Although not universally used, the term mustjuice appears in regional or technical contexts to differentiate the liquid portion from the solids. In general, must is a foundational stage in winemaking, with mustjuice serving as its fermentable component.

See also: Must (wine), Grape juice, Fermentation, Winemaking.