Red wine

Red wine is a type of wine made from dark-coloured (black) grape varieties. The actual colour of the wine can range from intense violet, typical of young wines, through to brick red for mature wines and brown for older red wines. The juice from most purple grapes is greenish-white; the red colour comes from anthocyan pigments (also called anthocyanins) present in the skin of the grape; exceptions are the relatively uncommon teinturier varieties, which produce a red colored juice. Much of the red-wine production process therefore involves extraction of colour and flavour components from the grape skin.

Production

Grape processing

The first step in red wine production, after picking, involves physical processing of the grapes. Hand-picked or machine-harvested grapes are usually tipped into a receival bin when they arrive at the winery and conveyed by a screw mechanism to the grape-processing equipment.

Destemming and crushing

On arrival at the winery there is usually a mixture of individual berries, whole bunches (particularly with hand-picked grapes), stems, and leaves. The presence of stems during fermentation can lead to a bitter taste in the wine, and the purpose of destemming is to separate grapes from the stems and leaves. Mechanical de-stemmers usually consist of a rotating cage perforated with grape-sized holes. Within this cage is a concentric axle with arms radiating towards the inner surface of the cage. Grapes pass through the holes in the cage, while stems and leaves are expelled through the open end of the cage.