Grape Processing Techniques

Grape processing techniques
Important families of phenolic compounds in grapes and wine
Anthocyanins (red color);
Tannins (provide bitterness, astringency and mouth feel);
Flavonols (co-factors for co-pigmentation).
Location of phenols
Skin Pulp Seed
Anthocyanins Hydroxycinnamic acid Tannins
Tannins Hydroxybenzoic acid
Crushing = grapes are usually crushed with a mechanical crusher in order to liberate the juice before fermentation.
Destemming = removal of grapes from the stems or more usually removal of the stems from crushed grapes.
Fermentation = decomposition of organic substances by enzymes often with release of carbon dioxide and production of alcohols, acids and other reaction products.
Racking = drawing off the wine from the marc towards the end of fermentation in vats.
Marcs = the solids of grapes consisting mainly of skins and seeds which are left in the fermenters after devatting and then pressed.
Pumping over = pumping fermenting must from the bottom of a fermenter to the top of the same fermenter to aerate the must by pumping the must over the cap to mix the content of the vat.
Defecation = holding must or wine in a vessel until the solid matter has deposited. The term is applied mainly to the clearing of the musts before fermenting for white wines.
Punching the cap = Pushing the cap below the surface of the liquid with a rammer during fermentation.
Stabilization = Treating wine to enable it to withstand cold, heat and exposure to light without becoming dull or cloudy.
Must = unfermented grape juice.
Wine= made by partial or complete fermentation of grape juice.
Malolactic fermentation= decomposition of the mailc acid in wine to lactic acid and carbon dioxide by bacteria.

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