Co-fermentation is the practice in

winemaking Winemaking or vinification is the production of wine, starting with the selection of the fruit, its fermentation into alcohol, and the bottling of the finished liquid. The history of wine-making stretches over millennia. The science of wine and ...

fermenting Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...

two or more

grape varieties This list of grape varieties includes cultivated grapes, whether used for wine, or eating as a table grape, fresh or dried (raisin, currant, sultana). For a complete list of all grape species including those unimportant to agriculture, see Viti ...

at the same time when producing a wine. This differs from the more common practice of blending separate wine components into a

cuvée ''Cuvée''Or Cuvee on some English-language labels. () is a French wine term that derives from ''cuve'', meaning vat or tank.J. Robinson (ed), ''"The Oxford Companion to Wine"'', Third Edition, p. 218, Oxford University Press 2006, winepros.com. ...

after fermentation. While co-fermentation in principle could be practiced for any mixture of grape varieties, it is today more common for red wines produced from a mixture of red grape varieties and a smaller proportion of white grape varieties. Co-fermentation is an old practice going back to the now uncommon practice of having

field blend Viticulture (from the Latin word for ''vine'') or winegrowing (wine growing) is the cultivation and harvesting of grapes. It is a branch of the science of horticulture. While the native territory of ''Vitis vinifera'', the common grape vine, ran ...

s (mixed plantations of varieties) in

vineyard A vineyard (; also ) is a plantation of grape-bearing vines, grown mainly for winemaking, but also raisins, table grapes and non-alcoholic grape juice. The science, practice and study of vineyard production is known as viticulture. Vineyards ...

s, and the previous practice in some regions (such as Rioja and

Tuscany Tuscany ( ; it, Toscana ) is a Regions of Italy, region in central Italy with an area of about and a population of about 3.8 million inhabitants. The regional capital is Florence (''Firenze''). Tuscany is known for its landscapes, history, art ...

) of using a small proportion of white grapes to "soften" some red wines which tended to have harsh

tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'', ...

s when produced with the winemaking methods of the time. It is believed that the practice may also have been adopted because it was found empirically to give deeper and better colour to wines, which is due to improved co-pigmentation resulting from some components in white grapes.

Use today

The only classical Old World wine region where co-fermentation is still widely practiced is now the Côte-Rôtie appellation of northern

Rhône The Rhône ( , ; wae, Rotten ; frp, Rôno ; oc, Ròse ) is a major river in France and Switzerland, rising in the Alps and flowing west and south through Lake Geneva and southeastern France before discharging into the Mediterranean Sea. At Ar ...

, while the use of white varieties in red Rioja and Tuscany wine has more or less disappeared. In Côte-Rôtie, the red variety

Syrah Syrah (), also known as Shiraz, is a dark-skinned grape variety grown throughout the world and used primarily to produce red wine. In 1999, Syrah was found to be the offspring of two obscure grapes from southeastern France, Dureza and Mondeuse B ...

and the aromatic white variety

Viognier Viognier () is a white wine grape variety. It is the only permitted grape for the French wine Condrieu in the Rhône Valley.J. Robinson ''"The Oxford Companion to Wine"'' Third Edition pg 754 Oxford University Press 2006 Outside of the Rhôn ...

(up to 20% is allowed, but 5–10% is more common) must be cofermented, if Viognier is used. The reason why Viognier has been kept in Côte-Rôtie (while for example the white grapes

Marsanne Marsanne is a white wine grape, most commonly found in the Northern Rhône region. It is often blended with Roussanne. In Savoie the grape is known as ''grosse roussette''. Outside France it is also grown in Switzerland (where it is known as ' ...

and

Roussanne Roussanne is a white wine grape grown originally in the Rhône wine region in France, where it is often blended with Marsanne. It is the only other white variety, besides Marsanne, allowed in the northern Rhône appellations of Crozes-Hermitage A ...

are hardly found any more in red Hermitage or other red Rhône wines where they are allowed) is that it adds signature floral aromas to the wines. The popularity of Côte-Rôtie has led to

New World The term ''New World'' is often used to mean the majority of Earth's Western Hemisphere, specifically the Americas."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: Oxford University Press, p. 3 ...

interpretations of this blend, most notably

Australian Australian(s) may refer to: Australia * Australia, a country * Australians, citizens of the Commonwealth of Australia ** European Australians ** Anglo-Celtic Australians, Australians descended principally from British colonists ** Aboriginal Au ...

Shiraz-Viognier blends, which are also produced by co-fermentation. The reason why co-fermentation is not more widely practiced is that it "locks in" a certain blend already at the start of the fermentation, which gives the winemaker less possibility to adjust the blend after fermentation. Co-fermentation is also performed in situations where

varietals are indistinguishable from each other, thus necessitating co-fermentation.

References

{{portal bar, Drink Winemaking Fermentation in food processing