Co-fermentation is the practice in

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

fermenting Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduced ...

two or more

fruits In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

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 or other fruits, 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 blends (mixed plantations of varieties) in

vineyard A vineyard ( , ) is a plantation of grape-bearing vines. Many vineyards exist for winemaking; others for the production of raisins, table grapes, and non-alcoholic grape juice. The science, practice and study of vineyard production is kno ...

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

Tuscany Tuscany ( ; ) is a Regions of Italy, region in central Italy with an area of about and a population of 3,660,834 inhabitants as of 2025. The capital city is Florence. Tuscany is known for its landscapes, history, artistic legacy, and its in ...

) 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 Precipitation (chemistry), precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' is widel ...

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 ( , ; Occitan language, Occitan: ''Ròse''; Franco-Provençal, Arpitan: ''Rôno'') is a major river in France and Switzerland, rising in the Alps and flowing west and south through Lake Geneva and Southeastern France before dischargi ...

, 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 ...

and the aromatic white variety

Viognier Viognier () is a white wine grape variety. It is the only permitted grape for the French wine Condrieu AOC, Condrieu in the Rhone Valley (wine), Rhône Valley.J. Robinson ''The Oxford Companion to Wine'', Third Edition, p. 754, Oxford Univers ...

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

Roussanne Roussanne () is a white wine grape grown originally in the Rhône wine region in French wine, France, where it is often blended with Marsanne. It is the only other white variety, besides Marsanne, allowed in the northern Rhône appellation d'Orig ...

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 used to describe the majority of lands of Earth's Western Hemisphere, particularly the Americas, and sometimes Oceania."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: ...

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 Aus ...

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

References

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