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IVES 9 IVES Conference Series 9 Relationship between terroir and acidity for the red wine grape cultivar Malbec N or Cot N (Vitis vinifera L.) in AOC “Cahors” and “Côtes du Frontonnais “

Relationship between terroir and acidity for the red wine grape cultivar Malbec N or Cot N (Vitis vinifera L.) in AOC “Cahors” and “Côtes du Frontonnais “


[English version below]

L’étude préliminaire, réalisée sur les principaux cépages de la région Midi-Pyrénées, a montré que le Cot N possédait des teneurs en acide tartrique dans les moûts et les vins plus élevées que celles des cépages Négrette N, Tannat N, Duras N et Fer Servadou N.
Ce travail a porté sur l’étude du comportement du cépage Cot N sur les terroirs les plus qualitatifs des deux appellations Cahors et Côtes du Frontonnais, ainsi que sur la mise en évidence de l’effet éventuel du terroir sur l’acidité des moûts et des vins.
Les résultats montrent le rôle important joué par la nature physico-chimique des sols sur l’absorption et la translocation des éléments minéraux, et en particulier du potassium par la vigne. Quelque soit le terroir, le Cot N synthétise des quantités similaires d’acides malique et tartrique, mais, celles-ci diffèrent significativement au seuil α = 5 %. Alors que l’acidité titrable et le pH des moûts varient très peu selon le terroir, les pH des vins varient beaucoup en fonction de la nature des sols. Sur les terroirs acides, ces différences sont faibles, alors qu’elles sont très importantes sur le terroir calcaire. Ceci confirme le rôle capital joué par le potassium, qui, au cours de la vinification, entraîne des précipitations importantes d’acide tartrique sous forme de bitartrate de potassium, et corrélativement, l’augmentation du pH des vins. La qualité des vins est donc très dépendante de la prise en compte de la nutrition minérale du cépage et de la pratique d’une fertilisation raisonnée.

A preliminary study on the main red wine grape cultivars of the Midi-Pyrénées area showed that The Cot N presents higher tartaric acid contents in musts and wines than the Négrette, Tannat, Duras and Fer Servadou grape cultivars.
The Cot N grape cultivar is widely planted in the most qualitive terroirs of the “Cahors” and “Côtes du Frontonnais” appellations. Our study focuses on the behaviour of Cot N and therefore, on the possible terroir
effect on Cot N must and wine acidity.
The results show the important role played by the physical and chemical nature of soils in plant nutrient uptake and translocation (particularly potassium). Whatever the terroir, Cot N synthesizes similar quantities of malic and tartaric acids; yet differences are significant α = 5 %. Even if titrable acidity and must pH do not vary much from one terroir to another, pH variation in wines is high depending on the nature of soils. On acidic soils, differences are insignificant whereas they are very important on calcareous soils. These observations confirm the main role of potassium during vinification. Indeed, it accounts for considerable precipitations of tartaric acid in bitartrate of potassium form and for a correlative increase in wine pH levels. The quality of wines depends on a good understanding of mineral nutrition and a reasoned fertilization practice.


Publication date: January 12, 2022

Issue: Terroir 2004

Type: Article


F. Attia (1), E. Besnard (2), F. Laffargue (2), D. Fort (1) and M. Garcia (1)

(1) Centre de Viticulture-Œnologie de Midi-Pyrénées; Avenue de l’Agrobiopôle Auzeville Tolosane, B.P. 107 F – 31320 Castanet Tolosan Cedex, France
(2) Association d’Expérimentation de la Ferme Départementale d’Anglars-Juillac – 46140 Anglars-Juillac, France

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Terroir, cot n, must and wine acidity, potassium, tartaric and malic acids


IVES Conference Series | Terroir 2004


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