Double maturation raisonnée: the impact of on-vine berry dehydration on the berry and wine composition of Merlot (Vitis vinifera L.).

Background: Double maturation raisonnée (DMR) is a potential canopy measure that affects grape and wine composition. The aim of this work was to study for the first time the DMR impact on the physical, biochemical and sensorial characteristics of the berries and wines of Merlot, one of the world's fastest-expanding grapevine varieties.
Results: DMR significantly increased the content of soluble solids (1.2-fold), free amino nitrogen (1.8-fold) and acidity in berries but decreased the weight of 100 berries on harvest (approx. 28%). Irrespective of the vintage, DMR-treated grapes had a significantly higher content of non-astringent tannins (0.73-0.78 mg L ^-1 ) and anthocyanin extractability (34.7-36.4%) but a lower index of astringency (31.2-33.7) when compared to the control. Consequently, the DMR wines achieved higher alcohol, total acidity and extract, hydroxycinnamic acids, flavanol and flavonol contents, whereas the content of anthocyanins was similar to that of the control. Sensorial evaluation showed that DMR wines were not rated higher and would not be appreciated more than control wines.
Conclusion: Changes in berries during DMR altered the wine characteristics only in terms of primary metabolites. A reduced accumulation of phenolics, especially anthocyanin content, in the berry skin of DMR-treated grapes was not reflected in their presence in wines. To the best of our knowledge, this is the first paper that has reported an impact of DMR on the grape and wine composition of Merlot, as one of the most promising red varieties. © 2017 Society of Chemical Industry.
(© 2017 Society of Chemical Industry.)