Double maturation raisonnée: effects on quality of grapes and wine composition in cv. Baga (Vitis vinifera L.)

Abstract

Yield control is an important current issue because of the strong correlation of excessive yield and frequency of some diseases. Costs, time consumption, inconsistency of results, technical difficulties to implement are usual problems associated with most common techniques for yield control. One of the most innovative and yet poorly studied yield control technique is the “Double Maturation Raisonnée”. Double Maturation Raisonnée consists on disconnecting from the vine part of the clusters, leaving them hanging attached to the vine wires and exposed to sunlight to dehydrate. The separation by cutting can involve the cluster and/or the shoots; the proportion of clusters to be separated must be carefully selected, as well as the timing of the separation and the number of days between the separation and the actual harvest date – the cutting can be made between berries unripe, fully matured, to over ripped, and the period of time of dehydration can go up to several weeks. A 3-year trial was performed to test Double Maturation Raisonnée in the high-yielding Portuguese cultivar Baga, and to study its effects on quality of grapes and wine composition. The technique was performed 15 days before harvest, leaving shoots and bunches hanging on the wires, using a complete randomized block experimental design with four replications. Baga is also prone to rot due to producing compact clusters and thin berry skin. In order to avoid rot, Baga is usually harvested early, sometimes producing wines of lower quality. Production, must and wine composition and sensorial scores are presented to assess the suitability of Double Maturation Raisonnée as a technique to improve wine quality of Baga. DMR reduced yield per vine, cluster weight, cluster compactness and Botrytis incidence. DMR also increased sugar concentration (and alcohol), color intensity and polyphenolic content, and the wines had higher tasting scores.