Harvest ripeness level has a larger effect than leaf removal on grape and wine quality in cv. Cabernet-Sauvignon from Maipo Valley

Abstract

The effect of fruit zone leaf removal and harvest maturity level was studied in a commercial Cabernet-Sauvignon vineyard in the Maule Valley (Chile) during three growing seasons from 2013/2014 to 2015/2016. Three factors were combined using a multifactorial yearly blocked design: (1) defoliation intensity, composed by two levels of leaf removal on the VSP cluster zone (a) 60% on the east side during pea size, and (b) 60% on the east side during pea size plus 40% on the west side during veraison; (2) type of defoliation, (a) hand-made or (b) mechanical; and (3) harvest maturity level determined by a commercial maturity tracking system, (a) fresh fruit profile and (b) ripe fruit profile. Research wines were processed with 700 to 800 Kg of fruit per treatment (24 experimental units). Measurements included climatic, physiological and canopy structural parameters as well as standard wine composition and phenolic characterization by HPLC-DAD. Compared to leaf removal, harvest maturity level had the highest effect on fruit and wine composition, by increasing must Brix and wine pH, alcohol, total tannins, color index, DO280, monomeric and total anthocyanins and by decreasing must yeast assimilable nitrogen and total acidity. Mechanical leaf removal was more severe than manual leaf removal, exposing the clusters more directly to the sun. The main effect of leaf removal was on must flavonols and monomeric flavan-3-ols, which increased with defoliation intensity.