The effects of canopy side on the chemical composition of merlot, Cabernet-Sauvignon, and Carmenère (Vitis vinifera L.) Grapes during ripening

Abstract

AIM: Evaluating the effects of canopy side on the chemical composition of Merlot, Cabernet-Sauvignon and Carmenère fruit during ripening of a Vertical shoot positioning, VSP, trained experimental vineyard with north-south row orientation.

METHODS: Cabernet-Sauvignon, Carmenère, and Merlot grapes were harvested from a VSP trained experimental vineyard with north-south row orientation, located in the O’Higgins Region of Chile (34°20’06.9″S 70°47’54.3″W). For each cultivar, three representative rows were selected, and 200 berries were randomly collected in a 50 m span, keeping samples of both sides of the canopy separated. Samplings were carried out fortnightly from the veraison to the harvest (i.e., 0, 7, 21, 35 and 49, days post veraison). Soluble solids, titratable acidity, and pH were measured according to OIV-MA-AS313-01 and OIV-MA- AS313-15 methodologies. The content of glucose, fructose, malic acid, and tartaric acid in juices were analyzed by commercial enzymatic kits. Phenolic extracts were obtained by ultrasound maceration in a 50% ethanol-water mixture from which condensed tannins by the methylcellulose precipitation assay, total phenolics by Folin-Cioacalteu, and low molecular weight phenolics by HPLC-DAD were analyzed.

RESULTS: Contrary to some investigations, our results did not show major differences in fruit composition between the varieties and canopy side, particularly when major juice parameters such as sugars or acids were analyzed. Like so, the phenolics extracts did not show statistical differences when total phenolics or condensed tannins were compared according to canopy side but was possible to identify differences and highest phenolic amount within Cabernet-Sauvignon and Merlot compared to Carmenère; however, some of the low molecular weight phenolics significantly differ when varieties from different sides of the canopy were analyzed. For instance, catechin was significatively higher in fruit from the westside of the canopy in Cabernet-Sauvignon and Merlot, whilst east facing cluster from the three varieties had higher malvidin-3-glucoside concentration. Besides the prior, significant differences in the concentration of phenolics lengthwise the ripening, were observed for the tree varieties under study.

CONCLUSIONS:

Under the conditions of this study, only minor differences on fruit composition by varieties and canopy side were observed, particularly when it comes to low molecular weight phenolics.