Chemical composition of Merlot, Cabernet Sauvignon, and Carmenère grapes (Vitis vinifera L.) during ripening, evaluated by canopy side

Paula A. PEÑA-MARTÍNEZ, Liudis L. PINO, María A. NAVARRO, V. Felipe LAURIE
Universidad de Talca

Email contact: paulapemar[@]gmail.com

AIM: Compare the the chemical composition of Merlot, Cabernet Sauvignon and Carmenère fruit during ripening, evaluated by canopy side, on a Vertical shoot positioned (VSP) trained vineyard with north-south row orientation.

METHODS: An 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) was used for this trial. 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 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: Besides their differential ripening paste, our results did not show major differences in fruit composition among varieties and between canopy side, particularly when juice parameters such as sugars or acids were analyzed. Phenolics extracts showed higher total phenolics and condensed tannin in Cabernet Sauvignon and Merlot compared to Carmenère, but no statistical differences were seeing when canopy sides were compared. The composition of low molecular weight phenolics significantly among varieties and canopy sides. For instance, catechin was significatively higher in fruit from the westside of the canopy in Cabernet Sauvignon and Merlot, whilst east facing clusters from the three varieties had higher malvidin-3-glucoside concentration.

CONCLUSIONS: Besides compositional differences due to the lengthwise of ripening, total phenolics and condensed tannin did vary among varieties. Moreover, only minor differences on fruit composition by canopy side were observed among the variables analyzed, particularly when it comes to low molecular weight phenolics.

References:

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