Dynamics of phenolic components during the ripening of grapes from sub-Mediterranean climatic zone of the Crimea: influence on the quality of red wines

Seed tannins cause the excessive tannic and astringent taste of red wines, while anthocyanins and tannins of grape skin cause the formation of intense and stable color, harmonious taste. Seed tannins are present in the free form at the beginning of ripening which makes them easily extractable in the wine extraction processes. The tannins and anthocyanins of the grape skin are associated with the macromolecules of the cell walls, reducing their ability to extract. The permeability of the cell walls of the berry skin and the extractability of anthocyanins are increased during the grape ripening and the extractability of galloylated seed tannins undergoing polymerization is reduced. The present publication is devoted to the extractibility of seed and skin polyphenols and their influence on the wine quality, depending on the sugar concentration (Brix) in the ‘Ekim cara’ and ‘Cabernet-Sauvignon’ grape cultivars from the southern coastal zone of the Crimea. The amount of seed tannins (Mp, %) and the percentage extraction of anthocyanins obtained under winemaking conditions (Ea, %) is determined by the Glories method; technological reserve of phenolic compounds (TRPh, mg L^‑1) – with the Folin-Ciocalteu’s reagent. Wines were produced and also studied. It is shown that the relationship of the sugar concentration in grapes and Ea and Mp is described by equations of the second degree (p≤0.05). Cluster analysis allowed the grapes to differentiate into 2 groups. For ‘Ekim kara’ the first group is characterized by the following parameters: – 21.5-25.5 °Brix, Ea=44-64%, Mp=8-11%, TRPh=1.9-3.4 mg L^‑1; for ‘Cabernet-Sauvignon’: – 21.5-23.7 °Brix, Ea=46-66%, Mp=9-15%, TRPh=2.4-3.4 mg L^‑1. Wines made from grapes of the first group have harmonious, velvety taste, intense ruby color, developed aroma; grapes of the second group have tannin astringent taste and significantly (p<0.05) differed in tasting evaluation.