IntroductionGrape quality is reflected in a balanced composition of primary and secondary metabolites, which constitute different parts of the fresh berries during their development and ripening. The accumulation of these metabolites within the berries is affected by genetic characteristics, cultivation practices, and climate conditions (Jackson and Lombard, 1993).The phenolic compounds in the skins of red berry grapevine varieties are mostly anthocyanins, hydroxycinnamic acids, stilbenoids, flavanols, and flavonols, which are also the building blocks of the grapes' and wines' sensorial properties (Jackson and Lombard, 1993;Gonzalez-Alvarez et al., 2013). In red grapes, anthocyanins are responsible for the red color of the skins and consequently define the color and quality of the must and wine (Liang et al., 2008). Other polyphenols, such as flavonols and flavanols, mostly contribute to wine flavor and astringency (Li et al., 2009). Phenolic compounds are biosynthesized through the phenylpropanoid and flavonoid pathways and originate from the amino acid precursor, phenylalanine. These pathways are among the most studied and thoroughly described secondary metabolic pathways in plants (Yang et al., 2012). Polyphenolic compounds play an important role in the sensorial quality of grapes and wines. Their transformation during the vinification process directly or indirectly influences the quality of the wine: its structure and sensorial properties (Cheynier, 2005;Noguerol-Pato et al., 2013).In order to change the composition of fresh berries and improve the quality of the wines produced from these, different canopy techniques, especially training systems, bunch thinning, defoliation, dehydration etc., have been introduced in viticulture ( Kyraleou et al., 2015;Liu et al., 2015). Grape dehydration, used for the production of late harvest, botrytized, and ice wines, represents a measure applied for the production of sweeter wines in general, in which the contents of soluble solids, phenolics, and aroma
