Inheritance and mutations are important factors affecting grape phenolic composition. To investigate the inter- and intra-varietal differences in polyphenolic compounds among grapes and wines, 27 clones belonging to eight varieties of Vitis vinifera L. were studied over two consecutive years. A total of 24 polyphenols (nine anthocyanins, three flavanols, five flavonols, and seven phenolic acids) were analyzed, and the physicochemical parameters of the grapes and wines were determined. Polyphenol profiles showed significant varietal and clonal polymorphisms, and malvidin-3-O-glucoside, peonidin-3-O- glucoside, and epicatechin were identified as key biomarkers distinguishing different grapes and wines when using an orthogonal partial least squares discriminant analysis. Further multivariate analysis classified these genotypes into three subclasses, and a somatic variant of \'Malbec\', MBVCR6, had the most abundant polyphenolic compounds that were related to the titratable acid content. The current results reveal that varietal and clonal variations are important for obtaining wines with high polyphenol content.

The grapevine (Vitis vinifera L.) berry coloring mechanism in response to seasonal rain during grape ripening remains poorly understood. Therefore, anthocyanin biosynthesis regulation, dynamic changes in anthocyanin accumulation, biosynthetic enzyme activities, and related gene expression patterns were investigated in Cabernet Sauvignon grown under rain-shelter cultivation and open-field cultivation. Results showed that anthocyanin biosynthesis was strongly repressed during the rainy season. Environmental fluctuation from seasonal rain provoked metabolic responses in grapes, and there was a significantly greater accumulation of most of the anthocyanins, mainly the compositions of non-acylated and non-methylated, under rain-shelter cultivation; these findings indicate that rain-shelter cultivation may help improve tolerance to seasonal rain-induced stresses. Obvious resilience was observed in anthocyanins of open-field-cultivated grapes at harvest. Hierarchical cluster analysis indicated strong correlations between anthocyanin contents, CHI and DFR activities, and VvMYB5b transcriptional level. These findings provide novel insight into the crucial factors that directly modulate anthocyanin biosynthesis and consequently control grape coloration.

Anthocyanins and flavonols are important flavonoid metabolites in grapes, making a dominant contribution to the color, the mouth feel and even the flavor of grapes and wines. The accumulation of these flavonoids in grapes is greatly influenced by a many, diverse but interacting factors, of which variety and climate are among the most important ones. In the present study, the anthocyanin and flavonol profiles of four grape varieties (Vitis vinifera L.), Cabernet Sauvignon, Carmenere, Syrah and Merlot, from five major wine regions in China were examined for two consecutive years (2006 and 2007). The results showed that the total anthocyanin content of the berry skins in these cultivars tended to increase from east to west in China, yet the proportion of the acylated anthocyanins displayed the opposite trend. It seemed possible that the western grape regions, with their high altitude and low annual rainfall, had an advantage in producing high level of anthocyanins. In addition, a high proportion of trihydroxylated flavonols were always found in the western region grapes, whereas dihydroxylated flavonols were more prominent in the lower altitude eastern regions. This suggested that the relative amounts of these flavonoid compounds may depend on their corresponding cultivar characteristics, while the amounts are more affected by the environmental factors where they were growing.

Copigmentation of anthocyanins accounts for over 30% of fresh red wine color, while during storage, the color of polymeric pigments formed between anthocyanins and proanthocyanidins predominates. Rosmarinic acid and natural extracts rich in hydroxycinnamic acids, obtained from aromatic plants (Origanum vulgare and Satureja thymbra), were examined as cofactors to fresh Merlot wine and the effect on anthocyanin copigmentation and wine color was studied during storage for 6months. An increase of the copigmented anthocyanins that enhanced color intensity by 15-50% was observed, confirming the ability of complex hydroxycinnamates to form copigments. The samples with added cofactors retained higher percentages of copigmented anthocyanins and higher color intensity, compared to the control wine, up to 3 months. However, the change in the equilibrium between monomeric and copigmented anthocyanins that was induced by added cofactors, did not affect the rate of polymerization reactions during storage.

Changes in the principal phenolic compounds and metal content during the vinification process and storage under modified atmosphere (50% N2, 50% CO2) of Merlot and Syrah wines, from grapes cultivated in Greece, have been investigated. Comparing the variation of metals at maceration process, with the variation of monomeric anthocyanins and flavonols, an inverse relationship was noticed, that can be attributed to complexing reactions of polyphenols with particular trace elements. Cu decreased rapidly, whereas a similar behavior that could be expected for Fe and Mn was not confirmed. Differences in the profile of anthocyanins and flavonols in the fresh Merlot and Syrah wines are reported. During 1 year of storage monomeric anthocyanins declined almost tenfold, probably due to polymerization reactions and copigmentation. Also, a decrease in flavonol glycosides and increase in the respective aglycones was observed, attributed to enzymatic hydrolysis. The concentration of total phenols and all metals remained practically constant.