Grape skin maturity

Kennedy, J.A., Matthews, M.A., and Waterhouse, A.L., Effect of maturity and vine water status on grape skin and wine flavonoids. Am. J. EnoL Vitic. 53, 268, 2002. 

Table VIII. Phenolic Compounds in Grape Skins at Crop Maturity in Vineyard SC...

Vivas, N.G., Nonier, M.-F, Guerra, C., Vivas, N. (2001). Anthocyanin in grape skins during maturation of Vitis vinifera L. cv. Caberent Sauvignon and Merlot Noir from different bordeaux terroirs. J. Int. Sci. Vigne Vin35, 149-156. 

Sun, B., Ribes, A. M., Leandro, M. C., Belchior, A. P, Spranger, M. I. (2006). Stilbenes Quantitative extraction from grape skins, contribution of grape solids to wine and variation during wine maturation. Anal. Chim. Acta, 563, 382-390. 

Grape pomace polyphenol composition is affected by many different factors. It is variety dependant [10-11] and, within the same variety, different parts have significantly different compositions. For example, the grape skins, have been found to be rich in anthocyanins, hydroxycinnamic acids, flavanols and flavonol glycosides, whereas the seed portion is a good source of gallic acid and flavanols [3, 11]. Polyphenol composition is also influenced by the growing location, climate, maturity and fermentation time [12]. 

Anthocyanins are relatively unstable and undergo numerous chemical reactions in beverages like red wines during fermentation processes, maturation and aging. The monomeric anthocyanins extracted from the grape skin are a crucial contribution to the colour of young red wine. Their intramolecular interactions and inter-molecular interactions with other wine constituents and especially... 

The following phenolic compounds are present in the grape skin at maturity benzoic and cinnamic acid, flavonols and tannins. They are distribnted in the cells of the epidermis and the first snb-epidermal layers in both white and red grapes. In addition, the red grape skin contains anthocyanins, essentially located in the hypodermal cell layers. Exceptionally, in certain years, the cells adjacent to the pulp can be colored. The pulp itself is colored in the case of Tenturier varieties and some American vines or direct producer hybrids. Antho-cyanin composition varies from cultivar to cultivar, depending on the anthocyanidin substitution and heterosidic nature of the cultivar (see Volume 2, Section 6.2.3). 

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