Grape berry samples were collected from a carefully replicated vineyard trial on Vitis vinifera cv. Cabernet Sauvignon at the H block in the Tokalon vineyard. Samples were divided into skins and seeds, and extracted with 75%acetone. The quantity and characterization of extracted flavan-3-ols and procyanidins was determined in seeds and skins over the course of ripening and at different levels of vine water status. In the seed, the per berry extractive yield of all polyphenolics decreased with maturity, but increased in the skin. The apparent size of the seed and skin polyphenols were measured by chromatographic analysis and by thiolytic degradation. The relative proportion of procyanidin extension and terminal units was also measured by thiolysis. Chromatographic analysis showed an increase in size with maturity, while the average degree of polymerization, determined by thiolysis, declined slowly with maturity. In seeds, The relative decrease in the subunits varied with subunit type, with the fiavan-3-ols decreasing the most rapidly followed by the procyanidin extension units and then the terminal units. Increased water stress increases the rate of decline for flavan-3-ols and their relative proportion. This is the first clear description of fundamental changes in polyphenol structure during the important period of the harvest maturity window. Due to the possible sensory implications of these changes, these observations may lead to polyphenols ripeness parameters for red grapes.
/wp-content/uploads/2017/09/AFV-Header-Logo.png 0 0 AVF /wp-content/uploads/2017/09/AFV-Header-Logo.png AVF1998-10-18 11:33:362017-10-18 11:34:27Grape Maturity and Vine Water Status: Effects on Tannin Composition in Red Grapes