Developmental changes of procyanidins in grapes of red Vitis vinifera varieties and their composition in respective wines

Merlot and Cabernet Sauvignon grapes were sampled during the growing season until harvest. The content of catechins ((+)-catechin, (-)-epicatechin and (-)-epicatechin gallate, procyanidin dimers B1 to B8, and trimer C1) in th e seeds and skin were determined. Procyanidin concentrations were found to be higher at veraison, then decreased, and remained relatively constant nea r harvest time. In general, Cabernet Sauvignon were richer in low molecular weight procyanidins than Merlot. Knowing that the dimer B4 is found only i n grape seeds, and that dimer B2 is derived from both skin and seeds, it wa s possible to estimate the contribution of skin and seeds polyphenols to th e total tannins in wines. At the end of vinification, the contribution of p olyphenols extracted from grape seeds was found to be greater in Cabernet S auvignon than in Merlot wines.