Concentration and compositional changes of procyanidins in grape seeds and skin of white Vitis vinifera varieties
1999
Freitas, V.A.P de | Glories, Y.
Grapes from Semillon and Ugni blanc varieties have been sampled over the periods just before coloration (stage I), veraison (stage II) and harvest (stage III), during the seasons 1991-92 and 1992-93. The content of total extractable proanthocyanidins, catechins ((+)-catechin, (-)-epicatechin and (-)-epicatechin gallate), procyanidin dimers B1 to B8 and trimer C1 in skin and grape seeds were further determined. The quantitative determination was performed through Fractogel TSK chromatography followed by HPLC analysis. The highest concentration of procyanidins is present in the grapes in the early stages of development. (+)-Catechin was the major constituent of flavan-3-ols in skin and grape seeds. Procyanidin dimers B1, B4 and B6 represent the majority of dimers in the early stage of grape seeds development, while in the last stage of maturation dimers B2 and B4 were predominant. Curiously, the decrease in the procyanidins concentration goes along with a corresponding increase of dimer B2 synthesis during grape ripening. Dimer B1 was always the major dimer in skin. The differences between the two seasons were more significant than those between the Ugni blanc and Semillon varieties. However, Semillon contains a higher concentration of total proanthocyanidins.
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