ISHS Acta Horticulturae 689: VII International Symposium on Grapevine Physiology and Biotechnology
THE PHENOLIC COMPONENTS OF GRAPE BERRIES IN RELATION TO WINE COMPOSITION |
| Authors: | J.C. Hazak, J.F. Harbertson, C.H. Lin, B.H. Ro, D.O. Adams |
| Keywords: | tannin, procyanidins, cell walls, binding, extraction |
| Abstract:
Most of the major solutes present in the grape berry at harvest contribute to wine composition in proportion to their amount in the fruit. However, many of the phenolic components are located in specialized tissues of the skin and seed, and because of differential extraction their representation in wine may not reflect their relative abundance in the fruit at harvest. We found that only a fraction of the tannin present in berries was extracted during winemaking and initial studies indicated that some of the non-extracted tannin was tightly bound to the insoluble matrix of the grape berry. We prepared a suspension of the insoluble cell wall material from ‘Cabernet Sauvignon’ berries and determined its capacity to bind tannins at different times during ripening. Mesocarp material collected from fruit 40 days after veraison had more than five times the capacity for tannin binding compared to fruit at veraison. The binding capacity appeared to decline as harvest approached. We also studied ‘Cabernet Sauvignon’ at several commercial vineyards in Napa Valley and found that the amount of insoluble matrix in skins and mesocarp varied among vineyards. We were able to determine that the capacity of the insoluble matrix to capture tannin can amount to more than 22% of the tannin present in the fruit. This result indicates that tannin binding to the insoluble matrix of grape berries may be an important factor in the ability to extract tannin from fruit during fermentation. | |
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