Reactivity of pure and commercial grape skin tannins with cell wall material

Abstract

Commercial enological skin-derived tannins were used to investigate the role that cell wall material (CWM) plays in proanthocyanidin adsorption and the effect of differences in cell wall composition and tannin composition on the extent of the interaction. Insoluble CWM, prepared from the skin of Vitis vinifera L. cv. Monastrell and Syrah berries, was combined with solutions containing four different commercial enological grape skin-derived tannins (proanthocyanidin-type tannins), and the results obtained were compared with those obtained using four different purified skin tannin fractions. The tannins remaining in the solution after fining with CWM were analyzed by phloroglucinolysis and size exclusion chromatography, which provided data on the extent of the interaction and quantitative and qualitative information for the non-adsorbed compounds. Cell walls from both varieties showed a strong affinity for the tannins, the highest interactions being observed for Monastrell CWs and for those tannins with the highest mean degree of polymerization. These interactions may have some enological implications, especially as regards the optimal moment for adding commercial tannins to the must/wine and also explain some enological differences observed in the extraction of tannins from grape to wine.