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We have adapted a tannin protein precipitation method for use with grapes and wine that was devised in 1978 by Hagerman and Butler. The simple assay is started with the addition of tannin to a protein solution. During the reaction a precipitate is formed when tannin combines with protein. The resulting precipitate is centrifuged to give a pellet. The pellet is washed and then re-suspended in a basic detergent buffer and Ferric Chloride is added to give a colored complex that can be measured at 510 nm. Recently we have combined Hagerman and Butler's protein precipitation assay with traditional bisulfite bleaching to provide a convenient analysis of polymeric pigments with tannins. This has revealed two classes of polymeric pigments in wine; large polymeric pigments (LPP), which precipitate with protein (BSA) and small polymeric pigments (SPP) that do not. We are currently investigating the presence of these classes of compounds in grapes and wines and how they change during winemaking and aging.
New Supercool Assay - New!!!
Protocol for Tannin Assay only - Updated
Links other Related Tannin SitesDr. Hagerman's Tannin Chemistry Page - http://www.users.muohio.edu/hagermae/