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Protein precipitation assay, tannin

The procedure in the polygon in Figure 1 is the Hagerman Butler assay for tannin. The only modification is that we retain the supernatant after centrifugation of the precipitation reaction mixture and bleach the monomeric anthocyanins with bisulfite. The residual absorbance represents pigments that do not precipitate with protein and do not bleach in the presence of bisulfite. We have designated this material small polymeric pigment solely to denote these two characteristics. The LPP removed from the sample by protein precipitation... [Pg.286]

Protein Binding—Tannins, as the name implies, characteristically form complexes with proteins based on multipoint hydrogen bonding, and this feature can be used to detect and remove tannins from crude extracts. A visible protein-tannin precipitate should be formed on addition of the tannin-containing extract to a relatively concentrated (approx 5%) solution of bovine serum albumin (BSA). The amount of BSA either remaining in solution or in the precipitate can be analyzed by various protein determination assays. [Pg.291]

Martin, J. S. and M. M. Martin, Tannin assays in ecological studies Lack of correlation between phenolics, proanthocyanidins, and protein precipitating constituents in mature foliage of six oak species, Oecologia (Berlin), 54, 205-211 (1982). [Pg.213]

As mentioned before, the amount of soluble tannin that causes astringency in persimmon fruits is usually estimated visually by the tannin print method and can be measured quantitatively by the Folin-Denis method. There is also a protein precipitation method for the measurement of soluble tannins (Hagerman and Butler 1978). In that method, the soluble tannin content is assayed by the addition of the sample to a standard solution of protein and the isolation of insoluble tannin-protein complexes. The complexes are dissolved in alkaline solution, to which ferric chloride is added. The absorbance of the solution at 510 nm is measured. [Pg.108]

In this assay, the interaction of tannins with protein in an agar gel is quantified. The insolnble precipitates form rings around an origin. The diameter of the rings is proportional to the tannin amonnts present. It needs to be added that not all tannins bind to proteins, and not all precipitates are insoluble. The method of this exercise follows the Tannin Assay as described by Hagerman (1987). [Pg.82]

One reason that precise and quantitative assays for tannin determinations have been difficult to develop is that tannins encompass a heterogeneous group of compounds and polymers. However, several assays have been developed to estimate tannin levels in extracts, and an excellent review is available (18). Many of these assays are based on either the reduction capabilities of polyphenols or the propensity of tannins to form precipitates with various proteins. The following two assays are best used as a qualitative analysis for the presence or absence of particular tannins, but can be used with standards for approximate tannin determinations. [Pg.291]

The ability of tannins to precipitate water-soluble proteins is the main activity by which various naturally occurring polyphenols are defined as tannins. Several methods for measurement of tannins based on these activities have been developed (Bate-Smith 1973 Porter and Woodruffe 1984 Hagerman 1989). Methods for the assay of relative astringency (RA) and relative affinity to methylene blue (RMB) have been used frequently in pharmacological studies for the measurement of the tannin content of plant extracts (Okuda et al. 1985). [Pg.83]


See other pages where Protein precipitation assay, tannin is mentioned: [Pg.276]    [Pg.277]    [Pg.281]    [Pg.210]    [Pg.83]    [Pg.101]    [Pg.155]    [Pg.279]    [Pg.354]    [Pg.355]    [Pg.31]    [Pg.177]    [Pg.360]   
See also in sourсe #XX -- [ Pg.276 ]




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