Proteins and polyphenols were combined in model systems, and the
resulting hazes were measured
by light scattering. The amount of haze formed depends both on the
concentrations of protein and
polyphenol and on their ratio. A conceptual model in which a
protein molecule has a fixed number
of polyphenol binding sites explains the observed behavior and has
implications for turbidimetric
methods for estimating haze-active protein and haze-active polyphenol
in beverages. The ranking
of haze-forming activity of the test polypeptides was different with
tannic acid than with catechin;
this indicates differences in binding site availability, bridging
ability, or specificity for the two
polyphenols. More haze was observed when model systems were
heated, suggesting that polyphenol
binding sites are exposed when protein hydrogen bonds are broken.
Freshly formed haze dissolved
when dimethylformamide or dioxane was added; this may be useful for
recovering compounds from
isolated hazes for analysis.
Keywords: Haze-active protein; haze-active polyphenol; beverages; model
systems; gelatin; tannic
acid
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