Separation and classification of the brown pigments of aqueous infusions of black tea

Rapid thin-film counter-current dialysis of a typical infusion of black tea indicates that 10–12% of the soluble solids are non-dialysable. the major components of this fraction are polysaccharides and a complex mixture which could not be separated into its protein and polyphenolic constituents. This latter complex accounts for 30–40% of the colour (E₄₅₀) of the infusion. Solvent extraction of the infusion followed by dialysis of the various extracts reveals that the polyphenol-protein complex may be approximately equated with ‘S_II thearubigins’. Chromatography of infusions and various extracts thereof on alkylated Sephadex allows a partial separation of the coloured components largely owing to differences in molecular size. At least 7 distinct zones can be recognised.