Analysis of Protein Moiety of Polysaccharide Conjugates Water-extracted from Low Grade Green Tea

Tea polysaccharide conjugates(TPCs) were water-extracted and purified from low-grade green tea. Although TPC contains 1.97% covalent binding proteins, Coomassie brilliant blue G250 and R250 could not detect this protein. The "should-shape" absorption peak observed at 250-280 nm in the UV-Vis spectrum was caused by quinone compounds derived from polyphenol oxidation during TPC extraction. The UV-Vis spectrum could be used to detect the decolorizing degree of TPC. TPC aqueous solution merely presented the negative charge properties of its polysaccharides instead of the acid-base property of its protein section, and exhibited higher stability at pH greater than 5.0. No precipitation or haze occurred in three TPC/epigallocatechin gallate(EGCG) aqueous mixtures during 12 h storage. TPC had emulsifying activity, which indicated that its protein moiety formed hydrophobic groups. It is proposed that some of the physicochemical properties of the TPC protein moiety are shielded by its polysaccharide chain.