Spectroscopy and Spectral Analysis, Volume. 32, Issue 4, 1051(2012)
Spectroscopic and Structural Characteristics of the Main Components of Theabrownin in Pu-erh Tea
In the present study, we fractionated the main components of TB in Pu-erh tea by dialysis and investigated their compositions, structures and properties. TB in the Pu-erh tea was fractionated by dialyses using films with different pore sizes. The highest TB concentration was obtained in the fraction with molecular weight species >25 000 Da. The carboxyl and hydroxyl concentrations also increased in fractions where the molecular weight size selection was highest (i.e., >25 000 Da). AFM images revealed that TB particles with different molecular weights had different morphologies and the TB particles appeared as scattered islands or aggregates. CP-MAS NMR experiments revealed that the TB fraction with molecular weight species between 3 500 and 25 000 Da in size was characterized by a polymeric material of polyphenols. This polymeric substance contained primarily multiple benzene rings, polysaccharides, protein residue groups and various other functional groups. After acidic hydrolysis, this fraction formed a black precipitate. CP-MAS NMR found that the precipitate was a polymeric material with multiple benzene rings. CP-GC/MS identified 16 candidate compounds from the pyrolysis products of the black precipitate obtained from the main fraction with molecular weight species between 3 500 and 25 000 Da.
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TAN Chao, PENG Chun-xiu, GAO Bin, GONG Jia-shun. Spectroscopic and Structural Characteristics of the Main Components of Theabrownin in Pu-erh Tea[J]. Spectroscopy and Spectral Analysis, 2012, 32(4): 1051
Received: Aug. 3, 2011
Accepted: --
Published Online: Apr. 16, 2012
The Author Email: Chao TAN (tctj_1212@163.com)