To study the spectroscopic and physicochemical properties of theabrownins in ripened Pu-erh tea “7572” produced by solid-state fermentation and the Pu-erh powder produced by natural liquid-state fermentation, two types of theabrownins were extracted with an organic solvent. The UV-visible results showed that liquid theabrownin had an additional absorption peak at ?380 nm compared to solid theabrownin. The IR results indicated that the two theabrownins had similar functional groups. Both of them were composed of phenolic and carboxylic compounds, along with proteins and polysaccharides. The quantitative analysis of the acidic functional groups in theabrownins showed that both types of theabrownins contained carboxyl and phenolic hydroxyl groups, and the number of the two functional groups in liquid theabrownin was more than that in solid theabrownin. Theabrownins were isolated and graded based on membranes. The results showed that the contents of the oligomer fraction (M <10 ku) in solid and liquid theabrownins were 26.74% and 18.84%, respectively. The contents of the high-polymer fraction (M >100 ku) in solid and liquid theabrownins were 56.98% and 70.72%, respectively. The reducing powers of two theabrownins were dose-dependent and had similar activities. The measurement of the reducing power of each fraction after the grading by membranes indicated that the reducing powers of the middle- (10 ku < M < 100 ku) and high- (M > 100 ku) polymer fractions in both the theabrownins were significantly higher than that of the oligomeric fraction.

教育部“长江学者和创新团队发展计划”项目(IRT1166)