普洱茶与液态发酵普洱茶粉中茶褐素的比较研究

Comparative Study on Theabrownins in Pu-erh Tea and Its Powder Fermented in Liquid State

采用有机溶剂萃取法提取液态自然发酵普洱茶粉和固态发酵工艺生产普洱熟茶"7572"的茶褐素,对两种茶褐素的光谱学性质及理化性质进行比较分析。紫外-可见光谱(UV-Vis)表明,液态茶褐素在380 nm左右比固态茶褐素多一个吸收峰;红外光谱(IR)分析结果显示,两种茶褐素所含官能团相似,均为多羟基的酚类化合物,还可能有蛋白质和多糖与其结合;对茶褐素酸性官能团定量分析表明,两种茶褐素均含有羧基和酚羟基,且液态茶褐素中的两种官能团均比固态茶褐素多;膜法分离分级茶褐素结果显示,低聚(M<10 ku)部分在固、液态茶褐素中含量分别为26.74%和18.84%;高聚(M>100 ku)部分在固态茶褐素中含量56.98%、在液态茶褐素中含量为70.72%;两种茶褐素总还原力均具有剂量依赖性,活性相似;对膜分级后各组分还原力测定表明,两种茶褐素的中聚部分(10 ku<M<100 ku)、高聚部分的总还原力均明显高于低聚茶褐素。

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 fimctional 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 〈 I00 ku） and high- （M 〉 100 ku） polymer fractions in both the theabrownins were significantly higher than that of the oligomeric fraction.