Structural Characterization and Non-Volatile Metabolite Analysis of Crude Theabrownins Prepared by Different Processes(不同工艺制备的粗茶褐素结构表征及非挥发性代谢物分析)

Using Yunnan large leaf tea as raw material, alkaline oxidation crude theabrownins (TBs-a) and enzymatic oxidation crude theabrownins (TBs-e) were prepared by alkaline oxidation and enzymatic oxidation, respectively. The crude theabrownin extracted from Pu-erh ripe tea (TBs-f) through water extraction was used as a control. The main components, structural characteristics and non-volatile metabolites of crude theabrownins prepared by three different processes were analyzed. The results showed that the relative contents of the main components of the three crude theabrownins varied greatly. The relative contents of theabrownins in TBs-a and TBs-f were higher than those in TBs-e, while the relative contents of free amino acids and caffeine in TBs-f were higher than those in TBs-a and TBs-e. The scanning electron microscope showed that the surface of TBs-a was smooth and wrinkle-free, the surface of TBs-e had a large number of round pores, and the surface of TBs-f was rough. The X-ray diffraction analysis showed that all three crude theabrownins were amorphous polymers. The Zeta potential results showed that TBs-f had the smallest particle size and the best stability, TBs-a had the middle particle size and good stability, and TBs-e had the largest particle size and the worst stability. The thermogravimetric analysis showed that the thermal performance of the three crude theabrownins was good. The relative contents of non-volatile metabolites of the three crude theabrownins were quite different. And amino acids, organic acids, saccharide, alcohols and fatty acids were the main differential metabolites. Among them, amino acids accounted for a relatively high proportion in TBs-a and TBs-e, while organic acids and alcohols accounted for a relatively high proportion in TBs-f. There were significant differences among the three kinds of crude theabrownins in terms of main components, structural characteristics, and non-volatile metabolites. The study hoped to provide a theoretical basis and technical reference for the efficient preparation and rational utilization of theabrownins.(以云南大叶种茶为原料,分别利用碱氧化法和酶氧化法制备碱氧化法粗茶褐素(alkaline oxidation crude theabrownin,TBs-a)和酶氧化法粗茶褐素(enzymatic oxidation crude theabrownin,TBs-e),并以从普洱熟茶中水提得到的粗茶褐素(Pu-erh ripe tea crude theabrownin,TBs-f)为对照,对3种不同工艺制备的粗茶褐素的主要成分、结构特征及其非挥发性代谢物进行分析。结果表明:3种粗茶褐素主要成分的相对含量差异较大,TBs-a和TBs-f中茶褐素和的相对含量高于TBs-e；而TBs-f中游离氨基酸和咖啡碱的相对含量高于TBs-a和TBs-e。扫描电镜分析结果发现:TBs-a表面光滑,无褶皱；TBs-e表面存在大量圆形气孔结构；TBs-f表面粗糙。X射线衍射分析显示,3种粗茶褐素均为非晶态聚合物。Zeta电位结果表明,TBs-f粒径最小,稳定性最好；TBs-a粒径居中,稳定性较好；TBs-e粒径最大,稳定性最差。热重分析显示,3种粗茶褐素的热性能均较好。3种粗茶褐素的非挥发性代谢物相对含量差异较大,氨基酸、有机酸、糖类、醇类和脂肪酸是三者主要的差异代谢物,其中,氨基酸在TBs-a和TBs-e中的占比较高,而有机酸和醇类在TBs-f中的占比较高。3种粗茶褐素在主要成分、结构特征及非挥发性代谢物方面均存在显著差异,研究旨在为茶褐素的高效制备及合理利用提供一定的理论依据和技术参考。)