| Anji white tea originates from An’ji county of Zhejiang, which is popular inrecent decades. It is a special kind of Chinese Camellia sinensis plant. The color ofits leaf buds change with the seasons: it is white before Tomb-sweeping Day, andthen gradually changes from white to green at summer. As we know, tea contains avariety of healthy ingredients for the human body, such as tea polyphenols, teapolysaccharides, proteins and amino acids, caffeine, vitamins, minerals and so on. Inrecent decades, tea polysaccharides becomes a research hotspot, because it haseffects in hypoglycemic, lipid-lowering, anti-tumor, enhance immune function andother effects. Currently, researches about Anji white tea focused on its albinomechanism and pharmacology research, and less on its physical﹠chemicalproperties, and polysaccharides. In this paper, Anji white tea produced in ZhejiangProvince was studied on polyphenols, polysaccharides, free amino acids, moistureand ash contents. Classification models of Anji white tea and Jing’an white tea onthe basis of near-infrared (NIR) spectroscopy associated after different pretreatmentmethods. At the same time, a series of comprehensive applications of modernresearch methods were employed to determine the monosaccharide composition,molecular weight, uronic acid content, protein content and IR of Anji white teapolysaccharides. The purpose above was to investigate the quality of Anji white teaand its polysaccharides and provide a theoretical basis for the quality control ofwhite tea. The main studies and results in this paper are mentioned as follows:1. Sensory evaluation was used to evaluate Anji white tea and Jing’an white tea.In additionm, tea polyphenols, free amino acids, moisture and ash content of Anjiwhite tea and Jing’an white tea were determined. The results are as follows: Anjiwhite tea polyphenols content was18.98±1.53%,free amino acids content was6.35±1.34%, moisture content was6.19±0.58%, and ash content was5.77±0.14%;Jing’an white tea polyphenols content was18.85±3.06%, free amino acids contentwas6.71±2.27%, moisture content was5.92±0.82%, and ash content was5.81±0.29%.2. Discriminant partial least-squares (DPLS) and discriminant analysis (DA)were employed to build classification models of Anji white tea and Jing’an white tea on the basis of near-infrared (NIR) spectroscopy associated after differentpretreatment methods.3. The extraction of Anji white tea polysaccharides were optimized by centralcomposition design and response surface analysis while good results were achieved.The main technical conditions were as follows: bath temperature of85℃，ultrasonictime of33min，solid-liquid ratio of1:40.4. The Anji white tea polysaccharides were extracted and its monosaccharidecomposition, molecular weight, uronic acid content, protein content and IR weredetermined. The results are as follows: polysaccharides content was38.7%, uronicacid content was5.26%, protein content was13.76%; Anji white tea polysaccharideshas two main components TPS1and TPS2, their Mw was4,250,000Da and402,000Da; infrared spectroscopy indicated that Anji white tea polysaccharides was aglycoprotein conjugate containing both pyran ring and furan ring.5. High performance liquid chromatography-mass spectrometry flight time wasused to determine white tea polysaccharide monosaccharide,the results indicatedthat Anji white tea polysaccharides composed of mannose, ribose, galacturonic acid,glucose, galactose, arabinose and xylose.6. Partial hydrolyzate of Anji white tea was analyzed by HPLC-ELSD. Theresults showed that the ability of glucanase, pectinase, cellulose degrading teapolysaccharides were more excellent; acid concentration, acid hydrolysistemperature and acid hydrolysis time had important effects on the partial hydrolyzateof Anji white tea polysaccharides. |
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