The Molecular Composition and Spectral Properties of Polysaccharide Isolated from Pu-Erh Tea and Its Material
GONG Jia-shun1, HU Xiao-jing1, PENG Chun-xiu2, ZHOU Hong-jie3
1. College of Food Science and Technology, Yunnan Agricultural University, Kunming 650201, China 2. College of Horticulture and Landscape，Yunnan Agricultural University, Kunming 650201, China 3. College of Pu-erh Tea, Yunnan Agricultural University, Kunming 650201，China
Abstract：Pu-erh tea, a kind of well-known tea from the ancient time, is originally produced in the Yunnan Lanchan River basin through a special solid state fermentation by fungi. It uses sun-dried green tea as its starting materials. To investigate the variation of composition and spectral properties of polysaccharide during solid state fermentation of pu-erh tea by using Saccharomyces cerevisiae as preponderant starter and using sun-dried green tea as materials in the present study. The results showed that the content of water soluble polysaccharide was increased，and the activity of hydrolase such as cellulase，pectinase and glucomylase were also enhanced. The content of neutral sugar increased with the ferment time increasing and the MW of raw polysaccharide showed significant difference during fermentation. The main polysaccharide TPS2 and TPS1 were isolated and purified from pu-erh tea and its materials by DEAE-52 and Sephadex G-150 column chromatography. TPS2 contains the higher content of uronic acid, but TPS1 contains the higher contents of neutral sugar and protein. Monosaccharide analysis by GC-MS revealed that TPS1 and TPS2 were composed of arabinose, galactose, glucose, rhamnose, xylose and mannose with molar ratios of 24.2∶23.6∶5.9∶3.2∶1.8∶1.1 and 19.3∶26.9∶3.2∶2.7∶1.3∶5.5, respectively. The average molecular weight of TPS1 and TPS2 was 1.68×104 and 1.21×104 Daltons, respectively. UV scanning spectrum showed that TPS1 and TPS2 had no characteristic absorption between 200 and 400 nm wavelength, it suggested that they contain trace protein. IR spectrum of TPS1 and TPS2 demonstrated that pyranoid rings were contained in them. As shown in the image of atomic force microscope, the molecular appearance of TPS1 and TPS2 resembled islands and apparently consisted of conglomerations. The height of conglomerations of TPS2 was about 40nm and the length or width was 0.5-0.8 μm, while the height of conglomerations of TPS1 was about 4nm and the length or width was 0.2-0.4 μm. TPS2 shows sheet conglomerations with rough surface, but TPS1 shows squama conglomerations with smooth surface in the image of scanning electron micrograph. The experimental data suggested that the variation of composition and spectral properties of polysaccharide isolated from pu-erh tea and its materials owed to the action of microorganism and humid and thermal action for long time process.
Key words：Pu-erh tea;Sun-dried green tea;Polysaccharide;Solid state fermentation;Spectral properties
龚加顺1, 胡小静1, 彭春秀2, 周红杰3 . 普洱茶及其原料多糖分子组成及光谱学特性研究 [J]. 光谱学与光谱分析, 2010, 30(07): 1960-1964.
GONG Jia-shun1, HU Xiao-jing1, PENG Chun-xiu2, ZHOU Hong-jie3 . The Molecular Composition and Spectral Properties of Polysaccharide Isolated from Pu-Erh Tea and Its Material. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2010, 30(07): 1960-1964.
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