Study On The Speciation And Extraction Of Selenium In Selenium-enriched Tea

Tea is one of the world’s three beverages. It has a huge consumer group because its contains a variety of functional composition which is good to human body. Selenium-enriched tea is the main tea in Shaanxi. It not only has the special properties of Selenium-enriched tea, but also has other functional components of ordinary tea, therefore, se-enriched tea is praised as the most natural selenium supplements. Selenium-rich tea main functional components of tea polyphenols, tea polysaccharide, selenium protein and γ-aminobutyric acid and so on, because of their functional role and they are widely used in food, medicine and chemical industry daily necessities and other fields, therefore Selenium-enriched tea has the very high research value. In summary, This experiment not only to carry on a research to the form of selenium in selenium-enrich tea, but also for the continuous extraction process of the main functional components and preliminarily study of γ- aminobutyric acid in elenium-enriched tea. It can improve the utilization rate of selenium-enrich tea resources, reduces process cost. The results showed that:(1) In this experiment, using the abandoned old leaf as material to study, provided by Shaanxi Ziyang County, Ankang Panlong natural selenium rich Green Tea Co. Ltd. The deposit morphology and content of selenium in selenium-enriched are determined tea through study in selenium content of tea polyphenols, tea polysaccharide, tea protein. Selenium content in tea polyphenol(76.77% purity) was 0.27 μg/g, in tea polysaccharide(73.84% purity) was 1.82μg/g, in selenoprotein was 5.02 μg/g. Make a continuous extraction on the functional content of selenium-enriched tea, use the extraction rate of tea polyphenols and teapolysaccharide as the index to judge the results of extraction. The results showed that, liquid to solid ratio had the greatest impact on extraction rate and ethanol concentration, extraction temperature and extraction time had less impact. Optimum conditions were:liquid to solid ratio was 35:1, ethanol concentration was 40%, extraction temperature was 65℃, extraction time was 60 min.The purity of tea polyphenols, tea polysaccharide and selenoprotein were low through continuous extraction. The purity of crude tea polyphenols was 43.29%, the crude tea polysaccharide was 37.67%, the crude selenoprotein was 52.65%. Selection of macroporous adsorption resin to make purification of tea polyphenols, the results showed that, HPD-400 is more suitable for purification of tea polyphenols, resin column volume was 37 m L, adsorption equilibrium time was about 3.5 hours, 80% ethanol as eluent, sample flow rate was 1.0m L/min, desorption velocity was 1.5m L/min. The purity of purified tea polyphenols was 23.53% higner than unpurified crude product. The purity of tea polysaccharide after protein removal by Sevag method was from 37.89% to 52.47%. Selected D101 resin for decolorization of tea polysaccharide, according to data analysis to determine the optimum technology of tea polysaccharide decolorization is: p H is 4, decolorization time was 11 h, decolorization temperature was 45℃. Under this process, the decolorization rate of polysaccharide was 71.23%, the purity of tea polysaccharide increased to 73.48%. Which purification of proteins by ethanol precipitation, 76.49% purity protein could be obtained, protein loss rate was 8.56%.Application of vacuum processing method and monosodium glutamate impregnation method were used to make enrichment of γ-aminobutyric acid in selenium-enriched tea, and compared their enrichment effect. The results showed that, the enrichment effect of γ-aminobutyric acid was the best in 10 h vacuum processing, the content of γ-aminobutyric acid content was increased to 0.87mg/m L, is 9.5 times to control products. The effect of enrichment of γ-aminobutyric acid was the best when soaked in 1% concentration glutamate solution for 12 h, the content of γ-aminobutyric acid was 0.62mg/m L, 6.8 times was the control product. Therefore, the best effect of vacuum treatment is 10 h. The content of γ-aminobutyric acid was detected by the high performance liquid chromatography with pre column derivative OPA, the chromatographic conditions: Intertsil ODS-C18 column(4.6 mm*250 mm, 5 μ m) as chromatographic column, mobile phase A was 15 mmol/L sodium acetate, 4% acetic acid was used to regulate p H to 5.90 ± 0.05, flow phase B was pureacetonitrile, flow rate was 1m L/min, column temperature was 30℃, sample size was 20 m L, detection wavelength was 332 nm, gradient elution.