Study On Distribution Of Fluorine In Tea Shoots And The Way Of Combination With Polysaccharides

Fluorine, one of the necessary trace elements of human beings is presented in the forms of inorganic and organic compounds in foods, such as F-, SiF62-, A1F63-, FeF63- etc. This topic firstly studys on the distributions of fluorine in tea shoots and tea extracts and the way of combination with polysaccharides, verifying the the way of combination fluorine with polysaccharides, providing new scientific evidence and theoretical basis to effectively reduce the fluoride content in tea.1. Study on the distributions of fluorine in tea shoots and tea extracts1.1 The distribution of fluorine in different tea shootsBy measuring the fluoride contents in different parts of tea shoot, the result showed that the fluoride contents increased first and then induced with the tea shoots grown up, and the peak value was the later section of the red stem,602.13 mg/kg, and the least was the green treetop,294.70 mg/kg. By measuring the fluoride contents in the stems and leaves, the result showed that the fluoride mainly existed in the leaves. F content in the leaves increased sharply with the shoot parts decreasing. F contents in the frontal gray section reached the highest,985.12 mg/kg, and F content in the later section decreased. F contents in the stems were less than 70 mg/kg and decreased with the tea shoots grown up.1.2 The distribution of fluorine in the tea extractsBy extracting with different polar solvents from black tea, green tea and brick tea, the fluoride contents in the tea extracts were measured. The results showed that the fluoride content in the brick tea was the highest in the three teas,3646.64 mg/kg, and the fluoride content in the sediment layer was the highest in the five layers accounting for about 80% of the total fluoride content of tea. The sediment layer is mainly tea polysaccharides. These suggested that most of fluoride in the tea combined with the polysaccharides.2. Study on the way of combination fluorine with polysaccharides2.1 The experiment on the complexation of tea polysaccharides, metal ions and fluorideBy combining tea polysaccharides with Ca, Mg, Fe, Al respectively and then combine with fluoride, the fluoride contents before and after combination were measured. The results showed that compared with TPS and TPS+F, fluoride contents in TPS+Ca+F and TPS+Mg+F increased obviously, higher than the fluoride content of polysaccharides only combination with fluoride, the tender tea 105.16% and 104.19% respectively, the old tea 30.41% and 28.82% respectively, fluoride contents in TPS+Fe+F and TPS+Al+F decreased obviously, reduced rate of the tender tea 8.68% and 57.96% respectively, reduced rate of the old tea 54.13% and 72.56% respectively. By combining tea polysaccharides with Mn, K, Na respectively and then combine with fluoride, the fluoride contents before and after combination were measured. The results showed that compared with TPS, fluoride content in TPS+Mn+F, TPS+K+F, TPS+Na+F increased obviously, compared with TPS+F, fluoride content in TPS+Mn+F increased unconspicuously, fluoride contents in TPS+K+F and TPS+Na+F decreased obviously. These suggested that Ca and Mg played a positive role on the combination polysaccharides with fluoride, and Fe, Al, K, Na played a negative role on the combination polysaccharides with fluoride.2.2 Study on the combination ability of several plant polysaccharides with fluorideIn five plant polysaccharides, the fluoride contents in TPS was the highest and the old tea polysaccharides was 6276.38 mg/kg, tender tea polysaccharides was 8753.64 mg/kg. After combining five polysaccharides with fluoride, the fluoride contents in TPS was still the highest and the old tea polysaccharides was 7671.00 mg/kg, tender tea polysaccharides was 9758.93 mg/kg. These showed the characteristic of the combination TPS with fluoride.2.3 Study on the dynamic changes of the fluoride content in the purification process of TPSBy separation and purification of TPS with the sevag method, hydrogen peroxide decolorization method, DEAE-52 cellulose column chromatography, the changes of the fluoride contents in TPS in the process were researched. The results showed that the fluoride contents had a little changes before and after deproteinizing, the fluoride mainly existed in the deproteinized polysaccharides,8725.04 mg/kg, the fluoride in the crude tea polysaccharides showed decreasing, especially, the fluoride substantially decreased after decolorization and dialysis,1007.13 mg/kg. In the four fractions by DEAE-52 cellulose column, the fluoride content in the TPS1 was the highest,657.80 mg/kg. As is stated above, the fluoride mostly existed in TPS as the form of combination with the small molecules, a part of fluoride possibly present in TPS as the form of combination with weak acid polysaccharides.