Study On The Technologies And Mechanisms Of Reducing Fluorine In Sichuan Brick Tea

Brick tea was a kind of necessary foods for minority nationality in China, but because of the physiological characteristic of adsorption and accumulation fluoride in tea plant (Camellia sinensis L.), Fluoride content in many brick tea products was very high, and it caused fluoriosis in many minority nationalities in China because of excessively consumptions. In view of existing situation that long time and heavily consumption high fluoride brick tea had induced fluoriosis in many minority nationalities, the knowledge of planting, processing, biochemistry and physical chemistry were utilized, and it took Sichuan brick tea to be the study object in this work, fluorine reducing technologies and mechanisms were studied and the results as follows:(1) Fluoride content in Sichuan brick tea was relatively high at large with a range of 663.3～1432.5 mg/kg, and the average content was 986.2±183.6 mg/kg. The fluoride content in Kangzhuan tea was 976.0±169.6 mg/kg and in Jinjian tea was 1000.4±204.0 mg/kg, there was not significant between them as well. Fluoride content in Sichuan brick tea was induced by the highly fluoride content materials including process packed tea (1112.5±289.8 mg/kg), raw packed tea (1111.6±86.8 mg/kg) and packed tea (951.6±115.0 mg/kg). It wasn't significant between the fluoride content in Sichuan brick tea and in its materials. More studies indicated that, the main reasons for the consumers extensively intaking fluorine (12.9～18.2 mg/day) were caused by consuming a large amount of highly fluoride Sichuan brick tea (18.2～26.5 g/day) with the consuming method of decocting.(2) In view of the situation of highly fluoride content in Sichuan brick tea, the author adopted the method of harvesting low fluoride materials in time by monitoring fluoride content in tea tips during its upgrowth and trial-producing low fluoride brick tea, and combined the methods of optimizing materials and adsorbing for reducing fluoride content in Sichuan brick tea much more.The results showed that, the fluoride content in low fluoride Kuangzhuan tea (432.4±12.7 mg/kg) and in low fluoride Jinjian tea (485.3±10.8 mg/kg) which were prepared by the materials that harvested in time by monitoring fluoride content in tea tips during its upgrowth, their fluoride content were lower than about 54.0% and 53.7% to the main Sichuan brick tea products in the market, respectively, and the fluoride reducing effect was remarkable. The low fluoride materials was as the main raw material and multivariate linear program model was adopted in the second work, and the typeⅠlow fluoride Kangzhuan tea and Jinjian tea whose fluoride contents were 360.5±4.4 mg/kg and 373.3±10.1 mg/kg was prepared, respectively, it reduced 16.4% and 24.3% of fluoride content to the low fluoride brick tea which was prepared with low fluoride materials, and it reduced 61.7% and 64.3% of fluoride content to the brick tea sold in markets. The fluoride reducing effect was extremely distinct. Simultaneously, the typeⅡlow fluoride Kangzhuan tea and Jinjian tea whose fluoride contents were 571.7±10.7 mg/kg and 572.7±15.0 mg/kg was prepared by optimizing the materials sold in markets by multivariate linear program model respectively, it reduced 39.2% and 45.3% of fluoride content to the brick tea sold in markets, and the fluoride reducing effect was significant.Moreover, two highly reducing effect reagents (LSG and YSZ) were selected from 11 available reagents for adsorbing fluorine in tea soup. The results showed that, during the decocting, LSG and YSZ were added into tea soup, they could reduce the fluoride content in tea soup, and about 40% fluorine was reduced. However, it wasn't beneficial to reduce the fluorine in tea soup when decocting with alkali for LSG and YSZ either, and it wasn't beneficial to reduce the fluorine in tea soup when decocting with salt for YSZ, as well.(3) The low fluoride brick tea prepared by the methods above and analyzed their quality. The results indicated that, the quality of those low fluoride, brick teas which were prepared with the method of harvesting low fluoride materials in time by monitoring fluoride content in tea tips during its upgrowth and with the method of optimizing the materials was better that that in the CK samples, especially the water extract in low fluoride brick teas was much higher than that in CK. For example, the water extract in low fluoride brick prepared with the method of harvesting low fluoride materials in time by monitoring fluoride content in tea tips during its upgrowth were 35.51% and 35.93% separately, and that in typeⅠlow fluoride Kangzhuan tea and Jinjian tea was 29.33% and 28.89% respectively, their qualities were superior to the CK samples. Simultaneously, the low fluoride brick teas decocted well, and they were superior to the CK samples on the organic evaluation, therefore, these brick teas were low fluoride and high quality brick tea products.At the same time, quality components in tea soup were reduced when reducing fluorine by adsorbing technology, and some quality indexes of the tea soup were inferior to that in CK tea soup, however, there existed little diversity of the quality on the organic evaluation to the CK sample, therefore, it proved that the fluoride content in tea soup could reduced by the method of adsorption.(4) For study the mechanisms of fluorine in the soup adsorbed on LSG and YSZ, the theories and technologies of adsorption equilibriums and adsorption kinetics were both adopted. Under the experimental conditions, fluorine adsorbed on LSG and YSZ could be well described by the Langmuir model. Fluorine adsorbed on LSG was a chemical process and the adsorption capacity was high to 10.627 mg/g, and fluorine adsorbed on YSZ was a physical adsorption and the adsorption capacity was high to 13.624 mg/g.Under the tea soup conditions, additional salt could induce the absorption capacity of fluorine on YSZ notably, but with no influence to LSG. Although the capacity of adsorbing fluorine on YSZ was decreased following increasing the adsorption time, the adsorption kinetic could be described by the pseudo-second-order rate model when the adsorption quality reaching to the equilibrations, and the Parameters measured actually existed some difference to that calculated. Simultaneously, the adsorption kinetic of fluorine adsorbed on LSG could be described by the pseudo-second-order rate model, as well.The experimental results of this thesis provided the fundamental theories for reducing fluoride content in brick tea. Meanwhile, it deepened the technology and approach to advace the quality of brick tea.