The Basic Research On The Fine Application Of Purple Tealeaf From Tea Plant, Camellia Sinensis

Purple tealeaf is a special tea resource for its higher contents of catechins and anthocyanidins as its characteristic components. For their comprehensive biological activities in scavenging free radicals and antioxidative activity, catechins and anthocyanidins could be wildly used in foods, health products, cosmetic and medicine, et al. In this thesis, the basic research on the f'me application of purple tealeaf was investigated basing on the studies of chemical features and biological activities of those characteristic components by ingeniously utilizing the principles of tea biochemistry, tea processing science, and natural products chemistry.Firstly, the occurrence status of purple tealeaf of tea plant was observed, and the results showed that the occurrence status of purple tealeaf was different in different tea plant and in different season. The purple tealeaf was mainly occurring in summer and autumn, which was coincident to the tea plant growth fact. The percentage of purple tealeaf was affinitive to the content of anthocyanidins, the sunlight and the temperature, and the percentage of purple tealeaf was positive relation to the total sunlight hours monthly, the average temperature monthly, and the anthocyanidins contents of purple tealeaf, and their correlation coefficients were 0,7387, 0.9328 and 0.9554, respectively.Then, the characteristic components of purple tealeaf were studied. The results of analyzing biochemical components showed that contents of catechins (132.97±7.32 mg/g)and anthocyanidins (1.14±0.05%) of purple tealeaf were higher than those of green tealeaf. Thin chromatography and column chromatography were employed to separated and identify the anthocyanidins constituents of purple tealeaf combing with UV-vis pattern and color reaction, and delphinidin was primarily identified. The threshold method was used to study the gustatory feature of purple tealeaf, and the results suggest that the higher contents of catechins and anthocyanidins of purple tealeaf were mainly responsible to its bitterness and astringency. The results of the research on the color-developing feature indicated that anthocyanidins were the main reason for the red of purple tealeafin acid condition.In order to extensively explore the fine application values of purple tealeaf, the antioxidative activity of those characteristic components of purple tealeaf were systemically studied by the researches of scavenging O₂^-,·OH and lipid free radical ability, also the antioxidative activity of constituents was investigated by using the chemical simulation calculation method. The experimental results showed that all the samples have strong scavenging effects to the 3 free radicals. According to their IC₅₀ value, the order of scavenging effect to the 3 free radicals is similar: catechins extract＞purple tealeaf water extract＞green tealeaf water extract＞anthocyanidins extract. The simulating computation results theoretically approved that the antioxidative ability of catechins were stronger than those of anthocyanidins, corresponding to the experimental results.Furthermore, the chelating casein ability of those characteristic components of purple tealeaf was studied, and the results showed that the chelating ability of purple tealeaf was stronger than that of green tealeaf, and the chelating ability of catechins was stronger than that of anthocyanidins. The results indicated that the bitterness and astringency of purple tealeaf would be reduced or restrained by adding edible protein in purple tealeaf.Based on the experimental results above, the fime application approaches of purple tealeaf were put into test. Firstly, the result of antioxidative effect to lard showed that the purple tealeaf and its characteristic components had strong antioxidative effect to lard, and the antioxidative ability of purple tealeafwas stronger 9.4,5.1,2.5 and 2.9 times than that of V_c,V_E,BHA and BHT, respectively. The order of antioxidative ability of samples was catechins extract＞purple tealeaf water extract＞green tealeaf water extract＞anthocyanidins extract. This research indicated that the catechins and anthocyanidins may be the main components responsible to the antioxidative ability of purple tealeaf, and the purple tealeaf would be directly used as a natural antioxidant.A mathematics model was built by using the experimental method of quadr-general- turning-assembly design to study the synergetic antioxidative effects of purple tealeaf water extract with V_c and V_E. With the help of digital processing system and the frequency analyses, the optimized formula was the dosage of purple tealeaf water extract was 0.169～0.205mg, the dosage of V_c was 2.494～2.523mg, and the dosage of V_E was 0.667～0.738mg, at this condition, the scavenging rates to O₂: and·OH could be up to＞80%.The bitterness and astringency of purple tealeaf could be efficiently reduced by adding casein (100mg/50g tea) into purple tealeaf in tea processing, and the tea quality was promoted. The red color-developing ability of the black tea condensed solution made from purple tealeaf was stronger than that of green tealeaf, and the condensed solution was limpid, the color value of condensed solution was stability in acid condition, and the condensed solution was stability to sunlight, food additives and temperature. These results suggested that the condensed solution made from purple tealeaf would be used to the manufacture of ice black tea.The experimental results of this thesis provide the fundamental theories for fineutilizations of purple tealeaf, and put forward some technical approaches to fine application of purple tealeaf. Also, the thesis had important theoretical significance to enrich the theory of tea fine processing, had practical value to guide the application of special tea resources.