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Directional Conversion Of Green Tea Polyphenols With Nano-CaCO3 Immobilized Enzyme And Bioactivity Of Their Products

Posted on:2006-11-29Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z T DingFull Text:PDF
GTID:1100360185450395Subject:Horticulture
Abstract/Summary:PDF Full Text Request
Green-tea polyphenols are the main element in tea leaves, constituting 18%-36% of total dry matter, the key component of which is catechins. Their efficiency for cleaning up suporoxid radical and hydroxyl radical is closely related with the mechanism of tea in human health protection and treatment of some diseases. Theaflavins, the oxide of green-tea polyphenols, are formed after oxidation of polyphenols, can dissolve in ethyl acetate and contain benzotropolones,which owns greater bioactivity than other members in tea pigments and their health function, extraction and isolation have been concerned worldwide. Theaflavins have been widely and deeply studied and got a number of encouraging progress in knowledge or practice of their composition, structure, properties, formation mechanism, analyzing technique, relation to black tea quality, factors affecting theaflavin formation, control, etc. Experiments testified that theaflavins own activities to effectively resist bacteria, viruses, cancers, and cardiovascular and cerebrovascular diseases, etc., with the efficiency being over tea polyphenols. Theaflavins have been widely recognized as a matter which possesses the greatest potential of useful activities in tea leaves, but its content is low in black tea, so it is difficult to realize factorial production.Extraction by in vitro enzymatic oxidation is a method for directional production of theaflavins relying upon the oxidation property of polyphenol oxidase. Using nano-CaCO3 as immobilizing material, the author immobilized the tea polyphenol oxidase , and investigated the effect of temperature, pH value, reaction duration, and substrate concentration on the activity of immobilized enzyme. As a result, a best technology for in vitro oxidation of tea polyphenols was established: the best parameters for oxidation were 37oC, pH 5.0, and 10 min. In comparison with free enzymes, the nano-CaCO3 immobilized polyphenol oxidase owns higher activity, has greater resistance to high temperature and more significant stability to pH values.Components of theaflavins in the oxide of green-tea polyphenols were analyzed by HPLC, taking the crude theaflavin extracts from black tea and the unoxidated...
Keywords/Search Tags:Theaflavins, Nanomaterials, Immobilized enzyme, Bioactivity, PC-3, Zn2+, Green-tea polyphenols
PDF Full Text Request
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