| Traditional Fuzhuan brick tea plays a vital role in the process of development of dark tea. The process of "fungal fermentation" has contributed to unique quality, flavor as well as the efficient benefit of the tea, which makes it very popular. "One would rather spend three days without foods, not a day without tea" is the best praise made by the frontier minorities. In recent years, thanks to popularization and application of "fungal fermentation with loose tea"(a special technique employed in tea processing), the processing technology and Fu brick tea industry develop rapidly and the shape of the tea becomes diverse which can be seen from the emerging of great variety of products. At the same time, the change in drinking ways of consumers and improvement of products in values have provided convenience for enhancing research methods and obtaining materials for scientific research. The research findings will help guide the innovative production of Fu tea and accelerate the growth of the industry. This study with the help of characteristics of "fungal fermentation with loose tea" has identified "Golden Flora" in different tea raw materials of Fu brick tea, analyzed its toxigenicity and the changing of biochemical components of Fu tea made by different raw materials during the main stage of processing. Based on UPLC-Q-TOF-MS technology, the changes in chemicals were studied during the process of "fungal fermentation" of Fu tea produced by four kinds of tea. The article has analyzed and identified the main specific biochemical compositions which are produced during the process of "fungal fermentation" of Fu tea produced by four kinds of tea raw materials by HPLC overlay. And the metabolic process of tea chemical component by Eurotium cristatum were studied as well. The main results of this research are as follows:1. This paper has identified "Golden Flora" in different tea raw materials of Fu brick tea and analyzed its toxigenicity. The fungus used in this research is Eurotium cristatum collected and tested in our lab. It was vaccinated in different tea samples such as Dahongpao tea, black tea, green tea, the raw material of Tianjian tea and the raw materials of Jinxiangyi brick tea by "fungal fermentation with loose tea" to obtain five kinds of Fu tea whose "Golden Flora" showed differences in morphological. This study analyzed the difference of it through microbial method and made systematic evaluations from morphology and DNA sequence analysis. Meanwhile, the toxigenicity has been studied. The results revealed that the "Golden Flora" is the same fungus in five kinds of Fu tea, also the same with the one on vaccination for test, which is classified as Eumycota, Ascomycetes; Euascomycetes; Eurotiales; Eurotiaceae; Eurotium Link ex Fires; Eurotium cristatum; Aspergillus Spiculosus Blaser. And the "Golden Flora" is not able to produce aflatoxins AFB1, AFB2, AFG1 and AFG2.2. This paper researched the changing of biochemical components of Fu tea made by different raw materials during the main stage of processing. The experiment took Dahongpao tea(A), Black tea(B), Green tea(C), the raw material of "Tianjian" tea(D) and the raw material of "JinXiangyi" brick tea (E) as raw materials of "fungal fermentation with loose tea" to investigate the changing of main biochemical components in the main processing stages (CK, YL,4D,10D). The results have showed that the tea polyphenols, tea catechins, flavonoids, amino acids, theanine, soluble protein, soluble sugar, gallic acid etc of the five kinds of tea have decreased to some degree. Organic acids presented a upward trend as "fungal fermentation" getting deeper. However, the caffeine content in five kinds of Fu tea have all showed the same change and has increased slightly compared with the raw materials. While theobromine and theophylline have reflected no regular change, and remained equal to that in the raw material eventually. The content of aqueous extract has relatively reduced during the process of "fungal fermentation" of five kinds of Fu tea, thus it set the foundation for pure tasting.3. Based on UPLC-Q-TOF-MS technology, the changes in chemicals were studied during the process of "fungal fermentation" of Fu tea produced by four kinds of tea. The paper researched the variations in the composition of the overall biochemical components from start to end "fungal fermentation" in different raw material of Fu tea by examining the huge difference in ingredients among the Dahongpao tea, Black tea, Green tea, the raw material of Tianjian tea and the raw material of Jinxiangyi brick tea along with the characteristics of metabolomics. The results have showed that, the number of metabolites varies in five kinds of Fu tea from start to end "fungal fermentation", the number of variant compounds are 49(Dahongpao tea),40(Black tea),51 (Green tea),52(raw material of Tianjian tea), and 49(raw material of Jinxiangyi brick tea) respectively. After comprehensively analyzing the specific variant compounds in five kinds of Fu tea from start to end "fungal fermentation", similar laws of changes in category were appeared, to be specific, Ester catechins have decreased significantly, while simple catechin component except GC have showed no substantial diversity, the content of EC, (±)-C, and EGC have raised compared to that in the raw material. Besides, procyanidine and several important alkaloids in tea as caffeine, theobromine, theophylline, xanthine and hypoxanthine also changed in the same way. Several common kinds of flavonol compounds such as Quercetin, Kaempferol, Vitexin and Rutin have raised in varying degrees. And the rheum emodin which belong to anthraquinones newly increased after "fungal fermentation" in five kinds of Fu tea.4. The article has analyzed and identified the main specific biochemical compositions which are produced during the process of "fungal fermentation" of Fu tea produced by four kinds of tea raw materials by HPLC overlay. With different tea samples (fungal solid state fermentation) generated from "fungal fermentation" as the research objects, this article has searched the main variant compounds through comparative analysis with the help of HPLC overlay. Meanwhile, targeted variant compounds have been constructed with preparative HPLC with preliminary identification by HR-MS and NMR, the experiment has indicated that under the detached condition of this study, diffenent kinds of Fu tea generated the same compounds after "fungal fermentation", which are both flavones, named quercetin and kaempferol respectively.5. The metabolic process of tea chemical components by Eurotium cristatum were studied. With representative compounds of EGCG, theanine, caffeine, theobromine and theophylline in tea selected as added substrate of fermentation system of Eurotium cristatum, the article has given a preliminary study of the metabolic process of the "Golden Flora" to the above five kinds of monomer components. The result has shown that the addition of EGCG has a certain influence on the growth, the reproduction of Eurotium cristatum, the pH value, the residual glucose concentration and the total protein concentration. Eurotium cristatum took the EGCG and its hydrolysis products as the basic nutrition to maintain its growth and reproduction, inferring that the spore enzyme secreted by Eurotium cristatum had a strong ability to hydrolyze EGCG and the product of the hydrolysis are EGC and gallic acid. The addition of caffeine can stimulate the growth of Eurotium cristatum to a certain extent. while Eurotium cristatum cannot consume it as carbon source to maintain its growth, nor to metabolize and decompose the caffeine. The theobromine and the theophylline are also important alkaloid of tea whose metabolism in the fermentation system is similar to that in caffeine, they can also stimulate the growth of Eurotium cristatum to some extent, but cannot be consumed as carbon source. However, tiny amounts caffeine can be detected in the fermentation broth of them, which means that Eurotium cristatum has the ability to synthesize caffeine with precursor of theobromine and theophylline. Similar to the group EGCG, Eurotium cristatum took the theanine and its hydrolysis products as the basic nutrition to maintain its growth and reproduction, the addition of theanine can stimulate the growth of Eurotium cristatum and postpone the autolysis of E.C. The content of theanine decreased sharply in the fermentation broth maybe owe to the hydrolysis by spore enzyme secreted by Eurotium cristatum, but the specific metabolite of theanine have not been analyzed because of the limitation of the detection method. |
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