"Jinhua Fungus": Its Taxonomic Position And Its Influence On Quality Of Fuzhuan Brick Tea

Fuzhuan Brick Tea is one kind of more important brick teas, it is well accepted by northwest minorities of China. On the surface of Fuzhuan Brick Tea, there are densely covered by kinds of bright yellow spots, commonly called "Jinhua" by providers and consumers. This is the most important character that Fuzhuan Brick Tea different to the others. The abundence of "Jinhua" is the important factor of the quality of Fuzhuan Brick Tea, but its taxonomic position is still unclear.In this study, firstly, "Jinhua Fungus" is isolated by different methods from each brick teas, the brick teas in different processing phase and the raw materials of tea. There is abundance "Jinhua Fungus" in Fuzhuan Brick Tea and it is the dominant fungus in Fuzhuan Brick Tea. A few "Jinhua Fungus" is also isolated from brick teas of Kangzhuan, Jinjian, Qingzhuan and the raw materials of Fuzhuan Brick Tea, indicating that "Jinhua Fungus" is widespread. In the results, 4 types of colony of "Jinhua Fungus" are obtained from the same Fuzhuan Brick Tea. A biodiversity was observed on colony of "Jinhua Fungus" in Fuzhuan Brick Tea.The influences of culture conditions, including culture media, pH of the medium, culture temperature, NaCl concentration and sucrose concentration in CZG medium on the isolates of "Jinhua Fungus" are investigated. On the condition of acidity, 25-35, these fungal isolates grow better, the optimum medium was PDA or CZG, on the general condition, 13 isolates produce cleistothecia, asci and ascospores; these isolates grow slower and produce conidium heads and conidia when they were incubated in CZG at 40癈, or on CZG plates containing 14% of NaCl or more, or 60% of sucrose. Mycological properties of 12 isolates are similar with that of E. cristatum, while remaining 5 isolates were significantly different. In this study, 17 "Jinhua Fungus" isolates are divided into 6 groups depending upon their growth on the media.Based on the morphological properties of cleistothecia, asci, ascospores, conidium heads and conidia, these 17 isolates prelimilary identified by classic taxonomy. All of these 17 isolates are identified to be involved within the genus of Eurotium. These isolates werealso analysed their esterase(EST) isozyme with PAGE and total soluble proteins by SDS-PAGE. Based on the electrophoresis patterns, a STATISTIC A cluster analysis was practiced. According to the morphological properties and cluster analysis: 15 fungal isolates were identified as E. cristatum, the remaining 2 isolates were identified as E. chevalieri. Different Eurotium species may involved in a brick of Fuzhuan Brick Teas, and usually the dominant species is E. cristatum. It was also proved that the EST isozyme electrophoresis is a useful method to identify Eurotium on species level in this study.To investigate whether the "Jinhua Fungus" plays any roles in the development of the flavor and quality of Fuzhuan Brick Tea or not, raw materials of Fuzhuan Brick Tea is inoculated with a "Jinhua Fungus" isolate and then incubated at 80 for 2 hours. Through analyses of the content of water extracts, tea polyphenols, amino acids, caffeine and flavone glycosides, the role the fungal inoculum plays was investigated. In the results, it was found that the content of caffeine was almost constant during the treatment, while all other substances listed above were significantly decreased. These were also observed on brick teas of Jinjian and Qingzhuan. By extraction with ether and analysis with GC-MS, decline of the total volatile flavor of Fuzhuan Brick Tea samples inoculated by the "Jinhua Fungus" was observed. However, volatile flavor elucidated during earlier 20 min was significantly increased, especially the content of linalool and its oxides. These indicated that the fragrance of Fuzhuan Brick Tea was possibly resulted by the "Jinhua Fungus". As a result, "Jinhua Fungus" may play an important role in changes of these biochemical components.Finally, through detection of existances of fungi and bacteria in the Brick Teas on the plates, fungi belonging to genera of Asperg...