Study On The Microbial Populations And Their Effect On The Formation Of Tea Quality In The Process Of "Fungi Growing On Loose Tea"

Fuzhuan brick tea is a treasure of various kinds of teas in China. It has always been a necessity of ethnic minorities’life in Chinese border area. Fuzhuan brick tea has a unique flavor and health care functions due to a unique fungi growing process, so it is widely accepted by tea consumers. However, traditional Fuzhuan brick tea has some defects, such as single product structure, complex processing, uncontrollable product quality, and inconvenient to drink. These disadvantages have hampered the further industry development of Fuzhuan brick tea. To solve the problems, a new technology of "Fungi growing on loose tea" was created recently, which has greatly shortened the production cycle and made the product quality more reliable and controllable. In this study, based on our previous research of "Fungi growing on loose tea", we have further amplified this process, analyzed the microbial groups, measured the activity of six microbial enzymes, and detected the content changes of main biochemical components during this process. The main results are as follows:1. Amplification trial of "Fungi growing on loose tea"In this study, the first-class Fu tea and ordinary green tea were used as test materials to improve and amplify the process of "Fungi growing on loose tea". In general, the temperature, humidity and water content in the amplification process were lower than those of previous research. We conducted16different test condition combinations to observe the amplification process of "Fungi growing on loose tea"; then, we analyzed the contents of biochemical components and evaluated the sensory quality of finished products. Based on the results, the optimum conditions for fungi growing on first-class Fu tea were water content of tea material28%, culture temperature23-26℃, and relative humidity70%, respectively, and those of ordinary green tea were water content of tea material24%, culture temperature23-26℃, and relative humidity70%, respectively.2. Systematic identification of microbial groups in the process of "Fungi growing on loose tea"We conducted the morphological and molecular identification of nine separated strains of fungi. The results were:1strain of Eurotium cristatum,1strain of Aspergillus niger,1strain of Aspergillu tabingensis,5strains of Penicillium, and1strain of other cladosporium sp, respectively.3. Activity determination of microbial enzymes in the process of "Fungi growing on loose tea"We analyzed the activity variation of cellulose enzyme, pectinase, amylase, beta glycosidase, protease, and tannin enzyme. The results showed that the activity of all these enzymes change from a low level to a high one; and the change tendency is highly correlated with the increase of microbial quantity.4. The content changes of biochemical components during the process of "Fungi growing on loose tea"We chose first-class Fu tea and ordinary green tea as test materials to process, and then investigate the content changes of main biochemical components during fungi growing. We found, for both kinds of teas, that the contents of polyphenols, catechins, flavonoids, amino acids, soluble proteins, soluble sugar, and crude fibre decreased during the whole process, but the decrease extent was different for different component. However, there was an increase in gallic acid content. Almost all alcohols and esters aromatic components’ content increased during the fungi growing process, including linolenic acid methyl ester, hexadecanoic acid, etc. Among these components, the increase of1-octen-3-ol, linalool, linalool oxide Ⅰ, and linalool oxide Ⅱ were the most significant. The increase of these components is very important for the characteristic aroma formation of loose Fu tea.