Flavor Compounds And Microorganisms In Pu'er Tea At Different Storage Period

During the piled-up fermentation procedure of Pu'er tea, the chemical component of sun-dried green tea (such as tea polypheol) have been transformed into special flavor and taste components after a series of complicated reactions because of the common effects from the extracellular enzymatic action of microorganisms, heat of microorganisms metabolism, and the water in tea leaves, which results in the special flavor and taste of Pu'er tea. Therefore, the formation of Pu'er tea flavor is due to the works of microorganism. Due to a series of complicated chemical changes such as oxidization, polymerizations, condensation, decomposition during piled-up, certain corresponding components are formed in the tea. This procedure turns the sun-dried green tea into Pu'er tea. During the fermentation process, the content of many components vary dramatically.Flavor and quality of Pu'er tea change during its storage life. This study took raw Pu'er tea at three different storage periods as materials to compare the variety and cell amount of microorganisms and some special flavor compounds such as water extracts, polyphenols, caffeine, soluble sugar, free amino acids. In this study, four types of selective medium were used to culture microorganisms from the fermented Puer tea at three different storage periods. The cell of microorganisms growing in each medium was counted. Then, the microorganisms were separated and their varieties were determined by morphology under microscope. Among them,16S rDNA of bacteria was analyzed to get further identification.Since then, there is no standard for identification of storage period of Puer tea. The primary objective of this study was to provide some basis for the identification of Pu'er tea. The conclusions of the research are as follows:1. The flavor compounds as the content of water extracts increase along with storage of raw Pu'er tea extension. But the content of polyphenols, caffeine and free amino acid decrease along with storage of raw pu'er tea extension.The content of soluble sugars has no significant difference for the three samples.2. The colony-forming units (cfu) of bacteria increase along with storage extension. But the colony-forming units (cfu) of fungus decrease along with storage extension.3. The largest amount of microorganisms in fermented Pu'er tea is bacterium and mold. The bacteria are gram-positive bacteria.4. The five species of bacteria are identified as follows:Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus megaterium, Bacillus cereus and Bacillus subtilis.5. Five kinds of mildew were isolated and identified. They are Aspergillus glaucus, Rhizopus spp., Trichoderma spp., A. niger and Penicillium chrysogenum observed under microscope.