The Research On Liquid Fermentation Of Pu-erh Tea

In order to study the effects of enzyme and microorganism on the biochemical ingredients of liquid-state fermentation of Pu-erh tea, different enzymes and microorganism were artifically infected into the process of liquid-state fermentation of sun dried green tea of Yunnan large leaf species. And comparative analysis of chemical and spectroscopic properties of theabrownins were committed between the liquid-state fermented Pu-erh tea with enzyme and the traditional one produced by pile fermentation to lay a foundation of the industrialiation of liquid fermented Pu-erh tea.The main contents and the results are as follows:In order to investigate the effects of the enzyme on the liquid-state fermentation, three enzymes including cellulase, pectinase and flavourzyme were used. On the base of single factor experiments, the optimal design with the content of the theabrownins was carried out using response surface methodology (RSM). It is feasible to optimize the enzyme in the process of the liquid-state fermentation of Pu-erh tea by RSM. The optimal concentrations of cellulase, pectinase and flavourzyme were 39.40 U/mL,33.00 U/mL,22.90 U/mL, respectively. Pretreated the raw material under the optimal concentration combination of enzyme, the content of theabrownins of fermentation broth is 27.23%, which is 18.39% higher than CK.Candida, Aspergillus awamori, Mucor, Aspergillus niger were inoculated into sterile sun dry green tea liquid medium to study their effects on the content of tea ingredients. The liquid medium inoculated with Aspergillus awamori TFCP-11 get the highest levels of theabrownins, followed by Mucor TFCP-14, Candida TYCP-06, Aspergillus niger, Candida TYCP-05. However, the content of theabrownins in fermentation liquor inoculated with any single strain was lower than that of liquid natural fermentation of Pu-erh tea.The effects of the liquid to material ratio, temperature, time on the content of theabrownins in Pu-erh tea were studied to determine the optimum extraction conditions of pile fermentation of Pu-erh tea. And the conditions were liquid-to-material ratio of 125:3(v /w), extraction temperature of 100℃, time of 100 min.UV-Vis shows that liquid theabrownins obviously showed a absorption peak at about 380nm while the solid one didn’t. Analysis of IR indicates that theabrownins is mainly composed of phenolic compounds and carboxylic compounds, accompanied with proteins and polysac-charides. Phenolic hydroxyl was the main acidic functional groups in both kinds of theabrownins; the liquid theabrownins contains more carboxyl and phenolic hydroxyl group than that of solid theabrownins. The activity of theabrownins in different processes was in a dose dependent manner.Membrane was used to divide the theabrownins into different fractionations based on the molecular weight. The present of oligomeric theabrownins whose molecular weight below 10 KDa in traditional Pu-erh tea and that fermented in liquid state were 26.74% and 18.84%. And the percent of those over 100 KDa in molecular weight were 56.98% and 70.72%, respectively. The reducing power middle poly theabrownins whose molecular weight rangs from 10 KDa to 100 KDa and the high poly theabrownind were simsignificantly higher than the oligomeric one.