Studies On Critical Chemical Composition And Regulation Of Liquid-state Fermentation Of Black Tea Beverage

In recent years, because of rapid development of tea industry, it requests greater demand of raw materials for good-quality and low-cost.There are many disadvantages in traditional processing methods, for example, the standards of production is not easy to control, and energy consumption is larger, etc. Compared with the traditional black tea fermentation process, liquid fermentation have many advantages, such as, the product quality is uniform, with the shorter time, lower production cost advantages, all these shows that liquid fermentation is a new ways to produce black tea drink. To realize the industrial production of liquid fermentation technology, there are still many technical problems, such as key chemical composition is not clear, can not be achieved online control technology and the interface with the traditional process, etc. To explore the critical biochemical components and control technology of liquid-state fermentation of black tea beverages, this experiment carried out biochemical dynamic changes during the liquid-state fermentation of black tea beverage, the correlation of biochemical compositions, the correlation and regression analysis of biochemical composition and sensory quality of black tea beverages and regulation technique of liquid fermentation. The main results are as follows:1. This experiment systematic analysis the biochemical dynamic changes during the liquid fermentation of black tea beverage. Varieties of fresh leaves, the main biochemical composition varies. In the liquid fermentation process, the polyphenol oxidase decreased rapidly to fluctuations in a certain range, and the peroxidase activity decreased rapidly. Tea polyphenols take part in the enzymatic oxidation in the first 30 minutes of liquid-state fermentation, keep in equilibrium state in the later period. EGCG, ECG, EGC content reduced a lot, GC, C, EC, GCG content also decreased. Little change in caffeine content, parts of free amino acids decreased, and the remaining fluctuate within a certain range only. Theaflavin contents first increased and then decreased, but the peak time of the different components was different.2. By analysing the correlationship of biochemical changes different varieties of liquid fermentation, the result shows that the increment of theaflavins monomers is closely related with reduction of GC, EGC, C, EC, EGCG in catechin monomers. Correlation analysis of main biochemical components in Homogenate liquid of fresh leaves and fermentation effects showed that there were significantly correlation with fermentation effect and the main biochemical components, the content of theaflavin monomers significantly correlated with GC, EGC, EC, EGCG, CG and total catechins. The linear regression equation is: TFs=-255.61+3.87CG+3.42ECG+5.13EGCG。Clear CG, ECG and EGCG in tea leaf were key components in liquid fermentatioin progress of black tea beverage. It can give some guidance to the selection of materials of liquid fermentation of black tea beverage.3. By analying the sensory evaluation results and biochemical composition of liquid fermentation of black tea beverage of 10 species, the results showed that the quality of 301/3 and 301/5 are better. Liquor color, aroma, taste, TQS were significantly negatively correlated with the catechin monomer content, were significantly positive correlated with thealfavins components. L, a~*, b~* and-a~*/b~* were extremely significant correlated with sensory quality. And the linear regression equation is color score=27.32-0.06L-0.15a~*+0.42b~*-6.48(-a~*/b~*). The reselts showed that it was possible to estimate the liquid effect by La~*b~* color values during the liquid fermentation of black tea beverage, and they can used to achieve the online process control of liquid fermentation.4. The expirence studied the regulation technology of liquid fermentation of black tea beverage, including the impact of different concentrations of the fermentation liquid on fermentation effect, and a new meterial which was mixing fresh leaf with tea extract. The results showed that it was appropriate to selecte 5°Brix in this experimental conditions. To prevent the slow oxidation of black tea later and to maintain tea quality, the best way is microwaving 60s to lose enzyme.To change the uniformity of materials in liquid fermentation, and to expande the applicability of liquid fermentation process, the experiment studied the feasibility of the mixed material which was adding the fresh leaves into tea extracts in liquid fermentation, The results showed that tea extract adding a certain percentage of fresh leaves, using liquid fermentation, can produce tea beverage products with good quality.