Studies On Reaction Characteristics And Optimization Of Liquid-state Fermentation For The Production Of Black Tea Beverage By Flesh Leaves

This paper studied the correlations between fresh leaf chemical components and fermentation effect, the relationship between fermentation system and the quality of black tea beverage, the dynamic changes of chemical components during the liquid-state fermentation and the optimization of flesh tea soup fermentation for the production of black tea beverage. The main results as follows:1,The correlation analysis between fresh leaf chemical components and fermentation effect showed that the fermentation effect had a very significant correlation with total Catechins, especially EGCG , EGC , ECG and Caffeine.2,Comparison of different fermentation systems on the quality of black tea beverage showed that different preparation methods had great differences among the tea leaf extract, yield, chemical composition, oxidation activity and sensory quality.The higher activity of the oxidase after low-speed crush of the fresh leaf was benefit to the liquid-state fermentation. Oxygen is significant to the color and sensory quality of liquid-state fermentation products. Fermentation temperature 30-35℃, fermentation time 30～75min have been found to be the optimum conditions for the formation of Theaflavins and Thearubigins with liquid-state fermentation.3,Reaction characteristics and main chemical components dynamic changes during liquid-state fermentation by fresh tea leaves have been studied. Oxidative enzyme activity decreased in liquid-state fermentation under high temperature. Of them Polyphenol Oxidase was more sensitive than Peroxidase to the high temperature. Total tea polyphenols including some catechins like EGCG,EGC,ECG and GCG had a significant reduction in the liquid-state fermentation. Individual Theaflavins increased first, then decreased with the extension of fermentation time at different temperatures. TF-3-G and TFDG were highly formed within the value of 30℃for fermentation temperature. The changes of GA, CG, Caffeine, protein and free amino acids were not obviously. Linalool, linalool oxide, dibutyl phthalate and other aromatic were well formed and reserved during the liquid-state fermentation and played active roles in the aroma characteristics of black tea beverages.4,Using Plackett-Burman design to selecte the key factors which affecting the value of Theaflavins and Thearubigins in the liquid-state fermentation. From these studies, fermentation temperature, fermentation time and Oxygen were further optimized by using Response Surface Methodology as significant factors. Fermentation temperature 35.27℃, fermentation time 60.34minutes and Oxygen 1.04 L/min were found to be the optimum conditions for liquid-state fermentation. The optimization of the black tea beverage reached a maximum of Thearubigins and Theaflavins for 17.29% and 1.32%, respectively, meanwhile their ratio was 13.05.