Application Of The Fresh Tea Leaf Homegenate Suspended Fermentation System To Prepare Tea Pigments With High-content Theaflavins

Tea pigments are the mixture of phenolic compounds, which formed from the oxidation of catechins and other polyphenols in tea leaves at the processing of black tea. The main components in tea pigments are theaflavins (TFs) and thearubigins (TRs), which contribute to black tea quality with characteristic of black liquid&black leaf. Moreover, the compositions of TFs and TRs and their ratio also play a key role on the formation of black tea quality. Recently, pharmacological studies have shown that tea pigments have a similar effect as catechins, even in somehow, are better than their effects because of the unique benzotropolone moiety of theaflavins. As an attractive natural products in tea, TFs has been tentatively used to the products of natural medicine, functional foods, household chemicals, functional drinks and so on. So, the current market requires a higher content of TFs in tea pigment preparations. With the traditional preparation from black tea, tea pigments have a relatively low amounts of theaflavins. Thus, the method to elevate the TFs contents in tea pigments will help developing the tea pigment products.In this study, a suspended fermentation system of fresh tea leaf homogenates has been applied for the preparation of tea pigments with high theaflavin contents. With the quantitation by high pressure liquid chromatography, the fermentation conditions were explored to determine their effects on theaflavin accumulation in tea pigments. The ratio of individual catechin have also been tested by orthogonal design and sysmatically analyzed by DPS software. Firstly, the factors affecting theaflavin formation in the suspended fermentation system were reviewed. The factors as pH, oxygen concentration, fermentation time, enzyme concentration, phenolic acid and catechin concentration were selected and exploited. The results have shown that the addition of phenolic acids, accounting for1.3%of the weight of fresh tea leaves, increase the theaflavin contents in tea pigment preparation; the lower pH for extraction increases the yields of tea pigments. The volume ratio of aqueous to ester phase at1:1in two-liquid-phase fermentation system has been in favor of the yield of tea pigments. In single-liquid-phase fermentation system, the optimal fermentation time is60min, while it is30min in two-liquid-phase fermentation system. The addition of acetone powder of fresh tea leaves is in favor of increasing product yields. The addition of individuals of catechins as epicatechin gallate (ECG),gallic catechin (EGC), epigallocatechin gallate gallate (EGCG) and epicatechin (EC), to the fermentation system, is in favor of increasing the product yields. When the dosage of EC is1.3%of the weight of fresh tea leaves, the TFs contents of tea pigments increase. For the addition of ECG, EGC and EGCG, each of their dosage is0.67%. Finally, the added dosage of ECG, EGC EGCG and EC was designed by orthogonal experiments. It is founded that thee ratio of ECG:EGC:EGCG:EC at2.0:3.0:3.0:0(their total ratio in the fermentation system up to5.90:5.18:8.52:1) is conducive to the accumulation of TFs and the final contents in tea pigments are up to26.49%.