Basic Research Of Theaflavin In Black Tea And The Regulation Of Formation During Simulated Fermentation

As the most interneational productive and trade volume of the largest class, Black tea had a wide distribution in our mainly country, and belonged to the fully fermented tea. As the main quality components of black tea, theaflavins were formed and polymerized by epi-typic catechins and epigallotypic catechins with polyphenol oxidase, and were closely related to the quality of black tea. The catechins and theaflavins were taken as index in this paper, firstly screened different kinds of enzyme source from tea cultivars fresh leaf, this article aimed on the basic theaflavins formed by the catechins components in vitro enzymatic oxidation and studied the interaction effect of and quantitative effect of theaflavins. The preliminary conclusions are as follow:1. By collecting 22 kinds of tea cultivars fresh leaf, determination the main biochemical components and the activity of enzymes, including the contents of polyphenols, soluble flavonoid, free amino acid, soluble total sugar and total catechins composition and the activity of polyphenol oxidase, peroxidase, protease and β-glycosidase. The most differences of fresh leaves were biochemical components in polyphenols and nonester type catechins, enzymes activities in polyphenol oxidase, peroxidase and β-glycosidase.The eight varieties of most contents total catechins are Longjing 43(137.87), Maohong(118.49), Juehuachun(118.41), Tieguanyin(116.57), Pingyun(116.52), Xicha No.11(114.01), Maoxie(111. 60) and Anhui No.3(111.10). The six varieties of highest Polyphenol oxidase activity are Zhenong 138(6.24), Zhongcha 108(6.11), Zhenong 117(5.96), Tieguanyin(5.53), Anhui No.3(5.16) and Jianbohuang No.13(5.06).2. By setting up different kinds of catechins(EC, ECG and EGC, EGCG) and volume ratio, we conducted enzymatic oxidation and fermentation experiments in vitro under the optimal conditions, and studied the different catechins and volume ratio on the formation effect and interactions effect of theaflavins.(1) In different volume ratio of two kinds of catechins in enzymatic reaction, as the extension of reaction time, two kinds of catechins tended to gradually reduce, theaflavins product all showed a trend of increase after decrease. The influence of different volume ratio on the peak of theaflavins was significant. The best volume ratio of EC and EGC is 3:7(1.184 mg/mL), followed by 4:6(1.155 mg/mL); the best volume ratio of EC and EGCG is 5:5(0.318 mg/mL), followed by 6:4(0.300 mg/mL); the best volume ratio of ECG and EGC is 3:7(10.417 mg/mL), followed by "(0.406 mg/mL); the best volume ratio of ECG and EGCG is 3:7(0.049 mg/mL), followed by 4:6(0.047 mg/mL). As the increased proportion of epi-typic catechins(EC or ECG) and the reduced proportion of epigallo-typic catechins(EGC or EGCG), the reaction times to reach the peak of theaflavins proportion got shorter.(2) In different volume ratio of three kinds of catechins in enzymatic reaction, as the extension of reaction time, three kinds of catechins tended to gradually reduce, theaflavins product all showed a trend of increase after decrease. The influence of different volume ratio on the peak of theaflavins was significant. The best ratio of EC and EGC, EGCG was 7:7:6(0.821 mg/mL); the best ratio of EC, ECG and EGC was 4:3:13(0.666 mg/mL); the best ratio of EC, ECG and EGCG was 5:3:12(0.105 mg/mL); the best ratio of ECG and EGC, EGCG was 5:8:7(0.398 mg/mL).(3) In different volume ratio of four kinds of catechins in enzymatic reaction, as the extension of reaction time, four kinds of catechins tended to gradually reduce, theaflavins product all showed a trend of increase after decrease. The influence of different volume ratio on the peak of theaflavins was significant. The best ratio of EC, ECG, EGC and EGCG was 5:2:8:5, total TFs peak of which was 0.575 mg/mL.3. We compared the effects the consumption of catechins and the formation of theaflavins between different varieties of tea fresh leaf enzyme and exogenous enzyme. Different enzyme sources from tea fresh leaf on TFs peak were significant, ZheNong 117(0.785mg/mL) > Anhui No.3(0.698mg/mL) > ZhongCha 108(0.631mg/mL) > ZheNong 138(0.575mg/mL) > Jiangbohuang No.13(0.569mg/mL) > POD(0.384mg/mL) and PPO(0.400mg/mL).4. By comparing the content of theaflavins, we found the polymerization of EC and EGC in preference to the polymerization and reactions of EC and EGCG, ECG and EGC, ECG and EGCG throughout the fermentation process. By comparing the TF/TF3 ratio, we found the nonester theaflavins were easier to form and accumulate during the fermentation process. In the fermentation process of in vitro enzymatic oxidation, epigallo-typic catechins(EGC and EGCG) had lower Redox Potential and tended to get priority oxidization to form quinones. In the late fermentation process, epigallo-typic catechins were depleted, however epi-typic catechins remained surplus. Thus we suspected appropriate supplementary of epigallo-typic catechins in the late fermentation process could promote the transformation of surplus epi-typic catechins and improve the content of theaflavins.