| Theafvlavins (TFs) is the hot-ingredient of in the research field of tea comprehensive development at present. There are extensive application prospects in the fields of natural medicine, functional foods, daily chemical industry, functional beverage etc. However, the contents of theaflavins is very low in black tea. It is difficult to separate and purify the theaflavins from black tea and the yield rate of TFs extracted from black tea is low which results in high cost and affects it's the industrialized production seriously and its wide application. This paper is based on the former experimental results, through probing into the best reaction condition, selecting different enzyme sources and its substrates, the higher content of theaflavins semifinished product can be gained by using enzymatic oxidation. The aim of this paper is to offer the semifinished product with higher TFs for further extraction, separation and purification. Popular apple and pear have firstly been used as natural Polyphenol oxidase (PPO) source to prepare theaflvavins in this research. A very good result has been attained, which offers a new efficient way to produce theaflavins by enzymatic oxidation.The results of reaction condition optimization showed that the optimum condition of theaflavins by enzymatic oxidation is that temperature is 30C, pH value of the present system is 4.8, the concentration of substrates is 0. 9 g/100ml, the concentration of enzymes is 28 g/100ml (based on the fresh weight), oxygen rate is 0.41/min. Temperatures and pH values in the reaction system are the most important influence factors (P <0.05).The selection of enzyme source of PPO indicated that there is following order based on the effect of formation and accumulation of TFs: Pear > Fresh Tea Leaf > Apple > Microbe. The content of TFs is 45.727% by using PPO from pear , and the yield rate of TFs is 41.11%. In the enzyme from tea leaf, Ping Yun is better than Zhu Yeqi. The content of TFs is 33.737% by using PPO from Ping Yun tea frozen, and the yield rate of TFs is 42.22%. The content of TFs is 14.5% by using PPO from Ping Yun tea unfronen, and the yield rate of TFs is 72.22%. Among the enzymes from self-screened microorganism , there is the sequence as No. 4 > No. 3 > No. 1 and No. 2.The substrates selection indicated that under this experimental condition, the oxidation efficiency of the catechins containing high EGC is the best. Meanwhile, the catechins extracted from the small tea leaf is better than the catechin extracted from big tea leaf.The research of bi-liquid phases system tests showed that there are different results with different enzyme sources at the experiments of bio-liquid phase. Regarding PPO from fresh tea leaf, the result of bi-liquid phase system is obvious and more remarkable than the single-liquid phase system. In bi-liquid phases system tests, the content of TFs is 49.308% by using PPO from Ping Yun tea unfrozen, and the yield rate of TFs is 59.44%. However, there is opposite results that single liquid phase is slightly better than bi-liquid phase when the PPO is from apple and pear.The comparison of buffer solutions showed that acetic acid-acetic acid sodium buffer solution is better than citric acid-disodium hydrogen phosphate buffer solution according to the content of TFs when flesh tea leaf is used as PPO source. However, the latter is better than the former based on yield rate of TFs. |
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