Formation Characteristics Of Theasinensins(TSs) And Competition Between TSs And Theaflavins(TFs) Under Various Conditions

TSs and TFs are formed by the oxidation of catechins. Catechins, under the action of rolling, could direstly contact with enzymes during tea processing, then TSs or TFs are generated. The research achievements indicated the physiological function, recently, rising concern of TSs and TFs. This research was based on the test method of catechins(EGCG, EGC, EC and ECG) enzymatic oxidization and fresh tea leaves were studied with the suspensed fermentation under the set factors and conditions.TSs and TFs were determined by HPLC. Results were as follows:The Formation and stability Characteristic of DTSA and TSA produced by the oxidation of EGCG were studied. The results showed that the amount of TSA was accumulated under acidic conditions, while TSA presents the tendency of increase first and reduction afterwards under neutral and alkaline conditions. DTSA and TSA were stable under the acidic condition, TSA was produced from DTSA under neutral or alkaline conditions; The stability of DTSA and TSA was negatively correlated with temperature, and significantly influenced the stability of TSA and DTSA in Fe2+ aqueous solution, while Cu2+, polyphenoloxidase(PPO) and O2 affected the stability of DTSA and TSA unsignificantly.To illustrate the formation mechanism of theasinensins(TSs), catechins(EGCG, EGC) were oxidized to form TSs monomers by enzymatic oxidation or chemical oxidant, and the experiments were performed under liquid fermentation at different pH values. The results showed that the TSs monomers were synthesized and accumulated continuously under acidic conditions, while the peaks of TSs monomers appeared in a short time but showed poor stability under neutral or alkaline conditions. Due to the magnitudes of the oxidation reduction potential(ORP) were variable for catechins, the enzymatic oxidative rates of catechins were different under different pH conditions. The dynamic changes of the content of TSs monomer were producted presents the first increased and then decreased slowly under pure PPO and Hosui Pear, however,content of the monomers were generated by chemical oxidant was very low, and easy to be oxidized by chemicalagent and reduced content of TSs. From the perspective of the maximum eigenvalues were equal(in some sense) to TSs content were formed under the PPO and Hosui pear. And both of TSs values were significantly higher than that of chemical oxidant(level), the deduction was that mixed enzymes in Hosui Pear were proposal lead to TSs maximum value appeared on dynamical change curve much sooner than the level of pure PPO.To illustrate the competitive formation between TSs and theaflavins(TFs), catechins(EGCG, EGC, EC and ECG) were oxidized to form TSs monomers or TFs monomers by enzymatic oxidation, and the experiments were performed under liquid fermentation at different pH values. The results showed that there was a competition between the formation of TSs and TFs: the content of TSs monomers transformed by EGCG and EGC was higher than TFs monomers under the neutral condition or pH=6, however, conversely under the condition pH=5.In order to investigate the influence on formation characteristics of TSs and competitive formation between TSs and TFs in suspension fermentation, this study was based on its process requirement and the content of TSs, TFs were detected by using HPLC, five effective factors, namely, pH value, oxygen rate, fresh tea leaves broken rate, temperature, solid-liquid ratio, were investigated in this paper by single factor single factor experiments. The results showed that:TFs were easy to be accumulated in the acid condition, as TSs generated in the neutral or alkaline condition; when the level of oxygen rate to a certain degree(over 0.8 L/min), the content of TSs generally become more prominent as the oxygen rate increases, but there were no obvious changes in the content of TFs; Up to a certain level of broken rate(60 s), there were no obvious changes in the content of TSs, the content of TSs was a increasing tendency with the decreasing of the broken rate. As for levels of temperature, there were no obvious changes in the TFs content, over 25℃, TFs content was negatively correlated with temperature. The content of TSs increased with the increase of solid-liquid ratio, but the increasing of TSs and TFs content were not significant in a certain range(75-125 mg/mL).