| Tea has a history of thousands of years in China.China is a large tea country,and more than 300,000 tons of tea are processed and manufactured every year.Studies have shown that theaflavins play an important role in coloring,aroma and taste for tea,and have antioxidant activity,anti-cancer,anti-caries,anti-aging,bactericidal and bacteriostatic effects,etc.,and have certain application value in food,pharmaceutical and fine chemical industries.However,the content of theaflavins in most teas is water-soluble,and the content of ester theaflavins is relatively small,so this study uses polyphenol oxidase to increase the output of ester theaflavins and increase its yield.it will expand the application of ester theaflavins in food and medicine.And make a systematic study on the ester theaflavins and clarify its biological activity,which can provide better theoretical support for the utilization of tea resources.In this study,taking tea as the research object,the extraction technology of theaflavins was investigated;the content of ester theaflavins was increased by polyphenol oxidase;different types of macroporous resins were optimized to purify theaflavins;theaflavins were further purified and separated by high speed countercurrent chromatography.the components of the four components were analyzed by LC-MS,and the antioxidant activity of ester-theaflavins was studied by antioxidant test in vitro and application of meat products.The main results are as follows:Theaflavins in tea were extracted by solvent extraction,and the response surface was optimized according to the results of single factor test.The optimum conditions of response surface are as follows:extraction time 56.6min,extraction temperature 93.3℃,material-liquid ratio to material 1:59.6 g/mL.The yield obtained from the verification test is 32.5,and the error value is only 0.2%,which is in good agreement with the theoretical value.Polyphenol oxidase was used to catalyze the conversion of catechins to theaflavins in crude products to increase the content of ester theaflavins.According to the results of single factor experiment,the PPO enzymatic conditions of buffer pH 5.0,temperature 40℃ and substrate concentration 0.1mg/mL were optimized.The value obtained by the actual experiment is 63.7%,the error is only 0.1%,and the content of ester theaflavins has been significantly improved.Through the static adsorption and desorption test of different types of macroporous resin,the AB-8 resin screened from five kinds of macroporous adsorption resin could well adsorb theaflavins,and the desorption rate reached 83%.Through the dynamic adsorption and desorption test of AB-8 macroporous resin,the optimum purification conditions of theaflavins were determined;the sample flow rate of pH=5.0,was 2BV/h,the elution rate was 1BV/kg/h,and the amount of desorption agent was 2BV/batch.After purification by macroporous resin,the purity of theaflavins increased from 3.76%to 21.5%.The purified theaflavins were separated under 280nm by high speed countercurrent chromatography,and four components,G(1,2,3,4)were obtained.The purity of theaflavin(TF1),theaflavin-3-gallate(TF2A),theaflavin-3-gallate(TF2B)and theaflavin-digallate(TF3)were determined to be 74.5%,81.89%,72.39%and 81.74%,respectively.The antioxidant activities of the four components of theaflavins were tested in vitro.The results showed that the scavenging ability of the four components of theaflavins was different,in the following order:TFDG>TF-3-G=TF-3’-G>TF.In the application experiment of meat products,the difference in antioxidant activity between TFDG and nitrite is the least,and the other components are slightly worse.The specific performance is that ester theaflavins have good antioxidant activity and can basically be accepted by the public. |
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