Study On The Pear Polyphenol Oxidase Biocatalytic Synthesis Of Theaflavins And The Applicationin In The Tea Extraction

Theaflavins plays a decisive role in the color,flavor and quality of the black tea,but also has the potential in human health-related,such as anti-oxidation,to prevent cardiovascular disease,lipid-lowering and anti-cancer effects.Currently domestic and foreign researchers had a great attention to the research of theaflavins.This article mainly is screening a suitable polyphenol oxidase to biosynthetic theaflavins though comparing different sources and applicating it to the extraction of the green and black tea,making full use of the rich tea polyphenols in green tea and generating higher yield of theaflavins,in the same time,making transformation of tea polyphenols to theaflavins in the black tea,increase the content of theaflavins in black tea extraction,thus to improve the quality of black tea.The results of experimental showed that the fengshui pear polyphenol oxidase catalytic catechin into theaflavins was the best.Through a selection,fengshui pear,xue pear,shuijing pear,bananas and potatoes-five kinds of polyphenol oxidase we got.The optimum pH value(4.4,6.0,4.8,4.4 and 4.8),the optimum temperature(30 ?,30 ?,30 ?,25 ? and 25 ?)and the optimum reaction time(15 min,30 min,15 min,15 min and 45 min),the abilities of five polyphenol oxidase synthesis theaflavins:Fengshui pear>Xue pear>Shuijing pear>bananas>potatoes,the yields of theaflavins were 0.3253 g/L,0.2872 g/L,0.1149 g/L,0.0900 g/L,0.0678 g/L.Study different conditions(pH value,reaction temperature,reaction time,substrate concentration,enzyme concentration)on fengshui pear polyphenol oxidase catalytic catechins into theaflavins,it can be concluded that the optimum temperature was 30 ?,the optimum pH value was 4.4,the optimum reaction time was 15min,the optimum substrate concentration of 1.0 g/L,and the optimum enzyme concentration of 600 g/L buffer,and the trend of various factors on four main theaflavin monomer TF,TF-3-G,TF-3'-G and TFDG had broadly consistent,the TF-3-G and TFDG are higer.Under the optimal conditions,the yeild of theaflavins was 43.02%,the yields of theaflavin monomers TFDG and TF-3-G were the most,the monomer yields were TFDG,20.06%;TF-3-G,12.49%;TF-3'-G,5.37%;TF 5.06%,and the consumption rate of catechins was 80.0%.We will get crude enzyme powder of the polyphenol oxidase FengShui pear though freeze-drying,this method was simple,less loss of enzyme activity,easy to store.The applications of crude enzyme powder on the the extraction of green tea.The optimal conditions in different conditions:pH value 5.0,temperature 30 ?,reaction time 45 min,the enzyme dosage 10 g/L tea extraction.Under the optimal conditions,the yield of theaflavins was 35.12%,the content of theaflavins was 0.3578 g/L,the proportion of the ester-type of catechins and theaflavins were all above 87%.Tea polyphenols content decreased from 1.410 g/L to 0.9093 g/L,the conversion rate of 35.52%.Study the effects of different factors affecting the extraction of black tea,the optimal reaction conditions:temperature 30 ?,pH value 5.0,reaction time 30min,enzyme dosage 1 g/L black tea extraction.Under the optimal conditions to obtain the maximum yield of theaflavins,which was 0.039 g/L,theaflavins concentration were 0.267 g/L,the concentration of theaflavin in black tea reaction solution had increased 17.2%.Catechins concentration were 0.5492 g/L,the consumption rate of catechins was 10%.In the same time,the proportion of ester-type of catechins and theaflavin in black tea reaction solution were all more than 70%.The color,smell and taste of black tea had improved to some extent.