Study On The Enzymatic Properties Of Polyphenol Oxidase From Tea Plant Flowers And Its Application In Tea And Tea Products

Tea plant flower is rich in beneficial ingredients and active substances,such as protein,tea polyphenols,amino acids,tea polysaccharides,tea saponin,flavonoids,vitamins,trace elements,superoxide dismutase(SOD),caffeine,which has a great value in use,but as a by-product of tea,it is often seen as a waste disposal by people,causing waste of resources.However,polyphenol oxidase(PPO)has always been a hot spot of research.There are many reports on PPO in tea,various kinds of fruits and microbes,but the research reports on PPO in tea plant flower are basically blank.Therefore,the research and application of PPO in tea plant flower not only makes reasonable use of tea plant flower resources and avoids wastage,but also has innovative significance.It also opens up a new way for the future research of tea plant flower.In this paper,the enzymatic properties of PPO from tea plant flowers were studied and they were applied to tea and tea products.The main results are as follows:(1)The tea plant flowers from two varieties,Nongkangzao(Nkz)and Shuchazao(Scz),were selected as the enzyme source material,and pear,Nongkangzao and Shuchazao tea were used as controls.The crude enzyme solution was extracted from acetone powder.Diphenols were used as substrates to study the effect of different p H,temperature,and substrate concentration on the activity of PPO enzymes and to determine the optimal reaction conditions for PPO.The results showed that the optimum p H values of pear,tea plant flower and tea PPO were about 5.6,5.4 and 5.6,respectively,the optimum temperature was 37?,and the optimal substrate concentration was 1%.In addition,under the same reaction conditions,the order of PPO activity was: pear> tea plant flower> tea.(2)Under the above optimal reaction conditions,tea polyphenols were catalyzed by PPO to produce theaflavins,and the enzyme additions were 2g,3g,and 4g(based on the fresh weight of pear,tea plant flower and tea).The results showed that the content of theaflavins in the samples treated with Nkz and Scz tea plant flowers were 7.23% and 6.94%,respectively.When the enzyme addition was 2g,while the content of theaflavins in the control samples treated with pears and Nkz and Scz tea were 2.01%,5.21% and 4.98%,respectively.When the enzyme addition was 3g,the content of theaflavins in the samples treated with Nkz and Scz tea plant flowers were 8.10% and 8.18%,respectively,while the content of theaflavins in the control samples treated with pears and Nkz and Scz tea were2.98%,6.15%,and 6.18%,respectively.When the enzyme addition was 4g,the content of theaflavins in the samples treated with Nkz and Scz tea plant flowers were 9.15% and9.35%,respectively,while the content of theaflavins in the control samples treated with pears and Nkz and Scz tea were 4.11%,7.20%,and 7.11%,respectively.The feasibility of the production of theaflavins by tea plant flowers as an enzyme source material was further verified.(3)Using low grade green tea as raw material,PPO was used to prepare broken black tea.Sensory evaluation of the samples were performed and the theaflavins contents were determined,and the enzymatic oxidation effects of the three types of enzyme sources were compared.The effect of the addition of tea plant flower PPO(based on the fresh weight of tea plant flower)on the content of theaflavins in broken black tea was also investigated.The results showed that when the enzyme addition was 50 g,the content of theaflavins in the broken black tea treated with Nkz and Scz tea plant flowers were 1.03% and 1.02%respectively,while the content of theaflavins in the control samples treated with pears and Nkz and Scz tea were 0.78%,0.87% and 0.92% respectively.When the enzyme addition was 75 g,the content of theaflavins in the broken black tea treated with Nkz and Scz tea plant flowers were the highest,which were 1.22% and 1.16%,respectively.And the broken black tea at this time has the highest sensory score,and the granules were tightly knot,heavy,uniform,smooth and lasting with the special aroma of the tea plant flowers,and the taste was fresh and strong with convergence,what's more,the soup has a bright red color,which can achieve the quality level of medium CTC broken black tea.(4)Using Nkz and Scz tea plant flowers as the enzyme source materia,and instant green tea was catalyzed to produce instant black tea.On the basis of the single factor test,the substrate concentration,enzyme addition and reaction time were used as the investigation factors and with the content of theaflavins as the index,which were used to optimize the processing technology of instant black tea by the central composite experiment.The results showed that the optimum technological parameters of instant black tea prepared through the catalysis of Nkz and Scz tea plant flowers were all as follows: substrate concentration1%,enzyme addition 2g,reaction time 40 min.At this time,theaflavins contents were6.46% and 5.49%,respectively,which was nearly 5 times higher than that of commercially available instant black tea.