Research On Oxidation Of Tea Polyphenols By PPO Of Natural Fruits And Vegetables

Theaflavins can be used as a natural food pigment with various biological functions suchas antioxidant, anti-aging, lowering blood sugar, antibacterial and anticancer etc. Content oftheaflavins in tea is very low, catechin can be transformed into theaflavin by polyphenoloxidase (PPO) enzymatic oxidative polymerization, so that theaflavins production has apractical value. PPO is widely present in plants (such as potatoes, litchi, peach, apple,mushrooms, beans, sweet potato and so on) tissues. This study aims to explore a lowerproduction cost, higher production efficiency way to produce quality indexes of thecontrollable "red tea" through oxidatiing tea polyphenol by extensive sources, low price ofnatural PPO, and taking theaflavins content and color as the main index. In hope of using theproduct as a natural pigment of bean products and other food. This study also can providescientific basis for synthetic depth of tea polyphenols industry utilization, improve economicefficiency and environmental friendly production.Firstly, the PPO activity of pears, potatoes, yams, apples and sweet potato werecomparatively studied. The PPO activity of pear PPO is633U/mL, yam PPO is310U/mL,potato PPO is286U/mL, sweet potato PPO is143U/mL and apple PPO is35U/mL.Secondly, the optimal reaction conditions for preparing theaflavin by pear PPO wasstudied. Study the ratio of polyphenols and pear from1:1to1:50,10℃to25℃, pH3.5to6.5,20min to60min by Single factor experiments. The effect of substrate material and enzymeratio, temperature, time, pH value on transforming tea polyphenols into theaflavins by PPOwere studied by orthogonal experiments. The univariate results showed: the mass ratio of TPand enzyme source1:40, the reaction temperature20℃, the pH5.5and reaction time40minresulting maximum a (24.1±0.18)chromaticity product and the red is the deepest. Theorthogonal experimental results showed: the optimal reaction conditions: mass ratio of TPand enzyme source1:40, temperature of25℃, pH5.5, reaction time40min. The content oftheaflavins in products is detected by HPLC, the results showed content of theaflavins in totalphenols of tea polyphenol mixture is76.95±0.12%and the maximum chroma a is24.7±0.23and the red is the deepest.Furthermore, the ability of pears, potatoes, yams, sweet potatoes, apples PPO on formingtheaflavins were comparativly studied. Experimental results show that the five kinds ofnatural polyphenols PPO against oxidative capacity were pear PPO> potato PPO> yamsPPO> potato PPO> apple PPO.Then, the ability of pears+potatoes, pears+yams, pears+sweet potatoes and pears+apples PPO on forming theaflavins were comparativly studied. Experimental results show thatthe four kinds of natural compounded polyphenols PPO against oxidative capacity were pears +potatoes PPO> pears+yams PPO> pears+apples PPO> pears+sweet potatoes PPO. Pears+potatoes prepared the optimal product in which the content of theaflavin in total phenolic is88.13±0.15%and is higher than the value(76.95±0.12%) of pear PPO.Finally, the temperature, ratio of polyphenols and enzyme source and pH value inpreparing theaflavin by pears+potatoes PPO were studied. The results showed: the optimalmass ratio of pears/potatoes is2:1, pH5.5, temperature20℃. In the final product the contentof theaflavins in total phenol is as high as94.55±0.17%. The product oxidated by Pear+potato PPO was determined by high accuracy of color measurement instrument and thechroma a was25.8±0.31.