Study On Laccase Catelyzed Oxidation Of Phenolic Compounds From Apple Fruit And The Caracterization Of Its End Products

As increasing of people awareness of importance of food safety and health,the natural pigment because of its physiological activity has been gradually attentioned. Developing new pigments, in particular the natural pigment, is increasing the extensive attention at home and abroad. Apple polyphenols has high biological activity. Useing enzyme technology can be directed to the transformation of biological activity for the new pigment material.The raw material extracted from the apple polyphenols in this experiment.A simulation test of vitro enzymatic oxidation has been established, oxidated apple phenolic compounds by laccase into a directional. Studied the oxidation conditions for apple model and mixed polyphenols on the enzymatic, the HPLC analysis of phenolic compounds, products of oxidation stability and antioxidant activity, the main results are as follows:(1) Trametes versicolor laccase was employed to measure enzymatic kinetics parameters for model substrates, catechol and epicatechin. The results showed that the maximum absorption wavelength of laccase-catalyzed end-product for catechol and epicatechin were 388, 408 nm, respectively; Optimum pH were pH value were 5.5 and 5.75, respectively; Optimum reaction temperatures were both 55℃.(2) The laccase-catalyzed oxidations for catechol and epicatechin fitted the Michaelis-Menten equation. Under the reaction temperature of 25℃Km values for catechol and epicatechin were 0.279, 0.145 mol/L, respectively; Vmax values were 0.114, 0.139 A/U/min, respectively. This indicates that laccase-catalyzed oxidation is of much more activity for epicatechin than for catechol。EDTA and Tween-80 with the enzymatic reactions were inhibited and facilitating role.(3) For the apple polyphenol extracts of enzymatic oxidation, the reaction optimum temperature, pH, reaction time, enzyme concentration, substrate concentrations were 55℃, pH5.5, 60 min, 3.5 U/mL, 2.5 mg/mL.(4) The apple oxidated products in 363 nm UV district office has strong absorption. Oxidation products solution show different color under different pH values. The products is stable in the light relatively and has a stronger heat resistance, for long-term placement, basic colors remain the same solution at room temperature.(5) Detected by HPLC, catechin, epicatechin, catechol and apple polyphenols enzymatic oxidation, some components of the former disappeared, a molecular weight of different polarity or a mixture of different size, after the formation of a new the product.(6) Examined by UV-scanning, to the former apple polyphenol of control.Studied the antioxidant activity of oxidated products. The result shows that on a different system of free radicals (·OH DPPH·), Apple polyphenols and its oxidation products have showed that the removal of a significant activity. In the same concentration of apple and its polyphenols·OH oxidation products of the largest clearance rates were 83.77 percent and 85.42 percent;In the low concentration of 0.1 mg/mL when the clearance rate was 68.52 and 62.02 percent to DPPH radical, the high concentration of 1 mg/mLwhen the clearance rate was 89.58 percent and 94.32 percent. Oxidation of antioxidant capacity is higth than apple in a certain concentration and the products of the reduction acctivity were declined in the reduction of the determination.