Studies On The Whey Protein Of Glycosylation Reaction And The Property Of Conjugates

As byproducts of manufacturing cheese and casein, whey protein is discharged as waste directly, however, whey protein is more valuable than other high quality protein, such as egg protein、soy protein and beef protein. But there is110million tons of whey protein as a result of the production of casein in all over the world, nevertheless only55%of which can be got further processing.WPC-IMO conjugate was prepared by Maillard reaction in this paper. The degree of graft of covalent compounds as an index, response surface methodology was used to optimize Maillard reaction factors in order to get Maillard reaction products with the highest degree of graft. The results indicated that reaction temperature90℃, weight ratio of WPC to IMO1:3.125, pH9.86and reaction time78.57min were the optimum reaction conditions. On these conditions, the highest degree of graft was25.75%. It was confirmed that the predicted and measured degree of graft values are consistent.The property and spectrum of the WPC-IMO corjugates were analyzed. The research showed that the solubility of conjugates first increase, then decrease with the reaction time extends. The result of DSC indicated when the WPC-IMO Maillard reaction comes to the end, the thermal stability became better. The FTIR and Ultraviolet spectrum analysis of the sample showed the same conclusion that IMO was grafted to WPC by covalent band. The fluorescence analysis of the sample showed that the conjugates have the strongest fluorescence intensity when emission was347nm and the excitation was420nm. The result ensured that the Maillard reaction was happened. According to the analysis of SDA-PAGE, subunit protein molecules undergo some changes, and the new bands of the grafts subunits were closer to the upper of separating gel.We have analysed the antioxidant ability change of WPC-IMO conjugates with different Maillard reaction time. The Maillard reaction was benefit to improving the inoxidizability of whey protein. The effect of different sugar to oxidation resistance of covalent compounds indicated that xylose and fructose were benefit to improving the reducing power of the conjugates, and other kinds of sugar were disadvantageous to the reducing power and the scavenging effects against DPPH of WPC-IMO conjugates.