The Study On Crosslinking Mechanism Of Milk Protein And Application By Transglutaminase

The possibility of crosslink between sodium caseinate and whey isolate(WPI) and the impacts on functionality after crosslinking by transglutaminase and the application of transglutaminase on yoghurt were studied.Firstly,The crosslink of sodium caseinate and whey protein isolate(WPI) at three different conditions using transglutaminase (Tgase) was studied. The extent of polymerization was detemined by SDS-PAGE,electron microscope and infrared spectrometer associated with gel image analysis. It showed: (a) it is impossible for the crosslink between sodium caseinate and whey protein isolate at the native condition by Tgase because of different spatial structures,and the addition of DTT and Preheating facilitated the crosslink between caseinate and whey protein isolate , for we found that 24h later 60% WPI and 74%CN were reduced simultaneously with addition of 20mmol/L DTT after preheated. Based on the result mentioned above and mono-factors experiments,the best craft conditions of four facators including temperature,time,pH and transglutaminase density on gel strength and viscosity of milk protein by transglutaminase was found using perpendicular circuitation regression design. It shows: the best combination of four factors on viscosity is pH9;35℃;24h;20U/g;Y2=33.98cp; and those on gel strenghth is pH7; 35℃;12h;15U/g;Y1=5214.68g .When the transglutaminase was applied in Yoghurt, two means of pour and three kind of quatatity were choose. It consists of 0.15/1000,0.25/1000,0.35/1000(g/mLmilk) and destroy and non-destroy transglutaminase after reaction.The best result depends on the change of gel strength, viscosity, viscosity in storage ,whey separation ratio and liquid-binding power.Tt shows: the best way of transglutaminase is non-destory and 0.15g/1000mL milk.