Rheological Properties and Thermal Denaturation after Enzymatic Modification of Whey Protein by TGase
|School||Chengdu University of Technology|
|Keywords||Transglutaminase Whey protein Protein cross-linking Viscosity Differential thermal|
Transglutaminase is an excellent protein cross-linking agent, the addition of a small amount of transglutaminase can significantly improve dairy quality and increase economic benefits. Transglutaminase between whey protein cross-linking and other protein cross-linking between reports, but there are still some controversy on the crosslinking conditions, and viscous and thermal denaturation characteristics of the product after crosslinking studies have not been reported. Therefore, it is necessary to explore and study them. The paper studied between transglutaminase under whey protein isolate, whey isolate protein with soy protein, whey separation optimized conditions of the cross-linking of the protein casein and crosslinked product viscosity and differential thermal changes characteristics, divided into three trials. SDS-PAGE electrophoresis and gel imaging analysis techniques, were compared in 80 ° C preheated 15min uncrosslinked transglutaminase crosslinking and 80 ° C preheated 15min 80 ° C preheated 15min after adding a certain amount of reducing agent (20 mmol / L) under denaturing conditions transglutaminase crosslinking between 6% whey protein isolate, whey protein isolate and soy protein, the crosslinking of whey protein and casein protein was separated. Lane protein bands changes through the gel imaging analysis, infrared spectroscopy and electron microscopy to determine the presence of cross-linked product. The catalytic time, catalytic temperature, pH, enzyme / protein proportion of single-factor test based on the four factors and five levels of (Catalytic time, catalyst temperature, pH, enzyme / protein ratio) orthogonal regression rotation combination design or four orthogonal test study of factors and four levels of whey protein isolate crosslinked by transglutaminase role was the best conditions, as well as cross-linking was viscous and differential thermal changes. The test results show that: SDS-PAGE electrophoresis Showing: between the whey protein isolate and whey separation between the protein and another two proteins by the 80 ° C preheated 15min and after a certain amount of reducing agent is DTT, cross-linking the resulting polymer , a better gel imaging map. Catalytic time of 4 h, the the catalytic temperature is 50 ° C, pH 8.0 and enzyme amount 20u / g whey protein crosslinking has a maximum viscosity value (4.05mPa.s), best transglutaminase role. Thermal denaturation studies found: without the transglutaminase treatment of the whey protein isolate freeze-dried cross-linked product of the highest thermal denaturation temperature of 61.07 ° C and the transglutaminase treatment of the whey protein isolate the highest thermal denaturation temperature of 101.11 ℃. In another experiment, when the catalytic time, 4h, the catalytic temperature was 50 ° C, pH 8.0, and enzyme quantity 10U / g of whey protein and soy protein a crosslinked product having optimum viscosity value (6.19mPa.s ), glutamine transaminase effects. Without the transglutaminase treatment of the whey protein isolate and soy protein, the highest thermal denaturation temperature of the freeze-dried product as 87.37 ° C, the transglutaminase after treatment of protein cross-linking the highest thermal denaturation temperature of 114 ° C. Found in whey separation of egg and casein cross-linking experiments: Catalytic time of 4 h, the the catalytic temperature is 50 ° C, pH 8.0, and enzyme amount 10u / g, crosslinked material has optimum viscosity value (5.55mPa.s ), glutamine transaminase effects. Separated by vacuum freeze dried whey protein thermal denaturation of transglutaminase treatment measured without transglutaminase processing of whey protein isolate and casein highest thermal denaturation temperature of 70.28 ° C, after Valley ammonia amides transaminase processed whey protein isolate the highest thermal denaturation temperature of 96.02 ° C. The above results show that: between whey protein, whey protein and soy protein and whey protein and casein protein under specific conditions can be crosslinked, and the results show that the changes in the functional properties of the product after crosslinking occurs. The study also provides a new approach to the development and use of whey protein.