Study On Phosphorylation Of Casein And Functional Nature

The protein in milk is mainly casein,it is a kind of protein containing phosphorus,the hydroxyl of lysine and serine has formed the ester key with phosphate radicals.Through phosphorylation phosphate radicals can be added to the active groups in the protein side chain, this may change the negativity of protein,also it enhance the electrostatic repulsion between molecules,so the molecules disperse and repel each another more in food system.Sodium tripolyphosphate is already applied as supplement in food industry,using STP to carry on the modification is safe and feasible.When the content of phosphorus is determined,we use the standard curve of phosphorus absorbency:y=56.686x+0.0048(R~2=0.9967,P<0.0001),data is true and effective.Visual analysis and orthogonal analysis are both used to analyze the phosphorylation result,best craft is confirmed:pH=9.0(P<0.01),STP concentration is 5%(P<0.01),reaction temperature is 30℃, reaction time is 3h,new adding phosphorus has reach its maximum value,the value is 0.0187 mgP/mg casein.Through infrared absorption spectroscopy and gel electrophoresis image analysis,the effect of phosphorylation on casein structure and its molecule weight can be verified,it approve the trueness and validity ofphosphorylation further.After phosphorylation,the functional nature improves significantly,this can be proved through the determination of solubility,emulsibility and foamability.When the content of water-soluble protein is determined,we use the standard curve of bovine serum albumin(BSA) absorbency:y=56.686x+0.0048(R~2=0.9967,P<0.0001),data is true and effective.Recent years edible protein film has become a hot spot in packing material research,it might be used as food packing film,also it is food enriching substance,the most important it can solve the environmental packing-rejecting problem.In this experiment,casein is used as chief film material,by adding suitable plasticizer(glycerine,polyethylene glycol and sorbitol) enable it to have certain flexibility and longitudinal strength,the,casein film is carried on certain analysis from longitudinal strength,elongation ratio and sense evaluation.