Study On The Preparation And Properties Of Casein Phosphopeptides

Casein was hydrolyzed by alcalase and trypsin separately or in combination with each other.The hydrolysis processes were optimized for maximum degree of hydrolysis(DH)using response surface methodology.The optimal hydrolysis conditions for alcalase were 9.14,4075.68U/g,50.63? and 4.81h for pH,enzyme dosage and time,respectively,while those for trypsin were 8.31,4235.64U/g,46.30? and 5.00h,respectively.On this basis,the combined and sequential use of alcalase followed by trypsin provided DH up to 31%,which was much superior to either of them.Then using calcium-ethanol precipitation to isolate crude CPP from casein hydrolysate,the optimal isolate condition was 5.5,55%,1.2g/L and 2.5h for pH,ethanol concentration,calcium chloride,precipitate time,respectively.Purificating crude CPP by using 717 anion exchange resin,dynamic adsorption-desorption condition was sample concentration2%,adsorption flow rate 0.5mL/min,sample volume 100 mL,desorption solvent concentration 0.2 mol/L and desorption solvent flow rate 1.0mL/min.Then using SDS-PAGE analysised the molecular weight distribution of casein and CPP,and the result showed molecular weight of casein mainly concentrated in 66.4KD=44.3KD,a few distributed in 29.0KD,while molecular weight of CPP is less than 14.3KD.L-8800 automatic amino acid analyzer showed CPP sample contained 17 kinds of amino acids,including 7 kinds of essential amino acids,which was 41.09 of the total.The product was light yellow without peculiar smell,and N/P 5.88.Determination and comparison of physical and chemical properties of casein and CPP,the result showed that CPP solubility near to 90%,casein solubility was 20%.,CPP bubble volume was about 5 times of casein by homogenizing,after 60 minutes,CPP foam stability 64.0±0.5mL,casein foam stability 0 mL.Casein emulsifying activity 43.4±0.5%,CPP emulsifying activity 47.3±0.5%,then stored at 25? 4h,Casein emulsifying activity 32.5±0.3%and CPP was 39.3±0.3%.By vitro CPP calcium ability test showed ability to hold calcium of CPP was best when added 0.25g/L to 100mL of the system.Explore the effect of ability to hold calcium of CPP in the food process.The result showed the ability to hold calcium was not affected by high temperature,and starch can improve this ability,optimum adding amount of glucose was 4g/100mL,citric acid 0.6g/100mL and sodium benzoate 0.04g/100mL.