The Study On The Preparation,Debitterizing And Functional Properties Of Casein Peptide

Using casein as the primary ingredient,ultrasonic-assisted papain hydrolyzed casein was studied by using the degree of hydrolysis as an index.The best protease to debitterize for casein peptides was screened.And the correlation among the soluble nitrogen,free amino acid content and bitterness value of casein peptides are research.The single-factor,Plackett-Burman and Box-Behnken experiments were used to optimize the process of bettering.Finally,the sensory,physical and chemical indexes and functional properties of casein peptides were determined;the main conclusions are as follows:(1)Papain was the best effect on hydrolysis of casein among alkaline protease,neutral protease,papain,trypsin and pepsin.the optimal parameters of the ultrasonic-assisted enzymatic hydrolysis of casein were as follows: pH6.2,enzymolysis temperature was 57?,enzyme addition was 8000U/g,enzymolysis time 2.5h.Under the optimal conditions,the degree of hydrolysis could reach 24.01%.the relative error with the theoretical value 24.12% was 0.46%.(2)The optimum parameters of ultrasonic-assisted papain hydrolysis were as follows: ultrasonic power was 460 W,ultrasonic temperature was 64?,ultrasonic time was 82 min,Under the optimal conditions,the degree of hydrolysis could reach 44.87 %,the relative error with the theoretical value 45.70% was 1.82%.Fourier transform infrared spectroscopy results show that the ultrasonic treatment of casein hydrolyzate compared with the results of untreated,secondary structure changes,making the case of the original dense casein becomes relatively loose,and promote the enzymatic hydrolysis of casein.(3)About the casein peptides debitterized,there was a significant positive correlation between 12% TCA-SN and pH4.6SN,there was a significant negative correlation between 12% TCA-SN and 5% PTA-SN,there was a significant negative correlation between free amino acid content and casein peptide bitterness value.(4)Laccase and flavor protease were better for effect of debitter than trypsin,papain and alkaline protease.The best parameters of the compound enzyme were as follows: pH6.5,enzyme addition was 1300U/g,flavor protease and laccase ratio 55: 1,enzymolysis time 3h,enzymolysis temperature 50 ?,substrate concentration 15%.Under this condition,the free amino acid content was 0.479mol/L,the relative error with the theoretical value 0.492 mol/L was 2.64%.(5)The bitterness value of casein peptide after debitterizing was 1.45,it taste basically no bitter.Physical,chemical,sensory indicators of casein peptide meet national standard for food safety of casein peptide(GB31617-2014).(6)The debitter casein peptides can effectively eliminate O2-,DPPH · and(· OH),and effectively inhibit calcium and ferrous ion precipitation,These properties were not significantly different from the commercially available New Zealand casein peptides products.