Preparation And Study Of Properties Of Antioxidant Activity Dairy Ingredients From Milk Casein

Low allergenic and antioxidant activity dairy ingredients were prepared, exploring thebest condition with the index of degree of hydrolysis and scavenging activity of hydroxylfree radical. Casein was hydrolyzed deeply by compound enzyme which screened from thealkaline protease, neutral protease, trypsin and chymotrypsin. Milk caseinhydrolysates(MCH) were isolated and purified by macroporous adsorption resin and gelfiltration chromatography. The isolates were prepared low allergenic and antioxidantactivity dairy ingredients after spray drying. The results indicated that:(1)MCH have higher degree of hydrolysis and a better scavenging hydroxyl freeradical than other hydrolysates. Using the single factor experiment and orthogonalityexperiment to ascertain the optimal hydrolysis conditions. The optimal condition ofcompound enzyme were: enzyme concentration of trypsin and neutral protease were2500U/g and3000U/g respectively,55℃, pH7.5and5h. Compared with the single enzymehydrolysates, degree of hydrolysis, concentration of peptides, scavenging activity ofhydroxyl and scavenging activity of DPPH· were enhanced60.05%,49.31%,24.08%,23.87%respectively.(2)Isolated and purified not only increases the antioxidant activity greatly but alsoreduces anaphylaxis of dairy ingredients from milk casein. Four components can be gotafter the MCH was isolated and purified by macroporous adsorption resin.75%ethanolelution components had higher antioxidant activity and EC50value of hydroxyl free radicalscavenging rate was0.14mg/mL.75%ethanol elution components were isolated andpurified by gel filtration chromatography, the antioxidant activity increased dramaticallycompared with the MCH. The EC50value of scavenging hydroxyl free radical of component3was0.0922mg/ml, which the value was minimum in the three isolates and the molecularweight was in the range of355.38~854.89u. Compared with the MCH, antioxidant activityof component3was increased33.84.75%ethanol elution components were isolated andpurified, the contents of peptides of molecular weight less than3238.05u is account for the total purified peptides by60.32%,30.09%peptides were oligopeptides which compositionof2~8amino acid.(3)Light, temparture and pH can effect the antioxidant activity of dairy ingredients,epecially direct light, high temperature, acidic and alkaline can reduce the antioxidantactivity of dairy ingredients significantly. So, casein peptide dairy ingredients should bestoraged at the environment of dark, separated from oxygen and low temperature, shouldavoid contact with the acid and alkali.