Processing Condition Investigation For Preparating Zinc Chelate With Peptides Of Rice Protein And Its Properties

Hydrolytic effectivenesses of protein of rice dregs by four proteases were compared in this investigation.Trypsin was ultimately chosen for the following experiments,the optimal conditions were showed as following;the quantity of enzyme used was 1%; pH at 8.0; hydrolysis time was 4 hours; hydrolysis temperature was 50℃; The ratio of rice dregs to water was 1;5.The degree of protein hydrolysis and extraction rate of the end product were 8.28% and 63.72% under the optimal conditions,respectively.Polypeptide was prepared by rice dregs by enzymolysis.Protein content increased from 61.9% to 76.3% after treatments; The contents of fat and ash dropped from 8.9% to 4.2%,and from 7.8% to 5.7%,respectively.There was no significant difference between amino acids among rice dregs and those of hydrolyzed peptides. Both are abounded with essential amino acid,which accounted for 40.7% and 39.1% of total amount in rice dregs and hydrolyzed peptides,respectively.The contents of minerals among rice dregs changed in diferent ways after enzymolysis.The content of Mg,Cu,Zn among rice dregs was higher than those among hydrolyzed peptides,while the content of Fe,Ca,Mn among hydrolyzed peptides was higher than those among rice dregs.Particle size of hydrolyzed peptides reduced 1/6 times as small as average diameter of rice dregs particle after process of enzymolysis.Hydrolyzed peptides showed immense solubility.Optimal conditions for preparating zinc chelator with enzymic hydrolysis peptides from rice protein were investigated by the single factor and ort-hogonal experiments, the optimal results were showed as followed;molar ratio of hydrolysis peptides and ZnSO4 in 2;1,pH at 5.5,chelating temperature at 70℃,duration of chelating reaction for 90 min.The rate of chelating was 70.1%.The product was confirmed as zinc chelator with enzymic hydrolysis peptides by chemical characterization and infrared spectrum analysis.The total content of zinc among aopu-zinc and rice peptided-zinc before and after the purification with ethanol were determined by flame atomic absorption spectrometry.The contents of zinc in aopu-zinc,polypetided chelator before and after ethanol wash purification were 6.1%,7.3% and 9.6%,respectively.Different kinds of Zn were added to three kinds of edible oils for storage experiments investgating catalyzing effects of lipid oxidation.It was confirmed that catalyzing effect of ZnSO₄ was significantly higher than that of zinc chelator with peptides and amino acids.Spray drying were used to produce rice peptide-zinc.The optimal parameters of spray drying were deterimied at;inlet and outlet temperatures of spray were 195℃and 96℃,respectively.Feed rate was at 20 mL·min^-1and air pressure of feed was at 0.12MPa/cm².The product was ecru powder,which was similar with aopu-zinc in index of sense organ.The contents of protein and total zinc of rice peptide-zinc were lower than aopu-zinc.The moisture content of rice peptide-zinc and aopu-zinc were about 3%,which were suitable for storage.