Preparation Of Duck Egg White Peptide By Enzymatic Hydrolysis And The Evaluation Of Its ACE Inhibition And Antioxidation

The protein in egg white is the best food protein, its composition of amino acid is suitable for human. As becoming solidification easily when heat it and strong viscosity , the protein was limited used in food industry. Along with the development of biotechnology, it found that the small peptides which were released by protein have many physiological functions also. Theses peptides were absorbed by human body without being intestinal enzyme degradation. Many study confirme that active peptides have many special physiological function. They can make blood pressure lower, prevent blood clots, enhance immunity, delay ageing, resist fatigue, promote absorption of vitamins, amino acids, protein, zinc, calcium, selenium, iron, magnesium and copper etc. The egg white is hydrolyzed by protease appropriately. The small peptides and polypeptides could increased protein absorption and become more absorbable to human.Four proteases(neutrase,papain,flavourzyme and alkaline protease) were used to hydrolyze duck egg white. The hydrolysis condition were optimized by the degree of hydrolysate (DH) based on the research of single factor and a two-step-hydrolysis method of duck egg white was studied.The results show that: the DH is highest when the egg white was hydrolyzed by papain in four single protease, the DH is 29.01%,when the the egg white was hydrolyzed by step-wise multienzymatic the DH has increased. Which protease was added first has influence on DH, in the 12 kinds of combinations of proteases, the DH is highest when papain and neutrase were used to hydrolyze duck egg white, it is 33.53%.The duck egg white was hydrolyzed by papain and used neutrase hydrolyzed duck egg white following papain, the hydrolysate was desalinized. The molecular weight was analyzed by HPLC and the results shows that the hydrolysate used papain without desalinating contained 46.68% peptides of the relative molecular weight lower 3000D. the hydrolysate used neutrase hydrolyzed following papain without desalinating were contained 46.81% peptides of the relative molecular weight lower 3000D, the hydrolysate used papain after desalinating contained 47.13% peptides of the relative molecular weight lower3000D, the hydrolysate used neutrase hydrolyzed following papain after desalinating were contained 46.27% peptides of the relative molecular weight lower 3000D.The ACE activity inhibition capability and the antioxidant activity of 4 peptid- es were studied. The ACE activity inhibition rate of the hydrolysate used papain w- ere studied. The ACE activity inhibition rate of the hydrolysate used papain without desalinating was 29.70% at the concentration of 1 mg/mL. The ACE activity inhibition rate of the hydrolysate used neutrase hydrolyzed following papain without desalinating was 32.80% at the concentration of 1 mg/mL. The ACE active- ty inhibition rate of the hydrolysate which used papain after desalinating was 14.65% at the concentration of 1 mg/mL. The ACE activety inhibition rate of the hydrolys- ate which used neutrase hydrolyzed following papain with desalinating was 18.96% at the concentration of 1 mg/mL. The 4 peptides have some antioxidant activity, the antioxidant activity of the hydrolysate used neutrase hydrolyzed following papain without desalinating is best but was lower than Vc.