The Preparation Of Egg White Peptide And Its Biological Functions Studied

In this paper, the technology of preparation antioxidant peptide of egg white was optimized.at first, and then pepsin was used as the hydrolytic enzyme. The enzymatic reaction conditions including enzyme concentration, substrate concentration, reaction time and pH value was studied successively by single factor experiment. The optimum enzymolysis condition of egg white was obtained with pepsin hydrolysis temperature 37℃, pH 2.0, substrate concentration 3%, dosage of enzyme 9000 U/g, and reaction time 5h.Membrane filtration technology was used for separating egg white crude hydrolyzate. According to molecular weight, egg white peptide was divided into four parts, including <1 KDa,1-2 KDa,2-5 KDa and>5 KDa. Then the antioxidant activity of the four egg white peptide were Evaluated, and the peptide with the molecular weight between 2-5 KDa showed the strongest radical scavenging activity. Compared with the crude egg white peptide, the antioxidant activity of egg white peptide with molecular weight 2-5 KDa increased by about 100%. The results of orthogonal test suggested that:the optimum operation conditions of the membrane with molecular interception of 5 KDa and 2 KDa was pressure 0.2 MPa, feed concentration 2%, pH 6.0, and at 35℃.Five in vitro methods were used to assess egg white peptides'antioxidant ability, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging, hydroxyl radical scavenging, superoxide anion-scavenging, reducing power and lipid peroxidation inhibition. The results showed that egg white peptide possessed strong antioxidant capacity and inhibition lipid oxidation capacity. Compared with the crude egg white peptide, the hydroxyl radical scavenging, superoxide anion-scavenging and reducing power of egg white peptide with molecular weight 2-5 KDa were increased 114.08%, 39.1% and 261.9%, separately.Subsequently, in vivo antioxidant capacity and resistance to fatigue of egg white peptide were determined by animal experiments. Compared with the control group of blank, the groups fed egg white peptide showed strong resistance to fatigue, and oxidative indicators in the mouse also showed that egg peptide peptide possessed in vivo antioxidant capacity; The body weight of groups feding crude and 2-5 KDa egg white peptide increased by 116.1% and 108.1%, repetively. And the body antioxidant indicators such as total antioxidant capacity of whole blood, glutathione activity of the group mice fed the high dose egg white peptide with 2-5 KDa increased by 119% and 64.3%, repetively, and MDA levels of the plasma decreased in 66.5%. For the fatigue index, exhaustive swimming time, muscle glycogen storage contentncreased by 119% and 40.8%, repetively, urine nitrogen and liver lactate content decreased by 40.9% and 41.1%, repetively.In order to understand the practical application value of the egg white peptide, the text also evaluated its stability and application of physical and chemical indexes. The storage stability, heat stability, pH stability and the effects of protection agents on the stability of the egg white peptide were determined. The results suggested that egg white peptide was more stable at low temperature, and the antioxidant capacity changed little after keeping for 90d at 4℃. High temperature is not conducive to maintaining biological activity of egg white peptide, and it relatively stable under acidic conditions. Moreover, the addition of protective agents in favor of increased the solubility of egg white peptide, but these had no effect on enhancing hydroxyl radical scavenging acticity. Egg white peptide has good foaming capacity, emulsifying capacity, water adsorption, water-holding capacity and oil absorption. The results all provided a foundation for its using in food and cosmetic industry.