Study On The Functional Properties Of Grass Carp Polypeptide Powder

Freshwater fish is famous for rich nutritional value and is very popular in People’s life. It is the important source of high protein, contains8kinds of essential amino acids for human body, and rich in unsaturated fatty acids especially DHA and EPA. With the improvement of living standards, plus the change of consumption idea, the demand for freshwater fishes is increasing constantly. Foods nutrition and health, convenience is a new trend in the development of food industry for more and more consumers put nutrition, health in the first place. Bioactive peptides have attracted much attention in recent years. Peptides have many advantages that can be easily digested and absorbed. Besides, they have many bioactivities including antifatigue and reduce cholesterol, grass carp protein through hydrolysis can get good function characteristics of the antioxidant grass carp peptides, in order to improve the added value of the grass carp and avoid protein waste of resources.To study enzymatic hydrolysis conditions and in Grass carp processing, Alcalase were used to hydrolyze grass carp. The effects of enzyme/substrate, pH value, temperature, liquid-material ratio and hydrolysis time on hydrolysis were analyzed. Box-Behnken design (BBD) and response surface methodology (RSM) were adopted to obtain the optimum formula on the basis of results of single-factor experiments. The results were as follows:enzyme/substrate1.8%, temperature55℃and pH9.0. On this condition, the degree of hydrolysis was up to23.20%. Different processes were adopted to compare with the different enzymatic hydrolysis effects from various microwave power, which showed that the primary effect of microwave was to promote temperature of the system quickly.Grass carp hydrolysate was desalted by using DA201-C macroporous adsorption Resin. The experiments of static adsorption showed that macroporous adsorption resin DA201-C had the highest adsorption-desorption capability and to Grass carp peptides among4resins. In further study, the optimal desalination conditions of Grass carp protein hydrolysate with the resin DA201-C were confirmed as follows:concentration of Grass carp peptides30mg/ml, flow rate of water washing2BV/h, and desorption rate of75%ethanol2.0ml/min. Under these conditions, the desaltion rate reached about97.17%.Grass carp protein after hydrolysis has good solubility and rheological properties.Grass carp peptides with DH10%exhibits better activities than those with other three DH value in hygroscopicity and moisture retention. At the same concentration, emulsification and foaming ability of hydrolysates from Grass carp peptides is higher than soy protein isolate and whey protein. The temperature can enhance the ability of grass carp peptides clearing DPPH free radicals. The peptide was stable in acid、alkaline and neutral conditions.The Fe2+and Zn2+at an increasing concentration significantly decreased the DPPH free radical scavenging activity activity of Grass carp peptide, while Mg2+, Ca2+and K+ions had no effect. Because of maillard reaction glucose and sucrose improved the antioxidant activity of Grass carp peptides peptide. salt had no significant difference on its antioxidant activity.Alkaline protease hydrolyzed grass carp protein, study the nutritional value of grass carp polypeptide and the residue is applied to bread after enzymolysis processing. The results showed that grass carp polypeptide chemical score (CS), amino acid score (AAS), biological value (BV), essential amino acid index (EAAI), nutritional index (NI) and amino acid ratio coefficient (SRCAA) were53.29,76.4,71.51,76.34,74.81,77.19. The results suggested that protein powder had high nutrition value and was a good protein resource.In vitro studies of different degree of hydrolysis of peptide antioxidant properties of grass carp, the results showed that the degree of hydrolysis of different peptides can scavenge DPPH radicals, hydroxyl radicals, superoxide anion radical, has some antioxidant activity. Where in the degree of hydrolysis of10%of the antioxidant capacity of the polypeptide grass carp is slightly better than the other peptides degree of hydrolysis. Molecular weight peptides grass will increase when the degree of hydrolysis decreases, there is no correlation between the degree of hydrolysis and antioxidant activity. Grass carp peptides can significantly increase serum and tissue protein content in mice, effectively improve the activity of SOD in serum and tissues, GSH-Px activity and T-AOC values, which can effectively reduce malondialdehyde (MDA) in serum and tissues of mice in the experiment content, has some antioxidant effects. Compared with the blank polypeptide group, the control polypeptide group may be extended exhaust swimming time of mice; maintain stable blood glucose concentration; expedite clearance of serum urea nitrogen, and accumulation of lactic acid in vivo; reduce creatine kinase levels in the body to some extent, to improve the lactate dehydrogenase activity in vivo in mice, which has some anti-fatigue effect.