| Changbai Mountain hazelnut powder is rich in nutrient content, its protein content reaches 20-30%, and hazelnut flour defatted protein content up to 40%, which is a potential plant protein resource of high-quality. Therefore, the study of Changbai hazelnut protein, the development of the emerging protein resources is of great significance.In this paper, defatted hazelnut powder is used as raw material, to determine the alkaline extraction pH, alkaline lift temperature, the ratio of water and protein alkaline extraction time on the concentration of hazelnut protein isolate, and then get separated by orthogonal design the optimal combination of protein extraction as: alkali extraction pH9.0, water ratio 1:12, alkali extraction time 80 min, alkali extraction temperature 45 ℃, under that conditions the concentration of hazelnut protein isolate reached 90.31%.Determined protein purity of hazelnut albumin, globulin, gluten separated by Osborne classification extraction method and the protein isolate separated by alkali solution and acid extraction and researched the four protein foaming ability and foam stability, emulsifying ability and emulsion stability functions nature. The results showed that: albumin, globulin, gluten and protein isolate protein purity respectively is72.32, 68.72, 40.60 and 90.31%. The solubility of four proteins has significant changes with pH changes, the lowest solubility shows at pH5.Foaming, emulsification, emulsion stability changes with pH changes consistent trends were pH5 lowest, while the foam stability with conversely when the highest pH5. Gluten water absorption(3.40mL/g) and oil absorption(2.52mL/g) is the highest of four proteins, then albumin water absorption(0.63 mL / g) and oil absorption(1.79 mL / g) is the minimum. Protein isolate total sulfhydryl content is up to 6.71μmol / g, albumin exposed sulfhydryl content is the highest 2.28μmol / g.Amino-acids analysis revealed that the amino acid content, hazelnut protein is rich in amino acids, which contains seven kinds of essential amino acids(tryptophan not measured), the other half contains essential amino acids tyrosine and essential amino acids histidine of infants. Results showed that methionine is the first limiting amino acid of four proteins, while lysine is the second limiting amino acid.Selecting changbai mountain hazelnut powder as raw material, using the method ultrasonic auxiliary extracts antioxidant active substances from defatted hazelnut powder, and determinines its antioxidant activity. Based on the single factor experiment, chooses the response surface analysis to determine the temperature, substrate concentration, enzyme amount and enzyme solution pH of hazelnut powder material to extract the antioxidant activity of DPPH removing ability. Optimum parameters for oxidation of active material: enzymolysis pH9.0, enzymolysis temperature 50 ℃, with enzyme quantity is 6300 u/g, the substrate concentration 3.2%, enzymolysis time 3 h, under this condition the enzymatic hydrolysis product of DPPH clearance rate was 88.02%.Based on response surface regression analysis we can conclude that the optimal extraction technology condition for enzymatic hydrolysis, then enzymatic hydrolysis product antioxidant activity experiment was carried out. Antioxidant activity results show that with the concentration of hydrolysates increasing, DPPH removing ability, ABTS+ radicals, superoxide anion and hydroxyl radicals scavenging and reducing power increased. In digestion biggest product concentration 16 mg/mL, the enzymatic hydrolysis product of DPPH scavenging effect reached 88.72% of Vc, then it shows that enzymolysis products have scavenging effect closing to Vc, and that the antioxidant activity is relatively strong. When the concentration of enzymatic hydrolysis product reaches 8 mg/mL, ABTS+ scavenging capacity reaches 99.44%, closing to 100% of Vc ABTS+ free radical removing ability, explaining that enzymolysis products have strong ability of removing ABTS+ free radical. At the maximum concentration of enzymolysis substrate, initial concentration of enzymolysis products of hydroxyl free radical clearance rate is 82.36% of Vc, indicating that its antioxidant activity is relatively strong. Hydrolysates superoxide anion scavenging rate is 67.71% of Vc, indicating that the superoxide scavenging capacity of hydrolysates is weak when compared with Vc. At the highest concentration of product, reducing power is 24.86% of Vc, indicating that hydrolysates have weaker reducing power. |
