Study On Extraction And Function Of Antioxidant Peptide And Dietary Fiber From Okara

As a byproduct of soybean,Okara is mostly used as feed or waste.However,the content of nutrients in okara is relatively high,which retains some functional characteristics of soybean.Therefore,how to make rational use of the bean dregs and exert its residual value has broad research prospects,especially the utilization of protein and dietary fiber in the bean dregs.Proteins can be hydrolyzed into peptides.Dietary fiber can promote beneficial physiological effects in the human body,including laxative,blood cholesterol and blood sugar.The preparation of antioxidant peptides and dietary fiber from bean dregs provides a theoretical basis for the rational utilization of soybean by-products.The antioxidant peptide was prepared by papain.The polypeptide content conversion is used as indicator.The enzymatic hydrolysis conditions were optimized to obtain the optimal process conditions.The substrate concentration was 6%,the enzyme addition amount was 5%,the enzymatic hydrolysis temperature was 60℃,the pH was 6.5,and the enzymatic hydrolysis time was 6h.The antioxidant peptides were separated by ultrafiltration.The antioxidant activities of the antioxidant peptides before and after ultrafiltration were determined,including DPPH·free radical elimination ability and OH·free radical elimination ability.In the determination of DPPH·free radical elimination ability,before ultrafiltration the EC₅₀ was 2.58 mg·mL^-1,and after ultrafiltration the EC₅₀ was 1.84 mg·mL^-1.In the measurement of the·OH radical elimination ability,the EC₅₀ was 1.99 mg·mL^-1 before ultrafiltration and the EC₅₀ was 1.03 mg·mL^-1 after ultrafiltration.Using deproteinized okara as raw material,SDF was prepared by cellulase,and the optimal enzymatic hydrolysis conditions of SDF were obtained by SDF extraction rate:substrate concentration was 3%,enzymatic hydrolysis temperature was 45°C,enzyme addition amount was 3%,pH was 4.5,the enzymatic hydrolysis time was 2 h.Determine the antioxidant activity of SDF under the optimal enzymatic hydrolysis conditions,including DPPH·free radical elimination ability,·OH free radical elimination ability and O₂^-·free radical elimination ability.The EC₅₀ of DPPH·free radical elimination ability was 1.39 mg·mL^-1.The·OH free radical elimination rate and the O₂^-·free radical elimination rate were the highest elimination rates of 46.37%and 43.68%,respectively.The physicochemical properties of dietary fiber were determined,including water holding capacity,oil holding capacity,swelling property,combined water power,glucose adsorption capacity and cholesterol adsorption capacity.Among them,the water holding capacity of SDF is 4.20 g·g^-1,the swelling property is6.37 mL·g^-1,the binding hydraulic capacity is 2.45 g·g^-1,the oil holding capacity is 9.56 g·g^-1,the glucose adsorption capacity is 1078.26μmol·g^-1,the cholesterol adsorption capacity is 20.74 mg·g^-1 under pH=2 condition,and 44.39 mg·g^-1under pH=7 condition.The water holding capacity of IDF is 4.37 g·g^-1,the expansibility is 4.96 mL·g^-1,the binding hydraulic capacity is 4.71 g·g^-1,the oil holding capacity is 6.15 g·g^-1,the glucose adsorption capacity is 893.43μmol·g^-1,the cholesterol adsorption capacity is 14.21 mg·g^-1 under pH=2 condition,and20.60 mg·g^-1 under pH=7 condition.The chemical modification and physical modification of dietary fiber were carried out.The hydration properties,including water holding capacity,expansibility and combined water power,were determined.The effect of modification on hydration properties was investigated.It was found that the effect of physical modification was better than that of chemical modification.To explore the effect of compound SDF,IDF on physical and chemical properties,the proportion of SDF was adjusted to 5%,15%and25%,respectively.By comparing dietary fiber mixture with SDF,IDF,it was concluded that for water holding capacity,with the increase of SDF ratio,5%SDF(9.54 g·g^-1),15%SDF(9.95 g·g^-1),Compared with SDF(5.84 g·g^-1),25%SDF(10.58 g·g^-1)increased by 1.63 times,1.70 times and 1.81 times,respectively.For oil holding capacity,the oil holding capacity of 15%SDF(10.29 g·g^-1)and 25%SDF(10.78 g·g^-1)increased 1.08 times and 1.13 times compared with SDF(9.56 g·g^-1).For cholesterol adsorption capacity,5%SDF(21.40 mg·g^-1),15%SDF(41.40 mg·g^-1)and 25%SDF(35.10 mg·g^-1)increased1.03 times,1.99 times and 1.69 times as much as SDF(20.74 mg·g^-1)at pH=2.At pH=7,5%SDF(45.50 mg·g^-1),15%SDF(63.10 mg·g^-1)and 25%SDF(54.60mg·g^-1)increased 1.03 times,1.42 times and 1.25 times compared with SDF(44.39 mg·g^-1).