Effect Of Modification On Structural Characterization And Functional Properties Of Walnut Glutenin

Walnut meal contains a lot of high-quality plant protein.However,walnut meal in China has not been fully utilized and a large number of protein resources have been wasted.In order to deepen the high-value refined processing of walnut and expand the application of walnut protein in the field of food and medicine.Therefore,walnut protein was modified to improve the theoretical data and achieve the experimental purpose of combining production,learning and research.The walnut protein was modified by chemical method(acylation and phosphorylation),enzymatic method(compound protease,glutamine transaminase)and glycosylation method(glucose,lactose and dextran)with walnut oil pressed as the direct material.Analyze qualitatively and quantitatively about the functional properties of the modified protein,the changes of chemical bonds between intermolecular and intramolecular,the molecular conformation and microstructure of protein.The main results of determination and analysis were as follows:(1)The chemical(acylation and phosphorylation)method was used to determine the optimum conditions of acylation and phosphorylation of proteins by single factor and response.The optimum modification conditions of acylated protein were obtained as follows:reaction temperature 51℃,time 1 h,pH 8.5,succinic anhydride to protein ratio 1:2.Under these conditions,the solubility of the acylated protein was 80.29%.The optimum modification conditions of phosphorylated protein were obtained as follows:reaction temperature 40℃,time 2 h,pH 9.5,the ratio of sodium tripolyphosphate to protein was 1:10.Under these conditions,the solubility of phosphorylated protein was 95.60%.The structural characterization and functional properties of the modified protein have different changes.(2)Enzyme treatment(complex protease)method was used to determine the optimum conditions of enzyme modified protein by single factor and response.The optimum modification conditions of protein were obtained as follows:reaction temperature 38℃,reaction time 40 min,enzyme dosage 0.3%.Under these conditions,the solubility of complex protease modified protein was 40.61%.(3)TG enzyme modification method was used to determine the optimum conditions of single factor and response to the modified protein.The results showed that the optimum modification conditions of TG enzyme modified protein were as follows:reaction temperature 51 ℃,reaction time 2 h,pH 8.0.Under these conditions,the solubility of glutamine transaminase modified protein was 34.29%.(4)Glycosylation(glucose,lactose,dextran)method was used to determine the optimum conditions of glycosylation protein by single factor and response.The optimum modification conditions of glycosylated protein were obtained as follows:reaction temperature 82 ℃,reaction time 1/3 h,pH 8.0,ratio of glucose to protein 1:4.Under these conditions,the solubility of glucose modified protein was 94.84%.In the condition of as follows:reaction temperature 58℃,reaction time 5 h,pH 10.0,ratio of lactose to protein 1:3,the solubility of lactose modified protein was 59.62%.In the condition of as follows:reaction temperature 81℃,reaction time 3 h,pH 10.0,ratio of dextran to protein 1:3,the solubility of dextran modified protein was 98.42%.(5)From the spectroscopic analysis,the changes of fluorescence intensity,red or blue shift of absorption wavelength,sulfhydryl and disulfide bonds,the changes of alpha-helix,beta-fold and beta-corner structure in protein secondary structure indicate that the internal structure characterization of protein molecules and the changes of external environment of protein molecules can cause the changes of hydrophilicity and hydrophobicity of protein,and also lead to the changes of functional properties of protein.It is concluded from the microstructure that the different modification and different methods of modification will affect the microstructure of protein molecules,and the characterization of this structure is ultimately reflected in the functional properties of protein.