Study On The Decolorization Technology Of Sunflower Seed Protein And Its Structural And Functional Properties

Sunflower seed protein is a kind of high-quality plant protein with high nutritional value.It has the characteristics of balanced amino acid composition,high biological potency and low allergenicity.However,the polyphenols contained in sunflower seed meal are easily exposed to alkaline conditions.The oxidation reaction occurs,resulting in the color of the extracted sunflower seed protein being dark gray or dark green.In addition,the natural sunflower seed protein has poor partial functional properties due to its own structure or external factors,which also limits its use in the food industry.In the application.Therefore,in this thesis,low-temperature defatted sunflower seed cake is used as the raw material,and the light-colored sunflower seed protein is extracted by the limited enzyme hydrolysis combined with the macroporous resin adsorption technology.First,the optimal decolorization process conditions of the sunflower seed protein are determined through a single factor orthogonal experiment.On this basis,analyze its impact on the structure and functional characteristics.In addition,this article also preliminarily discussed the effect of limited enzyme hydrolysis combined with macroporous resin adsorption and decolorization on the stability of sunflower seed protein emulsion.The main findings are as follows:1.Using low-temperature defatted sunflower seed meal as raw material,after limited enzymolysis,macroporous resin adsorption is used to prepare decolorized sunflower seed protein.The Lightness value(L~*)is used as the evaluation index,and the best is determined by single factor experiment and orthogonal experiment.Decolorization process.The results show that the best decolorization process for sunflower seed protein is to use alkaline protease at a temperature of 55?,p H 6.0,and an enzyme addition amount of 0.8%for 10minutes,and then add 12%AB-8 type macroporous resin.Adsorbed for 120 min at a temperature of 25?,under this process,the L~*value of sunflower seed protein increased from 55.7 to 84.5,and its color changed from dark gray to light white2.First,the effect of limited enzyme hydrolysis combined with macroporous resin adsorption and decolorization on the structure of sunflower seed protein was studied.Compared with the untreated sunflower seed protein,the structure of the sunflower seed protein changes after restriction enzymatic hydrolysis combined with macroporous resin adsorption and decolorization.With the extension of the limited enzyme hydrolysis time,the molecular weight and average particle size of sunflower seed protein gradually decreased;endogenous fluorescence and The content of sulfhydryl groups on the surface increased first and then decreased;after limited enzyme hydrolysis combined with macroporous resin adsorption and decolorization,the secondary structure of sunflower seed protein became more flexible,the content of?-helix and?-turn was significantly reduced,and?-sheet and The content of irregular curls increased significantly;scanning electron microscopy results showed that the powder structure of sunflower seed protein changed from a smooth and large flake structure to an irregular and small flake structure after limited enzymolysis combined with macroporous resin adsorption and decolorization.3.The effect of limited enzyme hydrolysis combined with macroporous resin adsorption and decolorization on the functional properties of sunflower seed protein was further studied.The results showed that compared with untreated sunflower seed protein,the functional characteristics of sunflower seed protein after limited enzymatic hydrolysis combined with macroporous resin adsorption and decolorization were significantly improved.The solubility increases gradually,and the emulsification,emulsification stability,foamability and water holding capacity all increase first and then decrease,while foam stability and oil holding capacity decrease.In addition,the rheological properties of sunflower seed protein after limited enzymolysis combined with macroporous resin adsorption and decolorization are also significantly improved.The storage modulus(G')and loss modulus(G'')show good gel curves.4.Based on the above research,the effect of limited enzymatic hydrolysis combined with macroporous resin adsorption and decolorization on the stability of sunflower seed protein emulsion was preliminarily discussed.The results showed that the emulsion of decolorized sunflower seed protein with macroporous resin after 10 min of limited enzyme hydrolysis was better than untreated sunflower seed protein in the range of p H 7.0?8.0,Na Cl concentration 0?50 mmol/L,and temperature<70?.The protein emulsion is more stable.