Study On Oat Protein Thermal Aggregation And Its Effect On Pepsin Digestive Properties

The purpose of this article is to study the related properties of "Bayou No.1" oat protein,the thermal aggregation characteristics of oat protein isolates and their effects on pepsin digestion.The subunit composition and functional characteristics of oat protein isolate under different pH and ionic strength be analyzed.Based on this,the aggregation characteristics of oat protein isolates after heat treatment at different temperatures was further analyzed.Finally,the effect of pepsin on the digestive properties of oat protein isolates treated at different temperatures was studied.The test results show that the starch content of "Bayou No.1" oats is 60.31%,of which the direct starch content is 24.77%,the protein content is 12.92%,the highest globulin content is 36.42%,and the fat content is 6.25%.The distribution of oat protein subunits are that the oat albumin subunits is distributed among the range of 10-100 k D.Oatin is composed of two subunits with molecular weights in the range of97.4-100 k D and 43-66.2 k D.Most of the subunits of oat prolamin are concentrated on 18.39-40.72 k D,and some subunits of oat glutenin are distributed between 20.67-26.66 k D and 43.29-50.80 k D,of which oat albumin and globulin contain disulfide bonds.Different extraction conditions have an effect on the subunit composition of oat albumin,gliadin and glutenin.Oat protein isolate is mainly globulin,which has the lowest solubility at pH 5.0-6.0(p I),the lowest foaming performance,the highest foam stability,but higher emulsification and emulsification stability under alkaline conditions;at pH 2.0 and 3.0 The acidic conditions caused partial hydrolysis of the soluble oat isolate peptide chain,forming a subunit band with a relative molecular mass of 31-43 k D.There is no significant difference under alkaline conditions.When the concentration of Na Cl is 0.05 mol / L,the solubility is the lowest.When the concentration of Na Cl is0.6-0.9 mol / L,the foamability,foam stability and emulsification are high.When the solubility is the lowest,the soluble protein is mainly composed of a relative molecular weight of 43 k D.The addition of Na Cl caused the peptide chain of soluble oat protein isolates to break,resulting in polypeptide chains with relative molecular masses of 43 k D and 66.2 k D,respectively.During the process of heating oat protein isolate at different temperatures,the oat protein isolate is partially dissociated into small molecular weight subunits.At this time,the main force to maintain the spatial structure of the protein is ionic bonding,and the peptide chain folded tryptophan residue is buried inside the molecule.As the temperature further rises,oat isolate protein further dissociates into small molecules,and the peptide chain stretches tryptophan residues to the hydrophobic microenvironment.These small molecular proteins aggregate under the action of hydrogen bonding,hydrophobic interaction,disulfide bonding,etc.The formation of large-molecular-weight insoluble aggregates is accompanied by the formation of disulfide bonds throughout the heating process.After heating at 110 ?,the formation of aggregates involves the participation of covalent bonds other than disulfide bonds.This conclusion needs to be further studied.The microstructures of oat protein isolate gels prepared under different pH and ionic strength treatment conditions are significantly different,and the forces that maintain their gel structure are different,and the protein subunits that are affected by each force are also significantly different.Unheated oat protein isolates have a higher degree of hydrolysis and are easier to hydrolyze into small molecular weight subunits.When the heat treatment temperature is lower than 70 ?,the dissociation of protein caused by heating destroys the pepsin action site and is not conducive to hydrolysis.At 70-80 ?,some oat protein isolates aggregate and change their original protein structure due to dissociation due to heating.The site of pepsin action is masked.As the hydrolysis time prolonged,the degree of hydrolysis of some pepsin action sites is increased,but due to the structural change caused by aggregation,large aggregates are difficult to hydrolyze into small molecular weight subunits.At 110 ?,oat protein isolates are heated to form larger aggregates,and similarly large molecular weight aggregates are difficult to form small molecular weight subunits.