| Glycosylated modification is an effective and green method to change the properties of protein,by this way,properties like solubility,emulsification and gelling,would be probably enhanced.However,the polysaccharide with large molecular weight is not conductive to glycation for their limit amount of aldehyde group and space shielding effect,thus the traditional glycation needs 6-72 h to obtain good effects.To improve the reaction rate of glycation,the dextran was oxidized with different content of periodate to obtain more reactive group of aldehydes.glycosylated sodium caseinate by dextran aldehyde with different degree of oxidation was prepared via maillard reaction,and characterized,protein structure,Physicochemical properties and encapsulation property of curcumin were studied as well.Through these tests,the crosslinking mode between dextran aldehyde and sodium caseinate is speculated.The main results are as follows:1.Firstly,dextran aldehyde with different degree of oxidation was analyzed,the effect of glycation by dextran aldehyde on the structure of sodium caseinate was explored and the reaction products were characterized.The more the oxidant used,the less the molecular weight and the higher content of aldehyde group of dextran oxidants.High oxidant degree of Dex70 caused a glycation degree of 44.39%,higher than 1.17% caused by dextran,browning degree and molecular weight of reaction products are growing up with the glycation degree.Surface hydrophobicity increased by 45.86% after glycation.After the glycation,microenvironment of tryptophan on the surface of sodium caseinate transferred from the nonpolar to the polar,and the secondary structure turned more disorderly.2.Secondly,functional properties of glycated sodium caseinate were studied.Emulsifying activity and emulsion stability of sodium caseinate were enhanced after being crosslinked with dextran aldehyde.Nano emulsion prepared with the assistance of ultrasonic exhibited high electrostatic repulsion(-36.5 ～-55.1 m V)and good stability against salt ions and heating treatment.Hydrophobicity contributed greatly to the gel formation and the crosslinking of aldehyde dextran could change the hardness and water holding capacity of gels.The glycation of aldehyde dextran was conducive to the solution viscosity but not good to the enzymolysis and foam stability.3.Crosslink mode between dextran aldehyde and sodium caseinate was speculated.In the ordinary glycosylated reaction,single polysaccharide molecule could be linked with one protein molecule at most.In this study,after the dextran was oxidized,the crosslinking between dextran aldehyde with low oxidation degree and sodium caseinate was easier contrast to that in the ordinary reaction,though single dextran aldehyde could be linked with several protein molecules,one protein molecule crosslinked with sever saccharide molecules still took advantage.With the increase of oxidation degree of dextran,in which the number of aldehyde groups further increased,dextran aldehyde could easily lead to protein intramolecular or intermolecular crosslinking.4.Lastly,the curcumin embedding property of glycosylated sodium caseinate was studied.Curcumin was loaded in sodium caseinate mainly by the hydrophobicity force.Curcumin was encapsulated in protein by inducing the structure shrink of sodium caseinate,for the sodium caseinate crosslinked by dextran aldehyde with high oxidant degree,curcumin induced protein self-assembly and was captured in the protein cage,forming larger particle.When subjected to heating for 3 h,the curcumin loaded in highly glycated sodium caseinate retained as much as20.49%. |
