Study On In Vitro Antidigestive Properties And The Potential Molecular Mechanism Of Corn Starch-zein Microparticles

Cooked starchy food usually contains a large amount of rapidly digestible starch,which could lead to a sharp rise in blood glucose levels,thus increasing the incidence rate of non infectious chronic diseases such as obesity,type 2 diabetes,as well as cardiovascular and cerebrovascular diseases.The interaction between starch and exogenous proteins could significantly mitigate starch digestibility and,in turn,the glycemic response and insulin resistance.However,due to the thermodynamic incompatibility of starch and protein,the stability of starch-protein complexes in most of the current studies is too poor to significantly reduce starch digestibility.Therefore,it is necessary to study the methods for the fabrication of high-stability starch-protein complexes,the influence of starch-protein interaction on the physicochemical properties and starch digestibility,and the mechanism underlying the starch-protein complexation process at the molecular and atomic levels.This study aimed to provide theoretical basis for the application of protein in starch processing and the development of novel starch-based food with low digestibility.In this study,based on the antisolvent method and protein crosslinking,the absorbent core-shell corn starch/zein microparticles and the swollen core-shell corn starch/zein microparticles were prepared,respectively,and their physicochemical properties and starch digestibility were studied.In this study,based on molecular dynamics simulation technology,the complexation process,major forces,and conformational stability of amylose-zein complexes were studied,and the effects of the number of zein molecule and the amino acids with different properties in zein on the conformational stability of the amylose-zein complexes were investigated.The major research contents are as follows:（1）Effects of different crosslinking periods（0,1,and 2 h）on the physicochemical properties and digestibility of absorbent core-shell corn starch/zein microparticlesThe volume average particle diameter of absorbent core-shell corn starch/zein microparticles with different crosslinking periods was 14.70～30.98μm.The shell thickness is0.48～0.95μm.With the prolongation of crosslinking periods,the thermal stability of absorbent core-shell corn starch/zein microparticles increased,the water solubility and swelling power decreased.The digestibility of native corn starch after enzymatic hydrolysis for 2 h was 93.44%.With the extension of crosslinking periods from 0 h to 2 h,the digestibility of absorbent core-shell corn starch/zein microparticles decreased from 75.64%to62.81%.The content of slowly digestible starch and resistant starch were 3.46 times and13.01 times,respectively,higher for CS-zein 2h microparticles after cooking for 30 min than for native corn starch after cooking for 30 min.（2）Effects of different zein concentrations（1%w/v,2%w/v,3%w/v）on the physicochemical properties and digestibility of swollen core-shell corn starch/zein microparticlesThe concentration of zein increased from 1%（w/v）to 3%（w/v）,the volume average particle diameter of swollen core-shell corn starch/zein microparticles increased from 36.09μM increased to 59.09μm.The thermal stability were higher for CS-3%zein microparticles than for CS-1%zein microparticles.In contrast,the water solubility and swelling power were lower for CS-3%zein microparticles than for CS-1%zein microparticles.With the increase of zein concentration from 1%（w/v）to 3%（w/v）,the digestibility of swollen core-shell corn starch/zein microparticles decreased from 66.87%to 50.67%.The content of slowly digestible starch and resistant starch were 2.48 times and 18.10 times,respectively,higher for CS-3%zein microparticles after cooking for 30 min than for native corn starch after cooking for 30min.（3）Study on the complexation process,major forces,and conformational stability of amylose-zein complexes based on molecular dynamics simulationThe central residues of amylose molecule were complexed with zein molecule,which is the key to preserve partial V-type helical configurations of amylose molecule in amylose-zein complexes.The conformational stability was significantly higher for amylose-zein complexes than for amylose in water.Furthermore,the amylose in amylose-zein complexes displayed the thermodynamically stable ⁴C₁conformation.（4）Study on the effects of the number（1,2,3,and 4）of zein molecule on the complexation process and the conformational stability of the amylose-zein complexesWith the increase of the number of zein molecules interacting with amylose,the complexation rate of amylose-zein complexes gradually slowed down,the conformational stability of the amylose-zein complexes in water gradually increased,and the proportion of antiparallel zein molecules increased,the conformational stabilities of the V-type helical structure of amylose and the amylose-zein complexes gradually increased.（5）Study on the effects of the amino acids with different properties（negatively charged,positively charged,uncharged,nonpolar）in zein molecule on the complexation process and the conformational stability of the amylose-zein complexesGlu,Arg,and Asn（three polar amino acids）were distributed outside the V-type helical structure of amylose when interacting with amylose,while the non-polar amino acid Phe was distributed inside the hydrophobic helical cavity of amylose when interacting with amylose.The interaction energy and the number of intermolecular hydrogen bonds between amylose and amino acids with different properties were in an order of Amylose-Glu>Amylose-Arg>Amylose-Asn>Amylose-Phe,while the order of root mean square deviation,radius of gyration,radial distribution function,and solvent accessible surface area were reverse.The results showed that compared with nonpolar amino acids,polar amino acid residues,especially charged amino acid residues,have stronger ability to bind starch and stabilize starch-amino acid complexes.