Effect Of Different Polymerization Methods Of Whey Protein On Physical And Chemical Properties Of Corn Starch

Starch and protein,two important functional polymers,are commonly used in food systems.They have an important impact on the rheological and texture properties of food.At present,the research on starch-protein mainly focuses on the naturally occurring interactions in plant seeds,there is less research on the interaction between exogenous proteins and starch,and the interactions between different types of proteins and starch are quite different,and the sources are different protein structures The difference is very large,it is difficult to clearly reveal the interaction between the two.This experiment mainly explored the difference and regularity of the effect of different polymerization methods of the same protein on the gelatinization and retrogradation properties of corn starch.Corn starch and whey protein concentrate（WPC）are used as raw materials,and the whey concentrated protein is treated in different ways to change its polymerization structure,so that it can be assembled to form conventional polymers and fiber polymers.Through transmission electron microscopy,thiosulfurin T（Th T）and surface hydrophobicity were measured to explore the differences in structure and properties;the differences and regularity of the influence of different structural properties of the same protein on the gelatinization properties and rheological properties of corn starch were investigated by measuring the leaching ability of amylose and rheological properties.;analyzes the change of the dissolution rate of amylose in the gelatinization process of corn starch and mixed system,and explores the causes of the differences in the macro characteristics of different systems.The differences in the retrogradation characteristics of different mixed systems are investigated by means of rheometer,retrogradation thermodynamics analysis and X-ray diffraction.The results of the study are as follows:Differences in structure and properties of different WPC polymers In terms of morphology,WPC polymerized under the conditions of p H 6.5 and 90℃heating for 10 h,and formed a large cluster of conventional polymers.WPC is gradually assembled from spherical particles to form slender linear fiber polymers（WPC spontaneous）under the conditions of p H 2.0and heating at 90℃for 10 hours.The two polymer structures are completely different.In terms of fiber content,the Th T value of conventional polymers is much lower than that of fiber polymers.For fiber polymers,WPC spontaneous and nucleus-induced two different polymerization methods are used to form fiber polymers.WPC spontaneously forms fibers with Th T fluorescence intensity that is significantly lower than those induced with fibers.And there were significant differences in Th T fluorescence intensity of fibers formed by different induction methods.The Th T fluorescence intensity of WPC induced by enzymatic hydrolysis was the highest,which was 1.86times that of WPC spontaneous.In nature,the surface hydrophobicity of conventional polymers is significantly lower than that of fiber polymers.For fiber polymers,the greater the amount of fiber,the greater the surface hydrophobicity.Amylose leaching ability The corn starch gelatinization process is accompanied by amylose leakage.The dissolution of amylose in different gelatinized samples was significantly different.Compared with pure corn starch,the addition of fiber polymers（enzymatic hydrolysis induction,secondary nuclear induction）had 74.76%and 53.55%amylose dissolution,a difference of 21.21%;while the addition of WPC conventional polymer（0h）was only 35.78 The dissolution rate of%amylose was 38.98%and 17.77%lower than that of the added fiber polymer（enzymatic hydrolysis induction and secondary nuclear induction）,respectively.It shows that the inhibitory effect of WPC conventional polymer on corn starch gelatinization is much higher than that of fiber polymer,and the inhibitory effect of fiber polymer on corn starch gelatinization gradually weakens with the increase of the amount of added protein fiber.Further explore the change of dissolution rate of amylose during gelatinization of different samples.The corn starch and mixed samples（df/dt）_maxwere in the second minute during gelatinization.At the second minute,compared with pure corn starch,the dissolution rate of amylose in the WPC conventional polymer-starch mixed system was reduced by 73.77%;the fiber polymer-starch mixed system was reduced by 53.91%,a difference of 19.86%.It shows that the addition of WPC did not change the dissolution law of amylose during gelatinization,but the two polymers inhibited the dissolution rate of amylose during gelatinization of corn starch,and the inhibitory effect of conventional polymers was more significant.Changes in the physical and chemical properties of starch gelatinization system The dissolution of amylose in different gelatinization systems directly affects the rheological properties of the system.The degree of influence of the WPC polymer formed by adding different polymerization methods on the rheological properties of corn starch is different.Compared with pure corn starch,the viscosity value,consistency coefficient K,dynamic viscoelasticity G’and the degree of decrease of G"is higher than that of fiber polymers.And the degree of inhibition of different fiber polymers gradually decreases with the increase of the amount of added protein fibers.The thermodynamic properties of corn starch and mixed systems are measured by DSC.Compared with pure corn starch,the gelatinization enthalpy of the conventional polymer-starch system decreased by 27.57%,and the fiber polymer-starch system paste The enthalpy of reduction decreased by 22.47%,indicating that both WPC conventional polymer and fiber polymers can inhibit the gelatinization of corn starch,but the inhibitory effects of WPC conventional polymer are more significant.Changes in starch retrogradation properties Different polymerization methods WPC have different effects on the regeneration of corn starch.WPC conventional polymers can promote the regeneration of corn starch,while fiber polymers can inhibit the recovery of corn starch.Among them,the retrogradation degree of the conventional polymer mixed system with WPC was11.26%higher than that of pure corn starch,and the retrogradation degree of the fiber polymer mixed system was 8.38%lower than that of corn starch.Compared with pure corn starch,the addition of conventional WPC polymers can produce a higher elastic modulus,and at the same time,it is observed that its water holding capacity is weaker than that of pure corn starch according to low-field nuclear magnetic measurement;while the addition of fiber polymers produces a lower elastic modulus but strong water holding capacity.Changes in the crystal structure of retrograded starch Further observe the crystal structure of corn starch and mixed samples after regeneration.The original corn starch has an A-type crystal structure.The WPC formed by adding different polymerization methods does not change the crystal form of the retrograded corn starch,and all show a B-type crystal structure after regeneration.However,the effects of different polymerization methods of WPC on the relative crystallinity of starch retrogradation are significantly different.WPC conventional polymers will promote the recrystallization of corn starch,while fiber polymers have a certain inhibitory effect on the recrystallization of corn starch.How WPC works with different polymers and corn starch Fourier transform infrared spectroscopy was used to analyze the interaction between WPC polymers and corn starch,indicating that there is no covalent bond between starch and protein,and that the two polymers interact with corn starch through hydrogen bonding during gelatinization;comparison The1047cm^-1/1022cm^-1peak ratio of different retrograded samples explored the short-range ordered structure and showed that the peak ratio of 1047cm^-1/1022cm^-1of the mixed retrograded sample with WPC conventional polymer was not much different from that of pure corn starch.The1047cm^-1/1022cm^-1peak ratio of the mixed regenerated sample was 3.46%lower than that of pure corn.Compared with fiber polymers,adding WPC conventional polymers to corn starch can form a more ordered structure with a higher degree of regeneration.To sum up,the degree of influence of the WPC polymer structure formed by the same protein composition and assembled in different ways on the gelatinization and retrogradation of corn starch varies greatly.WPC conventional polymers and fiber polymers can inhibit the gelatinization of corn starch,but the degree of inhibition is different.The addition of 2 polymers significantly reduced the dissolution rate of corn amylose during gelatinization.Compared with pure corn starch,amylose added with WPC conventional polymer（0h）and fiber polymer（enzymatic hydrolysis induced WPC）mixed system finally dissolved 35.78%and 74.76%,a difference of 38.39%.Different polymerization methods WPC have different effects on the regeneration of corn starch.WPC conventional polymers can promote the regeneration of corn starch,while fiber polymers can inhibit the recovery of corn starch.Among them,the retrogradation degree of the conventional polymer mixed system with WPC was 11.26%higher than that of pure corn starch,and the retrogradation degree of the fiber polymer mixed system was 8.38%lower than that of pure corn starch.