Preparation,Structure And Physicochemical Properties Of Dual-Modified Glutinous Rice Starch With Lactates And Phosphorylation

Starch modification used in food industry has always been a research hotspot in starch science.In order to improve the glutinous rice planting and processing economic benefits,enlarge the application range of glutinous rice starch,this topic with glutinous rice starch as raw material,on the previous glutinous rice starch phosphate modification,using phosphate,sodium dihydrogen phosphate,disodium hydrogen phosphate),lactic acid as modifier,single lactate and lactic acid of glutinous rice starch phosphate compound preparation and its modified structure characterization and physicochemical properties.The main results are as follows:1.On the basis of single factor experiment,through design expert The results showed that the reaction temperature,time and concentration of lactated modified starch were 114.48℃,119.36 min and 44.45%,respectively,and the degree of substitution of modified starch was 0.02310;the reaction temperature,time and concentration of dual-modified starch were 151.25℃,150.35 min and 7.25%,respectively,and the degree of substitution of the dual-modified starch is 0.01975.2.The morphology of modified and unmodified glutinous rice starch was observed by scanning electron microscope.The results showed that the glutinous rice starch granules were complete and the surface was smooth.There was little difference in the morphology between phosphorylated modified starch and lactated modified starch and glutinous rice starch.The starch with dual-modified starch had more adhesion.The crystallinity of glutinous rice starch and modified starch were 30.76%,27.11%,26.12%and 22.61%,respectively.The crystallinity of modified starch was lower than that of glutinous rice starch,but the A-type crystal structure of glutinous rice starch was not changed.In the Fourier transform infrared spectrum,the signal peak of ester C=O appeared at 1738 cm^-1 for lactated modified starch and dual-modified starch,which confirmed the esterification reaction.The P=O(1210 cm^-1)and P-O-C(810cm^-1)signal peaks did not appear in the modified starch,but the shift of fixed characteristic signal peaks appeared in the modified starch,such as O-H(3385 cm^-1),C-H(2931 cm^-1),and C-O(1160 cm^-1).³¹P NMR showed that mono-starch phosphate ester and distarch monophosphate ester were the main forms of phosphate ester in phosphorylated and dual-modified starch.¹³C NMR results showed that phosphorylated modified starch mainly occurred at C6,lactated modified starch mainly occurred at C6,C2,3,5,and dual-modified starch mainly occurred at C6,C2,3,5.3.The gelatinization properties showed that the viscosity of glutinous rice starch was reduced by phosphorylated modification,lactated modification and dual-modification.The gelatinization temperature and enthalpy of glutinous rice starch were decreased by three kinds of modification,and the dual-modified starch had the lowest gelatinization temperature and enthalpy.TG results showed that the degradation temperature and loss rate of modified starch decreased.The three kinds of modification did not change the characteristics of non Newtonian fluid of glutinous rice starch,which belonged to shear thinning system.The G’and G"of phosphorylated modified starch and dual-modified starch are smaller than glutinous rice starch,G’>G".the viscosity of lactic acid modified starch is too low,and the difference between G’and G"is not obvious.Three kinds of modified starch improved the freeze-thaw stability of glutinous rice starch.Lactic acid group improved the hydrophobicity of glutinous rice starch,phosphate group showed a certain degree of hydrophilicity,while dual-modification showed strong hydrophobicity.Phosphate group can improve the transparency of glutinous rice starch.