Study On Enzymatic Synthesis And Properties Of Dextrin Stearic Acid Ester

Dextrin stearic acid ester was syntheised with maltodextrin and stearic acid. According to its chemical structure, dextrin ester has outstanding performance such as emulsifying, thickening and stability. The dextrin ester is widely used as a food addition or a newly developed food processing and pharmaceutical auxiliary ingredient.In this article, the dextrin ester was syntheised with maltodextrin and stearic acid by enzyme. The synthesis conditions, purification, physical and chemical properties and emulsification of dextrin stearic acid ester had been studied. Then the application of dextrin ester was studied. Besides, in order to study the maltodextrin's ability in improving the composite coffee's solubility, it was added into the composite coffee as emulsifier.The highest degree of substitution (0.01542) was obtained when the reaction mixture consisted of t-butyl alcohol, the maltodextrin/stearic mass ratio of 4:1,7g/L enzyme at 65? for 60h.Ethanol was used to remove the maltodextrin by washing 3 times. Hexane was used to centrifuge to remove fatty acid. After normal temperature drying, white solid maltodextrin esters was obtained.The maltodextrin ester was analyzed by scanning electron microscope, infrared spectroscopy, differential scanning calorimetric and nuclear magnetic resonance. The results showed that after esteritication, the particles became smaller. The structure of maltodextrin ester was determined by IR and NMR. IR spectrimetris showed that the characteristic absorption peak of the ester bond was 1732cm-1. NMR results proved that the esterification reaction was successful. After calculation, the degree of substitution was 0.0152, which was close to the result obtained by the acid-base titration method. So the acid-base titration is verified. After modification, the water binding capacity of dextrin ester is weaken and the enthalpy value is lower than the original dextrin, the starting temperature, peak temperature and dissolved heat decreased.Hygroscopicity, solubility, transparency, retrogradation, freeze-thaw stability and characteristic viscosity were analyzed. It showed that, after esterification, the hygroscopicity and solubility decreased with the increasing of the substitution's esterification degree. The transparency decreased and with the esterification degree of substitution increased, the solubility decreased. The maltodextrin ester showed better retrogradation and freeze-thaw stability. Its characteristic viscosity increased.The emulsifying property of maltodextrin ester was tested. The degree of emulsitication was increased with the concentration of the maltodextrin ester increased. At the same concentration, the emulsifying properties of the maltodextrin ester increased with the degree of substitution increased. The emulsion droplets of maltodextrin and maltodextrin ester were observed under the microscope, the maltodextrin ester emulsion droplets were smaller and more uniform. The foamability and foam stability were gradually increased with the increasing concentration of the ester. The light scattering analysis showed that the diameter of maltodextrin emulsion droplets changed continuously, and the peak width was very narrow, indicating that the emulsion droplets shows uniform size and good emulsitying properties.The emulsifying property of maltodextrin ester was tested in the composite coffee. When the ratio of monoglycerides to maltodextrin stearic acid ester was 3 to 4 and the adding content was 7%, the emulsion stabilizer performed the best.