Studies On The Preparation Of Phosphate Starch By Microwave Solid-state Method In Low Temperature And Its Properties

The traditional production of phosphate starch requires higher temperature, generally reachs to 140～160℃, beaches of the effection of the heating efficiency, the reaction needs long time, high energy consumption. Microwave technology has high heating efficiency, short time features. It is the best way to prepare such modified starch. Study on the corn starch by microwave treatment, especially the role of catalyst in the phosphate starch reaction by solid-state method in low temperature. At the same time, properties and structure also were researched. The success of this study causes a new technology of phosphate starch preparetion prebably.The main conclusions were as follows:(1) The reaction can be carried out by adding certain catalysts, the degree of substitution increases and then decreases with increasing of the reaction promote dosage, and the effect was significant. Preparation of DS=0.080 of products, this method can be done at 110℃, and the general reaction of dry heat, you need 140～160℃high temperature. Make sure that the effects law of the amount of sodium pyrophosphate, stearic pyrophosphate ether, reaction temperature, reaction time, reaction pH, urea by single factor experiments on the DS phosphate starch. With the increasing or extending of the amount of sodium pyrophosphate, stearic pyrophosphate ether, urea, and reaction time, the degree of substitution increased and then decreased; with the increasing of microwave reaction temperature, the DS increased also; while, the rise of the degree of substitution had no significant effect upon the promotion higher than 110℃; the degree of substitution increased as the reaction pH increased, higher than 5.5, the substitution did not change significantly.(2) Obtained by response surface design experiment with four factors in the amount of sodium pyrophosphate, the amount of stearic pyrophosphate ester, reaction time and the amount of urea. The optimal parameters of the preparation of phosphate starch by microwave solid-state method in low temperature was:sodium pyrophosphate 6.08 g, accounting for 12.16% of starch quality; stearic pyrophosphate ether 2.25 g, accounting for 4.5% of starch; microwave reaction time 14.00 min; catalyst urea 1.50 g, accounting for 3% starch; the DS was 0.083. By the Design-Expert software, the optimal experimental points are given experimental results verify, the DS was 0.080±0.002.(3) Phosphate starch paste is shear thinning, belongs to non-Newtonian fluids. Shear resistance is not obvious advantages compared with native starch. However, the shear viscosity significantly higher than the native starch, it is still showing good viscosity after shearing. Compared with native starch, phosphate starch viscosity, the difference of its cold and hot viscosity is relatively small; paste retrogradation is not easy, the stability is higher, pasting good quality; phosphate starch paste transparency is much higher than the original starch and cemented good, but the acid resistance is poor.(4) Infrared spectra show that the substituted phosphate starch molecules in 1400 cm-1 near the characteristic absorption peak, that is, P=O stretching vibration absorption peak. X diffraction and TGA scans showed that; compared with native starch, phosphate starch crystalline regions damaged or lost, proof of esterification not only in the amorphous areas of starch, starch also occurred in the crystallization region. Scanning electron microscopy showed that the reaction disorder starch granules and the surface becomes rough and collapsible.