Preparation And Structure Characterization Of Oxidized And Cross-linked Cassava Starch Under Physical Fields

Ultrasonic and microwave technology as modified starch physical emerging technology, has attracted more and more attention. In this study,oxidized cassava starch was prepared with native cassava starch,sodium hypochlorite as modifying agent,under ultrasonic effect,and then oxidized and cross-linked cassava starch was prepared with oxidation cassava starch,sodium trimetaphosphate as modifying agent,under microwave effect. Study on the synthetic routes respectively, determined the preparation technology of cassava starch and cassava oxidized and cross-linked compound modified starch, at the same time,Study on the structure and properties of cassava starch and oxidized starch, oxidized and cross-linked starch,provided a reference for the further development of compound modified cassava starch, To lay the foundation for the application of ultrasonic and microwave technology in the production of modified starch, so as to make better use of ultrasonic and microwave technology.At first,cassava starch was modified by oxidation. Based on single factor test and orthogonal experiments,explore the effects of various affecting factors on the carboxyl content of oxidized starch. And under the condition of ultrasonic and non ultrasonic conditions respectively for preparation of oxidized starch, explore the effect of ultrasonic treatment on oxidized starch, Proved that ultrasound can improve the carboxyl content of oxidized starch,accelerate the oxidation reaction. On this basis,oxidized and cross-linked modified starch was preparation by single factor test and orthogonal experiments. And explore the effects of various factors on the degree of cross linking of the composite modified starch product. The results were as follows:Optimum process conditions of preparation of oxidized cassava starch as follows: reaction pH 8,the concentration of available chlorine:5%, reaction temperature 35℃,ultrasonic time 100 min,ultrasonic power 300W. Preparation of oxidized and cross-linked modified starch optimum process conditions was:the amount of sodium trimetaphosphate 1.5%,microwave time5 min,microwave power 200W, pH 10.Finally,under different processing conditions of the properties of cassava modified starch were studied. The products were characterized by modern analysis instruments. The SEM pattern showed that the native starch granules of smooth surface, no holes,The oxidized starch particle surface roughness, hole crackle、The X-RD spectrum showed that the diffraction peaks of denatured starch almost no change, not change the crystal type of modified starch. IR spectra showed that the chemical bond of oxidized and cross-linked starch was basically the same, The ester carbonyl peak appeared after crosslinking. The DSC pattern showed that the enthalpy value of native cassava starch was bigger than oxidized and cross-linked starch. And study on the solubility, transparency, retrogradation, whiteness, film, viscosity properties. The results showed that transparency, solubility, whiteness and film of oxidized starch were better than native cassava starch, But the freeze-thaw stability, acid stability, aging resistance and heat stability were not good, freeze-thaw stability, acid resistance, aging resistance, heat stability of oxidized and cross-linked modified starch were better.