The Study Of Ultrasonic Assisting ClO₂ To Oxidize The Cassava Starch

In this paper, oxidized cassava starch was prepared with the help of ultrasonic and oxidant of chlorine dioxide. The single factors and orthogonal experiments showed that: Catalyst can improve the effect of the oxidation starch.The carboxyl content of oxidized starch was biggest when the reaction temperature was 48℃, reaction time was 60min, ultrasonic power was 300W, m(C102):m(starch) was 0.6%, the starch solution concentration was 17%, pH was 6 and the m(Cu2+):m(starch) was 0.0425%, and the biggest carboxyl content was 0.301%; The carbonyl content of oxidized starch was biggest when reaction temperature was 48℃, reaction time was 50min, ultrasonic power was 350W, the m(C102): m(starch) was 0.625%, the starch concentration was 28%, pH was 6 and the m(Cu2+) m(starch) was 0.0400%, and the biggest carbonyl content was 0.364%.The cassava starch was solid center, its surface structure was compact, and its edges and corners were smooth. But, the appearance of cassava starch changed corrosion to the concave surface after oxidizing, and, more deeply oxidized the starch the more obviously sunken of starch surface; Infrared spectrum of native and oxidized starch showed that the -OH stretching band was strengthened, C-O-C stretching band was weakened and the carboxy group stretching band was strengthened, which indicated the crystalline region and hydrogen bond of starch was damaged after the role of oxidant and ultrasound. And starch structure no longer tightness, it became loose, thus, the-OH of molecular chain released. The starch was oxidized and the hydrolysis reaction was happened. Starch oxidation mainly occurred in the amorphous region, part in the crystal regions. After the oxidation, the ΔH of starch was decreased, and the crystallinity was decreased, and its transparency was increased, sedimentation volume was decreased, when the carboxyl content of oxidized starch reached 0.291%, it hardly happened condensation phenomenon to maintain the stability of starch. The white degree was raised. And it was easy to be gelatinized, and the cold and hot viscosity stability of starch was increased. The aging property was weakened, and its viscosity was decreased.In this paper, the kinetics of chlorine dioxide which used as oxidant under the condition of no ultrasonic and ultrasonic was studied. The results show that, when the reaction temperatures were 45℃ and 50℃, starch oxidation reaction conformed to first order reaction process with or without ultrasonic conditions. When the reaction temperature was 55℃, starch oxidation reaction conformed to second order reaction process. The reaction rates were higher in case of ultrasonic and it improved the starch oxidation rate.In the paper, we established the starch oxidation reaction kinetics mathematical model under the condition of ultrasonic. This kinetic mathematical model was...