Effects Of Ultrasonic Pretreatmen On Corn Starch And The Application In Preparation Of Cationic Starch

Cationic starch is a kind of starch derivatives obtained by introduction of cationic groups through etherifying, esterifying or grafting reaction of starch. It is widely used in paper-making, textile, printing and dyeing and has great practical value and wide market prospect. Because the closely configuration of the starch prevents chemical reagent contact with inner molecular, the reaction occurs mainly in amorphous region, resulting in low starch activity and low reaction efficiency. So it is significant to modify the closely configuration in crystalline region and improve the activity of starch, and has great research value in mending the properties of cationic starch and widening application. In order to modify the traditional wet process, primarily the effects of ultrasonic wave on visvosity and molecular weight distribution were investigated, and ultrasound technology was combined with wet process to explore the new process. Further more, applications of cationic starch in flocculation and decolorization were researched. Main results are as follows:(1) Ultrasonic pretreatment had remarkable effect on Peak viscosity and molecular weight distribution of corn starch:The result indicated that as the ultrasonic wave power increased, Peak viscosity of starch decreased and molecular weight distribution peak of amylopectin moved towards lower molecular weight. The ultrasound decreased molecular weight and degree of dispersion of amylopectin.(2) Optimum condition of ultrasonic pretreatment method obtained by response surface design was as follows:reaction temperature was 43?, pH was 12.0, ultrasound treatment time was 50 min, power was 150W. Under the conditions, the actual measured reaction efficiency was 74.25%. The result of infrared spectroscopy showed the correctness of Etherification structure.(3) Campared with cationic starch prepared by traditional wet method, cationic starch by ultrasonic pretreatment method had higher transmittance and freeze-thaw stability, and lower retrogradation. Ultrasonic pretreatment made cationic starch higher pasting peak viscosity, lower setback viscosity and gelatinization temperature.(4) Applications of cationic starch in flocculation and decolorization showed the superiority of ultrasonic cationic starch. Ultrasonic cationic starch got ideal decoloration ratio in lower additive amount (0.04 g·L-1) and lower DS (0.037), having a wider pH range (pH=3-7) for active red X-3B.