| Summary: | 碩士 === 國立中興大學 === 食品科學系 === 90 === In this study, cassava starch was used as test sample which was reacted by CHPTAC （3-chloro-2-hydroxypropyl trimethyl ammonium chloride）to form a cationic starch . The objectives of this study were to evaluate the optimal conditions for cationization of cassava starch by using an aqueous alcoholic-alkaline process and the physiochemical properties of cationic starches and its effect on the paper strength of recycled paper by different degree of substitution.
The optimal of reaction temperature for cationization of cassava starch, using an aqueous alcoholic-alkaline process of starch : water ratio ＝ 1:1:1.5,temperature is between 46.5 ~ 48℃, the optimal pH is between 11.5 ~ 12.0, and the optimal reaction time is about 5 hours.
Not only the crystal of kernel of cationic starch were not destroyed by different degree of substitution and extended reaction time, but also the kernel appearance and birefringence of cationic starch were remain intact. More over, the particle size of cationic starch also did not change with increasing the degree of substitution.
Results showed that the cationic starch with different degree of substitution had a higher peak viscosity than native ones. It seams irregular, although the holding strength and final viscosity among all samples were different. Unlike native starch, the viscosity curve of cationic starch after retrogradation had a rather flat line.
The enthalpy (△H), onset temperature (T0) and peak temperature (Tp) of cationic starch were lower than native starch. With the increase 10 cationic agent dosage, onset temperature and peak temperature were decreasing apparentls.
By added cationic starch in recycled pulp, the retention / dewatering and bursting strength of paper were increased but the ring crush were decreased.
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