치환도별 양이온성 옥수수전분의 물리화학적 특성

Cationic starch is widely used in the paper-making process as a wet-end additive to improve sheet strength and to provide better retention of fines as well as fillers. Cationic starches of different origins are available with various degree of substitution (DS). The physicochemical properties of cationic corn starches are characterized as having degree of substitution that range from 0.02 to 0.06. With the increase of DS, the water holding capacity of cationic starch increased to more than three times that of a natural starch. On the other hand, iodine absorption ability decreased as DS increases, possibly because the intensity of starch granules decreased, although the X-ray diffraction pattern displayed little changes in the peak intensity of the cationic corn starch. This suggested that the decreased integrity of starch granules was due to the substitution of cationic groups concentrated in the amorphous region. Rheological characterization showed that 1% gelatinized cationic corn starch was a pseudoplastic fluid, whereas natural corn starch was a Newtonian fluid. The viscosity of the cationic corn starch increased with increments in the DS, but decreased with rising electrical conductivity of the solution. The viscosity was proportional to the DS at a constant shear rate and swelling power sharply increased around the gelatinization temperature region.