Ultrasonic modification of starch - Impact on granules porosity

Rice, corn, wheat, and potato starch granules suspended in water or ethanol were treated with ultrasounds at frequency of 20 kHz and power 170 W for 30 min. Porosity of starch was investigated in terms of specific surface area (SBET), average pore size and pore size distribution using low-temperature nitrogen adsorption method. The significant increase of SBET was noted for all the studied starches sonicated in water and for potato starch modified in ethanol. Ultrasonic treatment influenced the average diameter of mesopores (2 nm < width < 50 nm) differently. The significant increase of this parameter was noted for wheat and rice starches suspended in ethanol and for potato starch granules suspended in water, but in the case of corn starch, the obtained value was slightly lower after sonication in water. Modification of starch with ultrasounds resulted in the formation of new pores in the studied range of diameter.