Preparation of physically modified oat starch with different sonication treatments

Oat starch granules were subjected to ultrasound treatment using either a 20 kHz horn sonicator at intensities of 39, 48, 63 W/cm2 or an ultrasound bath operating at an intensity of 5 W/cm2 for 10 and 20 min. Morphological, structural and functional properties of native and sonicated samples were investigated. SEM micrographs revealed the presence of fissures and pores on the surface of starch granules treated with the horn sonicator. An obvious size reduction was also observed at the highest sonication intensity. Ultrasound treatment increased the amylose content, swelling power, solubility, Transmittance, water, and lipid holding capacity; while the gel hardness diminished after sonication. The syneresis results revealed that higher amounts of water were expelled from the sonicated starch gels during 5 days of storage as compared to the native counterpart. The onset, peak and conclusion temperatures of gelatinization increased; while, the gelatinization temperature range decreased due to sonication. A decrease in the degree of crystallinity as well as the enthalpy of gelatinization demonstrated that the crystalline structures of oat starch granules were destroyed to some extent upon sonication, while the A-type crystalline pattern remained unchanged.