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Effects on the structure and properties of sweet potato starch under single frequency ultrasound of 25, 80 kHz and dual-frequency ultrasound of 25 and 80 kHz were investigated at the same treating conditions else. Dents and pores were found by SEM at the surface of starch with both ultrasounds. Starch-iodine complex analysis showed above ultrasounds destroyed amylopectin and starch chains. FT-IR indicated that with ultrasonic treatments, the functional groups of starch were not destroyed, but its crystal structure was damaged. As a result, its crystalline index decreased. Brabender curves showed that the peak viscosity of starch with dual-frequency ultrasound was 14.09% lower than that of the native starch. In addition, the solubility and transmittance of starch increased by ultrasound, and the solubility went up as ultrasonication time was increased. It reached the maximum when the starch was treated for 60 min by dual-frequency ultrasound, which increased by 2.69% compared to that of native starch. The starch being treated by dual-frequency ultrasound for 30 min showed maximum transmittance, increasing it by 5.1% compared to the native starch; however, continuously increasing ultrasonic treatment resulted in a decrease of transmittance. Therefore, compared to single frequency ultrasound, dual-frequency ultrasonic treatment caused more obvious changes to the structure and properties.

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After ultrasonic treatment, the transparency of corn starch paste improved, but its hardness, brittleness, elasticity, adhesiveness, conglutination degree, chewiness and recoverability decreased, as well as starch crystallinity and enthalpy values. DFU was found to be more effective than SFU.

Safflower seed oil rich in linoleic acid is a kind of functional health oil. The effects of various parameters, such as solvents, liquid–solid ratio and extraction time, on both ultrasonic‐aided and conventional safflower seed oil extractions were investigated through experiments. The results indicated that n‐hexane was a better solvent for the two above‐mentioned extraction methods. Under the following conditions: temperature 35C, liquid–solid ratio 5, extraction time 30 min and ultrasound power 300 W, the oil extraction yield reached 27.02%. However, with the conventional safflower seed oil extraction method, it was only 25.00% when the technical parameters were: temperature 50C; liquid–solid ratio 6; extraction time 60 min. Obviously, the advantages of ultrasonic extraction were as follows: reducing extraction temperature; decreasing solvent quantity; saving time; and improving oil yield. In addition, on the basis of Fick's first law, the kinetic models of ultrasonic extraction and conventional extraction were compared and authenticated. The results showed that a close match was found between experimental data and kinetic equations, and the equations could better simulate safflower oil extraction process. This approach provided a theoretical background for the extraction of safflower seed oil. PRACTICAL APPLICATIONS In this work, an efficient extraction method – ultrasound‐aided extraction method for safflower seed oil – was acquired. Compared with conventional extraction method, the advantages of ultrasonic extraction were: reducing extraction temperature, decreasing solvent quantity, saving time and improving oil yield. In addition, equipments used in ultrasound‐aided extraction and operation were simple and high efficiency. Therefore, this ultrasonic technology has a brilliant application prospect in extraction of safflower seed oil and other vegetable oils.