Effect of ultrasonic intensity on structure and properties of wheat starch-monoglyceride complex and its influence on quality of norther-style Chinese steamed bread

The effect of ultrasonic intensity on the wheat starch-monoglyceride complex (WSG) and the influence of WSG on the quality of steamed bread were investigated. With the increase of ultrasonic intensity, the complex index (CI) of the WSG first increased and then decreased. X-ray diffraction showed that with the addition of monoglycerides, the crystal type of starch changed from A-type to V-type. Fourier transform infrared spectroscopy showed that the absorption peak of the WSG was weaker than that of the control, and the characteristic peaks of the WSG complex appeared. Compared to native starch, the resistant starch (RS) content of WSG increased. When the ultrasonic intensity was 375 W, the CI value and RS content of WSG samples reached the maximum. WSG treated with 375 W of ultrasonic intensity was added to the steamed bread. The results showed that WSG addition decreased the specific volume and springiness of steamed bread, but dramatically increased its spread ratio, hardness, and chewiness. However, the excessive addition of WSG was not conducive to the quality of steamed bread. Flour blends with 5-10% WSG produced steamed bread with total scores comparable to the control flour. The results would provide new insights into starch under ultrasound treatment.