Effects of Ultrasonic Assisted Freezing on Physicochemical Properties and Molecular Structure of Wheat Starch in Dough

In this study, ultrasonication was applied in the whole process of dough freezing and in the maximum ice crystal formation zone, respectively, to explore the effects of ultrasonic-assisted freezing on the physicochemical and structural properties of wheat starch in dough. The results showed that compared with the frozen samples without ultrasonication, the peak viscosity of wheat starch in the dough decreased by 8.6% and 14.5%, the trough viscosity reduced by 17.1% and 13.7%, and the final viscosity increased by 11.3% and −3.6%, respectively, when ultrasonic-assisted freezing was applied in the maximum ice crystal formation zone and the whole process. The consistency coefficient and shear resistance of wheat starch system in dough were maintained to a certain extent by applying ultrasonic in the maximum ice crystal formation zone and the whole process. The consistency coefficient of starch decreased by 19.0% and 23.3%, and the shear structure resilience increased by 4.0% and 7.2%, respectively. Compared with the frozen samples without ultrasonication, the relative crystallinity of wheat starch in the sonicated dough was reduced, and the short-range ordered structure of starch molecules was reduced to a certain extent. In summary, the application of ultrasonic field refines the ice crystals and slows down the damage to the internal structure of wheat starch in the dough during the freezing process. A comparison between the two ultrasound processes, it can be speculated that the effect of ultrasonic application in the whole process of dough-freezing is significantly better than that in the maximum ice crystal formation zone.