Structural and Physical Changes in Ultrasound-Assisted Frozen Wet Gluten

Ultrasound-assisted freezing is a novel food-freezing technique which is of benefit to frozen food quality. Studies of the structural and physical changes in the ultrasound-assisted frozen wet gluten system illustrate how the ultrasound irradiation improves the frozen dough quality. The microtopography of ice crystals in frozen wet gluten was observed indirectly by scanning electron microscopy; the ice crystals were smaller and more uniform in wet gluten frozen using the ultrasound-assisted technique than in wet gluten frozen without ultrasound. Fourier transform infrared spectroscopy was used to monitor the changes in the secondary structure of a frozen gluten heavy water system during frozen storage. It was determined that there were no noticeable changes in the structure of the wet gluten frozen using the ultrasound-assisted technique. However, the structure of the wet gluten frozen without ultrasound became unordered. The freezable water content in the frozen wet gluten was determined by differential scanning calorimetry. Compared with conventional freezing, more water was frozen using ultrasound-assisted freezing. Furthermore, the freezable water content in the wet gluten frozen using the ultrasound-assisted technique did not increase during frozen storage. Ultrasonic cavitation promoted the primary and secondary nucleation of ice in the wet gluten and loosened the weak interactions between the gluten and the water. Consequently, the existence of a microstructure with small and uniform ice crystals was noted, which was determined to be beneficial with regard to reducing the deterioration of the gluten network and, hence, improving the quality of the frozen food.