Preparation and Physicochemical Characterisation of Aqueous Extracts of Wheat Bran Assisted by Low-frequency High-intensity Ultrasound

In this work, to achieve the comprehensive preparation and utilization of the main water-soluble components (proteins, polysaccharides, polyphenols) in wheat bran, low-frequency high-intensity ultrasound (constant power of 840 W, processing time of 10~30 min) was used to enhance the preparation of these water-soluble components, and then their physicochemical properties were characterised. It was found that the protein content of the aqueous extract obtained after 20 min of low-frequency high-intensity ultrasound was increased by about 16.1% compared with the control group, while the polysaccharide and polyphenol contents reached the highest level after 30 min of ultrasound treatment, which were increased by 12.0% and 18.8%, respectively, compared with the control group. In addition, the average particle size of the aqueous extract of wheat bran prepared by low-frequency high-intensity ultrasound-assisted treatment for 30 min decreased from 248 nm to 183 nm, the absolute value of the Zeta potential increased from 4.0 to 5.5 mV, and the microstructure showed a significant porous state. However, the thermal properties, spectroscopic and X-ray diffraction results pointed out that the aqueous extracts prepared by low-frequency high-intensity ultrasound-assisted treatment for 10 min had the loosest structure, higher degree of unfolding and crystallinity, and exhibited the strongest surface hydrophobicity (Ho), emulsifying activity and oil-water interfacial stabilisation, which were of superior value for application.