This research explored the influences of ultrasonic and thermal treatments on the structure, functional properties, and beany flavor of soy protein isolate (SPI). In comparison with traditional thermal treatment, ultrasonic treatment effectively induced protein structural unfolding and exposure of hydrophobic groups, which reduced relative content of α-helix, increased relative content of β-turn, β-sheet and random coil, and improved the solubility, emulsifying and foaming properties of SPI. Both treatments significantly decreased the species and contents of flavor compounds, such as hexanal, (E)-2-nonenal, (Z)-2-heptenal and (E)-2-hexenal in SPI. The relative content of hexanal in the major beany flavor compound decreased from 11.69% to 6.13% and 5.99% at 350 W ultrasonic power and 150 s thermal treatment procedure, respectively. After ultrasonic treatment, structural changes in SPI were significantly correlated with functional properties but showed a weak correlation with flavor. Conversely, the opposite trend was observed for thermal treatment. Thus, using ultrasonic treatment to induce and stabilise the denatured state of proteins is feasible to improve the functional properties and beany flavor of SPI.

• Ultrasound technology was used to modify rice bran protein. • Chlorogenic acid was combined with rice bran protein to prepare functional complex. • By ultrasonic treatment, the properties of the complex were improved. • The emulsification performance of the complex was better at 200 W 10 min conditions.

The present paper aims to study the effect of cellulase hydrolysis and high-pressure homogenization on the structural and physicochemical properties of rice bran dietary fiber (RB-DF). Scanning electron microscopy showed that cellulase treatment led to the formation of a porous structure on RB-DF surface. High-pressure homogenization affected the laminated microstructure of RB-DF, leading to the formation of an irregular and loose surface structure. X-ray diffraction demonstrated that joint processing destroyed the amorphous hemicellulose and cellulose regions, and changed the crystallinity of RB-DF, albeit with a minor impact on the crystalline region of cellulose. Fourier transform infrared spectroscopy indicated that combined processing promoted dissociation of some glycosidic bonds in fiber structure, exposing the hydroxyl groups in cellulose, thus improving their ability to bind water molecules. Thermogravimetric analysis showed a significant decrease in the thermal decomposition temperature of RB-DF (p <0.05) as well as a decrease in thermal stability after combined processing. Cellulase hydrolysis and high-pressure homogenization treatment did not improve their oil holding capacity, but significantly increased water holding capacity, swelling capability, and cation exchange capacity of RB-DF. Thus, enzymatic hydrolysis and high-pressure homogenization treatment can change the structure of RB-DF, exposing a large number of hydrophilic groups and enhancing hydration, obtaining uniform RB-DF particle.