Effect of high-intensity ultrasound on the compositional, physicochemical, biochemical, functional and structural properties of canola (Brassica napus L.) protein isolate

The objective of this study was to investigate the impacts of high-intensity ultrasound treatments on the compositional, physicochemical, biochemical, functional and structural properties of canola protein isolates (CPI). Aqueous canola protein suspensions were sonicated at 40 kHz for 15 min and 30 min. The moisture content, water activity, bulk density and the L-star and a(star) color parameters of the CPI decreased due to the ultrasound; however, the in vitro protein digestibility was not modified by the treatment. Glutelin (57.18%) was the main protein fraction in the canola protein isolate. SDS-PAGE demonstrated that there were no changes in the protein electrophoretic patterns, thus indicating that sonication did not break the covalent bonds. However, the ultrasound treatment improved the protein solubility, oil absorption capacity and the emulsifying, gelation and foaming properties, but these improvements depended on the pH and ultrasound exposure time. Scanning electron microscopy revealed that the ultrasound treatment disrupted the microstructure of the CPI by exhibiting larger aggregates as a lyophilized powder. In addition, there was an increase in the surface hydrophobicity and a decrease in the size of the particles of the canola protein due to the ultrasound effects, which indicates a destruction of the particles or a dissociation of the protein aggregates in the canola protein dispersions. These results suggest that ultrasound treatment is a valuable tool for improving the characteristics of canola proteins for use in foods.