Ultrasound-assisted process to improve proteins recovery from industrial canola and soybean byproducts

An ultrasound-assisted process is proposed to obtain protein isolates from canola and soybean byproducts. A laboratory-scale probe system (24 kHz, 400W) was used for protein extraction and six levels of energy density were analyzed. Different mixtures of solvents (water, ethanol, methanol, acetone) and temperatures were tested for removing phenolic compounds, and the best results were obtained with ethanol-water (8:2 v/v) and energy density of 104 kJ/L, which minimize protein losses at that step. After extraction of phenolic compounds, samples were alkalinized (pH 12 or 9.5), subjected to ultrasound treatment and the protein precipitated at the isoelectric pH. The highest yield on protein extraction was obtained with 1:20 meal: NaOH solution ratio, applying 150 kJ/L at constant temperature (30 °C), increasing the protein recovery, 72.5% for canola meal and 37.5% for soybean meal, compared to the conventional method. The solubility of both isolates obtained with ultrasound improved ~ 50% at a pH close to neutral and basic, with an increase in free sulfhydryl groups, without significant effects of ultrasound treatment on the subunit fractions of the proteins. These results provide alternatives to develop protein isolates from an undervalued by-product, with better techno-functional properties that can be employed in the food industry.