Impact of combined enzyme and ultrasound treatments on protein extraction from potato trimmings and soybean okara

Cell wall degrading enzymes are valuable tools for enhancing plant protein extractability. Here, enzymatic pretreatments of potato trimmings and soybean okara to improve the protein recovery during subsequent mild alkaline extraction were evaluated. Additionally, combinations with ultrasonication treatments were explored to further enhance the efficiency of the enzyme-assisted process. Cellulase pre-treatment increased the crude protein yield from potato trimmings (76%) compared to the control (57%). Pectin lyase pre-treatment of okara boosted the crude protein yield from 17% to 35%. For both types of biomass, applying ultrasound treatment (2000 J/g fresh weight [FW]) at pH 5.0 before, during, or after the enzymatic incubation proved less effective than performing ultrasound-assisted alkaline extraction (pH 9.0, UAAE) after the enzymatic pre-treatment. A pectinase treatment followed by a short UAAE (2000 J/g FW) increased the crude protein yield up to 80% for potato trimmings and up to 54% for okara. Ultrasonication pH is an important parameter to consider to optimally enhance protein solubilization, since the treatment is ineffective close the protein isoelectric point. The molecular weight distributions of extracted potato trimming proteins were similar for all tested treatments. Okara pectinase pre-treatment allowed the extraction of a less-aggregated protein fraction, while additional UAAE solubilized more aggregated proteins. In conclusion, this study provides new insights into combined enzymatic and ultrasonic strategies to increase the efficiency of plant protein extraction processes.