Improved protein extraction technology using deep eutectic solvent system for producing high purity fava bean protein isolates at mild conditions

This study aimed to extract fava bean proteins using an eco-friendly deep eutectic solvent (DES) containing choline chloride and a glycerol-based system. Protein extraction conditions were optimized using response surface methodology, and the extracted protein was characterized in comparison to the protein extracted using a conventional alkaline solution. The optimum conditions obtained using the RSM model were: 28:1 w/w liquid: solid ratio, 1:2 w/w choline chloride: glycerol molar ratio, 50 °C temperature, 1 h extraction time, and 40% w/w water content. Under these optimum conditions, protein content, protein yield, and protein recovery rates of 92.33 ± 2.28%, 65.42 ± 6.53%, and 23.15 ± 2.31% were achieved. Alkaline extraction showed similar protein content (92.50 ± 1.36%) but lower protein yield (60.76 ± 1.16%) and recovery rate (21.74 ± 0.19%) when compared to DES-extracted proteins (P < 0.05). The secondary structure analysis revealed an increased α-helix (21.37%) content in DES-extracted proteins compared to alkaline-extracted proteins (10.68%). Moreover, the alkaline-extracted proteins showed intermolecular β sheets as protein aggregates (7.61%) and an increased percentage of β-turns (19.71%). The molecular weight distribution pattern of proteins extracted from both methods showed more similarities. Overall, DES protein extraction could be an alternative to the conventional alkaline extraction method, promoting sustainable plant protein production from fava beans for use in new food formulations.