Betaine/urea deep eutectic solvent with non-precipitative recovery enables high-quality soy protein isolation: Mechanistic and functional characterization.

Abstract

Conventional alkaline extraction-isoelectric precipitation can induce protein denaturation and reassociation via pronounced pH shifts. Herein, betaine/urea deep eutectic solvent (DES-2)-assisted extraction was combined with membrane filtration and direct dialysis for non-precipitative soy protein recovery. The recovered protein showed purity comparable with that obtained via conventional alkaline extraction-isoelectric precipitation (85.09% ± 0.68% vs 85.91% ± 0.74%) and a higher yield (17.45% ± 0.95% vs 13.65% ± 1.35%). Quantum chemical calculations showed that betaine and urea formed a stable hydrogen-bonded network. Molecular dynamics simulations of 11S glycinin indicated enhanced solvation and conformational relaxation with increased radius of gyration and solvent-accessible surface area. Directly dialysed DES-extracted protein showed smaller particle size; less subunit reassociation; lower disulphide bond content; higher free sulphydryl group content; and improved solubility, foaming and emulsifying properties than commercial soy protein isolate. DES-2-assisted extraction combined with direct dialysis may improve soy protein recovery and techno-functional properties.

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