Interfacial engineering of alkyl-chain-tailored Pickering foams for quinoa protein fractionation: mechanisms and functional upgrading.

The continuous foam fractionation of low-surface-activity plant proteins, such as those from quinoa, is fundamentally hindered by the recovery-enrichment paradox driven by unstable foam dynamics. Herein, we engineered tunable Pickering stabilizers by in-situ functionalizing calcium carbonate nanoparticles (CNPs) with homologous alkyl-chain modifiers (C4, C8, C12) to precisely regulate interfacial drainage. Obeying Traube's rule, the long-chain laurate modified nanoparticles (SL-CNPs) optimized interfacial wettability (θ ≈ 90o) and maximized detachment energy at a minimal dosage (100 mg/L), achieving "arrested coalescence". During continuous separation, SL-CNPs effectively addressed the separation paradox, delivering a 94% recovery alongside a competitive 15-fold enrichment ratio. We mechanistically decoupled this performance, revealing that excessive particle dosage triggers detrimental "interfacial competitive displacement," while the isoelectric point (pH 4.5) induces "isoelectric aggregation" that plugs liquid drainage channels. Crucially, the intense gas-liquid physical shear did not passively separate but actively induced "interfacial-driven structural remodeling" of the quinoa proteins. This partial conformational unfolding drastically amplified the proteins' techno-functional properties (e.g., a three-fold increase in water holding capacity) and triggered a non-linear exponential surge in in vitro hypoglycemic (α-glucosidase inhibitory) activity. This work proposes a scalable, multiscale interfacial engineering strategy for the simultaneous purification and functional upgrading of sustainable plant-based proteins.