Enzymatic hydrolysis promotes the formation of iron-soy protein composite nanoparticles: characterization and...

Proteins with metal-chelating capacity hold the potential to form iron-protein composites, contributing to addressing suboptimal absorption and poor sensory quality of food iron fortifiers. In this study, uniform iron-SPI nanoparticles (50-90 nm, PDI < 0.3) with desirable colloidal properties could be successfully fabricated via coupled Flavorzyme hydrolysis with alkaline-heating treatment of soy protein isolate (SPI). Herein, enzymatic hydrolysis lowered the required heating pH from 12.0 to 10.0 by regulating the degradation and aggregation behavior of SPI subunits and strengthening the composite structure dominated by disulfide bonds. Compared with FeSO₄ and ferrous bisglycinate (Fe-Gly), the nanoparticles induced less organoleptic change and lipid oxidation in food matrices, demonstrating superior stability and sensory compatibility. Moreover, the nanoparticles retained over 80% soluble iron after in vitro digestion and exhibited improved bioaccessibility compared to FeSO₄ in Caco-2 cell models. These findings reveal the potential of iron-SPI composite nanoparticles as effective iron fortifiers.