Molecular Characterization of Whey Protein Hydrolysate Fractions with Ferrous Chelating and Enhanced Iron Solubility Capabilities

The ferrous (Fe²⁺) chelating capabilities of WPI hydrolysate fractions produced via cascade membrane filtration were investigated, specifically 1 kDa permeate (P) and 30 kDa retentate (R) fractions. The 1 kDa-P possessed a Fe²⁺ chelating capability at 1 g L^–1 equivalent to 84.4 μM EDTA (for 30 kDa-R the value was 8.7 μM EDTA). Fourier transformed infrared (FTIR) spectroscopy was utilized to investigate the structural characteristics of hydrolysates and molecular interactions with Fe²⁺. Solid-phase extraction was employed to enrich for chelating activity; the most potent chelating fraction was enriched in histidine and lysine. The solubility of ferrous sulfate solutions (10 mM) over a range of pH values was significantly (<i>P</i> < 0.05) improved in dispersions of hydrolysate fraction solutions (10 g protein L^–1). Total iron solubility was improved by 72% in the presence of the 1 kDa-P fraction following simulated gastrointestinal digestion (SGID) compared to control FeSO₄·7H₂O solutions