Development and characterization of a walnut protein hydrolysate-Fe-vitamin C complex: Enhancing iron bioavailability through phytase-assisted modification

  • Food Chem. 2025 Oct 3;496(Pt 1):146646. doi: 10.1016/j.foodchem.2025.146646.
Sibao Zhao  1 ,  Wenzhen Qiu  1 ,  Yang Sun  1 ,  Feng Jin  2 ,  Fengjun Wang  3
Affiliations
  • 1. State Key Laboratory of Efficient Production of Forest Resources, Beijing Key Laboratory of Forest Processing and Safety, School of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China; Hebei Province Key Laboratory of Sustainable Utilization and Development of Forest Food Resources, China.
  • 2. State Key Laboratory of Efficient Production of Forest Resources, Beijing Key Laboratory of Forest Processing and Safety, School of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China; Hebei Province Key Laboratory of Sustainable Utilization and Development of Forest Food Resources, China. Electronic address: [email protected].
  • 3. State Key Laboratory of Efficient Production of Forest Resources, Beijing Key Laboratory of Forest Processing and Safety, School of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China; Hebei Province Key Laboratory of Sustainable Utilization and Development of Forest Food Resources, China. Electronic address: [email protected].
PMID: 41086629 DOI: 10.1016/j.foodchem.2025.146646
Abstract

In this study, walnut protein was treated with phytase and Alcalase to produce walnut protein hydrolysate (WPHP). Phytase hydrolysis reduced phytic acid‑iron interactions, exposing peptide binding sites and enabling strong Fe2+ chelation rate of 80.78 ± 0.58 %. Vitamin C was subsequently added to form WPHP-Fe-vitamin C complex, which was stabilized through Fe-carboxyl and Fe‑carbonyl coordination and hydrogen bonding, accompanied by structural reorganization. The complex exhibited a porous microstructure, particle size of 345.76 nm, solubility of 90.22 % at pH 7.0, and stabilized under varying pH, ionic, and thermal conditions. Compared with WPHP-Fe, the complex showed higher iron retention. Caco-2 assays revealed that vitamin C mitigated the inhibitory effect of phytic acid and significantly enhanced Fe2+ uptake via the DMT1 pathway, reaching 9.47 ± 0.13 μg/well at 120 min. These results highlight the complementary roles of phytase and vitamin C and support the complex as a peptide-based iron supplement.

Keywords
Caco-2 cell; Iron; Phytic acid; Vitamin C; Walnut protein hydrolysate.
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