Ultrasound-assisted walnut ( <i>Juglans sigillata</i> ) peptide-iron chelates (U-LLECHS-Fe): Preparation, characterization, stability analyses, and iron absorption promotion

To enhance iron chelation capacity, walnut peptides-ferrous chelates were prepared by ultrasound-assisted chelation based on single factor optimization, with investigations into their chelation mechanisms and stability. Results demonstrated that ultrasonication significantly enhances chelation efficiency, with U-LLECHS-Fe with the highest ferrous ion content of 100.48 ± 3.79 μg/mg. The coordination bond between LLECHS and Fe2+ was predominantly mediated by Glu3, involving coordination bonds formed by the N-H, C=O, and -COOH. Stability analysis indicated that LLECHS-Fe and U-LLECHS-Fe exhibited high Fe2+ retention rates at 25 ~ 55 °C, exceeding 70% and 85%, respectively. At pH 10, iron retention rates reached 96.91% and 98.12%. The final iron released levels in the intestinal phase were 77.87 ± 0.61 μg/mL and 74.63 ± 1.05 μg/mL. The cellular transport efficiency of U-LLECHS-Fe was 2.5 and 5.8 times that of LLECHS-Fe and FeCl2·4H2O, respectively. This study provides a theoretical basis for developing novel, highly efficient iron supplements using ultrasound-assisted chelation technology, providing a theoretical basis for their application in functional foods and iron-fortified products.