A specific peptide with calcium chelating capacity isolated from whey protein hydrolysate

A specific peptide displaying calcium-binding capacity was purified from whey protein hydrolysate. The isolation procedures included DEAE anion-exchange chromatography, Sephadex G-25 gel filtration, and reversed-phase high-performance liquid chromatography (RP-HPLC). The amino acid sequence of the peptide was determined to be Phe-Asp (FD), using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). The calcium binding capacity of FD reached 73.34 μg/mg, and the amount increased by 116% when compared to the whey protein hydrolysate complex. The structural properties of the purified peptide were identified using fluorescence spectra, Fourier transform infrared spectroscopy (FTIR), and 1H nuclear magnetic resonance (NMR) spectroscopy, respectively. The results indicated that the amido and carboxy groups of the purified peptide were transformed during chelation. The oxygen atoms of the carboxy group and the nitrogen atoms of the amido group could chelate calcium to form coordinate bonds by donating electron pairs. Furthermore, FD-Ca chelate was found to be more stable and absorbable than CaCl2 under both acidic and basic conditions. Our findings suggest that the purified dipeptide Phe-Asp has the potential to be used as a calcium-binding ingredient in dietary supplements.