Walnut peptides-calcium chelate: fabrication, characterization and calcium release rate evaluation

The global increase in aging leads to a high incidence of metabolic bone diseases such as osteoporosis which have become a serious public health problem. The timely supplementation of calcium can effectively alleviate this problem. However, the lower bioavailability of conventional calcium supplements seriously limits its application. In the present study, a new calcium supplement was constructed with walnut peptides (WP) as calcium ion carriers, for which the structure was characterized, and its calcium release capacity was evaluated. Under the optimal preparation process conditions, the calcium chelation rate of walnut peptides-calcium chelate (WP-Ca) reached 92.64%. The incorporation of calcium ions significantly altered the structure of WP, as revealed by the redshift and enhancement of the original ultraviolet (UV) and fluorescence spectra. Morphological analysis displayed that the surface of WP-Ca was rough as granular crystal. Infrared spectroscopy and amino acid analysis indicated that the carboxyl, hydroxy and amino groups located on amino acid residues such as glutamic acid, threonine and arginine might be the binding sites between WP and calcium ions. WP-Ca exhibited outstanding calcium release rates under different temperature, pH and gastrointestinal digestion conditions, indicating its potential for further development as a novel calcium supplement.