Effects of Calcium Chelators on Colloidal Stability and Interfacial Activity of Egg Yolk Granules

Egg yolk granule is the sedimentary protein fraction of egg yolk. Granules are supramolecular assembly of high-density lipoprotein and phosvitin driven by Ca2+ bridges. Despite for high nutrition value and potential interfacial activity, the large particle size and poor colloidal stability severely restricted the functionality and industrial applications of granules. This study tried to dissociate granules with calcium chelators to improve their water dispersity and interfacial activity. The results showed that Na5O10P3, EDTA-2Na, and C6H5Na3O7 could dissociate micro-sized granules into nanoparticles with good colloidal stability at pH 7.0. The dissociation effect was less obvious or absent at pH 5.5 and pH 3.0. The non-protein binding Ca2+ concentration analysis confirmed that calcium chelators dissociated granules by chelating Ca2+ and disrupting Ca2+ bridges. FTIR and SDS-PAGE demonstrated that calcium chelators-induced dissociation was a physical process without any changes in chemical bonds or protein profiles of granules. The interfacial activity of dissociated granules was significantly improved. Dissociated granules could reduce the interfacial tension at the hexane-water interface more effectively. Emulsions prepared by dissociated granules showed small particle size and improved storage stability. The results of this study are beneficial to deep processing of egg yolk and applications of granules as a healthy emulsifier.