Emulsifying stability of enzymatically hydrolyzed egg yolk granules and structural analysis

Abstract Egg yolk granules (EYG) are natural and unique protein-lipid complexes, but their application in the food industry is limited because of their poor solubility and emulsifying properties. In this paper, the structural characteristics, emulsifying properties and interfacial adsorption were compared between the untreated granules (UG) and the enzymatically hydrolyzed granules (EG) (treated with subtilisin). EG-stabilized emulsion did not form cream at 0.2%–1.0% protein concentrations, while UG-stabilized emulsion formed a cream layer quickly after emulsification. The emulsion stability index of EG increased by nearly 8 times increased from 0.2% to 1.0%. The scanning electron microscope, confocal laser scanning microscopy (CLSM) and optical microscopy indicated that enzymatic hydrolysis changed the aggregation state of the EYG in powder, suspension and emulsions. Also, it was proven that enzymatic hydrolysis strengthened the internal hydrogen bonding and increased surface wettability and surface charge. The CLSM images confirmed that EYG are Pickering particles. The interfacial tension dropped to 8.4 mN/m after enzymatic hydrolysis. The SDS-PAGE analysis of the protein showed that enzymatic hydrolysis induced changes in the granules and interface, resulting in a strong adsorption capacity for EG at the interface. The enzymatic modifications of EYG promoted their emulsifying properties and showed that EYG have the potential to be used as novel food-grade particles through structural modification.