Kappa-carrageenan improves mechanical and rheological properties of egg yolk low-density lipoprotein gels with an interpenetrating network structure

Low-density lipoprotein (LDL) is the most nutrient-rich fraction in egg yolks, but the spherical particle structure of LDL limits its gel properties. In this study, we introduced κ-carrageenan (KC) into the LDL system to improve the texture, mechanical strength, microstructure, phase behavior and rheological properties of LDL gels. In particular, the gel hardness of LDL-KC hydrogels containing 1.25% KC increased to 604.87 g. In the LDL system alone, hydrophobic interactions, disulfide bonding, hydrogen bonding, and electrostatic interactions between LDL molecules resulted in a layered stacking structure. After the introduction of KC into the LDL system, the hydrophobic interactions and disulfide bonds in the system significantly increased, while hydrogen and electrostatic interactions were decreased, which was attributed to the inhibition of intermolecular hydrogen and ionic bonding of LDL by KC and activation of intermolecular hydrophobic interactions and disulfide bonds in LDL. These interactions allow LDL and KC to form an interpenetrating network structure with a backbone of KC and LDL aggregates uniformly distributed in the KC network. This study can guide related industries in using KC to modulate the rheological and texture properties of LDL and improve the quality of egg yolk-based food products.