Stability of high-density lipoprotein-calcium ion complex stabilized high internal phase Pickering emulsions based on ion cross-linking

Abstract

The present work aimed to explore the feasibility of using egg yolk high-density lipoprotein (HDL) as emulsifier to prepare high internal phase Pickering emulsions (HIPEs), and to understand the mechanism of Ca²⁺ as ion cross-linking agent in improving the emulsifying stability. HDL-Ca²⁺ complexes were formed via electrostatic interactions under different pH conditions and Ca²⁺ concentrations. The results showed that Ca²⁺ was able to connect the anion groups of HDL particles through ionic bridges. Ca²⁺ increased the oil–water interface activity of HDL via forming a thick HDL-Ca²⁺ interfacial layer. Moreover, Ca²⁺ ion further linked with HDL particles at the interface and inhibited the movement and coalescence of the droplets, increasing the stability of the HIPEs. The most stable HIPE was prepared under the condition of Ca²⁺ concentration of 10 mM at pH 5. The research showed that Ca²⁺ as a cross-linking agent is effective to enhance the emulsifying stability of HDL for preparation of HIPEs, which provides a new idea for improving the stability of protein based HIPEs.