Effect of interfacial compositions on the physical properties of alginate-based emulsion gels and chemical stability of co-encapsulated bioactives

Alginate-based emulsion gels with different oil fraction (0–20%) and interfacial compositions were developed to understand the filling roles of oil droplets, and the gels were used to simultaneously encapsulate a lipophilic and a hydrophilic bioactives. Glucono-delta-lactone (GDL) was used to induce the release of Ca2+ from CaCO3, which allowed the cross linking of alginate to form gel network and trap the oil droplets. The increase in oil fraction significantly reduced syneresis degree and improved water holding capacity (WHC) of the emulsion gels with tween 20 (TW), negatively charged WPI (-/WPI), whey protein aggregates (WPA) at the interface. Significantly increased fracture force was observed in the emulsion gels with positively charged WPI (+/WPI) with the increase in oil fraction. In the systems containing TW, -/WPI or WPA, the inclusion of oil phase mostly resulted in lower fracture force than the systems without oil. However, all the systems had higher relaxed stress (at equilibrium) with higher oil content. Swelling tests revealed that the systems with an oil content of 10% had the highest swelling ratio, and the gels containing +/WPI had the lowest swelling ratio among all the systems. When EGCG and β-carotene were encapsulated within the emulsion gels, they presented a synergistic effect on heating stability as both EGCG and β-carotene had higher stability when encapsulated simultaneously than individually.