Development and characterization of novel ultra-stable high internal phase Pickering emulsions gel: Interface structure, stabilization mechanism, and applications

While both protein-polysaccharide complexes and continuous phase gelation showed great potential for stabilizing high internal phase Pickering emulsions (HIPPEs), it is not known which strategies are more effective and adaptive. In this work, HIPPEs gel was prepared by Ca2+-induced continuous phase gelation of ovalbumin (OVA)-low methoxyl pectin (LMP) electrostatic complexes particles (OLECP)-stabilized HIPPEs. The microstructure, rheological properties, stability, and application of HIPPEs and HIPPEs gel were systematically investigated and compared at different LMP concentrations. The results showed that, compared to HIPPEs, continuous phase gelation effectively improved the viscoelasticity, water binding capacity, and hardness of HIPPEs gel due to its robust and developed interface architecture. CLSM and cryo-SEM observations revealed that OLECP interconnected with each other in the continuous phase to form an advanced network architecture in HIPPEs. Whereas, a firm gel network structure and a thick interfacial layer were found in HIPPEs gel. More importantly, with increasing pectin concentration, the cross-linking phenomenon of OLECP mainly at the interface, transformed into the gelation behavior of excess pectin molecules dominating in the continuous phase. LMP contributed to the formation of a finer 3D gel network structure and a firmer interfacial layer, providing a smaller oil droplet size and superior stability for HIPPEs gel. The photochemical stability of curcumin was increased from 16.1 ± 1.5 % to 93.7 ± 2.2 % after encapsulation in HIPPEs gel. In vitro digestion results testified that HIPPEs gel (10:15, w/w) can promote fat hydrolysis (from 32.35 ± 3.06 % to 45.52 ± 2.75 %) and enhance the bioaccessibility of curcumin (from 20.1 ± 1.5 % to 32.8 ± 2.6 %) compared to bulk oil. Besides, compared with HIPPEs, HIPPEs gel showed poor printability because of improper printing adaptability and liquidity. In a nutshell, our work provides valuable information for developing novel HIPPEs gels for various food applications.