High internal phase emulsions stabilized by pea protein isolate-EGCG-Fe3+ complexes: Encapsulation of β-carotene

Protein complexes have great potential for forming and stabilizing high internal phase emulsions (HIPEs) loaded with bioactive compounds. In this study, we investigated the potential of three types of complexes, namely pea protein isolate (PPI), PPI-epigallocatechin gallate (EGCG) and PPI-EGCG-Fe3+, to form and stabilize HIPEs with a 75% oil phase volume fraction. Initially, the impact of pH and emulsifier type on emulsions performance was investigated. Confocal laser scanning microscopy (CLSM) and particle size analysis showed that all three complexes could form HIPEs that remained stable under acidic and neutral conditions. These emulsions contained uniform oil droplets coated by a layer of the complexes. Notably, the PPI-EGCG-Fe3+ complexes formed HIPEs with the highest thermal and storage stability, which was attributed to the denser and thicker interfacial coatings. These emulsions also protected encapsulated beta-carotene from degradation when exposed to light and thermal stress conditions. Furthermore, we measured lipid digestion and beta-carotene bioaccessibility in the emulsions using an in vitro digestion model. The PPI-EGCG-Fe3+ stabilized emulsions not only exhibited slow fatty acid release but also enhanced beta-carotene bioaccessibility (46.5%) under simulated small intestine conditions. This study demonstrates the potential of using protein-polyphenol-Fe3+ complexes to form and stabilize HIPEs, which may then be used to enhance the bioaccessibility and bioactivity of hydrophobic nutraceuticals.