High internal phase emulsions stabilized with amyloid fibrils and their polysaccharide complexes for encapsulation and protection of β-carotene

In present study, lysozyme amyloid fibrils and their complexes with polysaccharides were investigated for stabilizing high internal phase emulsions (HIPEs). Linear polysaccharides, alginate and lambda-carrageenan and branching ones, low and high methyl esterified pectins electrostatically bind to amyloid fibrils in nematic phase, forming well dispersed coacervates showing birefringence under polarized light. Comparatively, the polysaccharides associate with the globule protein monomers, leading to the precipitated coacervate. Interaction with the polysaccharides enhances the strength of the amyloid fibrils network. After converting protein monomers to amyloid fibrils, the binding between polysaccharides and the proteins is significantly enhanced with the affinity constant (KD) from sub-nmol to pmol level. For the first time, amyloid fibrils are found to stabilize HIPEs with highly packed polyhedral geometries in microstructure, which is dependent on protein concentration and volume fraction of the internal oil phase. The HIPEs stabilized with the amyloid fibril-polysaccharide complexes are stronger than those stabilized with only amyloid fibrils, which is attributed to the increase in the modulus of the disperse phase. The HIPE systems can encapsulate and stabilize beta-carotene against ultraviolet irradiation, thermal treatment and iron ions in aqueous phase, which is mainly attributed to the protection effects of the interfacial lysozyme amyloid fibril membrane.