Stabilisation of oil-in-water emulsions under alkaline conditions by egg-white-gel-derived peptides and xanthan gum complexes

Xanthan gum (XG) was added to egg-white-gel-derived peptides to create complexes and stabilise nanoemulsion under high-pressure homogenisation. This procedure was performed to investigate the stabilisation of nanoemulsions by small-molecule peptides under alkaline conditions (pH 11.0). The emulsion stability, including ionic, temperature and storage stability, and lipid oxidation were explored. The inclusion of XG altered the spatial structure of the peptides, which created cross-linked entangled aggregates. Furthermore, the protein peptides forming complexes with XG following sonication and heat treatment were more stable. They exhibited higher absolute ζ-potential values, surface hydrophobicity, and lower interfacial tension. The emulsion stabilised by 2.0 mg/mL complexes at a pH of 11.0 revealed that the addition of XG enhanced the homogeneity of the nanoemulsion droplets, presenting a single high particle size peaks and absolute ζ-potential values. The surface-absorbed protein content and the concentrations of the emulsions stabilised by sonication and the heat-treated peptides and XG complexes were higher. Moreover, the fluorescence microscope observed a higher surface coverage thickness of the emulsion droplets, effectively preventing oil oxidation. The emulsion environmental stability measurements found that the prepared emulsions were sensitive to salt ions and stable to temperature. Together with heat-treated peptides and XG complexes, sonication-stabilised emulsions exhibited better stability during storage. This study advances the possibility of stabilising the nanoemulsions of small-molecule peptides under alkaline conditions.