Interactions with soy lecithin regulate the emulsification capacity of pea protein: Effects of soy lecithin concentration

Interactions between pea protein isolate (PPI, 1%) and soy lecithin (SL, 0.1%-2%) in bulk phase and the impacts on the emulsifying properties of PPI were investigated. Fluorescence spectra, molecular docking, and infrared spectroscopy verified that PPI and SL formed complexes in aqueous phase via hydrophobic interactions, hydrogen bonds, and electrostatic interactions. CMC of SL was increased to 1% in presence of PPI (1%). Increased particle size, surface charge, and surface hydrophobicity of PPI-SL complexes with increasing SL concentrations were observed. Addition of SL transformed the composition of oil/water interface from pure PPI into a mixture of PPI and SL, which decreased the surface tension and resulted in smaller droplet size of emulsions. The inclusion of all PPI-SL complexes enhanced emulsion stability during storage. Incorporating SL below 1% also showed similar protective effects for curcumin against UV irradiation compared to pure PPI. The study may provide a theoretical basis for the rational non-covalent combination of pea protein and lecithin as complex emulsifiers.