Development of Pickering emulsions stabilized by pea protein isolate particles: Responsiveness to protein concentration and induced heating

Abstract: Particles derived from plant proteins, such as pea protein, have received great interest due to their abundance and suitability for food applications. The stability of protein-stabilized emulsions is highly affected by parameters such as protein concentration and oil-to-water ratio. However, the underlying mechanism for enhancing emulsifying properties of plant proteins is a continually expanding research area. Although pea protein has been studied extensively, less work has focused on interfacial protein. Therefore, the objective of this study was to assess the effects of interfacial protein and heating on emulsion stability. Varying concentrations of soluble pea protein isolate in 0.01M phosphate buffer (pH=7) with 10% oil was used to produce Pickering emulsions. A high-shear mixer was used to pre-homogenize the dispersions prior to homogenization with a Microfluidizer at 20 and 40 MPa. Induced heating at 90℃ for 30 min before homogenization was also tested. Excess non-adsorbed protein was estimated by centrifuging emulsions and quantifying the protein in the aqueous fraction via bicinchoninic assay. Physical characteristics (size, zeta potential, and polydispersity index of the emulsions) were measured using a Zetasizer Nano ZS. The conditions that yielded the most stable droplets were the emulsions formulated with a protein concentration of 1.5 g/100 mL and high-pressure processing of 20 MPa (oil droplet size: ~200 nm). All emulsions formulated with 1.5 or 3 g/100 mL of protein exhibited a large proportion of non-adsorbed protein ( >50%). Heating did not appear to affect emulsion droplet size. However, the particle heating step might be beneficial for droplet size maintenance, preventing droplet coalescence. Overall, these findings suggest that factors other than interfacial protein (e.g., excess protein, processing conditions) can have notable effects on pea protein-stabilized systems. This work has broader industrial implications as it demonstrates strategies to improve ingredient functionality in emulsion-based systems.