Phospholipids as Co-Stabilisers of Pea Protein Emulsions: From Rapid Adsorption to Long-term Interfacial Structures

Although plant proteins often show good emulsifying capacity, their slow adsorption and limited ability to form viscoelastic interfacial networks can lead to droplet coalescence and compromise emulsion stability. Phospholipids can achieve high interfacial coverage rapidly and may enhance emulsion stability, provided they co-adsorb with the protein rather than displace it. Here, we investigate how saturated and unsaturated phosphatidylcholines (PC 18:0 and PC 18:1) affect interfacial adsorption, network formation, and emulsion stability by a globulin-rich pea protein fraction (GRF) across multiple timescales (milliseconds to hours) and length scales (molecular to micrometre). Microfluidics, confocal laser scanning microscopy (CLSM), droplet-size analysis, and interfacial shear and dilatational rheology, including General Stress Decomposition, were combined to relate interfacial structure to emulsion stability. GRF alone adsorbed slowly and formed weak interfaces, resulting in large initial oil droplet sizes that coalesced rapidly. The addition of phospholipids increased short-term coalescence stability and reduced initial droplet size. Saturated PC 18:0 adsorbed simultaneously with GRF, forming elastic mixed networks and enhanced emulsion stability on both short (ms-s) and long timescales (min-h). Unsaturated PC 18:1 exhibited high interfacial activity and displaced GRF at concentrations above the critical reverse micelle concentration (CRMC), resulting in viscous, PC-dominated interfaces (Gi’ < Gi’’) and low long-term emulsion stability. When PC 18:1 was applied at concentrations of one-tenth of its CRMC (0.1 x CRMC), predominantly elastic interfacial networks were formed (Gi’ > Gi’’), indicating co-existence with protein. Together, these results demonstrate that stable pea protein-phospholipid emulsions can be formed by tuning phospholipid structure and their concentration relative to CRMC.