Emulsifying behavior of plant proteins investigated via surface hydrophobicity and molecular weight distribution

Plant proteins exhibit wide variability in emulsifying behavior due to differences in composition, molecular structure, and processing history. This study investigated the relationship between intrinsic physicochemical properties and emulsifying behavior of eleven commercial protein isolates and concentrates derived from bovine milk, soy, canola, faba bean and pea. Key properties including solubility, surface hydrophobicity (SH), molecular weight distribution (MWD), and zeta-potential of the protein ingredients were characterized and evaluated in relation to emulsion droplet size. Among these parameters, MWD showed a moderate correlation with emulsion droplet size (R² = 0.64), while SH and zeta potential exhibited no meaningful correlation (R² < 0.1). When MWD and SH were evaluated together, a clearer trend and separation emerged. Plant proteins with both high molecular weight and low surface hydrophobicity showed a tendency to form heavily flocculated emulsions. This flocculation likely resulted from slower interfacial adsorption and incomplete surface coverage, leading to droplet flocculation at early stages of emulsification. Under a specific set of formulation and processing conditions, emulsions prepared with alkaline-extracted pea and faba protein had smaller droplet size than their air-classified counterparts, likely due to their lower MWD and modified interfacial behavior induced by alkaline treatment. These findings show that the combination of MWD and SH could be useful in understanding the emulsifying behavior of commercial plant protein ingredients and helping in the screening and formulation of plant protein ingredients for food and beverage applications.