Protein-Stabilized Emulsion Systems

Proteins are widely exploited as emulsifying agents due to their amphiphilic nature, allowing them to adsorb at oil–water interfaces and form stabilising layers around dispersed droplets. The adsorption process involves rapid diffusion of protein molecules to the oil–water boundary, unfolding and reorganisation of their tertiary structure to expose hydrophobic patches to the oil phase and hydrophilic regions to the aqueous phase. Such interfacial films reduce interfacial tension, inhibit droplet coalescence and creaming, and contribute to the viscoelastic properties of emulsions. Variations in protein source, molecular conformation, degree of modification and environmental parameters such as pH, ionic strength and temperature all influence colloidal stability. Crosslinking, enzymatic hydrolysis and complexation with polyphenols or polysaccharides have emerged as strategies to tailor film rigidity, droplet charge and digestion behaviour, with implications for controlled release, nutrient bioavailability and shelf-life. Applications span food formulations, pharmaceuticals, cosmetics and agrochemicals, where protein-stabilised systems enable delivery of lipophilic actives, reduction of synthetic surfactants and improvement of sensorial attributes. Recent research has increasingly emphasised the interplay between interfacial rheology, microstructure and functional performance under processing and simulated gastrointestinal conditions, reflecting a broader trend towards design of next-generation emulsions with predictable behaviour in complex environments.

Research from Nature Portfolio

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Research from all publishers

Innovative work on egg white protein–proanthocyanin complexes has demonstrated markedly enhanced emulsion stability and controlled lipid digestion. By forming covalent and non-covalent complexes between egg white proteins and proanthocyanins, researchers achieved a rigid interfacial layer that resisted aggregation and exhibited favourable wettability. Studies of digestion kinetics and free fatty acid release revealed that covalent complexes slowed lipid breakdown, offering routes to modulate nutrient absorption. Electrostatic and hydrophobic interactions were shown to underpin film thickness and mechanical strength.

Ultrasound-assisted whey protein isolate (WPI) emulsions containing black pepper essential oil have been characterised for their physical and bioactive properties. Ultrasonication reduced droplet size and improved protein adsorption, leading to nano-emulsions with enhanced antioxidant and antibacterial activity. Variation of WPI concentration enabled optimisation of viscosity, droplet morphology and stability, and evaluation of free-radical scavenging and microbial inhibition indicated potential for natural preservative systems in food matrices.

Protein-Stabilized Emulsion Systems publication trend

The graph below shows the total number of articles in protein-stabilized emulsion systems across all publications each year (not limited to Nature Index journals).

Technical terms

Emulsion: A biphasic dispersion in which one liquid (oil or water) is finely distributed as droplets within another continuous liquid phase, stabilised by surface-active agents.

Interfacial adsorption: The process by which amphiphilic molecules migrate to and bind at the boundary between oil and water, forming a film that reduces interfacial tension.

Zeta potential: The electric potential at the slipping plane of a particle in dispersion, indicative of surface charge and a predictor of colloidal stability.

Covalent complex: A structure formed when chemical bonds link protein molecules to ligands (e.g. polyphenols), enhancing interfacial film rigidity and resistance to digestion.

References

1. Egg White Protein–Proanthocyanin Complexes Stabilized Emulsions: Investigation of Physical Stability, Digestion Kinetics, and Free Fatty Acid Release Dynamics. Molecules (2024).
2. Effects of Whey Protein Isolate on Black Pepper Essential Oil Ultrasound-Assisted Emulsion on Physical Characteristics, Antioxidant Activity, and Antibacterial Properties. Jurnal Ilmu dan Teknologi Hasil Ternak (2022).