Lipid and Protein Interactions in Oil-in-Water Emulsions

Oil-in-water emulsions are colloidal systems in which lipid droplets are dispersed in an aqueous phase and stabilised by surface-active proteins. At the oil–water interface, proteins adsorb to form a viscoelastic film that governs droplet size, aggregation and stability. Lipid oxidation generates primary hydroperoxides and secondary aldehydes that can diffuse to the interface and react covalently with amino acid side chains. Such protein lipoxidation alters interfacial rheology, reduces emulsifying capacity and may compromise nutritional quality. Conversely, protein conformational changes and interfacial crowding can modulate oxygen diffusion and antioxidant partitioning, thereby influencing the kinetics of lipid peroxidation. Understanding these bidirectional interactions is crucial for the design of stable food, cosmetic and pharmaceutical emulsions, where oxidative stability, texture and bioavailability are paramount. Recent advances have shed light on the molecular pathways by which lipid-derived radicals modify protein structure and on strategies—such as antioxidant addition and protein engineering—to mitigate interfacial oxidation.

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Lipid and Protein Interactions in Oil-in-Water Emulsions publication trend

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Technical terms

Oil-in-water emulsion: A dispersion of oil droplets within a continuous aqueous phase, stabilised by amphiphilic molecules such as proteins.

Lipid oxidation: A chain reaction in which unsaturated fatty acids react with molecular oxygen to form hydroperoxides and secondary degradation products.

Protein lipoxidation: Covalent modification of proteins by lipid‐derived reactive carbonyl species, leading to structural and functional changes.

Whey protein isolate (WPI): A highly purified dairy protein fraction commonly used as an emulsifier due to its surface‐active properties.

Malondialdehyde (MDA): A reactive secondary product of lipid oxidation that readily forms adducts with protein amino groups.

Thiobarbituric acid reactive substances (TBARS): A spectrophotometric assay measuring the concentration of malondialdehyde and related compounds as an index of lipid peroxidation.

References

1. Epicatechin Inhibited Lipid Oxidation and Protein Lipoxidation in a Fish Oil-Fortified Dairy Mimicking System. Foods (2023).
2. Comparative Study of Oxidative Structural Modifications of Unadsorbed and Adsorbed Proteins in Whey Protein Isolate-Stabilized Oil-in-Water Emulsions under the Stress of Primary and Secondary Lipid Oxidation Products. Foods (2021).