Bioactive Protein-Phlorotannin Interfaces From Fucus vesiculosus Enhance Physical and Oxidative Stability of Oil-in-Water Nanoemulsions.

Abstract

Oil-in-water (O/W) nanoemulsions have been widely used in the food industry, but they face challenges such as droplet aggregation, creaming, and lipid oxidation. In the present study, the nanoemulsion itself was investigated as a food-relevant colloidal model system prepared with sunflower oil, soy lecithin, and protein and phlorotannin fractions extracted from the edible brown seaweed Fucus vesiculosus. Formulations were prepared by high-pressure homogenization and characterized for physicochemical, interfacial, emulsifying, rheological, microstructural, storage, oxidative, digestive, and release properties. The particle sizes of the nanoemulsions ranged from 166 to 260 nm, and the protein-phlorotannin mixtures had ζ-potential values as low as -58.10 ± 0.45 mV, indicating markedly increased negative surface charge. Interfacial protein adsorption reached 66.17%, and the apparent encapsulation efficiency (EE) of phlorotannins reached 97.88%. Phlorotannin-rich formulations markedly suppressed primary lipid oxidation, reducing the peroxide value increase rate by up to 98.3% compared with control T1 during 24 days of storage at 25°C, while also limiting secondary oxidation. Protein-containing formulations were more resistant to creaming, droplet growth, and turbidity loss during refrigerated storage. In vitro digestion showed that phlorotannins influenced protein hydrolysis, lipid digestion, and bioactive release. Spectroscopic, rheological, and microscopic analyses revealed formulation-dependent structural and interfacial characteristics, while molecular docking provided exploratory support for possible interactions between the selected F. vesiculosus protein model and nanoemulsion components. The results establish composition-interface-function relationships within the food-relevant nanoemulsion system and provide a basis for subsequent development of emulsion-based foods, in which matrix-, processing-, and sensory-dependent variables need to be evaluated separately. PRACTICAL APPLICATIONS: Fucus vesiculosus protein and phlorotannins can be used to create stable, antioxidant-rich O/W nanoemulsions, maintaining droplet integrity and controlling bioactive release. The nanoemulsion was evaluated as a food-relevant colloidal system, and the results clarify how interfacial composition governs its physical stability, oxidative protection, rheological behavior, digestion, and bioactive release. Because the study focuses on the intrinsic structure-function relationships of the nanoemulsion itself, incorporation into a specific finished food would represent a subsequent product-development stage involving additional matrix-, processing-, and sensory-dependent variables. The findings therefore provide formulation principles for the future design and evaluation of stable, antioxidant-enriched emulsion-based food systems.