Seaweed-Derived Proteolytic Extracts as Natural Interfacial Stabilizers for Oxidatively Sensitive DHA-Rich Oil-in-Water Emulsions

In this work, we examined how the choice of protease in sequential enzymatic/alkaline extraction affects seaweed-derived extracts and their ability to stabilize docosahexaenoic acid (DHA) oil-in-water emulsions. Extracts produced with Alcalase (Ac-A), Flavourzyme (Fz-A), and Formea Prime (Fp-A) were compared. Ac-A achieved the highest protein extraction yield (∼95%) and phenolic content (∼17 µg GAE/mL) and showed a significantly higher ratio of essential to total amino acids (p < 0.05). Although radical scavenging activity was similar among extracts, Ac-A exhibited stronger Fe²⁺ chelation (p < 0.05). Ac-A and Fz-A reduced interfacial tension more effectively than Fp-A, supported by confocal laser scanning microscopy. Emulsions showed comparable droplet size (75–82 nm), negative zeta potential, and viscosity (∼1.0–1.5 centipoise [cP]) (p > 0.05). All extracts improved oxidative stability compared to the negative control (no antioxidant); Ac-A and Fz-A showed lower peroxide value trajectories than Fp-A (p < 0.05), whereas butylated hydroxytoluene (BHT) remained most effective. Extracts delayed tocopherol depletion and reduced volatile formation, with Ac-A performing closest to BHT. Alcalase-derived extracts thus offer multifunctional interfacial and antioxidant protection for omega-3 emulsions.

Practical Applications: The findings support marine-derived extracts as clean-label ingredients for omega-3-enriched food products. They can be applied in systems where both physical and oxidative stability are required, such as fortified beverages, emulsified sauces, and nutraceutical formulations. Their dual functionality may reduce the need for multiple additives, simplifying ingredient lists, and improving product appeal. In addition, the use of seaweed-based materials offers opportunities for sustainable sourcing and valorization of marine biomass, which aligns with current industry trends toward natural and environment-friendly solutions.