Omega-3 microalgal oil-in-water nanoemulsions stabilized by red seaweed extracts: Physical and oxidative stability

Abstract

Seaweed extracts were obtained using a three-step extraction procedure involving pretreating Palmaria palmata in aqueous solutions of pH 3, 6, and 9, followed by sequential enzymatic/alkaline extractions. The extracts (Ext−3, Ext−6, Ext−9) obtained were characterized by measuring their protein, phenolic, and carbohydrate contents, as well as their degree of hydrolysis (DH), in vitro antioxidant activities, and dynamic interfacial tensions. Moreover, the effects on the physical and chemical stability of 5 % microalgal oil-in-water nanoemulsions were evaluated over 21 days. There were no significant differences in the droplet size of the nanoemulsions stabilized by the three extracts (p = 0.762–1.000). Additionally, Turbiscan analysis indicated that the nanoemulsions remained physically stable at the end of the storage period. Red seaweed extracts inhibited oxidation, with peroxide values of <10 meq/kg oil, compared to >20 meq/kg oil in the control nanoemulsion at Day 21. The control nanoemulsion had high levels of volatile oxidation compounds, including 1-penten-3-ol (4230 ± 200 ng/g), (E,E)-2,4-heptadienal (3110 ± 120 ng/g), and 2-ethylfuran (2400 ± 180 ng/g). The addition of the seaweed extracts significantly reduced the concentrations of these volatile compounds (p < 0.0001). These results suggest that seaweed extracts can be used as natural antioxidants in emulsified food products.