Curcumin-loaded nanoemulsions stability as affected by the nature and concentration of surfactant

Nanoemulsions containing 0.5% w/w corn oil enriched with 0.4% w/w curcumin, sodium-alginate (1.0% w/w) and 0.5, 1.0 or 2.0% w/w of surfactant, were assessed, including particle size (nm), zeta-potential (mV) and turbidity over time. Furthermore, nanoemulsions encapsulation efficiency (EE), antioxidant capacity (AC) and release kinetics were studied. Nanoemulsions showed particle sizes <= 400 +/- 3 nm and effectively reduced droplets interfacial tension with negative zeta-potential values (<= - 37 mV), regardless the concentration of surfactant. Nanoemulsions with 2.0% w/w lecithin did not suffer destabilization phenomena during almost 86 days of experiment, whereas those containing Tween 20 or SMP at the same concentrations were destabilized after 5 days or along 24 h, respectively. Despite EE of nanoemulsions was above 75%, just in lecithin-stabilized nanoemulsions it was directly correlated to AC. Therefore, this work contributes to elucidate the influence of lecithin, Tween 20 and SMP on curcumin encapsulation and stabilization of curcumin-loaded nanoemulsions.