CONICET | Buscador de Institutos y Recursos Humanos

O/W Nanoemulsions stabilized by sodium caseinate and containing sunflower oil as dispersed phase were prepared using a combination of a high-energy homogenization and evaporative ripening methods. The effects of protein concentration (1 to 4 wt.%) and sucrose addition (2 to 8 wt.%) on physical properties were analyzed by dynamic light scattering (DLS), Turbiscan analysis, confocal laser scanning microscopy, and small angle X-ray scattering (SAXS). To evaluate nanostructure from the SAXS patterns, the Guinier-Porod model was selected. Droplets sizes were smaller (~ 100 nm in diameter) than the ones obtained by other methods (200 to 2000 nm in diameter). The stability behavior was also different. If migration occurred (1 wt.%), sedimentation was noticed. However, in most cases, as droplets were so small, gravitational forces were negligible. On the contrary, when they showed destabilization the main mechanism was flocculation. Stability of nanoemulsions increased with increasing protein concentrations. Nanoemulsions with 3 or 4 wt% NaCas were slightly turbid systems that remained stable for at least two months. According to Turbiscan results, aggregates remained in the nano range showing small tendency to aggregation. Droplet sizes calculated from the SAXS model were in agreement with values measured by DLS. Guinier-Porod parameters showed that the ratio ?protein concentration at the interface/free protein? increased with the increased in total concentration, resulting in greater stability than conventional emulsions. Although in less magnitude, sucrose also increased droplet coverage. Due to the small diameter of flocs, protein-protein interactions were weak and therefore systems were stable for long time.