Sodium caseinate-stabilized nanoemulsions: physical properties and nano/microstructure

CANDAL, ROBERTO JORGE; JUAN MANUEL MONTES DE OCA AVALOS; HERRERA, MARÍA LIDIA

Roma

Congreso; Innovations in Food Science and Human Nutrition; 2018

Innovinc

Nanoemulsions are defined as a thermodynamically unstable colloidal dispersion with a dispersed phase containing small spherical droplets with radius sizes smaller than 100 nm. Nanoemulsions stabilized by sodium caseinate (NaCas) were prepared using a combination of a high-energy homogenization and evaporative ripening methods. The effects of protein concentration and sucrose addition on physical properties were analyzed by dynamic light scattering (DLS), Turbiscan analysis, confocal laser scanning microscopy (CLSM) and small angle X-ray scattering (SAXS). 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. These emulsions were not destabilized by creaming. 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. Selecting a protein concentration at which droplets aggregates were too small to interact to each other, flocculation may be avoided for a long time, even without addition of a co-adjuvant such as sucrose. The 4 wt.% NaCas-stabilized nanoemulsion was stable without sugar in the aqueous phase. CLSM images showed that nanoemulsions contained droplets sizes below microscope resolution. Homogeneous structures without flocs were obtained in all cases. Parameter Nagg (aggregation number) from SAXS model, which quantify the number of NaCas molecules on droplet surface, increased with protein or sucrose concentration indicating that sodium caseinate had less tendency to aggregation and therefore its molecules were absorbed on droplets surface.