Relationship between stability and structure of sodium caseinate-stabilized emulsions

JUAN M. MONTES DE OCA AVALOS; CRISTIÁN HUCK IRIART; FEDERICO L. JARA; MARIA V. BORRONI; ROBERTO J. CANDAL; MARIA LIDIA HERRERA

St. Louis

Congreso; AOCS Annual Meeting & Expo; 2019

AOCS

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 alsodifferent. If migration occurred (1 wt.%), sedimentation was noticed. However, in most cases, as droplets were so small, gravitationalforces were negligible. On the contrary, when they showed destabilization the main mechanism was flocculation. Stability of nanoemulsions increased with increasing protein concentrations. Nanoemulsions with 3or 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 sizescalculated 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 alsoincreased droplet coverage. Due to the small diameter of flocs, protein-protein interactions were weak and therefore systems were stablefor long time.