Structure of lipid emulsions formulated with sodium caseinate

CRISTIÁN HUCK IRIART; MARÍA SOLEDAD ÁLVAREZ CERIMEDO; ROBERTO J. CANDAL; MARIA LIDIA HERRERA

Congreso; Hiroshima International Forum on Functionality of Lipids; 2010

The development of an effective strategy to prevent undesirable changes in the properties of a particular food emulsion depends on the dominant physicochemical mechanism(s) responsible for the changes. In practice, two or more of these mechanisms may operate in concert. It is therefore important for food scientists to identify the relative importance of each mechanism, the relationship between them, and the factors that influence them, so that effective means of controlling the stability and physicochemical properties of emulsions can be established [1]. Stability of emulsions formulated with 10 wt% oil (concentrated fish oil, CFO, sunflower oil, SFO, or olive oil, OO), sodium caseinate (NaCas) concentrations varying from 0.5 to 5 wt%, giving oil-to-protein ratios of 20-2, and 0, 20, 30 or 40 wt% aqueous trehalose solution was studied by Turbiscan. Samples were also analyzed by particle size distribution, microstructure, relaxation times T1 and T2, and small angle X-ray scattering (SAXS). The main mechanism of destabilization in a given formulation strongly depended on oil-to-protein ratio. As evidenced by the BS-profile changes with time, emulsions formulated with 0.5 and 1 wt% NaCas destabilized mainly by creaming while for the 2 wt% NaCas concentration, both creaming and flocculation mechanisms, were involved. The main destabilization mechanism for the 3, 4 or 5 wt % NaCas emulsions was flocculation. Stability of emulsions was also affected by formulation. Creaming rate varied with the oil composition: the higher content of unsaturated fatty acids the slower creaming rate. The presence of a sugar in the aqueous phase notoriously decreased creaming and flocculation rates. Trehalose also diminished the volume-weighted mean diameter (D4,3) and modified T1 and T2 values. Emulsions behavior as described by NMR strongly suggested changes in their structure for sugar addition. It was reported that values of q in SAXS analyses, reciprocal lattice spacing, increased with NaCas concentration showing that the aggregation state of the protein changed as a function of its concentration [2]. The slightly increased of q values with trehalose also suggested that trehalose had an effect further than viscosity changes since the aggregation state of the protein changed with the aqueous phase formulation.