Structure of gels produced from sodium caseinate

CIRSTIAN HUCK IRIART; MARIA SOLEDAD ALVAREZ CERIMEDO; ROBERTO JORGE CANDAL; MARIA LIDIA HERRERA

Campinas

Otro; Activity Report Brazilian Synchrotron Light Laboratory; 2009

LNLS proyecto 6030

Previous studies in our laboratory showed that the main mechanism of destabilization in a given formulation depended on NaCas concentration and particle size distribution. Emulsions with mean diameter in volume (D4,3) around 0.5 µm and formulated with 0.5 and 1 wt% NaCas destabilized mainly by creaming of small particles. For the 2 wt% NaCas emulsion, both mechanisms, creaming and flocculation, were involved. Migration of small particles occurred during the first 24 h and then bigger particles formed by aggregation moved up. For the 3, 4, and 5 wt% NaCas the main mechanism was flocculation. Confocal images of these samples showed that the spatial distribution of droplets was markedly different for both, creaming and flocculation processes. The images corresponding to emulsions stabilized with 0.5 or 1 wt% NaCas showed a homogeneous droplet distribution. Differences in both images are in agreement with the decrease in D4,3 with NaCas concentration. A dye was dissolved in the fat phase which appeared in red. When protein concentration was 2, 3 or 4 wt% emulsions presented aggregates/flocculates which were absent in 0.5 and 1 wt% emulsions. In these emulsions there were more protein for the coverage of oil droplet surface and higher protein concentration in the aqueous phase. Surprisingly, a concentration of 5 wt% NaCas produced an emulsion with a very homogeneous droplet distribution and a lower D4,3. The absence of aggregates/flocculates is in agreement with the great stability with time showed for this emulsion. The structural dissimilarities among emulsions could result in differences in SAXS patterns. Therefore, the aim of the present work was to describe the structure of emulsions formulated with different concentrations of NaCas as stabilizer. The effect of fat phase type and sugar type and concentration were also examined.