Monitoring both fat crystallization and self-assembly of sodium caseinate in model emulsions using synchrotron X-ray diffraction

Abstract

X-Ray diffraction analysis at small angles is proposed as a nondestructive method for characterization of emulsions. The paper focuses on determinations of both, the concentration of sodium caseinate (SC) used as a stabilizer and the organization of triglyceride crystals, located outside and within emulsion droplets, respectively. Measurements performed at very small angles using ID 02a at a sample-to-detector distance of 6.5 m made it possible to monitor the SC submicelle size variations at q∼0.03 Å⁻¹ while exploring a SC/water binary system. Comparison with the scattering found in model emulsion shows congruent results. The characterization of the crystalline organizations of triacylglycerols was also performed simultaneously at q∼0.1 Å⁻¹. Phase transitions were directly observed within the emulsion droplets. Both characterizations allowed direct quantitative determinations of the submicellar SC concentration in the presence of emulsion and of the respective proportions of the various polymorphic forms of the fat within emulsion droplets. These experiments have shown that, knowing the primary concentrations of all ingredients, X-ray scattering at very small angles can be used, to monitor submicellar casein aggregation and fat polymorphism in a single analysis.

Acknowledgements: The authors thank Nestlé (Beauvais, Vers-chez-les-Blanc) and ANRT (Paris, France) for supporting this research. EEC support for ESRF beamtime at ID02a is also acknowledged.