A thermoreversible emulsion gel based on sodium caseinate

Abstract

Thermoreversible gelation is demonstrated for a milk protein-based oil-in-water emulsion system. The emulsifying agent is sodium caseinate with a controlled amount of ionic calcium added (15–30 mM, depending on the pH). On heating to 30–40°C, a concentrated liquid-like emulsion is converted into a flocculated emulsion gel that supports its own weight. Small-deformation rheology gives quantitative confirmation of the large increase in viscoelasticity on heating over an interval of just a few degrees in the range 35–45°C (depending on the pH). The emulsion gel ‘melts’ again slowly on cooling, and the return to the original low-viscosity state is accelerated by stirring. As followed viscometrically, the thermoreversible behaviour shows good reproducibility on repeated temperature cycling at different pH values in the range 5.5–6.8. The main driving force for the gelation is presumably an increase in the strength of hydrophobic interactions with increasing temperature.