Thermoreversible gelation of caseinate-stabilized emulsions at around body temperature

We have formulated food-grade protein-stabilized emulsions (30 vol% vegetable oil, 4 wt% sodium caseinate) which exhibit heat-induced gelation at around body temperature. Prior to emulsification, these systems have the continuous phase pH adjusted to between 6.8 and 5.3 and various concentrations of calcium chloride added. The minimum CaCl2 content required to cause gelation on heating decreases with decreasing pH, and the gelation temperature also decreases with decreasing pH. Under certain conditions the small-deformation rheological change associated with the heat-induced gelation has been found to be reversible on back-cooling to ambient. The systems have also been studied with regards to viscometry and phase separation. Emulsion compositions associated with depletion flocculation by excess non-adsorbed protein are shown to be sensitive to both the ionic calcium content and the pH. (C) 2003 Elsevier Science Ltd. All rights reserved.