Rheological properties of soybean protein isolate gels containing emulsiondroplets

Rheological properties of soybean protein gels containing various volume fr actions oil droplets have been studied at small and large deformations. Dyn amic viscoelastic properties of soybean protein isolate gels were determine d as a function of the volume fraction of oil droplets stabilised by the sa me protein, both in absence and presence of 0.2 M sodium chloride (NaCl). T he storage and loss moduli were higher if NaCl was added. For both conditio ns, they increased with increasing oil volume fraction during the heating a s well as the cooling stage. Furthermore, gel formation started at a lower temperature with increasing oil volume fraction. The increase in the moduli with increasing volume fraction of oil droplets was stronger than predicte d by Van der Peels theory for a simple filled gel containing single interac ting stiff emulsion droplets. This effect was attributed to aggregation of the emulsion droplets. Fracture properties of gels with different oil volum e fraction and oil droplet size were determined at pH 7.0, in the presence of 0.2 M NaCl, by a uniaxial compression test. Compressive stresses of the gels containing oil droplets of 1.17 mum were higher than those containing droplets of 2.70 mum, especially at higher volume fractions of oil droplets . The fracture strain did not depend on the volume fraction of oil droplets . (C) 2001 Elsevier Science Ltd. All rights reserved.