Linear viscoelasticity of O/W sucrose-palmitate emulsions

Abstract

Linear dynamic viscoelastic properties of concentrated O/W emulsions containing sunflower oil (60–80% O), water and a sucrose palmitate (1–5%) of HLB = 15 were obtained in this study. Droplet size distribution data was also analyzed.

All the emulsions presented a significant linear viscoelastic range that increased with oil and SE concentrations. The linear viscoelastic behaviour obtained is typical of a highly concentrated dispersion with strong elastic interactions that lead to an extensive flocculation and confer a high stability to the system. A plateau region, characteristic of an elastic network, is observed at intermediate frequency or time scale. After a critical shear stress the structural network broke down very rapidly.

The linear viscoelastic functions of these emulsions were reproduced by using the generalized Maxwell model having up to seven relaxation elements. The discrete relaxation spectrum obtained from this model turnsout to be useful in relation to the microstructure of the system.

An increase in SE or oil concentration increased the linear viscoelastic functions of the emulsions studied. This increase cannot be explained only in terms of droplet size and polydispersity. An increase in droplet interactions should be also considered.