Evolution of the rheological properties of oil-in-water emulsions during the emulsification process and storage

Abstract

This paper deals with the evolution of the rheological properties and droplet size distributions (DSD) of oil-in-water emulsions, stabilized by non-ionic surfactant, with time. The emulsification process has been followed by the evolution of the torque with the emulsification time and follows a first-order kinetic equation. From the experimental results obtained it is apparent that the rheology and DSD of the emulsions studied depends on the emulsification time and temperature of emulsification, as well as, the agitation speed. An increase in the emulsification time, at 15ºC, yields lower values of the mean droplet size and, subsequently, an increase in the linear viscoelasticity functions of the emulsions. However, above 25ºC, the emulsification process may be modified because a higher degree of coalescence may take place at long emulsification time. A «depletion-flocculation» mechanism due to the presence of surfactant, in form of micelles, in the continuous phase of the emulsions.

Keywords

• emulsification
• oil/water emulsion
• rheokinetic
• rheology
• viscoelasticity