Effect of the lupin protein/surfactant ratio on linear viscoelastic properties of oil‐in‐water emulsions

This work studies the influence of a low‐molecular‐weight emulsifier/lupin protein ratio on the linear viscoelastic properties of oil‐in‐water emulsions. With this aim, dynamic viscoelasticity tests, as well as droplet‐size distribution measurements, were done. Four types of low‐molecular‐weight emulsifiers were used. From the results, we conclude that emulsions stabilized by emulsifier blends show, in general, lower values of both the linear viscoelasticity functions and Sauter diameter than those found when lupin protein was used as the only emulsifier. Protein‐free emulsions may have similar parameter values when the surfactant induces a structured gel‐like continuous phase. Evolution of the linear viscoelastic functions with the composition of the mixed emulsifier has been explained on the basis of changes in interdroplet interactions, rheological behavior of the continuous phase, and surface viscoelasticity of the adsorbed emulsifier layer. However, the above‐mentioned behavior cannot be explained from changes in the emulsion droplet‐size distribution.