  Protein-stabilised emulsion gels can be studied in the theoretical framework
of colloidal gels, because both protein assemblies and droplets may be
considered as soft colloids. These particles differ in their nature, size and
softness, and these differences may have an influence on the rheological
properties of the gels they form. Pure gels made of milk proteins (sodium
caseinate), or of sub-micron protein-stabilised droplets, were prepared by slow
acidification of suspensions at various concentrations. Their microstructure
was characterised, their viscoelasticity, both in the linear and non-linear
regime, and their frequency dependence were measured, and the behaviour of the
two types of gels was compared. Protein gels and droplet gels were found to
have broadly similar microstructure and rheological properties when compared at
fixed volume fraction, a parameter derived from the study of the viscosity of
the suspensions formed by proteins and by droplets. The viscoelasticity
displayed a power law behaviour in concentration, as did the storage modulus in
frequency. Additionally, strain hardening was found to occur at low
concentration. These behaviours differed slightly between protein gels and
droplet gels, showing that some specific properties of the primary colloidal
particles play a role in the development of the rheological properties of the
gels.
