Rheology of protein-stabilised emulsion gels envisioned as composite networks. 1 -- Comparison of pure droplet gels and protein gels

TL;DR

This study compares the microstructure and rheological properties of protein-based gels and droplet-based gels, revealing similarities and subtle differences influenced by particle nature, which impacts their viscoelastic behavior.

Contribution

It provides a comparative analysis of protein and droplet gels, highlighting how particle properties affect gel rheology and microstructure, advancing understanding of colloidal gel behavior.

Findings

Protein and droplet gels have similar microstructures at fixed volume fraction.

Both exhibit power-law viscoelasticity and strain hardening at low concentrations.

Differences in rheological behavior are linked to particle-specific properties.

Abstract

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.