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

Abstract

Hypothesis 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. Experiments 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.

Rheology of protein-stabilised emulsion gels envisioned as composite networks. 2 - Framework for the study of emulsion gels

“…The rheological properties of the emulsion gel samples, whose compositions are presented in Figure 1, were measured during and after gelation. The storage and loss moduli of emulsion gels, defined arbitrarily at t gel + 2500 s, can be compared with the moduli of the gels of pure components presented in the first part of this study [18]. These results are displayed in Figure 2.…”

“…For the purpose of assessing the role of the composition of the mixtures in the strength of the gels they form, it is useful to normalise for the power law dependence on the volume fraction identified in the first part of this study for pure gels [18]. This normalisation by the total effective volume fraction can be achieved by dividing the storage modulus of the mixture G exp mixture by the modulus expected for a protein gel of identical volume fraction:…”

“…Similarly to the pure protein and droplet gels presented in the first part of this study, the frequency dependence of emulsion gels was measured after gelation, and is represented in Figure S2 of the supplementary material [18]. The dependence of the storage modulus of emulsion gels on frequency can be modelled by a power law, as was done for pure gels:…”

“…Emulsion particulate gels have attracted less attention, and they were considered to be similar to other colloidal gels [15,16,17]. An exception is the first part of this series, in which pure gels made of protein-stabilised emulsion droplets have been studied and their rheological properties characterised [18].…”

DMA Study of the Molecular Structure of Porcine Fat in-Water Emulsions Stabilised by Potato Starch

“…The increasing demand for low-fat products observed in recent years forces manufactures to modify product formulations, among others, by reducing fat content and replacing it, for example, by water. When the extent of fat replacement exceeds 70%, which occurs in the case of typically low-fat products, the continuous phase of the product is transformed into oil-in-water type of emulsion losing simultaneously rheological features characteristic for condensed emulsions [ 4 ]. This leads to considerable changes in the product quality parameters, in particular, texture and water binding capability [ 5 , 6 ].…”