Linear viscoelastic behaviour of oil-in-water food emulsions stabilised by tuna-protein isolates

Abstract

This work deals with the manufacture of oil-in-water food emulsions stabilised by tuna proteins. The influence of protein and oil concentrations on the linear viscoelastic properties and microstructure of these emulsions was analysed. Stable emulsions with suitable linear viscoelastic response and microstructural characteristics were formulated with 70 wt.% oil and, at least, 0.25 wt.% tuna protein. Similarly, emulsions with oil concentrations between 45 and 70 wt.% were prepared using 0.50 wt.% protein. All these emulsions showed a predominantly elastic response in the linear viscoelastic region and a well-developed plateau region in its mechanical spectrum. Rheological and droplet size distribution results pointed out an extensive droplet flocculation, due to interactions among emulsifier molecules located at the oil–water interface of adjacent droplets. As a result, the linear viscoelastic behaviour was controlled by protein–protein interactions, allowing the use of the plateau modulus to successfully normalise both the storage and loss moduli as a function of frequency onto a master curve, irrespective of the selected emulsion formulation.