Whey protein fluid gels for the stabilisation of foams

A Lazidis,R.D Hancocks,F Spyropoulos,M Kreuß,R Berrocal,I.T Norton

doi:10.1016/j.foodhyd.2015.02.022

A Lazidis, R.D Hancocks + Show 4 more

Open Access

https://doi.org/10.1016/j.foodhyd.2015.02.022

Copy DOI

Abstract

The ability of whey protein fluid gels to produce very stable foams was demonstrated. These systems were prepared by heat induced gelation within the turbulent flow field of a pin stirrer at pH 5 and 8. The effect of pH and final protein concentration on the morphology of the particles, the bulk, interfacial and rheological properties and finally the foaming properties of their aqueous suspensions were investigated. Whey protein fluid gels, when produced close to the isoelectric point, consist of small spherical protein aggregates without significant functionality. Micrographs taken suggest that the protein aggregates created have the ability to adsorb at the air/water interface. Nevertheless, the lack of further increase in interfacial viscosity or elasticity indicates that either the adsorption is easily reversible or that it is only partial due to lack of material available to provide complete coverage. By increasing the pH of these systems the protein entities present acquire a negative charge, which causes an increase to both the bulk and interfacial viscoelasticity and increase of the stability of foams. The proposed mechanism is that during foaming, the smaller and mobile protein entities diffuse fast to the interface and provide the necessary interfacial tension reduction to facilitate foam formation. Subsequently, the larger protein particles fill the free space between the air bubbles and increase the local bulk viscosity, which improves foam stability mainly by preventing drainage. Whey protein fluid gels were able to create the same amount of foam as non-treated whey proteins but with substantially increased stability.

Highlights

Aeration of foods is a process that is used both in traditional food products like bread and whipped cream and in contemporary ones such as aerated chocolate, hot beverages and gourmet dishes
This study focuses on exploring a process of producing gel micro particles that has a potential in future upscaling for manufacture through an industrially applicable process
whey protein isolate (WPI) fluid gels produced by thermally treating WPI under shear show interesting foaming properties which are dependent on both the pH at which these structures were originally formed and the pH at which they were aerated

Summary

Introduction

Aeration of foods is a process that is used both in traditional food products like bread and whipped cream and in contemporary ones such as aerated chocolate, hot beverages and gourmet dishes. The presence of air, usually in the form of bubbles, throughout the volume of food provides a unique texture, which is frequently associated with luxury and high quality. Aerated materials where the gas, in most cases atmospheric air, is distributed throughout an aqueous continuous phase are colloidal dispersions known as foams. These are thermodynamically unstable systems that generally have significantly shorter lifetime when compared to other colloidal dispersions such as emulsions (hours or even minutes compared to months) (Walstra, 2003). The main reason for the high instability lies to the fact that the interface between the dispersed and continuous phase, called film, is larger in size when looking at bubbles in contrast to emulsion droplets

Objectives

Methods

Results

Conclusion