The study, published in Food Hydrocolloids, investigated the potential of using gel micro particles containing whey protein isolate for the production of food foams in an industrially applicable process that has potential for upscaling for manufacturing - finding that whey protein fluid gels were able to create the same amount of foam as non-treated whey proteins "but with substantially increased stability."
Led by Aristodimos Lazidis from the University of Birmingham in the UK, the research team noted that consumer trend demands foods to be ‘natural’ and ‘wholesome’ accompanied by a ‘clean label’, there is a need of producing particles from readily available food ingredients
The team said that the whey protein isolate (WPI) fluid gels “show interesting foaming properties which are dependent on both the pH at which these structures were originally formed but also the pH at which they were aerated.”
“Whey protein fluid gel systems produced very stable foams with reduced drainage compared to native proteins alone,” they added.
Foams and aeration
Aeration of foods is a process that is used both in traditional food products like bread and whipped cream but also in contemporary ones such as aerated chocolate, hot beverages and gourmet dishes.
The team noted that 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.”
“Furthermore, when aeration is used effectively it can reduce the caloric value and the cost of foods by introducing an ingredient that costs nothing and has no nutritional value,” they noted.
However, Lazidis and his team noted that foams are notoriously unstable, and require additional stabilisation through the use of high molecular weight surfactants or particles.
The new study assessed the potential for whey protein isolate micro-particles produced from a fluid gel to improve the aeration and stabilisation of food foams.
The team prepared a variety of test systems via heat induced gelation within the turbulent flow field of a pin stirrer at pH 5 and 8. They then investigated 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.
When produced close to the isoelectric point, the team found that whey protein fluid gels consist of small spherical protein aggregates ‘without significant functionality’.
However, they said that by increasing the pH of the 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,” wrote Lazidis and his colleagues.
“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.”
Source: Food Hydrocolloids
Published online ahead of print, doi: 10.1016/j.foodhyd.2015.02.022
“Whey protein fluid gels for the stabilisation of foams”
Authors: A. Lazidis, et al