The study, published in the journal Food Hydrocolloids, suggests that using a mixture of commonly available emulsifying proteins and solid particles could lead to more stable emulsions and foams.
The research, led by Brent Murray, Professor of Food Colloids at the University of Leeds, working in partnership with Unilever’s R&D, concludes that a mixture of “active biopolymers” could be used to add stability to foams and emulsions - reducing the current requirement for surfactants in food production.
“Such mixtures could have an important role to play in the enhanced stabilization of food colloids in general,” wrote the researchers
Adding stability
Emulsifiers work by stabilizing oil suspended in water, binding the two together and creating a stable mixture.
Currently it is commonplace for surfactants to be used as stabilizing agents for emulsions and foams. However, there is a limited choice of food-grade surfactants, and there are strong links between surfactants and environmental damage.
A different way to stabilise an emulsion is to use solid particles - known as a Pickering emulsion, the use of solid particles such as proteins is a well documented alternative to the use of surfactant emulsifiers.
Surface active proteins – such as caseins and whey protein - are frequently used as emulsifying agents in foods, but other solid particles – including cellulose and ethyl cellulose complexes - can also be effective stabilizers of emulsions and foams. Up until now, relatively little was known of the effects when both surface active polymers and solid particles are used together as a stabilizer.
Combined effects
The aim of the new study was to asses the effects of surface active proteins and solid particles, both individually and together, on the stability of emulsions and foams.
Initially observing emulsions containing solid particles on their own had much stability than those containing only surface active proteins. However, in combination solid particles and proteins were seen to considerably enhance overall emulsion stability.
“When these particles are combined with proteins as surface active agents, there seems to be a synergistic effect … this increase seems to correlate with an increase in stability to coalescence and disproportionation,” stated the researchers.
The researchers also state that they observed “little evidence of attractive interactions between the particles and the proteins” – leading to the suggestion that there are no specific interactions - such as hydrogen bonds or hydrophobic bonds - between the particles and the proteins responsible for the enhanced stability.
Food potential
The study reports that using a mixture of surface active proteins and solid particles could create a more stable emulsions and foams for food products.
Using this process to enhance the stability of foods could also lead to the production of more stable low fat emulsions, as well as helping to make food more filling, due to the increased break down times.
“Further work on the structure and properties of such mixed protein + particle films is required to substantiate this,… but it does appear that such mixtures could have an important role to play in the enhanced stabilization of food colloids,” wrote the researchers.
Source: Food Hydrocolloids
Published online ahead of print, doi: 10.1016/j.foodhyd.2010.07.025
“Stabilization of foams and emulsions by mixtures of surface active food-grade particles and proteins”
Authors: B.S. Murray, K. Durga, A. Yusoff, S.D. Stoyanov