Researchers from the University of Birmingham, led by Dr Philip Cox, report these air filled emulsions could reduce the fat content of a food system by 50 per cent.
Furthermore, these three-phase (air/oil/water) emulsions remained stable during storage for 45 days, according to findings published online ahead of print in the journal Food Hydrocolloids.
Reduction of fat in products is a growing area of interest to food manufacturers as consumers continue to seek out low-fat and low-calorie versions of their favourite foods.
“All indications are that these stabilised air filled emulsions will be successful for producing reduced fat food products,” wrote Dr Cox and his co-workers.
“The reason is that the air cells in the air filled emulsion have a robust surface structure, given by the hydrophobin film, and this helps prevent disproportionation and ripening, over 45 days in our study.”
Fungal proteins and food foams
The key to air filled emulsions is hydrophobin HFBII, protein extracted from Trichoderma reesei. Previously, researchers from Unilever resported that hydrophobin HFBII at a concentration of 0.1 per cent could produce food foams with exceptional stability, and this could lead to improvements in the physical and sensory properties of a range of products, including low fat whipping cream, ice cream and sorbets.
Low fat foods
“It is possible that small, stable, air bubbles designed to resemble oil droplets in terms of their size and physical properties could be used to produce a new generation of low fat foods,” explained the researchers.
“However, a challenge remains to produce an air based fat mimic with acceptable shelf life for soft solid or liquid foods.”
In attempt to move closer to aerated, low-fat products, the Birmingham-based researchers used a sonication process to produce a ‘fat globule mimic’ by using the hydrophobins to coat and stabilize air cells. The cells ranged in size from 1 to 100 micrometres, with over 40 per cent in the 1 to 2 micrometres range.
Dr Cox and his co-workers report that the air cells were “capable of surviving high shear processing steps for up to 7 minutes shearing”.
This ‘air filled emulsion’ was then used to produce a prototype food with three phases: air in oil in water. The system consisted of 30 per cent air phase, and 30 per cent oil phase stabilized by Tween 60.
This tri-phasic system allowed the fat content of the model food to be reduced by more than 50 per cent, “compared to a rheologically similar oil water emulsion”, said Cox and his co-workers.
The tri-phasic emulsions were found to be stable in terms of both volume and air content over 45 days.
The study was supported financially by the BBSRC.
Source: Food Hydrocolloids Published online ahead of print, doi: 10.1016/j.foodhyd.2009.03.005"Hydrophobins stabilised air filled emulsions for the food industry" Authors: F. Tchuenbou-Magaia, I.T. Norton, P.W. Cox