Hydrophobins stabilised air-filled emulsions for the food industry

Abstract

Hydrophobin HFBII has been extracted from a culture of Trichoderma reesei. The protein has been used to construct air cells of approximately 1–100 μm in size, with approximately 40% of the air cells falling within the 1–2 μm range. We have termed these suspensions air-filled emulsions and propose their use for fat replacement in emulsion based food structures. The air cells in the air-filled emulsion have a surface elasticity, given by the hydrophobin film that helps prevent disproportionation and ripening. The air-filled emulsions show little if any change in individual air cell size when stored for up to 4 months at room temperature. Moreover the interface to the air cells is robust and capable of surviving long, high shear processing steps. Production of the hydrophobin film is an extremely rapid event and ordinarily it is difficult to control during emulsion formation. Here we have used a sonication process to produce the air cells. This process then allows us to control the hydrophobin assembly kinetics in order to ensure that they are not removed from the interface after aggregation, and thus rendered inactive. Using the air-filled emulsions we have created a, so called, tri-phasic system with up to 60% included phase of air and oil in an aqueous continuum and showing a greater than 50% reduction in lipid content when compared to a rheologically similar oil water emulsion. The tri-phasic emulsions are stable for up to 45 days in terms of droplet size and with no loss of air phase.