Tchuenbou-Magaia, Fideline Laure
(2012).
Hydrophobins and air filled emulsions.
University of Birmingham.
Ph.D.
Abstract
Suspensions of micron sized air cells, Air Filled Emulsions (AFEs), represent a new colloidal material with outstanding physical properties. They have the potential for technological applications in very different fields such as biomedical, environmental sciences and the food industry. This thesis focuses on the construction of AFEs and their use as ingredients to construct reduced fat and calorie emulsion-based products. These microstructurally complex materials have been termed triphasic A/O/W emulsions.
A sonochemical templating process has allowed for the construction of air cells (the majority around 0.5-10 μm) in the size range of oil droplets found in emulsion based foods. Air cells were stabilised with either hydrophobins, obtained from submerged fermentation and extraction, or other cysteine rich but more common proteins such as bovine serum albumin (BSA) and egg albumen (EWP). The air cells were stable against disproportionation and ripening for substantial periods of time. They resisted destabilisation effect of oil droplets and could survive unit operations involving mild vacuum treatment and centrifugal forces, relatively high shear forces, temperatures and pressures.
Triphasic A/O/W emulsions were created with up to 60% included phase of air and oil in an aqueous continuous phase. This gave a greater than 50% reduction in lipid content. Comparative rheology and tribology showed that the triphasic A/O/W emulsions could have similar if not better lubrication properties than a full O/W version. The molecular properties of the protein used for the AFEs played a crucial role in the determination of lubrication properties (mouth-feel). Moreover, AFEs and triphasic emulsions offer the potential for new structures and textures for the food industry due to their self interaction to give a weak gel
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