Week 7 - Food Emulsions - Learning Objectives To characterize dispersions to classify emulsions To discuss formation and destabilization of emulsions

Week 7 - Food Emulsions - Learning Objectives To...

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9/6/2016 1 Food Emulsions, Colloids, Surface Interactions 1 Learning Objectives To characterize dispersions & to classify emulsions To discuss formation and destabilization of emulsions To discuss colloidal interactions and understand their role in stability To explain the role of emulsifiers & to recommend suitable emulsifier for various food systems 2 Characterization of Dispersions (food chem view) Dispersion system of discrete particles in a continuous liquid Particles System Gaseous Foam Liquid Emulsion Solid Suspension (Walstra & van Villet, 2008) 3 Characterization of Dispersions (colloid chem view) Dispersion system of discrete “particles” in a continuous fluid 4 Characterization of Dispersions cont. Colloid a dispersion containing particles larger than small molecules (1 nm to some μ m) Colloids may be thermodynamically or kinetically stable Dispersion may be spontaneous (at a certain temperature kT energy) or require energy (e.g. emulsification) 5 Emulsion Emulsion - system containing two immiscible liquid phases one of which is dispersed in the other Dispersed phase Droplets typically 0.1 and 50-100mm (INTERNAL PHASE) Continuous phase - Matrix in which droplets are dispersed (EXTERNAL PHASE) Surfactant stabilise emulsions soaps, proteins, egg yolk (lecithin), etc 6 wiki/Emulsion Immiscible liquids Emulsion Unstable emulsion
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9/6/2016 2 Emulsions Oil in water emulsions oil/water o/w dispersed phase (oil) & continuous phase (water) conducts electricity, can be diluted with water Milk Water in oil emulsion water/oil w/o dispersed phase (water) & continuous phase (oil) feel greasy, can be diluted with oils or solvent margarine 7 Classification Based on vol % of internal Phase Internal phase ratio is defined as: F = Vi / (Vi + Ve) where Vi = volume of internal phase; Ve = volume of external phase F < 0.3, Low internal-phase ratio (LIPR) o/w: milk, ice cream, and cheese w/o: butter and margarine 0.3 < F < 0.7, Medium internal-phase ratio (MIPR) Heavy cream F > 0.7, High internal-phase ratio (HIPR) Mayonnaise and salad dressing 8 Oil-in-Water Emulsion Droplet Natural food emulsions contain amounts of natural emulsifiers In homogenised milk casein protein adsorbs on surface of milk fat globules and acts as a surfactant Formulated food emulsions are processed from ingredient components 9 Complex Food Emulsions Dispersed phase (oil) can be partially solidified e.g., in dairy creams % solidification of fat depends on Temp. Continuous phase may contain crystalline or gelled material e.g., ice cream where ice crystals are present e.g., gelled desserts where the continuous phase is a gel Food emulsions affect food texture and sensory properties 10 Formation of Emulsions cont.
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  • Chemistry, Emulsion, emulsions, Walstra, colloidal interactions, van Villet

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