2009 Proteins Part 2

2009 Proteins Part 2 - Proteins in Foods Part 2 Proteins as...

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Unformatted text preview: Proteins in Foods Part 2 Proteins as surfactants : Use in stabilization of foams and emulsions Foam: Dispersion of air cells in liquid (water) or semi-solid Emulsion: Dispersion of oil in water (or water in oil) Dispersions are thermodynamically unstable due to high surface tension (interfacial tension) at the boundary between the two phases Surfactants stabilize dispersions by : * lowering surface tension * providing a physical barrier between phases Foams and emulsions are dispersions of two physically incompatible phases : Phase dispersal Incr. total surface area Incr. system energy (instability) globular protein in native conformation in aqueous solution high energy water zone (surface tension) bulk water (lower energy) partial denaturation of protein caused by surface tension Unfolded protein spread out at surface Oil (hydrophobic) or Air high energy water zone no longer exists; protein provides barrier between water and air unfolded (hydrophobic) proteins tend to “stick” at the surface A B C air cell or oil droplet air cell or oil droplet Stabilization of foams and emulsions by denatured proteins Good protein surfactants: flexible , easily denatured by surface tension; amphipathic : possess both hydrophobic and hydrophilic regions within the same protein molecule charge repulsion (except at pI ) Unfolded proteins coat surface of air cells or oil droplets, stabilizing the dispersion Food emulsions Protein Functionality: Milk Proteins Milk is an oil-in-water emulsion : Aqueous (" skim ") phase with dispersed fat droplets “Skim” (aqueous, non-fat) phase : A. Soluble components 1. "Whey" proteins 15-20% of total milk protein...
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This note was uploaded on 08/12/2010 for the course FD SC 200 taught by Professor Hotchkiss,j./parker, during the Spring '09 term at Cornell.

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2009 Proteins Part 2 - Proteins in Foods Part 2 Proteins as...

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