Emulsions Flashcards
What are the 4 emulsions?
Oil-in-water
Water-in-oil
Oil-in-water-in-oil
Water-in-oil-in-water
What is in the dispersed phase?
Droplets (fat)
What is in the continuous phase?
Dispersion (water)
What is homogenisation?
Conversion of 2 immiscible liquids into an emulsion
What is a homogeniser?
Mechanical device that causes homogenisation
Why is energy required for an emulsions?
To increase size of interface between two phases and increase droplet size
How can fluids become miscible?
They have no interfacial tension
How can interfacial tension be reduced?
Phospholipids
What is temporary homogenisation?
Droplets are deformed and collide but then separate again
What is permanent homogenisation?
Droplet deformation and emulsifier adsorption causes stabilisation
What are the 3 emulsifier types?
Surfactants
Amphiphilic biopolymers
Electrostatic and steric stabilisation (pickering)
What is HLB?
Hydrophilic Lipophilic Balance and is the difference between head and tail on a phospholipid
What is CMC?
Critical Micelle Concentration and is the concentration at which a micelle is formed
How do surfactants stabilise?
Electrostatic repulsion causes reduction in interfacial tension
How do amphiphilic biopolymers work?
Hydrophobic and hydrophilic regions locate in oil and water phase where the emulsifiers change to maximise contact between phases
How do Pickering cells stabilise?
Electrostatic and steric (physical) repulsion of oil to prevent coalescence
Stability of emulsifiers
Surfactant=low
Amphiphilic=medium
Pickering=high
What is gravitation separation?
Separation by density, creaming causes oil to rise, sedimentation causes water to fall
What is flocculation?
Association of 2 or more droplets without losing integrity
What is coalescence?
Fusion of 2 or more droplets into a larger one
What is Oswald ripening?
Mass transfer of dispersed phase of small droplets to large droplets
What is phase inversion?
o/w emulsion to w/o or vice versa
What is the role of stabilisers?
Thicken and gel
Texture and mouthfeel
Reducing flocculation
Increase continuous phase viscosity
Apply charge to droplet surface
Reducing Oswald ripening
Narrow droplet size distribution
Triglycerides have negligible solubility in water
Reducing coalescence
Increase continuous phase viscosity
Apply charge to droplet surface
Reducing sedimentation
Increase continuous phase viscosity
Decrease droplet size
Match density of phases
Foam definition
Air bubbles dispersed in water
How can foam be formed?
Liquid forced around gas (whipping)
Gas forced through liquid (injection)
Generation of gas (chemical)
What is disproportionation?
Diffusion of gas between bubbles
What is coalescence of a foam?
Rupture of liquid between bubbles
How can you measure foams?
Overrun (whipping percentage)
Foam stability (foam loss percentage)
Foam capacity (air percentage)
What is isoelectric point?
The pH at which a molecule carries no net charge
