Emulsions Flashcards

1
Q

What are the 4 emulsions?

A

Oil-in-water
Water-in-oil
Oil-in-water-in-oil
Water-in-oil-in-water

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2
Q

What is in the dispersed phase?

A

Droplets (fat)

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3
Q

What is in the continuous phase?

A

Dispersion (water)

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4
Q

What is homogenisation?

A

Conversion of 2 immiscible liquids into an emulsion

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5
Q

What is a homogeniser?

A

Mechanical device that causes homogenisation

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6
Q

Why is energy required for an emulsions?

A

To increase size of interface between two phases and increase droplet size

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7
Q

How can fluids become miscible?

A

They have no interfacial tension

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8
Q

How can interfacial tension be reduced?

A

Phospholipids

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9
Q

What is temporary homogenisation?

A

Droplets are deformed and collide but then separate again

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10
Q

What is permanent homogenisation?

A

Droplet deformation and emulsifier adsorption causes stabilisation

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11
Q

What are the 3 emulsifier types?

A

Surfactants
Amphiphilic biopolymers
Electrostatic and steric stabilisation (pickering)

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12
Q

What is HLB?

A

Hydrophilic Lipophilic Balance and is the difference between head and tail on a phospholipid

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13
Q

What is CMC?

A

Critical Micelle Concentration and is the concentration at which a micelle is formed

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14
Q

How do surfactants stabilise?

A

Electrostatic repulsion causes reduction in interfacial tension

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15
Q

How do amphiphilic biopolymers work?

A

Hydrophobic and hydrophilic regions locate in oil and water phase where the emulsifiers change to maximise contact between phases

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16
Q

How do Pickering cells stabilise?

A

Electrostatic and steric (physical) repulsion of oil to prevent coalescence

17
Q

Stability of emulsifiers

A

Surfactant=low
Amphiphilic=medium
Pickering=high

18
Q

What is gravitation separation?

A

Separation by density, creaming causes oil to rise, sedimentation causes water to fall

19
Q

What is flocculation?

A

Association of 2 or more droplets without losing integrity

20
Q

What is coalescence?

A

Fusion of 2 or more droplets into a larger one

21
Q

What is Oswald ripening?

A

Mass transfer of dispersed phase of small droplets to large droplets

22
Q

What is phase inversion?

A

o/w emulsion to w/o or vice versa

23
Q

What is the role of stabilisers?

A

Thicken and gel
Texture and mouthfeel

24
Q

Reducing flocculation

A

Increase continuous phase viscosity
Apply charge to droplet surface

25
Reducing Oswald ripening
Narrow droplet size distribution Triglycerides have negligible solubility in water
26
Reducing coalescence
Increase continuous phase viscosity Apply charge to droplet surface
27
Reducing sedimentation
Increase continuous phase viscosity Decrease droplet size Match density of phases
28
Foam definition
Air bubbles dispersed in water
29
How can foam be formed?
Liquid forced around gas (whipping) Gas forced through liquid (injection) Generation of gas (chemical)
30
What is disproportionation?
Diffusion of gas between bubbles
31
What is coalescence of a foam?
Rupture of liquid between bubbles
32
How can you measure foams?
Overrun (whipping percentage) Foam stability (foam loss percentage) Foam capacity (air percentage)
33
What is isoelectric point?
The pH at which a molecule carries no net charge