Emulsions
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What are emulsions?
Dispersions of two immiscible liquids (oil and water)
What are two different types of emulsions?
Oil-in-water and water-in-oil
What are examples of oil-in-water emulsions?
milk, mayo, cream
What are examples of water-in-oil emulsions?
butter and margarine
Is it possible to make these emulsions by just mixing pure water and oil?
Yes but they easily separate.
What must happen in order for emulsions to not separate?
They must be kinetically stable
Are emulsions thermodynamically stable?
No, they are high in energy state
When can the energy required to create an emulsion be lowered?
When interfacial tension can be decreased
How can one decrease oil-water interfacial tension?
Add emulsifiers which have hydrophobic and hydrophilic sides meaning less energy is needed to generate emulsions. They are kinetically stabilized.
What are two types of emulsifiers?
Small molecules emulsifiers and plymeric emulsifiers
What are some common food emulsifiers?
Lecithin, Tween 20, and monoglyceride
What attaches the large globules in homogenized milk?
Dark clumps of casein micellar material on the oil-water interface
What stabilizes emulsions?
Proteins, increased viscosity, descreased interfacial tension
What are emulsions characterized by?
There average droplet size
What are four ways that emulsions are destabilized?
• Creaming • Sedimentation • Flocculation • Coalescence
What are two types of gravitational separation?
Creaming and Sedimentation
What is creaming?
When oil droplets are on top because they are less dense than water.
What is sedimentation?
When oil droplets are on bottom because they are more dense than water.
What is flocculation?
Droplets associate with each other without losing their individual identities meaning they will separate easily.
What is coalescence?
Droplets join together irreversibly (oil and water separate)
What are two types of droplet aggregation?
Flocculation and coagulation
Describe the emulsion making process
Oil and water soluble ingredients are blended together to form a coarse emulsion. They are then homogenized to stabilize and decrease droplet size.
Name some oil in water emulsions
milk, salad dressing, coffee creamer, mayo, falvoured beverages
Name a oil and air-in water emulsion
Ice cream