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Emulsions
Definition:
A collidal dispersion consisting of two completely immiscible liquids
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The word emulsion comes from the Latin word meaning "to milk" (milk is one example of an
emulsion of fat and water)
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Properties of Emulsions:
Emulsions usually appear cloudy or white because light is scattered off the phase interphases
between the components in the mixture
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Dilute emulsions may appear slightly blue because low wavelength light is
scattered more
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It's commonly seen in skim milk
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Because emulsions are liquids, they don't have a static internal structure
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Two
liquids can form different types of emulsions
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Further, they can form multiple emulsions, such as water in oil in water
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Distinction Between Colloid and Emulsion:
Sometimes the terms "colloid" and "emulsion" are used interchangeably, but the term
emulsion applies when both phases of a mixture are liquids
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So, an emulsion is a type of colloid, but not all colloids are emulsions
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Milk is an example of the oil-in-water type of emulsion
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Other examples are, vanishing cream etc
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These emulsion
are also termed oil emulsions
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Other examples are cod liver oil etc
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2 – 50 mm (Kinetically Stable)
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01 – 0
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Preparation:
Emulsion is prepared by shaking two immisible liquids or by mechanical mixing using
collidal mill known as homogenizer
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Oil, water,
emulsifier

Mix

Stir by
machine

Emulsio

Figure The flow chart of preparation of an emulsion with the Mechanical Method
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To have stable emulsions
we need emulsifiers
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Foods that consist of such emulsions
include butter, margarine, saladdressings(a sauce for salads, typically one consisting of oil
and vinegar with herbs or other flavourings
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Stabilizers maintain emulsions in a
stable form
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Emulsifyingagentsusedinfoodsinclude agar, albumin, al
ginates, casein, egg yolk, glycerolmonostearate, gums, Irish moss (species of red algae which
grows abundantly along the rocky parts of the Atlantic coast of Europe and North
America), lecithin, soaps
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The reduced interfacial tension depends on the concentration of the surfactant
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steric stabilization
2
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For example,
high-molecular-weight polymers can adsorb on the surface of the dispersed phase droplets
and extend significantly into the continuous phase, providing a volume restriction or a
physical barrier for particle interactions
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Surface-active solid particles such as clays have also been shown to sterically stabilize
emulsions
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In an electrostatically stabilized emulsion, an
ionic or ionisable surfactant forms a charged layer at the interface
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The charged
surface and the counter ions are termed a double layer
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If the repulsive forces are strong enough, the droplets are repelled
before they can make contact and coalesce, and the emulsion is stable
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Both electrostatic and steric forces can prevent aggregation or coalescence and hence
stabilize emulsions

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