This is part of IMK 209 - Physical Properties of Food, a second year level course in Food Technology, School of Industrial Technology, Universiti Sains Malaysia. Lecturer: Prof. Abd Karim Alias.

1. 1
FOOD COLLOIDS:
EMULSIONS &
FOAMS
Prepared & Presented by:
Professor Abd Karim Alias
Universiti Sains Malaysia
Abd Karim Alias, 2013 1
Photo
courtesy
of
Jangray1985,
Flickr
Photo
courtesy
of
Danny
Ngan,
Flickr
Emulsion & Foam by Prof. Abd Karim Alias is licensed under a
Creative Commons Attribution-NonCommercial-ShareAlike 3.0
Unported License.

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Abd Karim Alias, 2013 2
} Define these terms: disperse systems, colloids,
emulsion, foam, amphiphilic, lipophilic,
hydrophilic, emulsifier, stabilizer, surface
tension, interfacial tension, plateau border.
} Identify types of emulsion & foam
} Describe methods to form an emulsion &
foam
} Explain why energy is necessary to form an
emulsion
After completing this topic, you should
be able to do the followings:

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Abd Karim Alias, 2013 3
} Explain why an emulsion is inherently unstable
} Explain the role of emulsifier and stabilizer
} Decribe the DLVO theory
} Describe the various ways by which emulsion
and foam become unstable
} Explain the method to measure and predict
emulsion stability
} Describe methods to stabilize emulsion and
foam
After completing this topic, you should be
able to do the followings:

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Abd Karim Alias, 2013 4
} Food Emulsions: Principles, Practice, and
Techniques --D.J. McClements, CRC
Press, Washington DC, 1999
} Emulsifiers -- C.E. Stauffer, Eagan Press,
St. Paul, Minnesota, USA, 1999
} Analysis of Food Emulsions -- Chapter 35
in Food Analysis, 2nd edition (S.S.
Nielsen, ed.)
References

5. 5
5
What do mayonnaise, margarine, butter, milk
and coconut milk have in common?
–Ans: Emulsion
What do ice cream, meringue, marshmallow,
bread, and cake batter have in common?
– Ans: Foam
Emulsion & Foam are dispersed system
Questions:
Abd Karim Alias, 2013

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÷ The term Dispersed System refers to a
system in which one substance (the
dispersed phase) is distributed, in
discrete units, throughout a second
substance (the continuous hhase)
÷ Each phase can exist in solid, liquid, or
gaseous state
DISPERSED SYSTEM (DISPERSION)
6
Abd Karim Alias, 2013

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• COLLOIDAL DISPERSION (SOL) –
dispersions of two or more immiscible
materials, containing structural entities in
the size range 1 nm – 1 µm.
• The simplest type of colloidal system
consists of a single dispersed phase of
particles in a second continuous phase
called dispersion medium.
TERMINOLOGY
7
Abd Karim Alias, 2013

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Dispersed
phase
Continuous
phase
Interface
Abd Karim Alias, 2013

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SOLID LIQUID GAS
SOLID Some
glasses
Sol Smoke
LIQUID Emulsion Aerosol
GAS Solid
foam
Foam
CONTINUOUS PHASE
DISPERSEDPHASE
TYPES OF DISPERSED SYSTEM
Abd Karim Alias, 2013

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• A system containing particles >1 mm
which are prone to settle under gravity
is usually referred to as a suspension.
• A dispersion or suspension of liquid
droplets in a liquid continuous phase
is called an emulsion.
• A foam is a coarse dispersion of gas
bubbles in a liquid (or solid)
continuous phase
TERMINOLOGY
Abd Karim Alias, 2013

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Diameter /µm
0.1 1 10
Frequency/%
0
5
10
15
20
25
30
35
Emulsion 1
Emulsion 3
Emulsion 5
Polydispersity
• Monodisperse
• Polydisperse
Abd Karim Alias, 2013

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Volume Fraction
φ=Total
volume
of
the
dispersed
phase
÷
Total
volume
of
the
system
Close
packing,
fmax
Monodisperse
Ideal
~0.6
Random
~0.5
Polydisperse
Much
greater
Abd Karim Alias, 2013

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• In food systems, the term “colloids”
generally includes dispersions
containing larger particles (> 1 mm).
• Food dispersions encompass
suspensions such as sugar fondant
(solid sugar particles in a saturated
sugar solution), emulsions such as
milk, cream, and spread, and foams
such as found in beer, ice cream and
bread.
FOOD COLLOIDS
Abd Karim Alias, 2013

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Foam
Oil phase
(containing
flavours, fat
solublenutrients
Fat crystals
Sugar crystals
Aqueous phase (containing
flavours, water soluble
nutrients, salts, stabilisers
Emulsifier
layer around
droplet
Macromolecule
Macromolecule
adsorbed on droplet
surface
Abd Karim Alias, 2013