0
1	
  
FOOD COLLOIDS:
EMULSIONS &
FOAMS
Prepared & Presented by:
Professor Abd Karim Alias
Universiti Sains Malaysia
Abd Ka...
2	
  
Abd Karim Alias, 2013 2	
  
} Define these terms: disperse systems, colloids,
emulsion, foam, amphiphilic, lipophil...
3	
  
Abd Karim Alias, 2013 3	
  
} Explain why an emulsion is inherently unstable
} Explain the role of emulsifier and ...
4	
  
Abd Karim Alias, 2013 4	
  
} Food Emulsions: Principles, Practice, and
Techniques --D.J. McClements, CRC
Press, Wa...
5	
  
5	
  
What do mayonnaise, margarine, butter, milk
and coconut milk have in common?
–Ans: Emulsion
What do ice cream,...
6	
  
÷ The term Dispersed System refers to a
system in which one substance (the
dispersed phase) is distributed, in
disc...
7	
  
•  COLLOIDAL DISPERSION (SOL) –
dispersions of two or more immiscible
materials, containing structural entities in
t...
8	
  
Dispersed
phase
Continuous
phase
Interface
Abd Karim Alias, 2013
9	
  
SOLID LIQUID GAS
SOLID Some
glasses
Sol Smoke
LIQUID Emulsion Aerosol
GAS Solid
foam
Foam
CONTINUOUS PHASE
DISPERSED...
10	
  
• A system containing particles >1 mm
which are prone to settle under gravity
is usually referred to as a suspensio...
11	
  
Diameter /µm
0.1 1 10
Frequency/%
0
5
10
15
20
25
30
35
Emulsion 1
Emulsion 3
Emulsion 5
Polydispersity
• Monodispe...
12	
  
Volume Fraction
φ=Total	
  volume	
  of	
  the	
  dispersed	
  phase	
  	
  
	
  	
  	
  	
  	
  	
  ÷	
  Total	
  ...
13	
  
• In food systems, the term “colloids”
generally includes dispersions
containing larger particles (> 1 mm).
• Food ...
14	
  
Foam
Oil phase
(containing
flavours, fat
solublenutrients
Fat crystals
Sugar crystals
Aqueous phase (containing
fla...
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Introduction to Food Emulsions and Foams

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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.

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Transcript of "Introduction to Food Emulsions and Foams"

  1. 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.
  2. 2. 2   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:
  3. 3. 3   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:
  4. 4. 4   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   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
  6. 6. 6   ÷ 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
  7. 7. 7   •  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
  8. 8. 8   Dispersed phase Continuous phase Interface Abd Karim Alias, 2013
  9. 9. 9   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
  10. 10. 10   • 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
  11. 11. 11   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
  12. 12. 12   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
  13. 13. 13   • 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
  14. 14. 14   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
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