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FOOD EMULSIONS

Abd Karim Alias, 2013©

Prof. Abd Karim Alias Universiti Sains Malaysia

Photo  courtesy  of  Tim  Sackton  on  Flickr    

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} An emulsion consists of two immiscible liquids (oil & water), with one of the liquids dispersed as small spherical droplets in the other.

} In foods, the diameter of these droplets usually falls somewhere in the range 0.1 – 100 µm.

Food Emulsion

Abd Karim Alias, 2013©

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} Two types of simple emulsion: } Water-in-oil (w/o): margarine, butter, spreads

} Oil-in-water (o/w): mayonnaise, salad dressings, milk, beverages, cream, soups, sauces

} The dispersed and/or continuous phase of many food emulsions may be partly crystalline, rather than being completely liquid.

Food Emulsion

Abd Karim Alias, 2013©

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} Emulsion formation requires the dispersion of one phase into small droplets ⇒ this results in a massive increase in interfacial area between the dispersed & continuous phase.

} Homogenization is the process by which the dispersed phase is broken into small droplets; high pressure homogenizers (10 – 100 MPa) are now very common.

Formation of Emulsion

Abd Karim Alias, 2013©

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Formation of Emulsion

Abd Karim Alias, 2013©

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Formation of Emulsion

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Shear force

Abd Karim Alias, 2013©

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Importance of Large Interfacial Area

For a fixed composition: • Decrease size, increase number of

particles •  Increase area of interfacial contact

Increase area

Abd Karim Alias, 2013©

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Formation of Emulsion

Abd Karim Alias, 2013©