Download Lesson 4 - Emulsifiers

After completing this lesson you should be able to :
• Emulsions in food are mixtures of oil and water.
• To prevent oil and water components separating into layers, a soap-like
molecule known as an emulsifier is added.
• Emulsifiers for use in food are commonly made by reacting edible oils with
glycerol to form molecules in which either one or two fatty acid groups are
linked to a glycerol backbone rather than the three normally found in edible
oils. The one or two hydroxyl groups present in these molecules are
hydrophilic whilst the fatty acid chains are hydrophobic.
Emulsifier
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• Substances that will allow liquids that are normally immiscible to mix are known
as emulsifiers.
• When the two liquids mix in this way an emulsion is formed.
• The word emulsion comes from a Latin word meaning ‘to milk’.
• Milk is a natural emulsion of milk fat and water. A protein called casein acts as an
emulsifier, stopping the milk fat and water separating. Emulsifiers are one of the
most widely used types of food additive.
Milk is a good source
of thiamin, riboflavin and vitamin B12 .
Milk contains small amounts
of niacin, pantothenic acid, vitamin
B6,vitamin C, and folate and is not
considered a major source of these
vitamins in the diet. Milk contains the fat
soluble vitamins A, D, E, and K.
Emulsifiers Practical
An emulsifier is a substance that stabilises an emulsion (a mixture of one liquid
dispersed in another.) Detergent, egg yolk and mustard are emulsifiers, the others
are not. Students may observe colloidal mixtures in the other tubes, but they are not
oil and water emulsions and two separate layers should be clearly seen. (The
proteins in egg white act as emulsifiers and thickeners. Egg whites or egg
white powder can be used to create soft foams for molecular cuisine. You can also
use them to create meringues or add fluffiness to recipes. Egg yolks contain two
important things not found in egg whites: fat and lecithin.)
Mustard – where a variety of chemicals in the mucilage surrounding the seed hull
act as emulsifiers.
Lecithin (E322)
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• Emulsifiers have a structure related to soaps in
that the molecules have a part that is hydrophilic
and a part that is hydrophobic.
• The most common emulsifiers used in food
production are lecithin, E322, and mono- and diglycerides of fatty acids, E471
Emulsifier molecules
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To prevent oil and water components separating into layers, a soap-like molecule
known as an emulsifier is added.
Emulsifiers for use in food are commonly made by reacting edible oils with glycerol
to form molecules in which either one or two fatty acid groups are linked to a
glycerol backbone rather than the three normally found in edible oils. The one or
two hydroxyl groups present in these molecules are hydrophilic whilst the fatty acid
chains are hydrophobic.
The presence of this emulsifier is shown on packaging by E-numbers, E471 and is
one of the most common on food packaging. (mono and di-glycerides).
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Emulsifiers
Mayonnaise contains oil and water. The emulsifier
keeps these mixed and without it the oil and
water separate.
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Emulsifiers in food
Emulsifiers in food
Emulsifiers are among the most frequently used
types of food additives. They are used for many
reasons.
Emulsifiers can help to make a food appealing. They
are used to aid in the processing of foods and also
to help maintain quality and freshness.
In low fat spreads, emulsifiers can help to prevent
the growth of moulds which would happen if the oil
and fat separated.
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Emulsifiers in food
Foods that Commonly Contain Emulsifiers
Biscuits
Toffees
Bread
Extruded snacks
Chewing gum
Margarine / low fat spreads
Breakfast cereals
Frozen desserts
Coffee whiteners
Cakes
Ice-cream
Topping powders
Desserts / mousses
Dried potato
Peanut butter
Soft drinks
Chocolate coatings
Caramels
http://www.ltscotland.org.uk/higherscience
s/chemistry/animations/emulsions.asp
This animation explains the difference
between a stable and an unstable emulsion,
and goes on to show how addition of an
emulsifier can stabilise an emulsion which is
otherwise unstable.
The chemical structure of a typical
emulsifier is described and this is used to
explain the favourable properties of
emulsifiers
Homemade Mayonnaise recipe