Emulsification

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Definition: The process that produces an emulsion (stable combination of oil and water)

Lipids do not normally mix with water. A temporary mixture can be formed by shaking, like in salad dressing, however the oil will soon float to the surface of the vinegar

Homogenisation is used to break up and evenly distribute the fat globules to produce a permanent emulsion i.e. milk

An emulsifier is used to stop the separation of oil and water, it does this by having an attraction to both the lipid and the water acting as a bridge

An emulsion has three parts: the dispersed phase, the continous phase and the emulsifier

Factors affecting emulsification of lipids

Emulsions can be destroyed by high temperatures, freezing, agitation after formation and the addition of salt. These processes can break the bridge holding the emulsion together causing it to separate

Temperature:  High temperatures cause lipids to become more fluid and water to move more rapidly, making it harder for the emulsifier to hold them together. Freezing temperatures changes the state of both the water and oil, causing crystallisation of the emulisfier and splitting the emulsion

Agitation:   Is essential while adding the oil to give the oil access to the emulsifier. Continous beating of an emulsified mixture can break the connections between the emulsifier and the oil, destroying the emulsion

Addition of salt:   Salt attracts water causing the emulsion to separate


Go to this website to read about creating an emulsion

Watch
this video which explains what an emulsion is and how to make one

Watch Gordon Ramsay making
Homemade Mayonnaise

Aeration

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Definition: When air is added to a mixture, affecting its consistency and texture

Saturated fats produce more effective aerated mixtures than unsaturated as they have better plasticity

Examples of fat being used to aerate mixtures:

Creaming - The creaming of butter and sugar where the texture becomes light and fluffy and the colour becomes lighter. As the sugar crystals are pressed into the fat a small amount of air is included in each indentation

Rubbing in
(pictured)- This coats the flour particles shortening the gluten strands which are formed through agitation, making the mixture more crumbly. The butter creates an impervious layer between the layers of gluten, the air trapped in these layers causes the pastry to lift during cooking

Whipping
- Whipping cream aerates it forming a foam

Watch
this video on the creaming of butter and sugar

task

1. Define the terms emulsification, emulsion, emulsifier and homogenisation

2. Give 3 examples of food products that are stable emulsions

3. Why is most milk in Australia homogenised and what benefit does this provide to consumers?

4. Explain, using examples and images, how emulsifying agents work and give examples of some commercially used emulsifiers

5. Think of a problem you may have had when preparing food i.e. salad dressing splitting, large air bubbles in pastry when cooked, explain what happened and how it could be prevented in the future  


Use your Food Properties Practical Application workbook, Food Tech in Action textbook and the information contained in this site to answer the above questions