emulsification

• emulsions are formed when oily and watery liquids are shaken together
• milk, margarine and mayonnaise are all examples of emulsions
• usually, oil and water dont mix together so emulsions separate out again unless you keep shaking or stirring them - or use an emulsifier
• the molecules in an emulsifier have two different ends:

  one is hydrophilic - attracted to water - and the other is hydrophobic - repulsed by water
• when you add an emulsifier, the water molecules bond to the hydrophilic side and the oil molecules bond to the hydrophobic side. this holds the oil and water together in a stable emulsion, preventing them from separating
• emulsions can either be oil in water - milk, mayonnaise and salad dressings, or water in oil - margarine or butter
• egg yolks contain a natural emulsifier called lecithin which is used as the emulsifier in margarine and mayonnaise
• mayonnaise is a stable emulsion of egg yolk, oil and vinegar. when making stable emulsions, you need to ensure you add the oil or water gradually and that you mix the ingredients for long enough
• emulsions are often used as sauces and salad dressings
• hollandaise sauce is another example of an emulsion sauce - its made from butter, water, egg yolk and lemon juice
• to make hollandaise sauce:

  1. melt the butter in a pan
  2. mix egg yolks ad lemon juice in a bowl
  3. gently warm this mixture by placing the bowl over a pan of simmering water
  4. slowly add the melted butter to the mixture constantly whisking as you do
  5. keep whisking the sauce until its all mixed together smoothly
• when making any oil in water emulsion, its important to add the liquid and emulsifier first, before very slowly adding the oil / fat while mixing vigorously