fats and oils

• aeration

  • Aeration involves getting air into something.
  • We trap air in mixtures when we beat fats with sugar (known as creaming). 
  • The added air lightens the mixture and gives it a fluffy texture.
  • Aeration causes cakes to turn out spongy and light when they're cooked.
  • We can use different methods to aerate foods, including beating or whisking.
• plasticity

  • If something has plasticity, it can be spread and moulded. 
  • We can spread and mould fats because they are made up of different triglycerides that each have different melting points. This means fats don't melt at a set temperature but soften gradually across different temperatures.
  • Fats with more plasticity are easier to spread.
• plasticity (cont.)

  • Fats with more unsaturated fatty acids have more plasticity than those with less and are easier to spread.
  • Plasticity is useful in everyday cooking. For example:
  • Spreading peanut butter, aioli or butter on toast. 
  • Making cream cheese and smoked salmon sandwiches. 
  • Icing cupcakes with buttercream.
• shortening

  • Flour particles gain a waterproof layer when they're covered in fat. We can cover particles in fat by rubbing fat into flour.
  • We might choose to do this if we want to form baked goods with firm textures (i.e. cakes, biscuits or shortbread). This is because the coating stops long gluten molecules from forming when we add water to flour. The dough doesn't develop an elastic (stretchy) texture.
• shortening (cont.)

  • We use shortening to form pies and tarts because we want the base to be solid and not rise. 
  • Shortening fats don't contain any water - they are made of fat only. This prevents gluten from forming.
• ‘easy to spread’

  • You'll see some vegetable fat spreads labelled as 'easy to spread'.
  • These spreads are made up of triglycerides that melt at low temperatures (e.g. room temperature) so they're spreadable once they're out of the fridge.
• emulsification

  • When we shake watery and oily liquids together, we create emulsions. Droplets from one of the liquids disperse throughout the other liquid. 
  • We either create oil-in-water emulsions, like milk and vinaigrette, or water-in-oil emulsions, like butter and margarine. 
  • We need to keep stirring or shaking the oily water so that the emulsions don't separate - they do this because oil and water don't naturally mix together. We can also use an emulsifier.
• emulsifier

  • Emulsifiers are dual-ended molecules. They have a:
  • Hydrophilic end (water-loving) - bonds with water molecules.
  • Hydrophobic end (water-hating) - bonds with oil molecules.
  • The emulsifier keeps the water and oil together in what's called a stable emulsion. This means they don't separate.
• lecithin

  • Lecithin is a natural emulsifier found in egg yolks and soya.
  • It's commonly used in foods, like mayonnaise, which is made up of oil, vinegar and egg yolk in a stable emulsion.
• sauces and salad dressings

  • Mayonnaise and hollandaise sauce are examples of emulsion sauces. 
  • Vinaigrette is an example of an emulsion salad dressing.
  • You must add liquid and emulsifier before you add oil or fat when you're creating an oil-in-water emulsion. You must add the fat or oil very slowly and stir continuously as you add.
• recipe for hollandaise sauce

  • Place butter in a pan and melt.
  • Place lemon juice and egg yolks into a mixing bowl and stir.
  • Place the mixing bowl over simmering water to heat the mixture gently.
  • Slowly pour the melted butter into the mixing bowl, whisking continuously. 
  • Whisk until the mixture is smoothly mixed.