Functional + chemical properties of food

• Convection can happen in ovens
• Blanching involves boiling food for a short time to part cook it, before placing the food in cold / icy water
• Advantages of sweating?

  Cooks food tenderly + tastes sweet once cooked + food doesn’t brown
• Disadvantages of roasting?

  requires lots of energy + relatively unhealthy
• Dry frying doesn’t use any oil or fat. It’s healthier than stir frying and shallow frying
• Caramelisation is suitable for sweet and savoury foods + happens when sugar molecules are exposed to high heat
• what is lecithin?

  a natural emulsifier found in egg yolk and soya
• Protein denaturation?

  1. proteins have complex structure
  2. when cooked they denature (chemical bonds break down)
  3. the proteins unravel and their shape changes - in most cases this is irreversible
  4. proteins can be denatured in different ways:

  physical agitation, changes in temperature, acids
• Protein coagulation?

  1. once they have been denatured, protein molecules collide with other protein molecules and coagulate (join together)
  2. water becomes trapped between protein molecules
  3. coagulation changes appearance and texture
  4. if food is overcooked, coagulation happens too much, the protein tightens. Which forces water out of molecules making it dry and chewy
• Foams formed?

  1. form when gas becomes trapped (aeration) inside liquid
  2. when liquids containing proteins are agitated the proteins denature - this causes them to stretch and air becomes trapped in liquid
  3. when air becomes trapped it creates a foam
  4. over whisking causes new protein bonds to break, air escapes and foam collapses
  5. some foams form a solid structure when cooked eg: white foams become meringues
• Gluten allows doughs to stretch and rise

  1. gluten is a protein found in wheat flours
  2. formed when water is mixed with flour to make dough
  3. molecules of gluten are coiled - meaning they are able to stretch and bend giving dough elasticity.
  4. dough can be kneaded to ‘work’ the gluten - this causes the gluten strands to get longer, stronger and stretchier
  5. when it reaches a high temperatur, gluten coagulates and the dough stays stretched. This gives food like well risen bread a light, airy texture.