Chapter 3: Cooking Methods

  • Created by: ZR1
  • Created on: 14-06-17 16:39

Why is food cooked?

To make food safe to eat: High-risk foods must be thoroughly cooked to destroy food poisoning bacteria and natural poisons.

To develop flavour

  • Cooking causes chemical reactions in food that develop flavour.
  • Cooking concentrates flavour by causing water in food to evaporate.

To improve texture and appearance 

  • Starch granules swell and gelatinize causing food to thicken or soften.
  • Meat is tenderised.
  • Fats melt and give smooth ‘mouth-feel’.
  • Plant cells soften – vegetables and fruits become tender.Raw doughs rise and become light in texture.

To improve shelf-life of food: Cooking destroys micro-organisms and preserves foods.


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  • Atoms in metal pans and baking trays start to vibrate as heat energy from cooker goes into metal.
  • Vibrations transfer heat energy to other metal atoms.
  • Metal gradually heats up and passes heat energy to food.
  • Metals are good conductors of heat – very good for baked products.
  • Plastic, wood, air, thick cotton and wool are good heat insulators (poor conductors of heat) – used for pan handles and oven gloves. Wooden spoons to protect hands.
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  • When a pan of water is heated, heat is conducted through the metal pan to water molecules.
  • Water molecules move upwards then downwards in a circular motion (convection currents) taking heat energy with them and passing it into the food.
  • The more heat energy, the faster the water molecules move in circular convection currents.Also, happens in an oven with hot air currents.
  • Gas oven/ordinary electric oven – zones of heat: hotter at the top than bottom shelf due to convection.
  • Electric fan ovens – heat evenly distributed by fan – same temperature on each shelf.
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  • Grilled/barbequed food heated by radiant heat.
  • Infrared heat rays heat the surface of the food and are absorbed.
  • Food must be no more than 3.5cm thick otherwise may be undercooked inside.
  • Food must not be too close to grill or it may burn easily.
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Methods using moisture

  • Water used to transfer heat.
  • Boiling, braising, poaching, simmering, steaming, stewing.
  • Heat transfer: conduction → convection.
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Effects of water on ingredients

  • Starch absorbs water and gelatinises.
  • Proteins denature and coagulate – become solid.
  • Fat melts.
  • Water evaporates – sauces reduce.
  • Vegetables, fruits, pasta, rice, etc. tenderise.
  • Meat tenderises (collagen converts to gelatine) – can become indigestible if overcooked.
  • Colours change – e.g. meat from red to brown; vegetables bright green.Flavour intensifies.
  • Vitamins B1, B2 and C dissolve in water and are gradually destroyed by heat.
  • Vitamins B1, B2 and C can be conserved by preparing, cutting, grating, squeezing and cooking just before serving; using only a little water; limiting their exposure to light and oxygen; serving as soon as they are cooked.
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Methods using oil

  • Oil used to transfer heat.
  • Sautéing, shallow/pan frying, stir frying: conduction.
  • Roasting, deep fat frying: conduction → convection.
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Effects of oil on ingredients

  • Intrinsic sugars caramelise and make food go golden colour.
  • Flavour of foods intensifies as water evaporates.
  • Starch absorbs oil and swells.
  • Vegetables/fruits soften.
  • Protein denatures and coagulates.
  • Foods become crisp on outside – especially if coated with egg and breadcrumbs to protect food.
  • Meat shrinks and squeezes out juices.
  • Energy density of food increased.
  • Vitamins B1, B2 and C are gradually destroyed by heat.
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Methods using dry heat

  • Dry heat used to transfer heat
  • Baking: convection → conduction.
  • Grilling: radiation.
  • Dry frying: conduction.
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Effects of dry heat on ingredients

  • Gases from raising agents to expand and make food rise.
  • Protein denatures and coagulates – overcooking makes it less digestible.
  • Meat proteins in muscle cells shrink and squeeze out juices.
  • Free sugars melt and soften gluten in the flour. 
  • Sugars caramelise.
  • Fat melts and is released from meats – reduces energy density.
  • Starch granules absorb water/fat and swell and soften.
  • Gluten stretches as doughs rise then sets around gas bubbles.
  • Starch on outside turns to dextrin and goes golden brown.
  • Starch becomes more digestible.
  • Flavours intensify.
  • Vitamin B1, B2 and C destroyed by heat.
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  • Radiation: cooking by electromagnetic waves that vibrate water molecules and transfer heat energy very quickly.
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Effects of microwaving on ingredients

  • Protein denatures and coagulates quickly – will quickly overcook and become indigestible.
  • Fat melts.
  • Sugar caramelises and will burn easily.
  • Starch gelatinises.
  • Juices and water from meat are easily squeezed out.
  • A little damage to vitamin B1, B2 and C.
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