Cooking Food• Food is cooked to• Prevent food

poisoning by killing micro organisms.

• To make it more tasty and easy to eat

• To preserve it• To make it easier to

digest• So it is easier to

absorb the nutrients• To reduce the bulk.

Heat transference Heat transference

changes food physically and chemically.

Heat can be transferred using wet or dry methods.

When you heat /cook food you often use more than one method.

Conduction In conduction the

molecules are heated and begin to vibrate faster and so the bump into the next molecule and pass on the energy. This usually takes place in a pan or inside the food.

Convection• Convection takes place

in the air or in a liquid.• As the molecules

become hotter they rise and then fall when they become cold again.

• In a pan of boiling water you can see the hot liquid rising and the bubbles bursting on the top.

• Convection takes place in the air of the oven, in water and in hot fat.

Radiation Radiation is the

transfer of energy from a heat source such as a grill to the food.

The radiation waves usually travel in a straight line. The centre of the food is then cooked by conduction.

Microwave• This is a different type of

radiation wave as it travels deeper into the food. Electricity is converted into microwaves by the magnetron.

• The microwaves travel 5cm into the food .

• They then make the water molecules vibrate which causes friction which then makes the heat.

• Hot spots can be found inside of the food so it is important to stir the food or leave it to cool before eating.