Why do we cook food?
Cooking is a thermal technique. It destroys any microorganisms or toxins that may be present in food, thus preventing contamination. Cooked food is also easier to digest and more appetising, as cooking produces new textures and flavours.
What are the different methods for cooking food?
There are various means of transmitting heat:

• Thermal convection is when food is immersed in a hot liquid or gas, such as water, oil or air, or in steam;
• Thermal conduction is when food is in contact with a hot surface such as a frying pan, a hot stone or a grill;
• Electromagnetic irradiation involves the use of radio waves in a microwave oven or of infrared rays in an infrared oven, embers and barbecues.

How is food cooked in water?
Immersing ingredients in cold water and heating them slowly dissolves their juices. This method can be used to make stock or broth. Ingredients can also be immersed in a flavoured, boiling liquid. This is the method used to cook meat, for example. Water transmits heat to food by convection. Under normal conditions, the temperature of the water will not exceed 100°C. Food will therefore be cooked at this maximum temperature.

How is food cooked in oil?
Food is immersed in oil heated to a temperature of 160°C to 180°C. The surface of the food cooks quickly and traps the juices. Fried food is deliciously crispy.

How is air used to cook food?
Food cooked in an oven bakes in hot air. This is how we cook biscuits, cakes, terrines and gratins. The method of cooking in hot air dates back to Antiquity.

How is food steamed?
In 1679, the doctor Denis Papin invented the safety valve and fitted it to his meat-cooking machine, which he called a digester. Pressurised steam increases the boiling point of water to 140°C, thus reducing the energy required and the cooking time, and preserving vitamins and minerals.

How is food cooked on a hot surface?
The pot or frying pan is heated up and transmits this heat directly to any food which comes into contact with it. Adding a little fat enables the heat to be transmitted more effectively.
In 1912, Louis-Camille Maillard, a biochemist, discovered that carbohydrates and proteins react with each other at high temperatures. The Maillard reaction creates compounds that give cooked food an appetising colour and flavour.

How is food cooked in a casserole dish?
Cooking food in a casserole dish allows it to cook slowly and evenly at a moderate temperature. The food cooks in its own juice, which softens plant fibre and makes meat more tender.