Why food is cooked and how heat is transferred GapFill

The discovery of fire allowed humans to cook their food. But why do we need to cook food at all?

Firstly, we cook food to  make it securemake it safedisinfect itsoften it by killing harmful microbes such as bacteria and viruses. An example of this is  toxoplasmosisgluesalmonellashigella in chicken. Cooking also helps to damage toxic substances naturally present in foods, such as  solaninesalinefibresorgo in potatoes.

Secondly, we cook food to  limit the amount of saltenjoy it moredevelop aromadevelop flavours. During cooking the water evaporates from food, making the residue more pronounced. Cooking therefore also enhances the smell of food, which is a big contributor to the enjoyment of food. For example, before we have eaten the food, we can smell it and see its presentation on the plate. Also, during cooking new substances are produced, such as  caramelcaragenmaltosetruffle when cooking sugar at high temperatures. It can therefore be said that cooking contributes to the overall palatability of food.

Thirdly, we cook food to improve the feel, appearance, or consistency of food and aid digestion. During cooking foods change their  colourshapesizetexture – meats become more soft and tender, eggs set, bread rises, vegetables soften, etc. During cooking the chemical compounds in food, such as protein and dietary fibre, undergo changes which make them easier to  absorbbreak downdisintegraterecycle in the digestive tract. 

Fourthly, we cook food to improve  shelf lifewaste ratepalatabilitydate mark. This is because high temperatures kill bacteria and moulds that may be present on food. This way they cannot multiply and spoil the food, which then stays fresh and safe for consumption for longer.

Lastly, we cook food to give variety in the diet. There are many different cooking methods, preparation techniques and spice combinations which allow us to produce a number of dishes using the same ingredient.

During cooking, heat is transferred in three different ways:

• convection - can only be done by liquids and  gasesfatssolidsair, which heat and cool to create convection currents in pans or ovens. 
• conduction - heat is directly  besideunderneathtouchingabove a piece of equipment or food. Some equipment and food are better conductors than others.
•  radialradiationirradiationinvection - energy is transferred through space or air by electromagnetic waves, which are absorbed by food.

Cooking often uses more than one type of heat transfer. For example, oven cooking uses both radiation and conduction. Microwaving uses radiation and conduction, while slow cooking uses convection, conduction and radiation.