Cooking is the Art of Preparing Foods for the Nourishment of the Body by Means of Dressing or the Application of Heat.
Many foods to which heat is not applied serve to nourish the body. Fresh fruits, nuts, frozen dishes, salads, fruit beverages and some vegetables are prepared without the aid of heat. Dried cereals and most vegetables as well as some fruits require the application of heat as a preparation for digestion; but we are continually learning through scientific research the necessity of including in the bill of fare a more liberal share of natural foodstuffs which have not been subjected to the chemical changes produced by a boiling or baking temperature.
Heat is a result of combustion, a chemical process whereby oxygen is united with other substances. The term as usually applied means a rapid union of oxygen with some combustible substance, whereby heat and light are produced, such as occurs when wood or coal is ignited.
Oxygen is one of the eighty or ninety elements out of which all the material universe is made. It is an invisible gas in which substances burn readily but which of itself does not produce heat, although it is absolutely essential to combustion. It is the active constituent of the air, hence a draft—air—is necessary for heat production in a stove or range.
A fuel is a substance which unites with oxygen to produce heat. All fuels contain carbon in large quantities and hydrogen and oxygen in considerable quantities. The amount of heat produced by a fuel is dependent upon the proportion of these two elements. Carbon is the essential element in all of the solid and semi-solid fuels and is also a component part of the liquid and gaseous fuels. Charcoal and coke are almost pure carbon; anthracite coal is about ninety per cent carbon. Hydrogen forms an important part in all of the gaseous fuels and also enters into the composition of all the solid and semi-solid fuels with the exception of charcoal, coke and pure anthracite.