Cooking is a process of chemical and physical change in food items to create a complete dish in which more than two ingredients of food are combined and heated simultaneously by using various cooking methods and tools. Cooking gives variety to the menu, as one food item can be cooked in various ways and given different textures. For example mutton can be cooked as a soup, roast, steak, kabob or stew.
PRINCIPLES OF COOKING
Cooking can be defined as the transfer of energy from a heat source to a food. This energy alters the food’s molecular structure, changing its texture, flavor, aroma and appearance. But why is food cooked at all? The obvious answer is that cooking makes food taste better. Cooking also destroys understandable microorganisms and makes foods easier to ingest and digest. To cook foods successfully, you must first understand the ways in which heat is transferred: conduction, convection and radiation. You should also understand what the application of heat does to the proteins, sugars, starches, water and fats in foods. Perhaps most importantly, you must understand the cooking methods used to transfer heat: broiling, grilling, roasting and baking, sauteing, pan-frying, poaching, simmering, boiling, steaming, braising and stewing. Each method is used for many types of food, so you will be applying one or more of them every time you cook. The cooking method you select gives the finished product a specific texture, appearance, aroma and flavor. A thorough understanding of the basic procedures involved in each cooking methods helps you produce consistent, high-quality products.
HEAT TRANSFER
Heat is a type of energy. When a substance gets hot its molecules have absorbed energy, which cause the molecules to vibrate rapidly, expand and collide off one another. As the molecules move they collide with nearby molecules, causing a TRANSFER OF HEAT ENERGY. The faster the molecules within a substance move, the higher its temperature. This is true whether the substance is air, an aluminum pot or a sirloin steak.
CONDUCTION
Conduction is the most straightforward means of heat transfer. It is simply the movement of heat from one item to another direct contact. For example, when the flame of a gas burner touches the bottom of a sauté pan, heat is conducted to the pan. The metal of the he pan then conducts heat to the surface of the food lying in that pan. Some materials conduct heat better than others. Water is a better conductor of heat than air. This explains why a potato cooks much faster in boiling water than in an oven, and why you cannot place your hand in boiling water at a temperature of 2120F (100OC) , but can place your hand , at least very briefly, into a 400oF (200OC) oven. Generally, metals are good conductors, while liquids and gases are poor conductors.
CONVECTION
Convection refers to the transfer of heat through a fluid, while may be liquid or gas. Convection is actually a combination of conduction and a mixing in which molecules in a fluid (Whether air, water of fat) move from a warmer area to a cooler one. There are two types of convection: natural and mechanical. Natural Convection
Occurs because of the tendency of warm liquids and gases to rise while cooler ones fail. This causes a constant natural circulation of heat. For examples, when a pot of stock is placed over a gas burner, the molecules at the bottom of the pot are warmed. These molecules rise while cooler, heavier molecules sink. Upon reaching the pot’s bottom; the cooler molecules are warmed and begin to rise. This ongoing cycle creates currents within the stock, and these currents distribute the heat throughout the stock. Mechanical Convection.
Relies on fans or stirring to circulate heat more quickly and evenly. This explains why foods heat faster and more evenly when stirred. Convection ovens are equipped with fans to increase the circulation of air currents, thus speeding up the cooking process. But even conventional ovens (that is, not convention ovens) rely on the natural circulation patterns of heated air to transfer heat energy to items begin baked or roasted.
RADIATION
Unlike conduction and convection, radiation does not require physical contact between the heat source and the food begins cooked. Instead, energy is transferred by waves of heat of light striking the food. Two kinds of radiant heat are used in the kitchen: infrared and microwave.
INFRARED COOKING uses an electric or ceramic element heated to such a high temperature that it gives off waves of radiant heat which cook the food. Radiant heat waves travel at the speed of light in any direction (unlike convection heat, which only rises) until they are absorbed by a food. Infrared cooking is commonly used with toasters and broilers. The glowing coals of a fire are another example of radiant heat.