Methods of Heat Transfer and Cooking Methods

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Information about Methods of Heat Transfer and Cooking Methods
Health & Medicine

Published on March 5, 2014

Author: celinebruce



This presentation explains a few cooking methods and the methods of heat transfer with pictures and captions! Do enjoy!

The Different Methods of Cooking and Heat Transfer! Presented By: • Arianna Ali • Christa - Marie Arjoon • Kaia Boodoo • Celine Bruce • Fiona De Landro

What is Cooking? • Cooking is the application of heat to food to bring about the physical and chemical changes. • Cooking is also known as the practice or skill of preparing food by combining, mixing and heating ingredients.

Why do we cook foods? • Cooking improves the digestibility of food • Cooking destroys organisms and materials that may cause food – borne diseases • Cooking can make food more attractive and appetizing • Cooking makes the nutritive value of food available in an edible form • Cooking introduces variety in the diet • Cooking preserves food for later use • Cooking destroys natural toxins

What is Heat Transfer? • Heat is necessary for cooking, heat is also a form of energy that is produced when molecules in a substance vibrate and move quickly. • Faster movements produce more heat or kinetic energy. • Heat/ kinetic energy is measured on a temperature scale in degrees Celsius or degrees Fahrenheit. • Heat always flows from a higher temperature to a lower temperature.

Methods of Heat Transfer Conduction Radiation Convection

What is Conduction? • Conduction is the transfer of heat through a substance when there is a difference of temperature or of electrical potential between adjoining regions, without the movement of the material. when molecules get hot, they vibrate and move rapidly. The faster the movement, the more kinetic or heat energy is produced. The object to be heated must be in direct contact with the heat source. The heat causes those molecules of the material nearest to the heat source to vibrate also, producing heat. The heat is transferred right through the material with the result that the whole material becomes hot.

What is Convection? • Convection is the transfer of heat through air or gas or liquid currents. When gases and liquids are heated, the molecules becomes less dense or lighter and rise. The cooler, heavier molecules sink down to the bottom to take their place near to the heat source. These cooler molecules are then heated and rise, and the process continues in a circular pattern. • Convection cooking is a type of cooking in which hot air is forced to flow in convection ovens. This type of cooking focuses on saving energy. Foods cooked using this method lose less moisture and retain nutrients.

What is Radiation? Radiation is energy in the form of rays or waves. A hot object radiates heat rays. These rays travel in straight lines. Radiant energy is rapid because it travels with the speed of light in any direction. Heat rays can be reflected by a shiny or white surface, but dull black surfaces absorb and give off heat. During cooking, when the rays of waves reach the food as in grilling only the surface is heated by them, because the waves cannot penetrate below it. The rest of the food is heated by conduction. Radiation cooking is a heating process that does not require physical contact between the heat source and the food being cooked; instead, energy is transferred by waves of heat or light striking the food. Two kinds of radiation heat are used in the kitchen are infrared and microwave. Radiation is the propagation and emission of energy in the form of electromagnetic waves. The types of radiation include, light, heat and sound. The process of emitting those waves is also referred to as radiation.

Microwave Energy! Microwave cooking is an example of cooking by radiation because is uses electro – magnetic waves. Electro – magnetic rays are of several types. These are x-rays, light rays, heat rays or infrared rays and microwaves. When microwaves are absorbed into a material they heat it up by vibrating the water molecules at great speed. This means that foods with a high water content will cook faster than those with less water

Different Cooking Methods. Examples of Moist cooking methods are boiling, poaching, steaming, stewing, pressure cooking and deep fat drying. Cooking methods are broadly classified into moist and dry methods, based on the ways in which heat is transferred. While Braising is a combination method. Examples of Dry cooking methods are baking, barbecuing, grilling, roasting and dry frying.

The Moist Cooking Methods: • Boiling • Steaming • Poaching • Stewing

Boiling – Moist Cooking Method. Boiling is cooking food at 100 degrees Celsius. Heat is transferred mainly y conduction. Boiling is the method of cooking food in boiling water, or other water-based liquids such as stock or milk. Simmering is gentle boiling, while in poaching the cooking liquid moves but scarcely bubbles. Boiling is a simple, moist method that requires little attention and it softens tough cuts of meat, however, the soluble nutrients are lost in the water, the food may look unattractive and food may break up. Some suitable foods for boiling are staples, meat, vegetables, pulses, stocks, soups and ham dumplings.

Steaming – Moist Cooking Methods • Steaming is cooking by steam from boiling liquid. Steaming is a moist-heat cooking technique that employs hot steam to conduct the heat to the food item. Once water is heated past the 212°F mark, it stops being water and turns into steam. • Steaming is a lengthy method of cooking with no loss of nutrients of flavour, the food remains light, however, the lengthy process sometimes causes dishes can be unattractive because dishes need sauces and garnishes. • Steaming is a moist method of cooking where food is cooked from the steam of boiling water. Steaming works by boiling water continuously, causing it to vaporize into steam, the steam then carries heat to the nearby food, thus cooking the food. Some suitable foods for steaming are small fish/fillet, small pieces of meat, puddings and root vegetables.

Poaching – Moist Cooking Method • Poaching is cooking food in water at 100 degrees Celcius. Heat is transferred mainly by conduction. Poaching is a rapid method of cooking over slow heat with no loss of nutrients, however, it may be unattractive if not well garnished. • Poaching is typically reserved for cooking very delicate items like eggs and fish. But other proteins like chicken are often prepared via poaching, and some vegetables can be poached too. Among the advantages of poaching as a cooking technique are the fact that poached items will turn out moist and tender, which is certainly desirable in the case of fish where it is easy for fish to dry out when prepared using other cooking methods. And because poaching involves keeping the cooking liquid at a constant temperature — a fairly low one, at that — it makes it less likely that items will be overcooked. At least, it would take a lot longer to overcook something.

Stewing – Moist Cooking Method Stewing is cooking slowly in a small amount of liquid just below boiling point. Stewing makes tough meats tender in which small amount of heat is required and there would be no loss of nutrients but it takes a long time. Some examples of stewing are cheaper cuts of meat and dried fruits. The effect on nutritional value for stewing is there is no loss of nutrients as the liquid is served with the food.

The Dry Cooking Methods These are: • Baking • Frying • Roasting • Grilling

Baking. Grilling. Roasting. Frying.

Baking – Dry Cooking Method Baking is cooking in an oven by radiation and convection currents. Baking is a food cooking method that uses prolonged dry heat by convection, rather than by thermal radiation, normally in an oven, but also in hot ashes, or on hot stones. When baking the food has a crisp brown surface, the food keeps its shape and there is no loss of soluble nutrients. However, baking requires attention and it can waste energy if the maximum use is not made in the oven. Suitable foods for baking are Flour products, meat or chicken.

Frying – Dry Cooking Method Frying is cooking in hot fat which could be dry, shallow, deep fried or stir – fried. Frying is the cooking of food in oil or another fat. Frying is the method rapid of cooking, it browns food evenly, the food is tasty and the energy is increased by the fat. Some suitable foods are eggs, small cuts of meat, poultry and vegetables.

Roasting – Dry Cooking Method. • Roasting is oven cooking, but food is basted occasionally like in pot roasting. Roasting is a dry method of cooking that uses dry heat, whether an open flame, oven, or other heat source. • Roasting can enhance flavor through caramelization and browning on the surface of the food. Roasting uses indirect, diffused heat and is suitable for slower cooking of meat in a larger, whole piece. Meats and most root and bulb vegetables can be roasted. • In Roasting there is an attractive appearance, the food is tasty and it retains its full flavour and nutritive value but it requires some attention and basting to prevent dryness and hardness.

Grilling – Dry Cooking Method Grilling is cooking by heat radiated from a heated grill. Grilling is a form of cooking that involves dry heat applied to the surface of food, commonly from above or below (as in North America). It is sometimes incorrectly referred to as barbecuing which is a slow cooking technique. In grilling the food is quickly cooked, its tasty, and has a good colour with no loss of nutrients but grilling is suitable for the more tender cuts of meat and it needs constant attention.

Thank you! Thank you for viewing Group 4’s Home Economics Project. Hope you enjoyed!

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