Have you ever wondered what's actually happening when you're cooking food? While this is something that we usually take for granted, this process of heating food - known as heat transfer - is complicated and fascinating. Keep reading to learn more about the relationship between heat transfer and cooking and the important role it plays in your kitchen.
What is Heat Transfer?
Heat transfer is an exchange of thermal energy between two objects. The rate of heat transfer depends upon the temperatures of each entity and the medium through which the thermal energy is being transferred. In cooking, heat transfer refers to heating your food items through a cooking appliance, such as a stove, fryer, microwave, or oven.
How is Heat Transfer Used in Cooking?
Heat transfer is a very important aspect of the cooking process. Heating food destroys potentially harmful bacteria and other microorganisms, which makes food safe to eat and easier to digest. When food or liquids become hot, their molecules absorb energy, begin vibrating rapidly, and start to bounce off of each other. As they collide, heat energy is produced and transferred, which warms and cooks our food.
3 Types of Heat Transfer
Each of these three methods of heat transfer features its own unique characteristics, but there is some crossover between the different types.
What is Conduction?
Conduction is the process of heat being transferred between objects through direct contact, and it's the most common type of heat transfer. For example, in cooking the burners on stoves will conduct heat energy to the bottom of a pan sitting on top of it. From there, the pan conducts heat to its contents.
A deep fryer also uses conduction heating as the hot oil cooks the food when it comes into direct contact with it. Additionally, conduction heat is responsible for moving heat from the outside of the food to the inside. As a result, conduction heat also happens when cooking with convection and radiation heating methods.
Conduction is the slowest method of heat transfer, but the direct contact between the cooking surface and the item to be heated allows food to be cooked from the outside in. When cooking a steak in a cast iron skillet, for example, conduction produces an evenly cooked exterior and a moist, juicy interior that guests are sure to love.
Examples of Conduction Cooking
Here are a few examples conduction heating:
- Burning your hand on a hot piece of metal
- Grilling steak, chicken breasts, or pork chops
- Using ice water to blanch vegetables after steaming to keep them from losing their color
What is Convection?
Convection combines conduction heat transfer and circulation to force molecules in the air to move from warmer areas to cooler ones. As the molecules closest to the heat source become warm, they rise and are replaced by cooler molecules. There are two types of convection that are based on the movement of the heated molecules.
Natural convection occurs when molecules at the bottom of a cooking vessel rise and warm while cooler and heavier molecules sink. This creates a circulating current that evenly distributes heat throughout the the substance being prepared.
For example, when a pot of water is placed on the stove to boil, conduction heat warms up the pot, which then heats the water molecules inside. As these molecules heat, convection causes them to move away from the interior of the pot as they are replaced by cooler molecules. This continuous current creates convection heat transfer within the water.
Mechanical convection occurs when outside forces circulate heat, which shortens cooking times and cooks food more evenly. Examples of this include stirring liquid in a pot or when a convection oven uses a fan and exhaust system to blow hot air over and around the food before venting it back out.
Examples of Convection Cooking
Here are a few examples of how heat transfer via convection works:
- Water coming to a boil and circulating in the pot
- Running cold water over frozen food, which transfers heat into the food to thaw it more quickly
- Room temperature air moving around frozen food to thaw it
What is Radiation Cooking?
In cooking, radiation is the process where heat and light waves strike and penetrate your food. As such, there is no direct contact between the heat source and the cooking food. There are two main radiant heat cooking methods: infrared and microwave radiation.
Infrared radiation utilizes an electric or ceramic heating element that gives off electromagnetic energy waves. These waves travel in any direction at the speed of light to quickly heat food, and are mainly absorbed at the surface of whatever you're preparing. Examples of things that create infrared radiation are glowing coals in a fire, toaster ovens, and broilers.
Microwave radiation utilizes short, high-frequency waves that penetrate food, which agitates its water molecules to create friction and transfer heat. If you're heating a solid substance, this heat energy is transferred throughout the food through conduction, while liquids do so through convection.
Microwave heat transfer usually cooks food faster than infrared radiation, as it is able to penetrate foods several inches deep. Keep in mind that microwave radiation works best when cooking small batches of food.
Examples of Radiation Cooking
Here are a few examples of how heat transfer via radiation works:
- Warming your hands over a fire
- Lying in the sun to get warm
- Heating up dinner in the microwave
Whether you're using a pan on a stove, a convection oven, or a heavy-duty microwave, conduction, convection, and radiation are all around us. Knowing and understanding what heat transfer is, how it works, and which type of heat transfer is happening as you cook can help you better understand the science of cooking and improve your skills as a chef.
Posted in: |By Richard Traylor
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At its most basic, cooking is the transfer of energy from a heat source to your food. That energy causes physical changes in the shape of proteins, fats, and carbohydrates, as well as hastens the rate at which chemical reactions take place.How is heat transfer used in cooking? ›
During cooking, heat is transferred from the source of heat to the food through conduction (e.g. grilling steak on a grilling pan sitting on a stove), convection (e.g. running cold water over frozen food to speed up thawing process) and/or radiation (roasting marshmallow over fire).What is the relationship between temperature and the heat transferred? ›
Heat is always transferred from the object at the higher temperature to the object with the lower temperature. For a gas, the heat transfer is related to a change in temperature. The temperature, pressure, and volume of the gas determine the state of the gas. Heating a gas changes the state of the gas.What is the relationship between time and temperature when cooking? ›
It is true that there is a negative correlation between cooking time and temperature: the higher the temperature, the shorter the cooking time.What are the four types of heat transfer in cooking? ›
Answer: 1) The different methods of cooking or heat transfer are broken down into conduction, convection, and radiation. Every method of cooking involves one or more of these heat transfer methods.What type of energy is used for cooking and heating? ›
Answer: Thermal energy is used to cook food. Thermal energy is heat. It's converted from either electrical potential energy or chemical potential energy, depending on the cooking appliance.What happens when food is cooked? ›
The process of cooking food breaks down some of its fibers and plant cell walls, making it easier for the body to digest and absorb the nutrients ( 17 ). Cooking also generally improves the taste and aroma of food, which makes it much more enjoyable to eat.What is convection heat transfer in cooking? ›
Convection is one of five heat transfer methods commonly used in cooking, including conduction, boiling, condensation, melting, and radiation. Convection is the process by which food is heated by a moving heat source, such as the hot air in an oven, or even the motion of boiling water in a pot.What is the relationship between heat and work? ›
Heat and work are two different ways of transferring energy from one system to another. The the distinction between Heat and Work is important in the field of thermodynamics. Heat is the transfer of thermal energy between systems, while work is the transfer of mechanical energy between two systems.What is the relationship between heat and energy? ›
Heat is the transfer of thermal energy between two bodies that are at different temperatures and is not equal to thermal energy. Work is the force used to transfer energy between a system and its surroundings and is needed to create heat and the transfer of thermal energy.
First, it changes the temperature of an object. If heat is transferred from an object to the surroundings, then the object can cool down and the surroundings can warm up. When heat is transferred to an object by its surroundings, then the object can warm up and the surroundings can cool down.What is the relationship between food temperature and food safety? ›
Everyone should practice general food safety precautions at all times: Bacteria can grow in the danger zone between 4 °C and 60 °C (40 °F to 140 °F). Keep cold foods cold at or below 4 °C (40 °F) and keep hot foods hot at or above 60 °C (140 °F).Why is temperature important in cooking? ›
Controlling the temperature of food is extremely important in ensuring that food is safe to eat, and you must ensure that food is always cooked, cooled, chilled or reheated properly to minimise the risk of harmful levels of bacteria in the food that you sell.Why is temperature and time important cooking? ›
Some foods require time and temperature control to maintain safety (TCS foods), also known as potentially hazardous foods (PHF). These foods require time/temperature control to limit the growth of pathogenic microorganisms or the production of toxins.What are the two different types of heat used for cooking? ›
These methods can be broken down into two categories: moist-heat cooking and dry-heat cooking. Moist-heat cooking methods use water, liquid or steam to transfer heat to food. Common moist-heat cooking methods include: poaching, simmering, boiling, braising, stewing, pot roasting, steaming and en papillote.What type of heat transfer is used in baking? ›
In an oven, the hot air flows by natural or forced convection while heat is distributed from the heating element by radiation. During baking process, heat is also transfer by conduction from the baking metal container to the baked product.Which of the following is a method of cooking? ›
The three types of cooking methods are dry heat cooking, moist heat cooking, and combination cooking. Each of these methods uses heat to affect foods in a different way. All cooking techniques, from grilling to steaming, can be grouped under one of these three methods.What is the source of energy used for cooking? ›
Abstract. Recent household surveys from 52 developing economies that include questions about energy use show that the most commonly cited primary energy for cooking is wood, followed by gas, natural gas and, where natural gas is not available, liquefied petroleum gas (LPG), and then by electricity.How much energy is used for cooking? ›
The U.S. Department of Energy estimates that cooking alone generally accounts for 4 to 5% of total home energy use, and this figure doesn't include the energy costs associated with refrigeration, hot water heating, and dishwashing.Which energy is used in cooking food? ›
Heat energy helps cook food and keeps us warm in winter, while mechanical energy is associated with movement.
Note: There are three important temperatures to remember when cooking meat or eggs at home: Eggs and all ground meats must be cooked to 160°F; poultry and fowl to 165°F; and fresh meat steaks, chops and roasts to 145°F. Use a thermometer to check temperatures.What type of reaction is cooking? ›
The Maillard reaction occurs in cooking of almost all kinds of foods, although the simple sugars and amino acids present produce distinctly different aromas.What happens when you heat up food? ›
Food should be heated to an internal temperature of 70°C (158°F) and it must stay at this temperature for at least two minutes. Cooking causes the proteins in any bacteria to break up and the germs start to die at around 60°C (140°F).What is the difference between conduction and convection in cooking? ›
Conduction transfers the heat using direct contact; food is heated directly in a metal pan, in a liquid, or surrounded by air. Dropping an egg into a pan of boiling water is a good example. Convection occurs by the movement of air, liquid, or steam around the food.Who discovered the relationship between work and heat? ›
James Prescott Joule, (born December 24, 1818, Salford, Lancashire [now in Greater Manchester], England—died October 11, 1889, Sale, Cheshire), English physicist who established that the various forms of energy—mechanical, electrical, and heat—are basically the same and can be changed one into another.What is the method of heat transfer? ›
Heat can be transferred in three ways: by conduction, by convection, and by radiation.What are the similarity between work and heat? ›
Heat is similar to work in that both represent ways of transferring energy. Neither heat nor work is an intrinsic property of a system, that is , we cannot say that a system contains a certain amount off heat or work.What is the relationship between heat temperature and kinetic energy? ›
Relationship between heat and temperature
Temperature is a measure of the average kinetic energy of the atoms or molecules in the system. The water molecules in a cup of hot coffee have a higher average kinetic energy than the water molecules in a cup of iced tea, which also means they are moving at a higher velocity.
Heat is a concept that is important to understand in various engineering fields. It is particularly relevant for civil, mechanical and chemical engineers because heat transfer plays a key role in material selection, machinery efficiency and reaction kinetics, respectively.What are the effect of heat short answer? ›
Answer: Four effects of heat are as follows: Change in temperature - When water is heated, its temperature increases and it starts boiling. Change in State - On boiling water, steam is evolved, i.e., the its liquid state changes to its gaseous state.
Conduction heat transfer is the transfer of heat through matter (i.e., solids, liquids, or gases) without bulk motion of the matter. In another ward, conduction is the transfer of energy from the more energetic to less energetic particles of a substance due to interaction between the particles.Is cooking the same as heating? ›
Cooking is a special form of heating - it has the aim of denaturing the protein within the meat that is being cooked. Heating is a very generic term - it simply means applying a higher temperature to the meat - in your case chicken.What is the relationship between heat and electricity? ›
There is no fundamental relationship between heat and electricity. You can make heat by running an electrical current through a resistance, but almost any process involving energy will produce some heat.Does cooking require heat? ›
At its most basic, cooking means applying heat to food. Whether the food is baked, fried, sautéed, boiled, or grilled, it's all cooking.Is heat necessary for cooking? ›
Cooking can also occur through chemical reactions without the presence of heat, most notably with ceviche, a traditional South American dish where fish is cooked with the acids in lemon or lime juice. Another example is cooking with liquid nitrogen.Do you need heat to cook something? ›
Yes. Cooking means applying heat to food in order to change the state of the protein molecules and kill pathogens. Everyone uses 'cooking' in this way, even if they don't consciously realise it.What is the relationship between energy and heat production? ›
Heat or thermal energy
Thermal energy (also called heat energy) is produced when a rise in temperature causes atoms and molecules to move faster and collide with each other. The energy that comes from the temperature of the heated substance is called thermal energy.
Resistance of the wire: The amount of heat H produced in the wire is directly proportional to the resistance R of the wire, i.e., H ∝ R.What is the relationship between power and energy? ›
Power is how fast energy is used or transmitted - power is the amount of energy divided by the time it took to use the energy. Its unit is the watt, which is one joule per second of energy used.How does temperature affect food and why? ›
Bacteria grow most rapidly in the range of temperatures between 40 ° and 140 °F, doubling in number in as little as 20 minutes. This range of temperatures is often called the "Danger Zone." That's why the Meat and Poultry Hotline advises consumers to never leave food out of refrigeration over 2 hours.
Food is central to our sense of identity. The way any given human group eats helps it assert its diversity, hierarchy and organisation, but also, at the same time, both its oneness and the otherness of whoever eats differently.