Heat transfer

The Three Types of Heat Transfer

Conduction

  • Refers to heat transfer that occurs in solid materials or directly between materials that are in contact
  • Heat is conducted from high temperatures to low temperatures
  • In cooking, conduction happens when heat is applied directly - such as in frying, where heat from the pan is conducted to the food
  • Many metals are good conductors of heat, which is why metallic pots and pans are commonly used in cooking
  • Some materials, such as wood and plastic, are poor conductors, which allows them to be used as handles on cooking utensils so they don’t get hot

Convection

  • Convection involves the transfer of heat through a fluid (liquid or gas)
  • It functions on the principle that when a fluid is heated, it becomes less dense and rises, allowing cooler fluid to take its place – this results in a continuous circulation pattern and even heating
  • When boiling water or baking in an oven, convection currents are created to distribute heat evenly
  • Conventional ovens use convection to circulate heated air around the food

Radiation

  • Radiation is a method of heat transfer that does not require a medium (air, liquid, or solid) to transfer heat - it can transfer heat through a vacuum
  • In cooking, grilling is an example of radiation, where heat is radiated from the grill elements to the food
  • Microwaves also utilise radiation - the microwave rays penetrate the food, heating it from the inside out
  • It’s important to note that in comparison with conduction and convection, the process of heat transfer via radiation is typically much quicker.

The Importance of Heat Transfer

Cooking Food Properly

  • Heat transfer ensures that food is cooked evenly, improving its taste and texture
  • Consistent heat in cooking is critical for food safety, as it ensures harmful bacteria are killed

Enhancing Flavor

  • Different types of heat transfer can be used to achieve various effects on food - for example, the Maillard reaction (browning) that occurs in baking, broiling, grilling, and frying

Understanding Recipes and Cooking Instructions

  • A knowledge of how heat transfer works can help you understand why certain cooking methods are recommended in recipes and can help you make adjustments if necessary.