How Heat Works: The Fundamental Physics of Cooking - Section 2: Methods of Heat Transfer

Heat doesn't behave in just one way—it moves and interacts with food through three distinct mechanisms: conduction, convection, and radiation. Understanding these methods of heat transfer helps explain why different cooking techniques produce different results.

Conduction is perhaps the most straightforward method of heat transfer. It occurs when heat moves directly from one substance to another through physical contact. When you place a steak on a hot cast iron pan, heat transfers directly from the pan's surface to the meat. Conduction also happens within food—heat gradually travels from the exterior to the interior. This is why thick cuts of meat take longer to cook through than thin ones, even at the same temperature. The heat must conduct through more material to reach the center.

Conduction works particularly well with dense, solid materials. Metals conduct heat efficiently, which is why they make excellent cooking vessels. Water also conducts heat well, though not as efficiently as metal. Air, however, is a poor conductor, which explains why foods cook differently in dry versus moist environments. When you understand conduction, you can make better choices about cooking surfaces and techniques for different foods.

Convection takes heat transfer a step further by adding movement to the equation. In convection, heat circulates through a liquid or gas, creating currents that distribute heat more evenly throughout the cooking environment. When you boil pasta, water near the bottom of the pot heats up, becomes less dense, rises to the top, and is replaced by cooler water in a continuous cycle. This circulation helps cook the pasta evenly.

We see convection in action in many cooking scenarios. Convection ovens have fans that circulate hot air to cook food more quickly and evenly than conventional ovens. When simmering a stew, the gentle bubbling creates convection currents that distribute heat throughout the pot. Understanding convection explains why stirring is so important in some recipes—it manually enhances the convection process to ensure even heating.

Radiation differs fundamentally from the other methods because it doesn't require a medium to transfer heat. Instead, energy travels in waves directly from the heat source to the food. When you grill over charcoal or use your oven's broiler, the food cooks primarily through radiant heat. The infrared energy penetrates the food's surface and converts to heat energy.

Radiation explains why food browns well on a grill or under a broiler—the direct energy creates high surface temperatures that trigger Maillard reactions and caramelization. It's also why turning food is necessary when using these methods, as radiation typically comes from one direction. By understanding radiation, you can better position food relative to heat sources for optimal cooking results.