How heat cooks food
See the three ways heat reaches your food and the one split that matters most: dry heat or wet heat. After this you can look at any recipe step and say what the heat is doing.
THE BIG IDEA
Cooking is moving heat into food
Heat changes food: proteins firm up, starches soften and swell, tough tissue slowly melts, surfaces brown. Every cooking method is just a different way of delivering heat, and the way it arrives decides the result.
The same chicken thigh can be pale and soft (simmered in a stew), golden and crisp (pan-fried) or smoky and charred (over charcoal). Same ingredient, three ways of delivering heat.
Three ways heat travels
- Conduction: heat passes by direct contact. Hot pan to the underside of an egg, and then from the outside of the food to its centre.
- Convection: heat is carried by a moving fluid: boiling water around rice, hot air moving in an oven, hot oil around a falafel.
- Radiation: heat travels as rays, with no contact needed: glowing charcoal under a kebab, the grill element at the top of the oven, a toaster.
Check yourself
Match each kitchen moment to the main way the heat is arriving
Show the answer
- An egg setting where it touches the pan → Conduction
- Potatoes cooking in bubbling water → Convection
- Kebab colouring above glowing charcoal → Radiation
Heat walks in from the outside
However heat reaches the surface, it gets to the centre only by conduction, and food conducts heat slowly. Picture heat as a crowd walking in through the doors of a hall: the people near the door arrive long before the middle fills up. That's why a thick piece on fierce heat burns outside while the centre is still raw. Where the analogy breaks: the crowd keeps walking after you close the doors. Food keeps cooking for a while after you take it off the heat, which you'll use in lesson 3.
Check yourself
Nima puts a thick chicken breast in a very hot pan. Four minutes later the outside is nearly black and the middle is still pink and raw. What went wrong?
- The pan was the wrong material for chicken
- Heat reached the surface much faster than it could travel to the centre
- He should have added water to the pan first so the chicken browned evenly
- Chicken breast can't be cooked in a pan
Show the answer
Heat reached the surface much faster than it could travel to the centre
Right. The surface took heat far faster than the meat could pass it inward. A thinner piece, or a lower heat for longer, lets the centre catch up.
The split that matters most
Dry heat
Pan-frying, roasting, grilling, deep-frying. No water around the food, so the surface can climb far above 100°C. It dries, crisps and browns, and browning is flavour. Best for tender things that cook fast.
Wet heat
Boiling, simmering, steaming, stewing. Water or steam surrounds the food, so it never gets hotter than about 100°C. It cooks gently and evenly, keeps food moist and softens tough cuts over time, but it can't brown.
Check yourself
Dry heat or wet heat?
- Aubergine slices roasting in the oven
- Lamb simmering in a stew for two hours
- Falafel frying in deep oil
- Rice cooking in boiling water
- Chicken wings over charcoal
- Fish fillets in a steamer basket
Show the answer
Dry heat: Aubergine slices roasting in the oven, Falafel frying in deep oil, Chicken wings over charcoal
Wet heat: Lamb simmering in a stew for two hours, Rice cooking in boiling water, Fish fillets in a steamer basket
| Method | Rough temperature | What it's good at |
|---|---|---|
| Simmering | 85–95°C | Gentle, moist, softens tough cuts |
| Boiling / steaming | about 100°C | Fast, even, no browning |
| Oven roasting | 180–220°C air | Browning all round, drier surface |
| Hot pan or deep oil | 160–200°C+ | Fast browning and crisp edges |
Check yourself
Leila has lamb neck pieces and wants them soft enough to fall off the bone, with deep flavour. Which plan fits best?
- Brown them in a hot pot, then simmer gently in liquid for a couple of hours
- Boil them hard for 20 minutes
- Grill them quickly over very high heat so the outside chars and the inside stays juicy
- Steam them so they stay pale and moist
Show the answer
Brown them in a hot pot, then simmer gently in liquid for a couple of hours
Yes. Browning with dry heat builds flavour, and the long gentle simmer is what turns a tough cut tender.
Check yourself
Turning the flame up under a pot of boiling water makes it boil faster but does not make it any hotter.
Show the answer
True
True, and it catches most people out. Once water is boiling it stays at about 100°C, and the extra flame only turns more of it to steam, faster. That is the ceiling on every wet method, which is why boiled chicken stays pale however long you leave it.
Lesson recap
- Heat reaches food by conduction (contact), convection (moving water, air or oil) and radiation (charcoal, grill element).
- Inside the food, heat travels slowly from the outside in, so thick pieces need lower heat and more time.
- Dry heat goes far above 100°C and browns; wet heat stays around 100°C, cooks gently and can't brown.
- Tender ingredients suit fast dry heat, tough cuts need long wet heat, and browning first then simmering gives you both.