ELI5 food science
Heat transfer ELI5 (conduction, convection, radiation)
Cooking moves energy into food until proteins set, water leaves, starches change, and surfaces brown. That energy arrives by conduction, convection, and radiation — usually mixed, with one path in the lead.
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ELI5
Cooking moves energy into food until proteins set, water evaporates, starches gelatinize, and surfaces brown. That energy arrives three common ways in a kitchen.
Most real cooking mixes all three. A steak in a cast-iron skillet is mostly conduction at the crust, some convection from hot air and fat around the sides, and a little radiation from the hot metal. An oven roast leans convection, plus some radiation from hot walls. A broiler is radiation-forward.
- 01Conduction — heat through direct contact (pan to steak; probe tip to roast interior).
- 02Convection — heat carried by moving fluid (hot air in an oven; circulating oil in a fryer; simmering water).
- 03Radiation — energy as electromagnetic waves (broiler glow, charcoal, toasting under a red element) without needing the air molecules as the main courier.
What it matters on the stove
Why sear needs a hot pan: conduction only browns hard once surface water is gone. Wet food steams — a convection-dominated mush — instead of crusting.
Why rest after hard heat: conduction into the center continues as carryover; slicing too soon dumps juices.
| Mode | Kitchen picture | Practical lever |
|---|---|---|
| Conduction | Sear in steel or iron; contact grilling | Dry surface, preheated pan, good contact, don’t crowd |
| Convection | Oven roast, convection fan, poaching, frying | Air or liquid movement and temperature; rack position; don’t block fans |
| Radiation | Broil, open flame, infrared | Distance to the element or flame; watch for scorch before the center catches up |
How to use this without a physics degree
- 01Name the main path. Pan sear is conduction. Oven is convection plus wall radiation. Broiler is radiation.
- 02Match the tool. A thick roast wants an oven’s gentler gradient after or instead of only screaming conduction. A thin cutlet can finish on conduction alone.
- 03Mind gradients. Radiation and hard conduction brown the outside before the inside catches up — finish lower or rest.
- 04Move the fluid on purpose. Fan-on convection ovens; don’t overcrowd a fryer; a simmer and a hard boil are different agitation.
Common misconceptions (cooking lens)
- “The pan seals juices by conduction” — no. Browning is not sealing.
- “A convection oven is magic radiation” — the fan mainly improves hot-air convection.
- “Only one mode ever happens” — kitchens are mixed. We teach the dominant path.
What this page will not do
- Diagnose burns, prescribe diets, or claim heat modes detox food
- Replace appliance manuals or food-safety temperature charts
- Overclaim precision beyond culinary teaching accuracy
Educational food science — no nutrition-cure, medical, or diet claims. Science pass 2026-09-25.