Cooking science

Heat recovery after a cold load

A hot pan is a store of energy, and cold food takes that energy. Put too much in at once and the pan cools below the temperature at which anything useful happens — and thin pans never recover.

The pan pays for the food

Heating cold food takes energy, and in the first seconds that energy comes almost entirely from the pan itself rather than from the burner. The pan cools; the food warms.

How far it cools depends on two things: how much cold food went in, and how much energy the pan was holding. A heavy cast-iron pan holds a great deal and barely notices one steak. A thin aluminium pan holds very little and drops immediately.

Once the pan is below the temperature where browning happens, the food releases moisture, that moisture holds the surface at boiling point, and the whole thing turns into a steamer. Recovery from that is slow, and everything cooks in the meantime.

What decides recovery

Pan mass

Heavy pans recover fastest because they were holding the most energy. Cast iron and thick steel; not thin aluminium.

How much food

The single thing you control most easily. Half a panful at a time.

Food temperature

Fridge-cold food takes far more energy than food at room temperature.

Water content

Wet food takes an enormous amount of energy to dry before it can brown.

Burner power

Matters less than people think in the first thirty seconds; it is the pan that pays initially.

Oil volume in deep frying

A large bath of oil holds much more energy and recovers far better than a shallow one.

What to do about it

• Cook in batches. Half of what you think will fit. This is the fix for browning mince, mushrooms, vegetables and meat.
• Preheat properly and for longer. A pan that feels hot is often not yet saturated with heat.
• Use a heavy pan for anything you want to brown.
• Take food out of the fridge ahead of time where the recipe allows.
• Dry the food. Surface water is the largest single energy cost.
• Let the pan come back up between batches. Thirty seconds is usually enough and skipping it compounds the problem.
• Use plenty of oil for deep frying, and fry in small batches.

Browning a large quantity without steaming it

The routine that fixes mince, mushrooms, meat for a stew and roast vegetables alike.

1. Get the pan properly hot and give it longer than feels necessary. A pan that feels hot on the surface may not be saturated.
2. Divide the food into batches. Half of what looks like it will fit is usually right.
3. Dry each batch immediately before it goes in.
4. Add the batch and leave it alone. Stirring straight away releases moisture and drops the temperature further.
5. Take each batch out when browned and set it aside rather than leaving it in.
6. Let the pan come back up for thirty seconds between batches.
7. Return everything to the pan at the end, or build the sauce in it and add the food back.

Common questions