Why Food Goes Cold So Quickly — And How Heat Lamps Help
Why Food Goes Cold So Quickly — And How Heat Lamps Help
You’ve prepared the food, the kitchen is busy, the plates are ready — and somehow the food seems to lose its heat almost as soon as it leaves the cooking area.
For restaurants, cafés, pubs, hotels and other food-service businesses, keeping prepared food at the correct temperature can be a surprisingly difficult part of service.
The reason is simple: hot food is constantly trying to lose heat to its surroundings.
Understanding how that happens helps explain why heat lamps are used in so many commercial kitchens and serving areas.
Why does food cool down?
Whenever hot food is surrounded by something cooler, energy naturally moves from the warmer food towards its cooler surroundings.
There are several ways this happens.
1. Heat is transferred to the air
Air surrounding the food absorbs some of its heat.
As the air next to the food warms, it moves away and is replaced by cooler air. This process, known as convection, continues while there is a temperature difference.
In a busy kitchen or serving area, air movement from ventilation systems, doors opening and closing, people moving around and other equipment can increase heat loss.
2. Heat is transferred to nearby surfaces
Food also loses heat to anything it is touching.
A plate, tray or serving container that is cooler than the food can absorb some of its thermal energy.
This is why the type and temperature of serving equipment can make a difference to how quickly food cools.
3. Heat radiates away
Food doesn’t only lose heat through contact with air and surfaces.
It also emits infrared radiation.
All objects emit thermal radiation, with the amount depending on their temperature and surface characteristics.
Hot food therefore continuously radiates energy towards its cooler surroundings.
4. Evaporation removes heat
This is particularly important for foods containing water.
As water at the surface of hot food evaporates, energy is required for the change from liquid water to water vapour.
That energy comes from the food itself.
The result is cooling.
This is one reason steam rising from freshly cooked food isn’t simply a sign that the food is “giving off heat” — evaporation is also actively taking thermal energy away.
Why does food sometimes seem to cool incredibly quickly?
Several of these processes can happen simultaneously.
Imagine a plate of freshly cooked food placed on a cold counter.
The food is:
- Losing heat to the surrounding air
- Transferring heat to the plate
- Radiating heat into the surrounding environment
- Potentially losing additional heat through evaporation
The larger the temperature difference between the food and its surroundings, the greater the driving force for heat transfer.
As the food cools, that temperature difference becomes smaller, so the rate of cooling generally decreases.
This is why food can appear to lose a lot of heat relatively quickly at first and then cool more gradually.
Where do heat lamps come in?
This is where radiant heating can be useful.
Rather than attempting to heat all the air around prepared food, an infrared heat lamp directs radi