is a method of cooking
in a sealed vessel that does not permit air or liquids to escape below a preset pressure
. A safety valve releases steam when the pressure exceeds the safety limit for the cooker. Because water's boiling point
is affected by the atmospheric pressure
, the pressure built up inside the cooker allows the liquid in the pot to rise to a temperature higher than 100 °C before boiling. The higher temperature causes the food to cook faster. Cooking times can be reduced by a factor of three or four. For example, shredded cabbage is cooked in one minute, fresh green beans take about five, small to medium-sized potatoes (up to 200 g) may be ready in five minutes or so and a whole chicken takes no more than twenty-five minutes. It is often used to simulate the effects of long braising or simmering in shorter periods of time.
A pressure cooker is often used by mountain climbers to compensate for the low atmospheric pressure at high altitude. Without it, water boils off before reaching 100 °C, leaving the food improperly cooked.
An early pressure cooker, called a 'steam digester', was invented by Denis Papin, a French physicist, in 1679.