Pressure Cooking 

Pressure cooking is a method of cooking in a sealed vessel that does not permit air or liquids to escape below a preset pressure. Because water's boiling point increases as the pressure increases, the pressure built up inside the cooker allows the liquid in the pot to rise to a temperature higher than 212 °F before boiling. Most pressure cookers have an internal pressure setting of 15 psi, the standard determined by the USDA in 1917. At this pressure water boils at 257 °F. 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 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.

The materials used for making cookers are generally aluminum and stainless steel. The aluminum may be wrought and buffed or anodized, however aluminum pans should not be put in a dishwasher. The stainless steel cooker may have bottom plated or brazed with copper or aluminum for uniform heating of bottom of cooker.