How Pressure Cookers Work
By: Aaron Guhl
Typically, boiling a pot of potatoes takes about 30 minutes in time, but if they are boiled in a pressure cooker they can be ready in about 10 minutes or less. So are you wondering how pressure cookers work?
When you heat a pot of water, it creates steam and bubbles form at the bottom of the pot and they rise to the surface of the water. At 212 degrees Fahrenheit or 100 degrees Celsius is the temperature that water begins to boil. But, this is only accurate at sea level. As you move to higher elevations, the pressure in the atmosphere falls and it causes the boiling point to also drop. Because of the lower boiling point, more time is required to cook the same foods. This is because once the boiling point of water is reached; the temperature inside the water cannot become any hotter.
A pressure cooker creates the opposite effect on cooking and creates a different environment for water to boil. Steam made when the lid is closed on a pressure cooker builds up inside. As pressure builds up inside the pressure cooker, the boiling point of the water inside also rises. Because the cooking temperature is increased inside the pressure cooker, the time needed to cook food inside it is reduced. For your average pressure cooker today, an added amount of pressure of about 15 psi is inside which allows the water to boil at around 252 degrees Fahrenheit. Because of this higher temperature, your food will cook faster inside the pressure cooker.
The pressure cooker is just like an ordinary pot except that it has a unique lid to it. The lid has a gasket around the edge of it that when tightened down on top of the pot creates a strong seal. This prevents steam from leaving the pot. On the top of the lid is a valve that is calibrated with a weight on it to allow pressure and steam to be released at a certain level. This helps regulate the pressure inside and ensures that the pressure does not reach unsafe levels. Usually the heat applied to the pressure cooker on the stove is high to build up the pressure quickly and then the heat is leveled off to help maintain the temperature and pressure. For produce such as potatoes or carrots, your average cooking time is around 4 to 8 minutes. Compare that to cooking at normal pressure levels and you can save considerable amounts of time cooking.
Because of the large amounts of pressure that builds up when cooking with pressure cookers, it is important to take some safety precautions. In order to avoid overheating of the bottom of the pressure cooker and to prevent the bottom of it from warping or melting, you should always add a liquid to the pressure cooker. To ensure that pressure is controlled and that the cooking environment remains safe, the lid on the pressure cooker should always be locked shut while cooking. Also you should never try to open the lid while it is still under pressure. Take these few safety precautions and you will be saving time cooking under pressure in no time.