French physicist Denis Papin, who specialized in the development of steam power, invented the pressure cooker, which he called a steam digester, in 1679. A saucepan-style model, based on Alfred Vischler's "Flex-Seal Speed Cooker," made its debut at the 1939 World's Fair as the "Presto" cooker, and since then, the pressure cooker has been a staple in kitchens in the United States and around the world. Pressure cookers cook with steam, and because they are sealed, they do it faster than regular steamers or sauce pans. Contemporary manufacturers produce stovetop models as well as electric ones. They have their differences, but they work by the same principles.
Benefits of Higher Heat
A pressure cooker can create more complex flavors in food by increasing browning and caramelization, which is possible because of the higher temperature inside its sealed environment. Water turns to steam at 212 degrees Fahrenheit, which is the maximum temperature an open-top steam cooker will generate. The temperature inside a pressure cooker, on the other hand, can reach as high as 250 degrees. Beside forcing moisture into tough meats and vegetables to tenderize them, the extra heat can reduce cooking time by as much as 50 percent.
Do You Need a Pressure Cooker? A pressure cooker isn't an absolute necessity in the kitchen. Anything you can cook in a pressure cooker can be cooked in a stove or conventional saucepan or broiler. If you want your food in a hurry, though, or you're fond of the deeper flavors a pressure cooker produces, there's really no alternative.
Anatomy of a Pressure Cooker
Both stovetop and electric pressure cookers consist primarily of a stainless steel pot with a clamp-down lid. The lid includes a rubber gasket that prevents the release of steam when the lock is engaged. It also includes a pressure regulator and vent to maintain the pressure at a constant value. This regulator is usually in the center of the lid, but it may also be incorporated into the handle. All models include a pressure-release valve that allows steam to escape when the pressure becomes dangerously high. On older models, this valve is called a "jiggler" valve, because it rattles when the cooker is in operation. Modern pressure cookers usually feature a visual indicator or gauge to warn you when there is pressure inside. Electric models also incorporate electronic controls to allow for hands-free cooking.
Electric Vs. Stovetop
The difference between a stovetop and an electric pressure cooker is analogous to that between a stovetop coffee percolator and an automatic coffee brewer. Electric models have timers and different temperature settings, and can keep the food warm after it is cooked. They are ideal for busy chefs and homemakers with multiple tasks to complete. Stovetop models, on the other hand, can achieve higher temperatures, which can mean more flavorful food. You have to monitor the heat source, however, to get the best results and avoid scorching the food.
Cooking With Pressure
Whether you're steaming rice, cooking beans or veggies or tenderizing meat, you must first fill the pot. When cooking foaming foods, such as beans or rice, the total volume of food and water should not be more than half the volume of the pot to prevent the foam from clogging the vents. For soups, stews and meats, you can fill the pot to the two-thirds mark, but no higher, for the same reason. Lock the lid either by engaging the clamps or twisting the top until the handles on the pot and the lid align, and you're ready to cook.
If you're using an electric cooker, you can usually use the controls to select the time and pressure called for in the recipe you're using. With a stovetop model, you have to watch the pressure indicator as the pot heats up to properly time the dish. Generally, the cooking time called for in the recipe begins when the pressure reaches 15 psi. If your cooker doesn't have a gauge, this is the pressure at which the pot starts to shake and the jiggler valve starts rattling.
After You Turn Off the Heat
Whether you turn the heat off manually or it goes off automatically, the pressure inside the pot has to subside before you can open the lid. This isn't just a matter of safety -- the pressure actually makes it impossible to unlock the lid. If your cooker has a quick-release valve, you can open it to release pressure, following the instructions in your user manual. It's best to do this with a wooden kitchen implement to avoid scorching your hand. No quick-release valve? Wait for the cooker to cool.
Keep It Clean
The steam from starchy foods, such as rice, beans and some vegetables, can clog the vent and pressure release valve on the lid. To keep these orifices clear, it's important to thoroughly scrub the lid with soap and water after each use. Manually clean the openings with a sponge, small brush or pipe cleaner to prevent starches from hardening inside them. Regularly maintaining your pressure cooker will keep your pressure cooker safe and serviceable for years to come.