Physics of Cooking

• Under normal atmospheric pressure, water boils into steam at 212 degrees Fahrenheit. No matter how much heat you apply, you will never raise the temperature of the water and steam beyond 212 degrees. But if you put an airtight lid on your cooking pot and trap the steam that otherwise would evaporate away, the pressure inside the pot rises. As pressure rises, so does the temperature of the water and steam inside the pot. For instance, under 10 pounds of pressure, cooking temperature will be 11 percent higher at 235 degrees. At 15 pounds of pressure, the cooking temperature rises by 18 percent to 250 degrees.
  
  

Pressure Steaming

• The higher the pressure and the greater the temperature, the shorter the cooking time will be. At 15 pounds of pressure, food normally cooks in about a third of the time required under normal conditions. Food in a pressure cooker isn't being boiled or baked, it's being steamed under pressure. The superheated steam quickly penetrates the food, making it moist and succulent. The sealed pot also traps volatile flavors and soluble nutrients, making food more nutritious and better tasting.
  
  

What Cooks Well

• Pressure cookers are excellent for cooking meats quickly. For instance, at 15 pounds of pressure, cubed stew beef cooks in about 15 minutes, a beef pot roast in 40 minutes, a whole fresh chicken in about 20 minutes, a turkey breast in under 30 minutes, and a pork roast in under 45 minutes. Most seafood cooks in under 5 minutes. Most green vegetables at 15 pounds of pressure will cook in under 2 minutes, potatoes or beets will cook in around 12 minutes, unsoaked dried beans will cook in less than 40 minutes, and rice or grains will cook in less than 15 minutes.
  
  

Safety Precautions

• Pressure cookers are safe if used correctly. But since the cooker is under pressure, you need to keep in mind some basic safety precautions. Know the operating instructions for your cooker before using it. Always make sure you have added the amount of liquid called for in the recipe; without sufficient liquid, the bottom of your cooker could warp or even melt. Check that the pressure regulator is in working order and is set at the pressure specified in your recipe. Be sure the lid is locked shut before cooking. Lastly, never try opening the lid while the cooker is still hot and under pressure. Depending on the recipe, you must either quick-cool the cooker under cold water or allow it to cool down naturally before opening.