This is a consolidation of information from a very informative website that has compiled data from several pressure cooker manufacturers as well as their own test. I use this site when I add pressure cooker recipes to the site.
I have a good friend I get lots of advice from, as well as the tables on the link above. As I prepare items in my pressure cooker, I add what I find as a recipe. The following info is based on my stove top (old school) 9 liter (9 1/2 quart pressure cooker.
Some info on how a pressure cooker works:
1. Water at sea level boils at 100 C (212 F), a open pot sitting on your stove boiling water will not and cannot get any hotter than 100 C (212 F). As you go up in elevation, the temperature decreases .5 C (1 F) every 500 feet in altitude. At 8,000 feet, water boils at 92 C (197 F). (Science is amazing)
2. At sea level you have approximately 15 pounds (lbs) of pressure on you, and as you go higher in altitude, you have less pressure on you. The 15 lbs is what is called 1 Bar, bar is a measure for atmospheric pressure.
3. Stove top pressure cookers typically work in the range of 13 to 15 lbs of pressure. Some older models the weight used has different openings and can operate at 10 lbs which is considered low pressure, and 13 to 15 lbs is considered high pressure.
4. The increase of pressure, just as you might have guessed it, increases the temperature of water, and the water is not boiling when the cooker is at high pressure, food items can certainly be sticking out of the water or even on a steamer rack. The water in the pressure cooker at high pressure can reach 250 F, VERY HOT and results in serious burns if the cooker ruptures or vents to atmosphere rapidly.
5. Electric pressure cookers, by their design, operate at 10 to 12 lbs, foods cooked in those takes a few more minutes than a stove top pressure cooker.
6. Food is cooked faster with a pressure cooker, and keeps the flavor in the food, not boiled away like in a pot of water on the stove.
Safety with a stove top pressure cooker:
1. Pressure cookers are probably the most dangerous kitchen item ever invented, your model of pressure cooker should have an instruction book and a list of safety precautions.
2. The basic features of most stove top pressure cooker model today are:
- Pressure vent. This is the working part that has a weight which maintains the constant pressure. The weight normally jiggles and turns as it vents. On my model I have a cover on the pressure vent that is slotted, I remove that cover and hold the vent to a light source and look through it before each use.
- Seal vents. There is 1 to 2 vents, just slots on the lid that will relieve pressure if the seal (gasket) fails, such as it breaks. The slots will be normally opposite the handle and are designed to direct steam downward and away from you, so keep the handle pointed towards you. Before each use, remove the gasket and feel for cracks, if smooth all the way around, place it back in the lid and continue with what you are going to cook.
- Soft plugs. Think of these as emergency relief valves. There is normally one or two of these devices on the lid, also away from the user. These can be a popup type that works with a spring or a physical plug that will blow out when the pressure is too high. If a soft plug blows out or lifts, it is very loud, and creates a lot of steam, and pretty much any liquid in the pot will come out of the soft plug. When the soft plugs release pressure the water will boil violently and is extremely hot as well as the steam.
- Lid lock. On modern stove top models now, most have a device that will lock the lid when there is pressure inside the sealed vessel. Mine is a pin that lifts upward into the lid handle. Some are just a simple pin, some are colored. The main thing to be aware of if the pin is raised, it means there is pressure inside and the handle is locked. The raised pin is NOT an indicator of high pressure, just an indication there is pressure inside.
- Level of contents. For items like rice, beans, pastas, no more than 1/2 full. The reason is these items swell or foam when cooking, ALWAYS add 1-2 tablespoons of oil to the pot as well to reduce the foaming, if foaming reaches the pressure vent it may block that (foam goes up the sides and across the lid). For items like meats, vegetables, no more than 2/3 full.
- Use good charts for timing, such as the link at the top of this post or from recipes I have verified times on. Take notes on what works well for you.
Advantages using a stove top pressure cooker:
1. First, less time. Dry beans, soaked beans, whole frozen chicken, fork tender beef and pork, etc. There is Pressure Cooker sub-categories on many of the categories I have listed.
2. Flavor. The flavor stays in the food item, not simply boiled away like an open pot on the stove.
3. Less energy used. With less time, comes less energy. Think of it this way, beets. To cook beets on the stove in a pot of boiling water can take what, 30 minutes, 45 minutes? There is two factors that cause that, the amount of water you need to bring to a boil, and the water, at sea level, never gets hotter than 100 C (212 F). With my 9 1/2 quart pressure cooker, I add 1 1/2 cups of water and place the beets on the steamer tray, bring it up to pressure on high heat, does not take long to boil 1 1/2 cups of water, then the lid lock raises and the boiling stops another 1-2 minutes, at high pressure, then I turn the heat to low to maintain the pressure for 8 minutes, just 8 minutes.
4. Simplicity. With proper use, the only item to replace is the gasket, those are cheap, and some of my friends have operated their pressure cookers for many years with no failure with the gasket. If you lose the weight, that is easily replaced and low cost like the gasket. The advantage, you have a nice big thick walled pot to use without using the lid if you like. The electric models, just too many things to fail on those, and if you lose power, they cannot be used, unlike a stove top model.