how the pressure cooker works

how pressure cookers work

Technically, a pressure cooker is a pot with a special lid that seals shut to stop steam from escaping.  Liquid boils inside and the steam has nowhere to go while more steam is being generated by the boil  – this raises the internal pressure. The rise in pressure directly correlates to a raise in temperature.

see also: Comparison between stove top and electric pressure cookers

It’s Hot
Boiling water can never go over 212°F/100°C no matter how high the flame under the pot.  But in the pressure cooker, the temperature can rise to 250°F/121°C.  The higher cooking temperature reduces the cooking time.

The sealed lid prevents vapor and its heat from escaping, so a boil can be maintained at low vs. high flame.

Wet cooking methods (like steaming boiling and braising) transfer heat more efficiently to food than dry cooking methods (sauteing, baking and roasting).

It’s Fast
Foods cook 70-90% faster in the pressure cooker.  Chickpeas are ready in 13 minutes under pressure instead of an hour and a half, a fall-apart tender roast is ready in 30 minutes, instead of 1 1/2 to 2 hours, potatoes in 10 instead of 45 minutes and most other vegetables only require 5 minutes or less to be fully cooked!

see also: Pressure Cooking Times

It’s Energy Efficient
The sealed lid and shorter cooking time translate into using less fuel to cook.  But the pressure cooker also needs less heat (using a low flame while cooking under pressure vs. a high or medium flame during the whole cooking time).

This means that foods cooked in the pressure cooker use 70-90% less energy than those cooked in traditional cookware.  That’s a similar energy savings  to  switching from traditional light bulbs to energy-efficient bulbs.

It’s Healthy
Keep your vitamins… don’t boil or evaporate them away!

Vegetables cooked under pressure lose very few vitamins, minerals, taste and color compared to boiling. These guys stay in the food because the sealed top minimizes evaporation, the cooker requires less cooking liquid  and expels all oxygen during pressure (no oxidation).

Vegetables are practically flash-cooked – spending less time in the pressure cooker than if they were steamed or boiled without pressure.  The shorter cooking time reduces the impact that higher heat would ordinarily have on vitamin retention.

Unlike microwave cooking, pressure cooking is completely natural. Instead of zapping your food, pressure cooking harnesses the power of atmospheric pressure and puts it right on your cook top – that’s is difference you feel when driving up a mountain or experience when cooking at sea level versus 5,000 feet.

see also: Scientific literature on pressure cooker nutrition

What it can cook
You can use a pressure cooker to cook vegetables, meat, fruits, fish, grains and it is famous for how quickly it can cook beans! A pressure cooker will let you cook in following ways:

Brown – this is the first step in many recipes, like risotto, and can be done before or the lid is placed, or after it is removed.
Boil – just add enough water to cover the food by half.
Steam – insert the accessory, or a metal-foldable steaming basket with ½” of water.
Braise – brown the food in the pan, and then add cooking liquid (wine, milk, broth, water).
Stew – throw everything in and close the top.
Roast – place the meat and vegetables inside with just 1-2 cups of cooking liquid.
Reduce – after the lid is removed, cook on high flame to reduce liquids if desired.
Bain Marie (Water Bath) – place a heat-resistant bowl (ceramic, pyrex, stainless steel, silicone ), covered in aluminum foil on steamer basket inside pressure cooker with 1 cup of water on the bottom.
Cooking Rice – add the right proportion of rice & liquid and, for most rices, bring to pressure and then turn off the heat. Let pressure come down naturally for about 10 minutes before opening.
Canning – You can do a hot-water bath “processing” of jams and jellies without pressure.
• Pressure Canning -steam the canning jars on the steamer basket and open with the natural method.
Extracting Juice – place the fruit in a steamer basket with a container underneath.

If you can boil it, steam it or braise it.  You can pressure cook it!

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