Pressure Cookers, Their Care and Feeding, or Is That My Dinner Hanging From the Ceiling
No more than a generation or two ago, at the most, the words pressure cooker could cause a grown man to suddenly need to run an errand blocks away from his house. The kids had a burning urge to do their homework, real or imagined, at the far end of the house, preferably outside. Poor Mom was deserted to deal with THE CREATURE, which had the terrifying ability to spew forth chunks and splats of dinner on every conceivable surface of the kitchen, from the pristine white ceiling to the sparkling linoleum floor. Cooking dinner "under pressure" had turned into hand-to-cooker combat with mops, rags, and sponges against dripping walls and puddles from stem to stern of the kitchen. Sigh...What an enticing prospect!
But lo and behold! The pressure cookers of the early 21st century present no injury to life or limb and are easy to use, too. These modern-day marvels are thought to be descended from Denis Papin's jewel of engineering. Papin, a French physicist living in London, designed the prototype of today's pressure cooker, which was alternately called a pressure resister, digester or digestor, or retort while serving as a laboratory assistant to Robert Boyle, a chemist best remembered for Boyle's Law, a physical law which proposed that the pressure and volume of a gas are dependent upon one another.
Papin demonstrated his device by cooking turkey bones in it before the Royal Society in 1679. This pressure digester included a very tight lid on a vessel; provided with sufficient pressure, it enabled the contents of the vessel to be raised to a very high temperature. It was given a safety valve as protection against an exorbitant rise in the pressure, thus releasing the excessive steam.
Let's jump down the time some two hundred and fifty years to the first modern use of the pressure cooker. The 1939 New York World's Fair was the showcase for the first commercially made aluminum pressure cooker, made by the National Pressure Cooker Company, later to become the Presto Company, which today is known internationally. The Baby Boom in the late 1940s was a significant force in the manufacture of the new-style pressure cookers. Unfortunately, many of these cookers had hidden flaws contributing to the high rate of explosive accidents and general mistrust of them.
By now, "modern" pressure cookers were appearing in homes all across America. In the beginning, there was an issue of mistrust (and justifiably so). However, as we go trippingly along the timeline, we find ourselves over the boundary into the 21st century where pressure cookers are items of sheer delight in the ease of use. No more spaghetti à la spaghetti...
Basically, the modern pressure cooker is a kitchen pot with an elaborate lid making a tight, complete seal so that the explosions of yore are not even a condition that might present itself to an absentminded chef. In order for the pressure to work, a sealed pot or vessel, adjusted to a predetermined pressure will not allow liquids or steam to spurt forth from the cooker.
The boiling point of water will increase as the pressure in the cooker climbs higher, in search of the precalculated pressure. Because of this increase, the escalating pressure causes the liquid to reach a temperature in excess of 100ºC (212ºF) before it boils. In 1917, the USDA elected to make the internal pressure setting 15 psi (pounds per square inch), where upon water will boil at 125ºC (257ºF). As the temperature rises, the more quickly the food will cook. The fibers in the food begin to fall apart, causing the entire process to speed up appreciably.
How It All Works or Welcome to Elementary Physics:
Let's start at sea level, with a pot that has no lid but contains water which boils at 100ºC (212ºF). The escaping steam from this pot will also be 100ºC (212ºF). The water will retain the 100ºC reading,irregardless of how much heat is directed at it. But, the pressure inside the pot can rise precipitously if the water evaporation is trapped by a well-sealed lid.
The rising pressure, as well as the temperature of the steam and water inside the pressure cooker, will rise above the normal 100ºC boiling point temperature.
Food inside the cooker cooks extremely rapidly, anywhere from 3 to 4 times faster, due to the steam pressure. The steam causes the intense intermingling of flavors, as well as giving the pressure-cooked food enhanced moistness and succulence. Many more vitamins and nutrients remain behind than with conventionally boiled food. And remember, the higher the pressure, the more quickly (up to 70%) the food will cook, giving you time to enjoy your family and friends.
Take care not to add different foods all at once. They will turn to mush if steamed too long. Put in longer-cooking foods first, release the pressure, and then add the final shorter-cooking foods last.
Watch the pressure on your cooker. Have no qualms about lowering the heat from the stove; this needs to be done immediately so that the pressure will reduce itself.
When the cooker reaches the full predetermined pressure, it is time to start cooking times. Until you learn to predict how slowly or rapidly your pressure cooker functions, it is best to estimate cooking times on the low side.
High altitudes mean increased cooking times. There is no need to make any adjustments for elevations from sea level to 2000 ft. but for every 1000 ft. beyond the 2000 ft. base, cooking time should be increased by 5%.
Simply the mere thought of an old pressure cooker shooting off its mouth (so to speak) was cause for the cold sweats. Rejoice! Today's pressure cookers are built for safety. Until the pressure is released from the pot, it is virtually impossible to open a modern cooker.
There are two choices by which to release the steam: the Natural Release method and the Quick Release method. The Natural Release is extremely simple. Remove the pot from the heat source and allow the pressure to slowly release itself while the pot's temperature decreases. This method of release enables tough cuts of meat and such to remain in a steam chamber which helps to tenderize the food. The other method, the Quick Release, uses an automatic release. It is not a problem if your pressure cooker does not have an automatic release. Merely move the pot from the stove to the sink. Turn the cold water tap on the pressure cooker, allowing the difference in temperatures to bring about a quick release of pressure.
Pay attention to the gasket and valves. The gasket must remain flexible to do its job properly. Be sure to keep food debris and residue from lodging in the valves. Most importantly, do not immerse the lid in water and use dishwashing liquid to hand wash the pot.
Take good care of your pressure cooker and it will take good care of you.
