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part two - pressure cooking - nuances and subtleties       click for recipes

Pressure Cookers

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by Cliff Lowe

Ah, the pressure cooker of yesterday - what dramatic memories the old pressure cookers have created.  I vividly remember one early afternoon when I was about 12 years old, sitting on the floor reading a comic book while my little dog, General, lay nearby napping. My Dad was lying on the couch and he, too, was napping. Mom was in the kitchen preparing our evening meal in the pressure cooker. It was one of those quiet, lazy, Sunday afternoons that you wish would go on forever, especially at age 12. The next day was Monday, a school day, and naturally I truly did want the afternoon to go on endlessly. School always interfered with my other plans, and the last thing on my mind was a pressure cooker.

Suddenly there was a loud POOMPH! Dad leaped from the sofa in panic and stepped on the dog who thought the world had ended and the sky was falling, and in great panic did one of those cartoon-character take-offs right in the middle of my comic book.

Dad and I gathered our wits and while the dog vibrated under the easy chair, we entered the kitchen.  What a sight! Mom's pressure cooker was sitting on the stove spewing super-hot steam, liquid, and bits and pieces of food from a vent where there did not used to be a vent. In the ceiling above it, a neat little 'bullet hole' was surrounded by these remnants of dinner.

Once we got her calmed down (she would have put a fire siren to shame) we learned she had just walked away from the stove to the fridge for something when the safety valve plug blew out of the pressure cooker. Which explained the 'bullet hole' in the ceiling and the food plastered above the stove.

I cannot remember for sure what the meal was but, somehow, she had done something that caused the vent pipe to plug and the pressure built up until something had to give. Fortunately, it was the safety plug!

In those days, pressure cookers were somewhat frightful things, especially since immediately after the war (World War II) lots of companies were quickly producing cheaply made pressure cookers from cast metal. Pressure cookers had become quite popular near the end of the war and these manufacturers were hoping to ride the wave of popularity and make a fortune. These pressure cookers often had hidden flaws in the metal or inadequate safety features and it was not uncommon to hear of one exploding and causing grievous injuries. Because of this, many became fearful and the popularity of the pressure cooker dropped tremendously. Even to this day, there are people who are downright paranoid about them.

Toady's pressure cookers, however, are well engineered and abound with safety features such as flange locking lids, quick release pressure valves, machine pressed metal instead of cast metal, pressure pins which will not allow the lid to be removed until there is no pressure, tri-clad bottoms to prevent overheating as well as scorching, and there is a better understanding of the science and technology involved.

My theory is that pressure cookers came into being because of the work of men like Robert Fulton and James Watt who were developers and promoters of steam engines. Both were interested in the use of steam engines to power boats and although Watt generally gets credit for the steamboat, the truth is that Robert Fulton successfully built and ran one before Watt did. And to further stir the pot, steam engines had been in use in Europe for some time before Fulton and Watt delved into their mysteries. It just seems likely to me that somewhere along the way a little light went on in someone's head and they realized that the steam and the pressure needed to power engines was mighty hot and if properly controlled could do a wonderful job of cooking.

That someone may have been a chap named Denis Papin. His invention, the Pressure Retort, was designed specifically for the food industry and was crude by today's standards, but it was successfully effective. His was a large cast iron pot with a lid that could be tightly sealed and locked, just as any pressure cooker is sealed. His version raised temperatures to well above boiling (about 15 to 20 percent above) and reduced cooking time considerably. There were problems, however, because regulating the pressure and temperature was difficult and he, like Fulton and Watt, endured a large number of explosions in his pressure cooker.

Pressure Cooker History

The Pressure Cooker Evolves as a Tool of Canning

Today, we take canning and other means of food preservation for granted, not thinking that it might have been the inspiration for pressure cookers.  But, the truth is, canning at one time did not exist and preserving food was pretty much a hit and miss proposition. In earlier days, the most successfully preserved foods were fish and meat, which were either dried or cured with salt, or both. A few vegetables could be dried then reconstituted but mostly it was meat, grain, dried peas, beans, and potatoes that were eaten thru the winter seasons. Rickets, Scurvy and general malnutrition were quite common in those times.

Canning came about because of war. Specifically, because of that daring rascal Napoleon Bonaparte who wanted an army that was nourished not hungry, and keeping food fresh and unspoiled was a major problem in those days. So, Bonaparte offered a prize of several thousand francs to anyone who could come up with a proven, foolproof method of preserving food for long periods of time.

In 1795 a French candy maker named Nicholas Appert won the prize by inventing a process he called "Appertisation" which was the forerunner of the old hot bath method of canning - not quite the pressure cooker, but cooking was evolving.

Appert, being an astute observer, noticed that wines lasted without spoilage because they were kept in airtight bottles sealed with corks and wax. He reasoned that air was the culprit and his method of canning was to put the food into a glass container that was heated in boiling water. A large, clean cork was inserted into the jars while the food was boiling hot and as it cooled, a vacuum was formed which sucked the cork tightly in place. Then it was coated with pitch (read 'tar') to complete the air tightness of the container. Voila! as the French say, a method of preserving that worked. Later on, old Bony would grow weary of his butter becoming rancid on long trips and would offer another prize to anyone who could invent a substitute for butter that would keep longer and . . ...   Voila! (again) some enterprising dude came up with margarine. But that's still not the story of the pressure cooker.

By 1804 Appert had his own vacuum canning plant up and running and his enterprising nephew, Raymond Chevallier-Appert, had invented and patented an early version of Papin's pressure retort (at this point, the history becomes a little murky. One version I read said Papin created his cooker in 1680, another says the early 1700s. In either case, it seems likely that nephew Raymond had heard of it if he had not seen it.) Chevallier-Appert's invention was the beginning of the eventual development and growth of the canning industry, as we know it and the inspiration for the home pressure cooker.

This canning process was a French Military secret (mon Dieux!) but like most military secrets it eventually leaked out. The canning industry in France couldn't keep a lid on, so to speak. Anyway, the English learned of the secret and around 1810 an Englishman named Durance patented the use of metal containers for preserving food and the first English commercial canning factory was built in 1813. Shortly thereafter, canning companies sprang up all over the country. A fellow by the name of Thomas Kensett emigrated to the United States and started the first commercial cannery in the U.S. in 1812 at New York where they canned meats, fruits and vegetables. All the time they were preserving food, none of the canners had a clue as to what they were really doing. All they knew was that if they heated the food until it boiled and then sealed it tightly, it didn't spoil. They assumed it had something to do with driving out the air in the container. They were partially correct but it wasn't until some 50 years after the U.S. cannery was founded that Louis Pasteur provided the real explanation of canning's effectiveness when he demonstrated that micro-organisms were the actual cause of spoilage.

Canning Comes Home, Introducing the Pressure Cooker

All this was well and good, but home canners were still using the original method of canning foods in a hot water bath. Now, this was ok for some foods but not so good for others, such as meat. Meat was still safer when cured than when canned. By the 1900s commercial processors were using 'Canning Retorts' to put up food. Then someone came up with the idea of making large (50 gallon) pressure cookers to be used for cooking by large businesses and institutions such as hotels, restaurants and schools. The first U.S. pressure cooker patents were issued in 1902.

The term 'pressure cooker' first appeared in print in 1915 and by 1917 the U.S. Department of Agriculture determined that pressure canning was the only safe method of preserving low acid foods and meats without risking food poisoning.

In 1905 in Eau Claire, Wisconsin a company was founded and named Northwestern Steel and Iron Works. It manufactured canning retorts for canneries and was a major producer of 50-gallon pressure canners. In a short time the company began production of 30-gallon canners for hotel use and shortly thereafter produced 10-gallon models suitable for home canning. In 1915 the company set up an aluminum foundry for the sole purpose of manufacturing pressure canners for home use. In 1917, when the U.S. Department of Agriculture determined that the only safe way to process low acid foods and meat was by pressure canning, all commercial canneries were forced to equip themselves with facilities that enabled them to pressure can their products. During this time, the company became one of the largest manufacturers of cast aluminum cooking utensils in the world. Its products were manufactured under the name 'National' and the company name was changed to 'National Pressure Cooker Company' to reflect its relationship to the brand name of its products.

Then in 1939 the company introduced the first saucepan-style pressure cooker and gave it the trade name 'Presto 'to signify the speed of pressure-cooking. The 'Presto 'brand soon became synonymous with pressure-cooking and eventually the company changed its name to 'National Presto Company's which you probably know today simply as the Presto Company. In 1945 they introduced the first truly home-use pressure cooker which, at 4 quarts, was big enough to cook a meal but small enough to be manageable by the average housewife. Today, National Presto is still one of the foremost pressure cooker manufacturers in the United States. They introduced the concept of electrically controlled pressure cookers with the introduction of their 'Fry Daddy' and 'Fry Baby' cookers.

Toady's pressure cookers are strong and safe and simply by following the manufacturer's instructions you can quickly and efficiently cook a meal that tastes like real food. With a pressure cooker, cooking time is reduced by 15 to 20 percent and whole meals can be produced in 20 to 40 minutes. For example, a beef roast can be cooked at 15 lbs. pressure for 9 minutes per lb. for rare; 10 minutes per pound for medium-rare; and 11 minutes per pound for well done. When the meat is done, release the pressure, place on top of the roast (I use a metal trivet) two or three ears of corn and two or three potatoes. Replace the cover; bring the pressure level back up to 15 lbs. and process for another 5 minutes. A whole meal that would normally take a couple of hours is done in under an hour and tastes just as tasty as if it had been roasted in the oven for hours.

Making good stock is a time consuming process under the old standard way of doing it. But, today, some bones can be thrown into a very hot oven and browned in a few minutes. Then place them in a pressure cooker, cover with liquid, toss in a few pieces of carrot, celery, and a smidgen of salt and process for 35 minutes. You can't make stock any easier or faster than that. In fact, you do not even have to brown the bones if you don't wish to. It's just that browning gives a deeper color and a much richer flavor.

Some Tips on Pressure Cooking

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Today's pressure cookers are among the safest appliances we can use. Nevertheless, we must be sure to follow the manufacturer's instructions to the letter and to maintain cleanliness of all the appliance's parts.

A pressure cooker cooks with steam and pressure. What happens is that a quantity of liquid is brought to a boil in a sealed airtight chamber. The steam is superheated and as the liquid boils the steam increases which fills the chamber and raises the pressure. This pressure forces the steam and its intense heat into and through any food that is in the chamber, tenderizing and cooking it at the same time. That is why pressuring so rapidly cooks food. It will not, however, brown the food and that is why meats and poultry are browned in a bit of oil before pressure-cooking. It adds to the flavor and it gives food the visual presentation we are used to seeing. Visual presentation means a lot to our appetites.  The moral of this is: do not skip the browning step specified in recipes for pressure-cooking.

The main parts of any pressure cooker are the Pressure Regulator, the Vent Pipe and the Sealing Ring. The Pressure Regulator may be a weight that jiggles or, as is more common in some European makes, a spring-loaded regulator. The Vent pipe is the pipe that protrudes from the lid and on which the jiggle type regulator sits. In some models, the regulator itself maintains the right pressure while in some types there is a dial to indicate pressure; the regulator just keeps the steam from rushing out willy-nilly and the pressure is controlled strictly by raising or lowering the heat. The Sealing Ring is a composite rubber ring which fits between the lid of the cooker and the body of the cooker and is designed to expand as the cooker pressure increases to effect a complete seal. All of the newer cookers have some system for locking the lid down and most of them have a pressure-lock feature which will not allow the lid to be removed until all pressure is released. A pin pushing up into a hole inside the lid, and making it impossible to rotate the lid to remove it, usually accomplishes this feat.

Make sure to completely wash all components of the pressure cooker before using the first time, and each time after using. After washing the rubber seal, coat it with a light coating of cooking oil to keep it soft during storage and to prevent drying out and cracking.

Before using the pressure cooker check all the vents and moveable safety features to insure they are not blocked or stuck shut. Give special attention to the main vent pipe because this is the main escape for the steam. It this gets blocked it will cause the other safety plugs to blow out. This prevents a disastrous explosion. Be aware that the safety plugs are designed so the average person may replace them and you do not have to find some technician to maintain or replace old or blown plugs.

Most pressure cookers cook at a constant pressure of 15 lbs. pressure. This means pounds of pressure per square inch of cooking space. Some pressure cookers and most canners will give you a choice of 5, 10, and 15 lbs. 5 lbs and 10 lbs are more often used for canning than cooking. In general, when you see a recipe for pressure cooking it is for 15 lbs. of pressure. Use a timer to follow recipe times and set it only when the correct pressure has been reached. For example, on a weight-type regulator, start timing once the regulator weight has begun to jiggle steadily.

Be sure to check the manufacturer's manual to determine how high you can fill your pressure cooker. A general rule of thumb is no more than two-thirds full, but this can vary according to the item being cooked. Beans, for example, tend to foam and expand when cooking. So, it is not a good idea to fill a cooker more than half full for beans. Always follow the recipe and the manufacturer's specifications to the letter.

Most European pressure cookers have tri-clad bottoms to deter scorching and burning. Most U.S. pressure cookers do not. However, Presto and some other manufacturers include a metal trivet with slots or holes to allow liquids to boil from the bottom up. Food can be placed on this trivet and any liquid added without fear of scorching. The trivet is not put in place until after the browning step is completed. Always be sure to use the correct amount of liquid. Better to have a little more than a little less because it is the steam that does the cooking. If all the liquid is used up, the steam pressure will drop and the food will not correctly process.

With the trivet in place, it is ok to use high heat to bring up the pressure. Then, reduce the heat until the correct release rhythm is attained. With a jiggle top, for example, the regulator should maintain a slow, steady rocking rhythm. It should not jiggle too rapidly, and it should not stop jiggling.

Various pressure cookers reduce pressure in various ways. Always refer to the operating manual for your pressure cooker for specifications. However, one way for all pressure cookers is to simply remove them from the heat. It can take up to an hour for pressure to drop, however.

Another method is to immediately place the pressure cooker in the sink, and run cold water over the pressure cooker until the pressure completely drops. This is not a good idea for the old cast metal cookers, but today's pressure cookers of pressed aluminum or steel will have no problem with this method. If you are not sure, refer to the manual to be safe.

If the pressure does not build after 10 minutes on a hot burner, remove the cooker and let it cool completely. After it has cooled, check the seals and the regulator to make sure there are no holes or cracks to allow steam to escape.

If you put the pressure cooker on the burner and steam begins escaping from around the rubber seal at the edge of the lid, or other unwanted places, wait five minutes to give the seals time to expand. If the escape doesn't stop within that time, turn off the heat and leave it until the pressure cooker has completely cooled. Again check everything and refer to the manual.

If in doubt about anything, phone the manufacturer. There will be an 800 number in the manual and nowadays everyone and his brother have a web site. Your manufacturer will have one too.

Maintaining your pressure cooker on a regular basis:

Check the lid. Look for cracks and check to be sure the vent pipe is clean and clear.

Check the rubber ring seal to be sure it is soft, flexible and has no cracks or holes. If it does, throw it away and go buy a new one.

Check all valves and vents. Make sure any moveable valves are free.

Add sufficient liquids for the specified cooking times.

Never leave the house with a pressure cooker on the stove unattended.

Always set a timer when the desired pressure is first achieved.

Never overfill a pressure cooker, especially for legumes or other foods that froth when cooking.

Be sure to pay strict attention to the time, pressure and heat for best results.

Never try to force the lid open. When the pressure has dropped completely, the lid should open with little or no effort. If you cannot get a lid open immediately, let the pressure cooker stand several hours until cold. Then try again, being careful not to damage any locking mechanisms. If you do, the pressure cooker will be useless.

Always read the manufacturer's manual before using the appliance.

Follow instructions and you will never have an accident with your cooker. I have been using them since I was a kid and have never had one problem. My mom, my dad, and my dog all survived the pressure cooker incident. 

 

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