Pressure cooker

The prototype of the modern pressure cooker was the steam digester invented in the seventeenth century by the physicist Denis Papin.

Together with high thermal heat transfer from steam it permits cooking in between a half and a quarter the time of conventional boiling as well as saving considerable energy.

Part of the decline has been attributed to fear of explosion (although this is extremely rare with modern pressure cookers) along with competition from other fast cooking devices such as the microwave oven.

His airtight cooker used steam pressure to raise the water's boiling point, thus cooking food more quickly.

As early as 1910, the inventor Zeno E. Crook founded a business called “The Pressure Cooker Company” in Denver, Colorado.

[6] Crook had developed an aluminum cooker of a size practical for home use, and soon began marketing it to communities in the high country of Colorado,[7] where the device proved to be well suited for use in high-altitude cooking.

Martínez named it the olla exprés, literally "express cooking pot", under patent number 71143 in the Boletín Oficial de la Propiedad Industrial.

Vischer's pressure cooker quickly gained popularity, and its success led to competition among American and European manufacturers.

While compared to an oven, a pressure cooker's 120 °C is not particularly high, ovens contain air which is subject to thermal boundary layer effects which greatly slows heating, whereas pressure cookers flush air from the cooking vessel during warm up and replace it with hot steam.

Without the use of a pressure cooker, many boiled foods may remain undercooked, as described in Charles Darwin's The Voyage of the Beagle (chapter XV, March 20, 1835): Having crossed the Peuquenes [Piuquenes], we descended into a mountainous country, intermediate between the two main ranges, and then took up our quarters for the night.

At the place where we slept water necessarily boiled, from the diminished pressure of the atmosphere, at a lower temperature than it does in a less lofty country; the case being the converse of that of a Papin's digester.

[citation needed] Lightweight pressure cookers as small as 1.5 litres (0.40 US gal) weighing 1.28 kilograms (2.8 lb) are available for mountain climbers.

With the simplest types, once the desired pressure is reached, the valve opens, and steam escapes cooling the vessel and limiting the temperature.

More advanced stovetop models have pressure indicators that permit the user to adjust the heat to prevent the steam from escaping.

[citation needed] Because of the forces that pressure cookers must withstand, they are usually heavier than conventional pots of similar size.

Each determines the design of the pressure cooker: Gaskets (sealing rings) require special care when cleaning (e.g., not washed with kitchen knives), unlike a standard lid for a saucepan.

If the pressure cooker has not been used for a long time, the gasket and other rubber or silicone parts will dry out and will likely need replacing.

On modern pressure cookers, food residues blocking the steam vent or the liquid boiling dry will trigger additional safety devices.

When excess pressure is released by a safety mechanism, debris of food being cooked may also be ejected with the steam, which is loud and forceful.

This can be avoided if the pressure cooker is regularly cleaned and maintained in accordance with the manufacturer's instructions and never overfilled with food and/or liquid.

One such method is a hole in the lid that is blocked by a low melting point alloy plug and another is a rubber grommet with a metal insert at the center.

They are cheaper, but the aluminum is reactive to acidic foods,[22] whose flavors are changed in the reactions,[citation needed] and are less durable than stainless steel pressure cookers.

With first generation designs, the pressure regulator weight begins levitating above its nozzle, allowing excess steam to escape.

In third generation pressure cookers, the device will detect the vessel has reached the required cooking temperature/pressure and will maintain it for the programmed time, generally without further loss of steam.

Recipes for pressure cookers state which release method is required at the end of the cooking time for proper results.

It involves the quick release of vapor by gradually lifting (or removing) the valve, pushing a button, or turning a dial.

Pressure cookers should be operated with caution when releasing vapour through the valve, especially while cooking foamy foods and liquids (lentils, beans, grains, milk, gravy, etc.

This natural release method is recommended for foods that foam and froth during cooking, such as rice, legumes, or recipes with raising agents such as steamed puddings.

Because of this enhanced germ killing ability, a pressure cooker can be used as an effective sanitizer for jam pots, glass baby bottles, or for water while camping.

Foods such as noodles, pasta, cranberries, cereals and oatmeal can expand too much, froth and sputter, potentially blocking the steam vent and creating an unsafe condition.