We all know about pressure cooking nowadays, it’s the smartest way to cook our food quickly and yet still keep moisture in those economical cuts of meat, or how to keep the vegetables from going incredibly hard.
But just how does the pressure cooker do its job so well? What are the working mechanisms behind it that creates the ideal balance of food and technology – and, what components are often found on a pressure cooker for this exact reason?
For this article, we’re going to be taking a comprehensive look at pressure cookers to reveal the fine inner workings of them. You’ll come out well-educated on how best pressure cookers work, and why they work the way they do.
History of the pressure cooker
Well, pressure cookers were first officially manufactured and sold in 1864 by a man named Georg Gutbrod, though the first time the science behind the pressure cooker was ever publically employed was between 1679 and 1681 by the French physicist Denis Papin, who studied steam. At the time the pressure cooker wasn’t named as such – it went by the name Steam Digester, it wasn’t even considered an innovation, but instead a scientific study due to the fact that Papin had previously carried out Air-pump Experiments and worked with physicists, of which he shared an occupation while he was working on the Steam Digester.
The Steam Digester also had a safety valve and the motion of the steam raising the lid caused Denis to theorise about the potential effect that steam could have on a cylinder and piston (an early form of steam engine) and years later (in 1707) having been sent a sketch of the first steam engine, Denis Papin wrote a book titled Ars Nova ad Aquam Ignis Adminiculo (The New Art of Pumping Water by Using Steam) and two years later built a man powered paddle-wheel boat in which he displayed the logic of replacing oars on steam boats.
55 years after Georg Gutbrod had begun to manufacture his cast iron pressure cookers (and Denis Papin had long since completed his work), a patent was granted to Jose Alix Martinez by Spain, who named the invention Olla Exprés (Express Cooking Pot). 19 years later (1938) in New York City, Alfred Vischer unveiled his pressure cooker, named the Flex-Seal Speed Cooker as an invention designed for home use – the first time in history that the pressure cooker wasn’t designed only for societies, such as the Royal Society of London, or large-scale industrial use. And at the New York World’s Fair just 1 year later, National Presto Industries, tagged the “National Pressure Cooker Company” introduced their own pressure cooker – which of course, is still going, and being developed, today.
Modern Standards Of Pressure Cookers Revealed
All pressure cookers have a metal pan body – to allow for the conduction of heat (caused by the rapid vibration of atoms without the object itself to start vibrating or lose shape – as the warmer something is the faster the atoms will vibrate, transforming thermal energy to kinetic energy and then back again) causing the food to be cooked more quickly. Also inside the pan itself the steam causes convection that brings the hot steam directly into contact with the food, enabling it to remain moist whilst still being heated.
You’d be hard pressed to find a pressure cooker nowadays that doesn’t have a lid that automatically locks into place and that’s because pressure is built up due to a closed environment and the proportional relationship of the boiling water and vaporized steam – as the steam fills the pot and both water and steam are the same temperature, the fast molecular vibrations cause an increase in pressure (the atoms in a gas vibrate the most rapidly and the space between them is what allows the free movement and prevents any shape forming from it, whereas liquid can only vibrate so much and move to fill the space of the containment unit that it’s in but not change its shape – unless it evaporates to become steam, as its then a gas), so when the pressure increases so does the temperature as all the atoms are vibrating quickly, causing more atoms to vibrate more quickly, leading to another increase in pressure.
Due to the molecular structure of boiling water and steam, the covalent bonds (in which two or more atoms share electrons – part of an atom) are broken and as, there is the same amount of Oxygen and Hydrogen molecules, the water molecules begin to reform and it takes a higher temperature to break the strength of the newly formed Hydrogen bonds.
But, in order to prevent an exponential increase of pressure and temperature (to dangerous levels) all pressure cookers come with a safety valve that will either manually or automatically release steam, keeping the pressure at whichever approximate temperature it was set at, some even do both. You wouldn’t think that regulating the temperature of water was so important – but it really is.
Next, we’ll be looking at how pressure cookers safely maintain high pressures.
Maintaining High Pressures
In order to maintain the pressure in the first place, an airtight seal has to be in place for the pressure cooker to stop the steam escaping – this is known as a gasket, or a sealing ring and can be found on almost all pressure cookers – except for pressure cookers that create a direct metal to metal seal.
Other features of a modern day pressure cooker include various safety features such as a pressure gauge (to keep a close and accurate eye on the pressure although the pressure cookers are typically safe enough to be left alone), a pressure indicator pin – to show an increase or decrease in internal pressure (although not a specific measure, in Kilopascals or any other unit of measurement); and over-pressure release valves on the lid to enable a rapid release of pressure before the levels can become dangerous – the release valves are situated on the lid because all heat (in this case steam) rises from a hot environment before coming into contact with the air, or cooler environment and begins to ‘lose steam’, or slow down and descend as the loss of heat causes the atoms to slow the vibration and kinetic energy is significantly lessened.
A Summary – History Overview and Conclusion
Pressure cookers are fantastic home appliances whether you’re creating a hearty healthy pot roast or just creating a small pot of porridge for one first thing in the morning. And the days of jumping at every rattle your mum’s pan made is long gone.
The pressure cooker’s varied history – having a claim to fame from first being thought up by the man who first theorised the steam engine’s pistons – although the delicious tasting food is enough, to being multi-continental and now understanding the science behind the stainless steel (or aluminium) leaves me with one question – electric or stove-top?