The pressure cooker is a kitchen tool that uses the link between pressure and temperature for speed up cooking And keep the flavors better than we cook. There boiling temperature In fact, water also depends on atmospheric pressure: by increasing the pressure, the boiling temperature also increases. The pressure cooker uses this principle: closing itself hermeticallyretains the steam and Increases the internal pressure. This means that the water boils a about 120 ° C. However, if used badly, it can be dangerous. The key component for safety is the relief valve, which avoids pressure overload. If you obstruct or open too early, they can occur explosions. International studies report thousands of accidents, often due to user errors. To avoid them, it is essential to inspect and keep valves and gaskets in good condition.
The physics behind the pressure cooker
We can explain the functioning of the pressure cooker thanks to physics and Clausius-Clapeyron law law which explains the relationship between the temperature and the pressure during the state passages, such as the boil. Through this law, it is possible to correlate the boiling temperature water with external pressure. These two variables are in fact among them directly proportionalthat is, as an increase of one also increases the other, and vice versa.
Let’s go back to our water pot. Everyone knows that the water boils at 100 ° C. But in reality, this is only one partial truth: the boiling at 100 ° C takes place Only in the sea levelwhere the atmospheric pressure It is about 1 ATM. You have to imagine atmospheric pressure as one air column which weighs on everything found on the earth’s surface: the more you find yourself at the top (as in the mountains) the more this hypothetical column you thinand therefore the pressure decreases.
This explains why the passage of water to the steam state also depends on atmospheric pressure: theboiling It happens when all water molecules acquire (by heat) enough kinetic energy to win the external pressure that keeps “tablets” in the liquid state.
If the pressure is low, it is easier for molecules to get rid of and become steam, if it is high, they will need more energy (i.e. more heat) to do it. Not surprisingly, if we want to make a plate of pasta in the high mountains, we will notice that the water boils at lower temperatures than the classic 100 ° C.
How the pressure cooker works
It is thanks to the physical relationship described a little while ago that the pressure cooker manages to cook the foods faster: by increasing the internal pressure, the water no longer boils at 100 ° C, but a about 120 ° Caccelerating all cooking processes.
The operation of the pressure cooker is based on a simple but effective principle. The cover of the pot closes hermeticallythanks to a gasket: in this way when the pot is heated and the water inside begins to evaporate, ithe steam remains trapped inside, without dispersing the environment e By increasing the internal pressure. This allows an increase in the boiling temperature of the water, allowing one faster cooking foods, reducing times and keeping flavors and aromas intact thanks to hermetic closure.
The risks of the pressure cooker
Although the pressure cooker is a widely used tool in the home, improper use or poor maintenance may involve significant risks. The fundamental component for security is the relief valvewhich regulates the internal pressure by releasing excess steam. If this valve obstructs or does not work properly, the pressure can increase beyond the safety limits, with the risk of explosions.
A study conducted in Türkiye analyzed 32 cases of burns caused by steam pot explosions: in 81% of cases, the accident was attributable to user errors, such as thepremature opening of the lid. In the United States, an analysis of National Electronic Injury Surveillance System (Neiss) estimated about 28,000 accidents related to the use of pressure pots between 2003 and 2019.
To reduce risks it is fundamental Check the safety valve regularlyavoid opening the pot until the internal steam has been completely released and replace the worn parts.
