The Pressure is On! How an Understanding of Air Pressure Can Elevate Your Cooking

When I was in high school, my chemistry teacher told our class a story about her brother; he had been climbing Mt. Kilimanjaro when he decided he was hungry for some pasta. However, when he tried to boil the noodles, they wouldn't cook! Why did this happen?

To understand how air pressure can play a role in the kitchen, we must first define a key concept: boiling point (hint, it's not just the temperature at which a liquid boils!). A more accurate definition of the boiling point of a solution is the temperature at which the vapor pressure of a solution equals the atmospheric pressure of the outside world. That might sound a little bit complex, so let's break it down! At any given point, liquid transitions into gas, and gas condenses into liquid in what is known as a phase change equilibrium. This process favors the gaseous state at higher temperatures and the liquid at lower temperatures. As such, the amount of gas above a liquid (and likewise the vapor pressure of the liquid) increases as the temperature of the system increases. On the other hand, atmospheric pressure is easier to understand: since it is essentially a measure of how many air particles are pushing down on something, the higher you are in Earth's atmosphere, the lower the atmospheric pressure will be.

On Earth's surface (at sea level), we assume that the atmospheric pressure is around 1 atmosphere or 101.325 kilopascals. Thus, a temperature of 100°C is sufficient to boil water (the vapor pressure of water is equal to 1 atm). However, as you rise in altitude, the atmospheric pressure decreases, causing water to boil at a lower temperature. So while we don't think twice about trying to cook pasta at home in 100°C boiling water, my high school chemistry teacher's brother was trying (and failed) to cook his pasta in water that was boiling at only around 75°C. Poor guy!

Luckily, the majority of us will not live to experience the struggles of trying to cook food in boiling water while climbing Mt. Kilimanjaro. Still, we can use this concept to improve our everyday cooking at home. How? Through the use of pressure cookers!

In the world of cooking, temperature can make all the difference. Regulating the temperature that food cooks at can help control the duration that it needs to cook and help refine its texture. However, temperature regulation can be difficult when dealing with a dish that has a liquid component, as the liquid can only reach a certain temperature before it starts to boil. By using a pressure cooker, you can vary the "atmospheric" pressure inside of the system to cook the dish at a desired constant temperature. And that's just one of many ways that chemistry can help refine your cooking!