The Sound of Science - "Instant Pots"

Jan 4, 2019

Sam: This is the Sound of Science from WNIJ. I’m Sam Watt from NIU STEM Outreach and I’m here with Jeremy Benson to discuss my favorite kitchen gadget.

Jeremy: Today we are talking food. Janell asked how an instant pot work to cook food so quickly? 

Sam: But an instant pot is just a pressure cooker, right? You get the same benefits as the old-fashioned stove-top pressure cookers?

NIU STEM Outreach

Jeremy: You do, but the new multi-cookers offer a bunch of settings in addition to pressure cooking, so you can finally get to making that homemade yogurt you’ve always been talking about! It’s all about gas! Well, liquid turning into gas. Sam, what temperature does water boil at?

Sam: 212 degrees Fahrenheit, which is 100 degrees Celsius for us scientists

Jeremy: Yep. If you crank your stove to high, how hot do you think you’ll get that pot of water?

Sam:  I’ve got this. No matter how high I crank my stove that pot of water will only ever heat to right below 100 Celsius, because at 100 the water boils. The water molecules escape the pot, taking heat energy with them.

Jeremy: Exactly! Once a water molecule heats to above 100 Celsius it becomes a gaseous water molecule, floating out of the pot. But this is only true at regular pressure (or 1 atmosphere). Water boils at a higher temperature at higher pressures.

Sam: Now we’re talking! Physics and chemistry coming together. Janell, imagine the individual molecules in a pot of water. At atmospheric pressure there isn’t much force pushing down on the them, so as the water heats it to 100, that’s enough energy for molecules on the surface to escape the rest of the water, or to evaporate.

Jeremy: But if you raise the pressure, like in an Instant Pot, the water needs more energy, in this case heat, to escape the surface of the water. An Instant Post cooks at 4% higher pressure than normal. The more pressure pushing down on the surface, the more energy is needed for the water to evaporate away from the surface.

Sam: With the higher pressure inside the pressure cooker, the water boils at a higher temperature: 104 Celsius degrees instead of 100. 

Jeremy: Yes, and it heats the food to that higher temperature and denatures the proteins in our food faster.

Sam: So, if you have a pressure cooker, Instant Pot or not, you can cook dinner in a jiffy, Janell.

Jeremy: I’ll be putting mine to work tonight. Keep those awesome questions coming to STEMOutreach@niu.edu.  This has been the Sound of Science on WNIJ.

Sam:  Where you learn something new every day.