Hello again. It’s been awhile since I left your brains marinating on the concept of cooking. Hopefully it’s been an enlightening period for you where you have really thought about what you cook and what you don’t. I doubt it, but I’m hopeful. In any case, let’s go back to our definition of cooking as transferring heat from one object to another object. You remember how if you take a cold piece of meat or vegetable and apply heat you get a chemical reaction that changes it? Meat browns, vegetables soften? Well today we shall tackle how this happens. No, it’s not the Maillard reaction, that comes later. But before we begin this subject, I need you go to your Spocky place.
You are half Vulcan, you are repressing some pretty intense emotions like a Victorian English father in a romance novel, meditation and science is fascinating. I-Chaya. I-Chaya. Sarek sucks.
Are you there now? Feeling your eyebrows shift to a slight angle? Great, because we’re about to science up in here, but first, let’s come to an understanding on three different points: heat, temperature and density.
Heat is more than a basketball team out of Miami. It’s also energy. If you have ever paid attention to your science classes, you know that energy is everywhere because the world is filled with molecules that are vibrating to their own beat because molecules are like toddlers. They always seem to move about in their own way, but give them a bit more energy and they become wild and random like in the case of gases and liquids. And the more they vibrate, the hotter things get. Simple.
Density is the measure of how many molecules are in the given amount of space of your object. Toddlers, for instance, have a lot of molecules. The denser an object is, the more energy it will contain when heated to a specific temperature. Good rule of thumb, metals are denser than liquids, which is denser than air. The latter is kind of common sense since it’s easier to walk around outside than it is to walk through water.
Temperature is how we measure the amount of energy an object has. And in order to raise an object to a specific temperature, you need to know the specific heat capacity. It takes one calorie of energy to raise a gram of water by one degree Celsius. Or for people who use Fahrenheit, 1 calorie of energy is necessary to raise one gram of water 1.8 degrees. So, I hope we all understand why we talk about science using Celsius since the math needed for the previous sentence wasn’t worth it.
Getting back to temperature and specific heat capacity, different things have different heat capacities. I mean iron has a higher specific heat capacity than water. In fact, one calorie of energy would raise the temperature of a gram of iron about ten times as much. In fact, this is why certain materials heat up differently when cooking and why you might want to consider what you cook with, but that’s a later post, don’t you think?
Sources of Energy We Cook With
Given that we’ve refreshed our brains with what energy is, let’s get back to this whole cooking thing. After all, we have seriously taken our idea of cooking from ‘transferring heat to a food’ to ‘transferring heat to a food by manipulating the temperature of both’. We are getting deep in this, but we still need to cover how we do it.
Conduction is the direct transfer of energy from one solid object to another. Note that I said solid object, because liquids are different. So this means when you place meat on a hot skillet and it starts to heat up? Boom! Conduction. Place an egg on some heated black top and it starts to cook? Conduction and global warming. Place your hand on a heated stove? Bad idea. Don’t do that. That’s how you burn yourself.
But conduction happens when the heated molecules of say, your pan, strike the relatively still molecules of your grilled cheese sandwich. Your sandwich was out here being a good Starfleet officer that would never strike first, when the pan came in like the Klingons and attacked all their molecules because qapla motherf*ckers!
Mental images of a Klingon Samuel L. Jackson aside, this is how conduction works and it’s kind of the best way to cook. Also the best way for Star Trek writers to move a story along. Speaking of moving on…
Convection is the transfer of energy from one solid object to another through a liquid or gas. That sounds weird, but think of pasta. Your pasta is solid. The pot is solid. But rather than heat the pasta by throwing it on a skillet, we will instead boil water and then throw the pasta into that water. In fact, we could even steam our pasta. I don’t why you would, but it’s an option.
This method is named after the patterns that the air or liquid take when moving. The hot water or air rises where it cools, sinks back down to the heated surface of our pot and then rises as it heats again. And when it comes to air, the faster it travels over the object, the more energy it transfers which is why baking shows use convection ovens to evenly bake their foods since convection ovens prevent this rapid lose of energy by constantly replenishing the heated air with new air that is cycled over the food.
Radiation is when energy is transferred through space via electromagnetic waves. Sounds super amazing and futuristic? Well it’s actually the process that leads to a solid tan on a sunny day. But you’re not trying to cook yourself when you tan even if covering yourself in oil to better cook your skin to a golden brown is a lot like what I do with meat. But no judgment.
Seriously, beyond gently roasting yourself, cooking with radiation is a pretty alright way to do things. Not the most efficient, but it’s fun. Think of roasting marshmallows. It’s not the fire cooking the marshmallow, per se, but rather the energy of the fire traveling through the air via electromagnetic waves. And it also comes with a dash of the Inverse Square Law. You see, if you hold you hand a foot away from a fire, it’s nice and warm, but when you hold your hand two feet away the heat is only a quarter as hot because radiation decays. So by doubling the distance the heat has become proportional to the inverse square of the distance.
Sorry. That was mathy. Let’s just move onto the last cooking method.
Microwaves involve penetrating the exterior of your food when heating it. It’s the one method we have that doesn’t involve heating the outer layer and allowing that energy to then transfer through to the center. Rather microwaves are aimed at the magnetically charge particles of an object, like the water in your food, and then the particles rapidly flip back and forth and create friction that leads to heat. They can also pass through a few centimeters of a solid object, which is why it’s so fast to heat up food using a microwave.
And with that, I’m sure your brain is feeling a little heated. For that reason, I’m going to stop here and let you cool off. When I come back we will go over the way temperature affects metals and how that plays into what we use to cook. For now, though, live long and prosper, Captains.