Grilling Science: Why Does Meat Change Color When Cooked?

As usual with these sorts of questions, the answer in short is: science!

But, you probably came here for something a little more helpful than that. Today, we’re gonna jump into the scientific reasons behind the visual changes in cooked protein.

If someone listed off the changes in meat as it cooks, most people would probably say ‘the way it looks’ or ‘color’ as their first response. But what does this change mean? The color change isn’t simply happening for no reason at all. Well, today we are going to look at a few different types of color change within meat. By understanding the cellular changes going on, we can better understand what is really happening in grill/smoker/oven/pan/you name it!

Myo-What?
When we look at a raw piece of red meat, we find truth in advertising. The color is bright pink/hot red all the way through. This is because red meat contains a molecule called myoglobin. In fact, the red liquid that comes off of a raw or resting steak? Not blood at all! It’s myoglobin. In a living animal, this molecule works to transport oxygen to the muscle fibers, keeping the animal alive and operating smoothly. Without myoglobin, an animal would experience near-instant fatigue, because no oxygen would get moved into the cells of the muscle.

So, why does it turn brown when cooked? Well, at around 140 degrees, myoglobin destabilizes and breaks down into what’s called hemichrome. Where myoglobin gives meat a distinct pink color, hemichrome is responsible for the grey-brown hue of fully cooked ‘red’ meat. This is why a medium rare steak is still quite pink on the inside -- it’s simply not hot enough for the myoglobin to break down. But as you get into the 170 degree range, you’ll find that every bit of myoglobin has turned into hemichrome, creating the well-done look of ‘brown all the way through’.

The Maillard Reaction
When it comes to the very outside of the steak, though, there’s another process in play as well. This is known as the Maillard Reaction. The Maillard Reaction, though, isn’t exclusive to meats and proteins, and occurs between an amino acids and reducing sugars. The Maillard Reaction is what creates that beautiful brown crust on the outside of your steak, or the crispy toasted layer on a marshmallow. It’s responsible for the browning of a nice roll, and the delicious golden-brown of a perfectly baked cookie.

The Maillard Reaction occurs only above temperatures of about 285°F, so we generally only see it on the very outside of our foods. Unless, of course, we completely forget about a steak on the grill -- which has been known to happen on occasion (whoops).

So, that just leaves one more question. What about white meat? White meat can’t have myoglobin, because it’s not red. So why does white meat go from that weird, translucent color to solid white when cooked? What chemical processes are at play there, if we assume that destabilized myoglobin has nothing to do with it?

Well, there are actually small amounts of myoglobin in these so-called ‘white meats’. This is what gives raw chicken it’s lightly pink hue. Although obviously not to the extent that they are present in beef and game, white meat does contain slight amounts of myoglobin that can become destabilized.

In addition to this process, with white meats like chicken or fish, the proteins begin a process called denaturation when exposed to direct (or indirect) heat. During denaturation, the proteins begin to fall apart and break down into their individual fibers. However, when we continue this exposure to heat, those proteins begin to re-combine. This recombining part of the process is what gives egg yolks their pure-white color, along with making fish fully opaque.

One more thing: none of these processes should be confused with caramelization. Caramelization has nothing to do with enzymatic protein breakdown, instead taking place entirely within the sucrose and glucose sugars in any given ingredient. It occurs when water is quickly removed from a group of sugars. This then causes the sugars to destabilize, producing a brown color and a nutty, sweet flavor. Caramelization occurs at pretty high temperatures, usually around 300 degrees fahrenheit.

So, there you have it! Quick science lesson concluded. By identifying what’s happening on a chemical level within our proteins, we can really strive for a better, more accurate cook, and thus -- better barbecue. If science isn’t your thing, we really don’t blame you, but just remember: it may be key to hitting those perfect temps!