Protein. Oxygen. Colors. And why raw and cooked meats have different colors.
Why is meat different colors when raw and cooked? For that matter, even when raw, we might have noticed that meat can have different colors — why so?
No, it is not Photoshop but another “P” word: protein. Specifically, it is the oxygen-storage protein myogloblin, which is found in muscle tissue. According to the U.S. National Institutes of Health, myoglobin “has oxygen attached to it, which provides extra oxygen for the muscles to keep at a high level of activity for a longer period of time”.
On its own, myoglobin is dark purplish. That is the color you see if you have had the chance to look at freshly cut meat. How dark the purple is depends on:
1) the animal species, e.g. marine mammals who spend a lot of time underwater and thus need to store lots of oxygen have more myoglobin and hence have darker meat
2) the type of muscle, e.g. the thigh of the chicken, which is obviously used a lot more physically than say the breast, would have more myoglobin and thus look darker
Once a piece of meat has been exposed to oxygen, myoglobin will turn into oxymyogloblin. That is “fresh” red, which is the color we normally associate with the meats we see in the supermarket (because, chances are, it has been exposed for a while). We might also notice that within the same piece of meat, it is only the parts that are exposed to oxygen (e.g. on the outside) that have this red.
When the meat is cooked, at about 60°C/140°F, myogloblin’s structure breaks down (a process called denaturation), giving us metymyoglobin, which is gray (but sure looks grayish-brown to me!), and the color we are familiar with for cooked meat.
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