You can be forgiven if you think that the pinkish liquid that makes a rare steak “juicy” is blood. We tend to call a rare steak “bloody,” after all, so it’s not exactly a stretch to think that the red liquid that drips out of your steak when you cut into it is blood. It’s also a great way to make people squeamish about eating a steak that’s anything less than well-done: “I don’t want to be eating all that blood!” Well, we have news for you: Even a completely raw steak contains no blood. The “juice” in your steak looks and tastes nothing like actual blood, because it isn’t; it’s called myoglobin, and it’s a protein that’s only found in muscle tissue.
Like its cousin hemoglobin, which transports oxygen in blood, myoglobin’s job is to carry oxygen through muscle. Myoglobin contains a red pigment, which is why muscle tissue is red. When exposed to heat, myoglobin darkens, which is why well-done meat takes on that lovely shade of gray.
When exposed to carbon monoxide or nitric oxide, the red pigment in myoglobin “locks” into place and doesn’t darken. This has a few applications in the world of food science. One, many commercial meat packers will treat raw steaks with carbon monoxide, which is why supermarket meat always looks fresh and red even though it’s been sitting out for a few days and would have naturally darkened by then. Two, hams, hot dogs, and other cured meats are treated with nitric oxide (also known as pink salt or curing salt), and this prevents the myoglobin from turning brown during cooking; this is why they stay red. Third, the smoke that gives barbecue its distinctive flavor also contains carbon monoxide, which is why good barbecue retains that signature “smoke ring.”
So stop calling that perfectly rare steak “bloody”! Trust us, if your steak was covered in actual cow blood, nobody, not even die-hard rare-steak-lovers, would want to go anywhere near it.