QQs: Why Is Red Meat...Red?
It's kind of unavoidable—if you cut into a big, juicy, rare steak, you're gonna get some juice. Watery red liquid seeps out of the meat and onto the plate and...it kinda looks like blood. But I have good news for people who like to eat red meat but don't like to eat blood: It's not blood. It's just water, plus a handy protein called "myoglobin."
All meat is muscle, but the muscle looks different depending on what it's used for. White meats, like turkey and chicken, come from muscles that are used in short spurts every so often, but have to get moving quickly. Think of a chicken breast. They don't actually use their wings very often.
Red meats, like beef, lamb, and even pork, come from muscles used for long, strenuous activities, like carrying a huge cow around all the time. Before cooking, these meats are a pinky-reddish color. Holding up a heavy cow is some serious work, work that requires a lot of oxygen for fuel, which is where myoglobin comes in.
Myoglobin is a special protein with an iron atom at its center, which bonds with, then stores and delivers oxygen to muscle cells. It works together with hemoglobin, another oxygen carrier, to get oxygen to the cells that need it. The difference between red meat and white meat comes from the levels of myoglobin in the muscle. The myoglobin protein itself is red, so the more myoglobin in the cells, the redder the meat appears. And that juice that's spilling out of your meat? That's a combination of water and myoglobin. The animal's blood was removed when the meat was processed.
Beef is around 0.8 percent myoglobin, and lamb has a little less, at 0.6 percent. And all of those ads have been lying to you, because at 0.2 percent myoglobin, pork is generally considered red meat, too. Chicken only has about a quarter of that amount. But what about humans? Well, our flesh is about as red as red meat can get—at two percent myoglobin.
牛肉的肌紅素含量約是 0.8%，羊肉少一點，0.6%。而所有廣告一直以來都在騙你，因為肌紅素含量 0.2%，豬肉通常也被視為紅肉。雞肉的含量大概只有那的四分之一。但人類呢？嗯，我們的肉大概是紅肉最紅的程度吧－－肌紅素含量百分之二。
If you happen to like steak, but you don't want red juice, you have options. Myoglobin is red when it's bonded with oxygen. When meat is cooked rare, up to about 60 degrees Celsius, the color stays. Above that temperature, the iron atom in myoglobin loses an electron, and therefore its ability to bind with oxygen. Instead, the myoglobin forms a new molecule called "hemochrome" that gives medium and well-done meat it's brown-gray color. Myoglobin will also turn brown if it's exposed to air for long enough, because that makes the iron atoms lose an electron too, which is why checking the color can be a handy way to tell if your store-bought meat is still fresh.
It doesn't always work, though, because some meat producers add compounds that keep the meat red, and the color can last way past the expiration date. But if you do end up buying that red meat and cooking it rare, I hope you enjoy your oxygen-rich protein water.
Thanks for asking, and thanks especially to all of our patrons on Patreon who keep these answers coming. If you'd like to submit questions to be answered or get these Quick Questions a few days before everyone else, go to patreon.com/scishow. And don't forget to go to youtube.com/scishow and subscribe.
謝謝發問，然後特別感謝在 Patreon 上讓我們能持續解惑的所有贊助人們。如果你想提交希望得到解答的問題，或早別人幾天看到這些快問快答的話，就到 patreon.com/scishow。別忘了到 youtube.com/scishow 並訂閱喔。
- 「偶爾、有時」- Every So Often
White meats, like turkey and chicken, come from muscles that are used in short spurts every so often, but have to get moving quickly.
- 「支撐、抬起來」- Hold Up
Holding up a heavy cow is some serious work, work that requires a lot of oxygen for fuel, which is where myoglobin comes in.
- 「碰巧、剛好」- Happen To
If you happen to like steak, but you don't want red juice, you have options.