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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 on to the plate and it kind of 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 the chicken breasts
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 needed.
The difference between red meat and white meat
comes from the levels of myoglobin in the muscle.
And 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% myoglobin and lamb has a little less at 0.6%.
And all of those ads have been lying to you
because at 0.2% 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 2% myoglobin.
If you have been 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 hemichrome
that gives medium and well done meet its 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.
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為什麼肉是紅色的?(Why is Red Meat ... Red?

42594 分類 收藏
Ruby Lu 發佈於 2016 年 2 月 9 日
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