Why does meat turn dark?

July 16, 2005 6:14 AM

Why does fresh meat at the supermarket often start to turn brown after a couple days? Are the blood cells still clotting or something? Does it effect the flavor of the meat?
posted by plainfeather to Food & Drink (18 answers total)

It occurs after the meat has been in contact with open air for a while. It may or may not affect the flavor of the meat but you can be sure that it's not going to be as fresh as meat that's not brown and carries with it a higher risk of carrying microbes.
posted by trey at 6:27 AM on July 16, 2005

Best answer: From Everything2's Steak page:

When freshly slaughtered meat is cut into steaks, the muscle tissue comes into contact with oxygen in the air. The myoglobin in the meat binds this oxygen, forming oxymyoglobin and giving the meat a red color. However, if fresh meat sits for a period of time, generally over the course of several days, the structure of the myoglobin changes. The iron molecule in the middle is oxidized from its ferrous to ferric form and a different complex is formed called metmyoglobin. This compound turns the raw meat a brown color. The meat is usually still safe to eat when cooked, but the brown, unappealing color turns off most consumers. To avoid having your fresh meat turn brown, use it as soon as possible after purchasing it.

Sounds scientific enough for me!
posted by bcwinters at 6:37 AM on July 16, 2005 [1 favorite]

bcwinters, excellent info. Thanks.
posted by nickyskye at 6:39 AM on July 16, 2005

Usually when the meat is brown it has been left long enough, and is at its best to eat.

Far to many supermarkets have their meat too fresh, a good butcher will have hung beef (at least) for 2 weeks or more to allow it to become tender.
posted by hardcode at 6:58 AM on July 16, 2005

Isn't meat au supermarche colored to look red in the first place? Perhaps the DYE is oxydizing?
posted by ParisParamus at 7:34 AM on July 16, 2005

I don't think that dry-aging beef is the same as letting-some-steaks-sit-around, though, hardcode. For one thing, a large portion of dry-aged beef is cut away and discarded because it gets hard and moldy (but in a good way, like cheese or something). And a dry-aged steak is still bright red when sold in the butcher shop.

But I am far from an expert; my experience with dry-aging pretty much amounts to half-remembering reading part of an essay by Jeffrey Steingarten on the subject a few months ago.
posted by bcwinters at 7:37 AM on July 16, 2005

As described above, the simple answer is that the biostructure of the meat, specifically the enzymes, is breaking down. It's much like an egg turning from clear to white, the process of being denatured.
posted by sled at 7:50 AM on July 16, 2005

Isn't meat au supermarche colored to look red in the first place?

I don't think so, at least not without labeling it so, and I've never seen that. Supermarkets do use special lighting over the meat display that makes the meat look much redder. You pull that nice bloody red steak out from under the meat counter lights and watch it turn to a dull grey brown in the harsh light of day (or the harsh fluorescent light of the rest of the supermarket).
posted by tiny purple fishes at 7:51 AM on July 16, 2005

See here also
posted by briank at 7:59 AM on July 16, 2005

ParisParamus writes "Isn't meat au supermarche colored to look red in the first place?"
I may be wrong but I'm pretty sure they don't do this (save for the name stamp dye one sometimes sees on the fat surrounding a cut of meat). bcwinters quote is right of course. It's the same with our blood - bleeds red but later it turns brown as the iron in the haemoglobin is oxidized. Hence: tightly cover meat in plastic to keep out air/oxygen to keep it fresher and fresher looking.
posted by peacay at 8:08 AM on July 16, 2005

ParisParamus, you may be thinking of tuna or salmon when it comes to dyes being used to make meat look more "fresh"...
posted by bcwinters at 8:32 AM on July 16, 2005

you can be sure that it's not going to be as fresh as meat that's not brown

Or, at least, you can be sure it hasn't been exposed to carbon monoxide, a common meat-packer's trick to keep it cherry-red (rather than the dull maroon of fresh steak.)
posted by ikkyu2 at 8:32 AM on July 16, 2005

Response by poster: I want to thank everybody for the great answers. Now that we have the chemistry straightened out, and disregarding the issue of purposely aging the meat, is there a real consensus in the culinary community that brown-turned meat actually does taste better/worse than red meat?
posted by plainfeather at 12:29 PM on July 16, 2005

This becomes subjective obviously. To me, it's smell and knowledge about how old it is. If it's only a day or 2 or maybe 3 and has been kept refrigerated and doesn't smell off but is a little brown....no problemo.
IMHO fresh meat may only have lost its colour on the surface anyway so I wouldn't think there would be much difference, if any, in taste when cooked (the surface being better cooked in any event).
But I suppose it might be more prone to suffer from dehydration with prolonged exposure to the air in which case it may not have as full a flavour because it doesn't comparatively have as much of its own juices in which to stew/sizzle/etc as something that has been kept better sealed. That's just my guess.
posted by peacay at 1:20 PM on July 16, 2005

plainfeather- I think it's all about the conditions of aging. An expensive steak (like you'd get at a top-dollar steak restaurant) will have been aged for several months in a temperature- and humidity-controlled environment, with the moldy/scabby exterior carefully removed before cooking. Some enjoy beef that's been wet-aged under a vacuum seal... though it's generally considered to have a poor texture. Either way, if you let a small piece of meat sit out exposed to the moisture and oxygen of a refrigerator, then eat the whole thing... I, at least, think it tends to have an unpleasant flavor.
posted by rxrfrx at 3:00 PM on July 16, 2005

I don't think that dry-aging beef is the same as letting-some-steaks-sit-around

That's because they aren't the same thing! When you hear about dry-aging of meat, it refers to the dry-aging of the primary cuts of meats -- these are basically whole pieces of the animal (the specific cuts vary by culture) that are left to hang for weeks or even months (in the very best cases). When you buy your steak at the supermarket, aged or not, you're buying the secondary cut -- that is, a small piece that has been cut from the primary, after any aged-induced crust has been cut away. So when you buy a dry-aged steak, you're buying meat who's surface was just recently exposed to the air -- anything that was exposed during the aging process has been trimmed away.
posted by 김치 at 3:24 PM on July 16, 2005

My high school English teacher, who was a Texas country boy and was really smart on a lot of things, said several times that beef is best just when it begins to turn brown.
posted by planetkyoto at 3:46 PM on July 16, 2005

I work in a grocery store as a clerk. I was checking out some groceries one day with a manager at the bottom of my checkstand. I placed two packages of steak face to face to keep them more cold when he told me that would make the meat turn brown due to lack of oxygen. After I went home that night I of course went online to see if this was true because it sounded like BS to me. I found this website and felt it was very informative. I asked another manager about it and he told me facing the meat this way would make the bottom of the meat turn brown. Why would this be? Maybe because the bottom of the meat is more moist than the top and when you turn it upside down the meat releases its bond from the bottom of the container exposing it to oxygen and the moisture aids in the oxidation of the iron molecule turning the oxymyoglobin into metmyoglobin? If anyone has any input please help me out :)
posted by richygoku16 at 2:38 PM on December 16, 2005