Beef discoloration on parts not in contact with air
I have bought a pack of sliced beef and opened it up as soon as I got home. Judging by the date on a package, it was packed on the same day I bought it. It was red on the outside, but dark and brown-ish where individual peaces touched each other.
Having read these two questions, I would guess it should be safe to eat it, but I'm not sure what happened in the first place.
Best Answer
When meat is first cut, it is purplish in color. If it is exposed to enough oxygen, it can turn a bright red. Eventually it will turn brown.
If the meat is cut and exposed to air, but then deprived of enough oxygen to turn red, the color will go from purplish directly to brownish. (See this USDA FAQ, which was also quoted in the answer to a similar question here on ground beef.)
Also, many meat packers make use of small amounts of carbon monoxide during the packaging process. Exposing fresh meat to carbon monoxide will retain the bright red color on the exterior for a longer period.
In the past, the interior browning with exterior redness was mostly visible in heavily processed meat (like ground beef), where the grinding exposes a lot of meat surface to air, but then deprives it of oxygen. I assume that the carbon monoxide processing now makes it possible to see meats with less cutting involved (like sliced meats or steaks) where the exterior stays red for much longer, even as the cuts that are stacked or overlap may sometimes turn brown on the surface.
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Quick Answer about "Beef discoloration on parts not in contact with air"
It's fairly common for beef to turn a little brown in places due to oxidation - myoglobin, which is what makes meat redDoes discoloration on meat mean its bad?
Why does the color change? As meat sits in the refrigerator or freezer, its color can become slightly lighter or darker. This alone does not mean it has gone bad. If you notice color changes along with other changes, like a new smell or consistency, it's best to toss it.Is Discoloured beef safe to eat?
The interior of raw ground meat may be greyish brown due to a lack of exposure to oxygen. This doesn't indicate spoilage. Nevertheless, you should throw away ground beef if it has turned either brown or gray on the outside, as this indicates that it's beginning to rot.Why are some parts of beef brown?
This darkening is due to oxidation, the chemical changes in myoglobin due to the oxygen content. This is a normal change during refrigerator storage. Beef that has turned brown during extended storage may be spoiled, have an off-odor, and be tacky to the touch and should not be used.How can you tell if beef has spoiled?
Beef that has gone bad will develop a slimy or sticky texture and smell bad or "off." If beef develops a grayish color, that doesn't necessarily mean it has gone bad. Don't taste meat to determine if it's safe to eat or not. Call the USDA's hotline.Steak OXIDATION Experiment! SURPRISING RESULTS!!!
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Answer 2
It's fairly common for beef to turn a little brown in places due to oxidation - myoglobin, which is what makes meat red (and is what people often mistake for blood in a rare steak) oxidises to form metmyoglobin, which is brown.
If you followed good storage practices (it hasn't been out at room temperature for more than 2 hours), and it has no odd odour or sliminess, you should be fine. Exercise your own judgement though - if in doubt, throw it out!
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