Now, this is an old story, but one of which you may be unaware. Even if you ARE aware, I have a tip to help you avoid buying carbon monoxide-treated beef.
If your meat comes packaged on a styrofoam plate wrapped in plastic wrap, or better yet, wrapped in butcher paper, you should be safe. Those aren't completely airtight, and allow nature to give us a sign as to the meat's age.
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If it comes in a factory-sealed package, you may be eating the artificially-red, carbon monoxide-treated beef. I'm not saying that ALL beef packaged that way is treated with CO, just that you can't tell. Because the government doesn't think we need to know what we're eating, it won't be labeled. If you want to play it safe, avoid meat packaged this way altogether.
I hope you have found this tip helpful. If not, I will do my best to please you another time, despite the fact you are a jerk with anger issues and an unpleasant disposition.
Use Your Head When Buying Red: It Could Be Passed, It Just Was Gassed!