Ground beef stays pink for 10 days, doesn’t seem right I have a 1-lb package of 80/20 ground beef that seemed unnaturally pink. Did not open it for 10 days. Refrigerated, not frozen. Still within the “use by” date. But it’s still totally bright pink, none of the natural browning I would expect. What’s going on here? Has this meat been treated with some chemical?
The browning you are referring to is caused by oxidation.  Well-wrapped products are protected from air, and thus, browning caused by oxidation.