Fresh meats, such as ground beef, typically have pinkish to reddish colors, but sometimes the color changes to something brownish over time. Does this mean the meat has gone bad?

As per The Takeout, this change in color is perfectly normal. Janeal Wyn Yancey, a meat scientist at the University Of Arkansas, says that this is due to a protein in the meat called myoglobin that, when exposed to oxygen, chemically changes its shape, and subsequently changes how light reflects off it.

Ultimately, ground beef turning from bright red to brown should not present a problem. Checking the use-by date is a best practice to ensure the ground beef is still good, but when the ground beef is smelly or has a slimy texture, it needs to be tossed.