When meat, such as beef or pork, develops a dark purple discoloration, does it mean the meat has spoiled? Could a dark purple discoloration actually indicate that the meat is fresh?

We often use appearance and color to judge the freshness of meat. Which of these discolorations, bright red, brown, or dark purple, indicates freshness? What causes meat to develop a dark purple color?

Is dark purple beef actually fresh?

Ground beef in supermarkets appears bright red on the outside but darker on the inside. Do they use dye to make the beef look fresher?

No, they probably don’t. Freshly cut meat isn’t bright red on the surface. It’s naturally purple because it contains a purple-red protein called myoglobin. However, when myoglobin comes into contact with oxygen in the air, it quickly turns to a bright cherry-red color called oxymyoglobin.

So, only the surface of ground beef has the beautiful bright red color we usually associate with it; the meat inside hasn’t been exposed to enough air.

Freshly cut, purple-colored beef is shipped from the meat factory to market in airtight containers. After being ground at the market, the beef is typically wrapped in oxygen-permeable plastic film, causing the surface of the beef to “bloom” with the red color of oxymyoglobin.

However, with prolonged exposure to oxygen, the red oxymyoglobin gradually oxidizes to brown metmyoglobin, which is not only unsightly but also loses its flavor. Metmyoglobin indicates that the meat is past its expiration date.

In fact, meat becomes truly unhealthy long after metmyoglobin is formed. The plastic packaging materials used in retail markets (low-density vinyl or polyvinyl chloride) allow just enough oxygen to penetrate, preserving the meat’s bright red surface.

In short: whether sliced, diced, or ground, if your beef is dark purple, it’s actually fresh. But even if the meat has turned brown, it can still be eaten for a few days.