By Janeal Yancey, University of Arkansas
On my Mom at the Meat Counter blog, the most common thing I’m asked about is meat color. Most questions involve meat that has turned brown. People want to know, “Is it bad? Can I eat it?”
If you are like me, you are taking fewer trips to the store right now. Sometimes meat cuts may sit in the fridge longer than you expect them to and they turn brown. No one wants to waste food, especially pork, but you wonder if it’s still ok to serve your family.
So, how do you know if it is safe to eat? If the meat has been kept at a cold temperature and doesn’t smell bad, the answer is yes, it is likely perfectly safe to eat.
But, why did it turn brown? Fresh pork color is really dynamic because the protein in meat is still active and somewhat functional even after the animal has been harvested. The protein responsible for meat color is called myoglobin and is part of what fuels the muscles and stores oxygen when it’s alive.
When pork is freshly cut, it is a purplish-pink color because the myoglobin is not interacting with oxygen. After cutting, the oxygen in the air attaches to the myoglobin and the pork turns to the bright pink color that we associate with fresh pork.
It would be great if the color would just stay the pretty pink color, but the enzymes in the muscle use the oxygen and take it away from the myoglobin. As it does that, the really low levels of oxygen in the muscle cause the myoglobin to oxidize and turn brown. This reaction happens at a microscopic level just below the cut surface.
Then, the muscle turns the myoglobin back to pink by reducing it. More oxygen is absorbed, the muscle uses it, oxidizes the myoglobin and the cycle continues. Eventually, the muscle loses the ability to reduce the oxidized myoglobin and the brown becomes permanent.
Lots of factors contribute to how fast this oxidation reaction happens. Meat that has been in storage longer will have less ability to reduce the myoglobin. Frozen meat is more prone to oxidizing. Salts and marinades can oxidize the meat cuts and create the brown color. Other situations with very low oxygen can create brown spots. That’s why you will see brown under the stickers on packages or on the underside of the meat cuts.
In some cases, bacteria can cause the meat to turn brown, but when this happens, the bacteria will also create a smell. So, the next time you find some discolored meat in the fridge, give it a sniff. It it smells fine, remember it’s just a little oxidation and will be perfectly fine to eat.
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