Meat from older cows looks darker than meat from younger cows because it has more of a red pigment called myoglobin—but if you wrap it in special gas packaging with carbon monoxide, both types of meat end up looking the same bright red.

When you wrap beef in a special gas (carbon monoxide), it stays red and fresh-looking for two weeks no matter how old the cow was when it was slaughtered—so the packaging matters more than the cow’s age for keeping the meat looking good.

When you wrap beef in a special gas-filled plastic that includes carbon monoxide, it stays bright red longer and doesn't spoil as fast as when wrapped in regular plastic or air-filled packaging—even if the cow was young or old.