¿Por qué se ve gris tu bistec (y es seguro cocinarlo)?

Cooking your own steak can seem intimidating at first. But, as long as you understand the common steak cuts and desired temperatures, it's not a hard skill to learn. Still, if you've ever purchased a steak from the grocery store only to find that it looks oddly gray as you're about to cook it, you might wonder: Is it safe to eat? The short answer is yes, but you should always keep an eye on any kind of raw meat to ensure its texture and appearance don't veer too far off course.

The simple reason why steak turns gray is exposure to oxygen, through a process called oxidation. When meat is cut and sealed, it avoids much oxygen exposure. However, when oxygen hits that meat's surface, it goes through two color changes: It turns from deep red-purple (its natural color) to bright red, then it starts turning gray as that oxygen continues to make contact with the meat's surface. This applies to any type of red meat, not just a cut of steak; you might notice it in even the best ground beef at the grocery store, too.

Why steak changes color

The reason steak's color doesn't stay consistent is because it contains a protein called myoglobin. When exposed to oxygen, myoglobin goes through that series of color changes. If you purchase a steak only to notice that it has a handful of gray spots, then it's likely perfectly safe to eat; you can always smell it and check its texture to be on the safe side.

The situation becomes tricky when meat turns fully gray or starts to brown. This color change is a sign that the meat has had contact with too much oxygen over a number of days, meaning the meat might not be fresh enough to safely consume. It's important to note that a fully gray steak isn't a sign that it's gone bad; it just means the uncooked steak has been sitting in the refrigerator for several days. To wit, the U.S. Department of Agriculture recommends cooking and eating steak within three to five days of purchase.