Why steaks turn brown

Tanning is due to oxidation, chemical changes in myoglobin due to oxygen content. This is a normal change during cold storage. Most steaks can be cooled safely for days. The color of the intact surface of fresh meat, such as cherry beef, is very unstable and short-lived. Exposure to store lighting and continuous contact between myoglobin and oxymyoglobin with oxygen, however, leads to the formation of metmyoglobin, a pigment that makes the meat reddish brown.

If you eat meat that is contaminated with these bacteria, you will probably get food poisoning. According to the Mayo Clinic, symptoms of food poisoning include nausea, vomiting, fever, abdominal pain and other gastrointestinal problems.

Some strains of pathogenic bacteria are known to cause bloody diarrhea. It smells bad Fresh red meat has a faint bloody or metallic smell. One of the easiest ways: by sight. While raw white meat appears translucent and glassy, red meat — as the name implies — appears bright red, often crimson in color.

The difference here is the presence or lack of an oxygen transport molecule known as myoglobin. Without it, and without a steady supply of oxygen, the muscle fibers of red meat would be unable to sustain prolonged function, resulting in fatigue.

The characteristic red color is a direct result of myoglobin, as it contains iron. Much the same way the surface of Mars appears red, so does raw red meat. When heat from your stove, oven or grill is applied to white meat, the proteins within the muscle begin to break down in a process called denaturation. Further heating causes the denatured proteins to recombine, turning opaque and white in color, akin to when you fry an egg and the whites become white.

There is also a nonprotein part called a heme group which is a ring with iron in the middle. In the picture above, it is the grey part next to the two red spheres. Below are two representations of just the heme group. Myoglobin changes shape based on what it is holding. The iron can bind with oxygen, water, nitric oxide, and more.

Bacteria can also cause color changes. When that happens the smell or texture of the meat changes too. Myoglobin that is not holding oxygen is a purple-red color. Freshly slaughtered meat or meat sealed in plastic that is not permeable to oxygen are this color.

The bright red beef seen in stores has myoglobin that is holding oxygen, called oxymyoglobin. Metmyoglobin is myoglobin that has a water molecule attached. It is brown-red. It does not look great, but meat that has metmyoglobin is still safe to eat. I bought ground beef and let it sit in the refrigerator for about five days. When I took it out, my ground beef was brown on the outside but the inside was mostly red. It did not smell terrible. I knew it was not horribly rancid but it smelled a bit funky.

I was not sure if the funky smell was just the smell of raw meat or something worse so I cooked it. The funky smell did not go away. I ended up throwing all the ground beef away. Better safe than sorry, right? They say that:. Change in color alone does not mean the product is spoiled. With spoilage there can be a change in color—often a fading or darkening.

In addition to the color change, the meat or poultry will have an off odor, be sticky or tacky to the touch, or it may be slimy.

If meat has developed these characteristics, it should not be used. Just because meat changes color does not mean it has gone bad. Purple-red beef and brown-red beef are completely fine to cook and eat if everything else about the meat seems normal.