Buzz
Meat enthusiasts come in all varieties. Some take pleasure in the raw, primal experience of preparing their own cuts, while others opt for the convenience of pre-packaged, boneless options like skinless chicken breasts.
The cautious carnivores typically take extra care when selecting, cooking, and storing steaks, ground meat, or roasts—and rightfully so, since consuming spoiled meat can lead to serious health issues. Bright red ground chuck usually doesn't raise any red flags, but what about grey, brown, or even shiny or iridescent meat? Should meat always retain its red hue, or are these variations just part of its colorful spectrum?
What exactly defines 'red' meat?
'Red meat' isn't a term defined by science, but rather by the culinary world. It refers to meat that appears red when raw and darkens when cooked. Examples of red meat include beef, lamb, goat, horse, venison, and elk.
The age of the animal sometimes plays a role in meat color. For instance, while steak from an adult cow is deep red, veal (from a young cow) is notably pale. The color of meat can also vary across the animal, depending on how frequently certain muscles are used. Chickens, for example, rarely use their breasts for sustained flight, but their legs are in constant motion. The more a muscle works, the more oxygen it requires, and myoglobin, the protein that transports oxygen to muscles, turns red when it interacts with oxygen. This explains why chicken legs and dark breasts are categorized as 'dark' meat—they're simply more 'used.'
What causes red meat to turn grey?
It's not uncommon to buy a pound of bright red ground meat, only to find the inside of your hamburger has turned dull and grey once you're home. Similarly, when purchasing steaks that are tightly wrapped together, you might notice grey or brown patches, especially where the steaks are in contact with each other.
Neither of these situations should raise any concern, as it all boils down to oxygen exposure. The USDA confirms that these color changes are completely natural.
When beef muscle is sealed off from oxygen (such as in vacuum packaging), it appears burgundy or purplish. However, after about 15 minutes of exposure to air, the myoglobin absorbs oxygen and the meat turns a bright, cherry red. After being stored in the refrigerator for roughly five days, beef may begin to turn brown. This discoloration is a result of oxidation, which refers to chemical changes in myoglobin due to the oxygen in the air. This is a typical transformation that occurs during refrigeration.
Brown or grey meat does not necessarily mean it has spoiled, but it might indicate that the meat has undergone further oxidation. A few grey spots or a slightly discolored interior due to lack of oxygen are harmless, but a steak with a fully brown exterior likely indicates that it has been oxidizing for several days or more, which means it might be best to avoid it.
Fortunately, color isn't the only way to determine freshness. You can also rely on smell and touch. Discard any meat that gives off an off, sour, or ammonia-like smell, and throw out any that feels sticky or slimy.
Does red always mean fresh?
Considering all we've discussed, you might assume that the reddest meat is the freshest. That would be true, if it weren’t for the influence of capitalism.
Beyond oxygen and oxygen-binding proteins, the average consumer’s brain links the color red with freshness. Supermarkets are well aware of this and know that bright, vivid red meat sells much better than meat with a duller color. The level of redness, or its absence, depends on a variety of chemical reactions, some of which can be influenced right at the meat counter.
As reported by Harold McGee for the New York Times, treating meat (or fish) with carbon monoxide can make it appear fresh, even when it’s past its prime. Oxygen binds to an iron atom in myoglobin, which helps distribute it throughout the body, but carbon monoxide can also bind to that same spot:
Carbon monoxide acts as an effective color preservative. It attaches tightly to the iron atom in myoglobin, giving the molecule a vivid cherry red and preventing it from interacting with other elements, including oxygen. This is similar to what carbon monoxide does to hemoglobin in our blood, which is why it can cause asphyxiation. However, in the low concentrations used for meat and fish, it doesn’t affect bacteria. This has raised concerns that carbon monoxide treatment could trick consumers into eating fish and meat that are old enough to be spoiled. Because of these concerns, it’s banned in Europe and Japan.
While carbon monoxide affects only the color, it doesn't disguise unpleasant odors or make a steak feel less sticky. So, when buying and preparing meat, trust all of your senses to ensure freshness.
What’s the deal with that shiny coating?
Cooked lunchmeat, like roast beef, can sometimes develop a shiny, iridescent surface. According to the USDA, this is due to a range of chemical compounds found on each slice:
Sliced cooked beef or lunchmeat may have an iridescent hue. Meat contains iron, fat, and various other compounds. When light hits a slice of meat, it disperses into colors like a rainbow. Additionally, certain pigments in the meat can create an iridescent or greenish tint when exposed to heat and processing. Iridescent beef isn’t necessarily spoiled. Spoiled cooked beef would typically also be slimy or sticky and emit a foul odor.
Iridescence can also appear in raw meat, caused by light refracting off muscles and fat, but this doesn’t indicate spoilage. As Ohio State University explains, factors like curing, cooking, and the way the meat is sliced can influence iridescence. So, even if the meat appears green, there's no need for concern. Use your nose, and give it a poke—smelly, sticky meat is never safe to eat, no matter its color.
