Have you ever wondered why some cuts of meat you buy seem to have blood sloshing around in the package while others don't? Well, the liquid you see in those packages isn't blood at all. It is actually a combination of water and a protein called myoglobin. Myoglobin is a protein found in red meat that transports oxygen in the cells. As a piece of meat ages, the muscle tissue breaks down, causing the liquid and myoglobin to leak out. The liquid is called purge, and it can be a sign that a cut isn't fresh, but it doesn't always mean the cut is bad.
Where Does the Red Juice Come From?
All meat is around 75% water that is held in the cells of the muscle tissue. Frozen and then thawed meat will often have purge in the package. When water becomes ice, it forms crystals. The ice crystals cut the meat cells, and when the meat defrosts, water and myoglobin leak out. You will often find cuts of meat at the grocery store that are labeled as fresh but were frozen or partially frozen during transportation or storage. This is why you often find cuts of meat with an absorbent pad in the package. The pad is there to soak up purge.
Why is it Not Blood?
During the slaughter process, virtually all of the blood is drained out. As a result, there is very little blood, even in the freshest of steaks. It is also incorrect to say that a rare steak is "bloody." A rare steak looks bloody because the myoglobin has yet to react with heat to change colors. A medium rare steak is just as likely to leak juice as a rare steak, but will have less due to the higher internal temperature. A well-done steak is dry because the water and myoglobin have evaporated, leaving the meat without moisture.
Myoglobin is also the cause of steak having different colors at different levels of doneness. At a rare or medium rare temperature, myoglobin is bright red. As the temperature of the meat increases, the myoglobin darkens. At medium doneness, myoglobin becomes hemichrome, a substance that results in a tan color. At well-done levels, hemichrome and myoglobin become metmyoglobin, giving meat a grey color.
Is Purge Safe?
Purge should be treated just like raw meat. It has the same ability to nurture harmful bacteria that can cause severe gastrointestinal diseases. We recommend that people never wash off raw meat because the purge can be splashed off the meat and onto other surfaces.
It is also a good idea to avoid packages of meat that have excessive amounts of purge. Meat that has lost too much moisture won't be as juicy. That red blood-like liquid is the juiciness of your steak.
What Myoglobin Can Tell You About a Steak
We are naturally drawn to bright red steaks. The natural interaction of myoglobin and oxygen causes the color. When you cut into a fresh, raw steak, the inside of the meat will have a purplish hue. Leave it on the counter for a few hours, and it will turn red.
Some cuts of meat naturally have higher levels of myoglobin. Dark red cuts like tri-tip or ribeye have the dark red pigment from an abundance of myoglobin. Fat and myoglobin are often found together and both contribute flavor and juiciness to the steak. The next time that you are looking at a counter full of New York steaks, pick ones that are darker red for more tenderness and flavor.
Purge in the bottom of a container indicates the muscle cells have lost the protein, myoglobin. Age can cause moisture loss, but only when the meat is stored at above-freezing temperatures. Once a cut of meat is frozen, the thawing process will result in purge. Avoiding buying cuts of meat with lots of purge in the package may result in better-tasting and juicier steaks.
Red Meat vs White Meat
The difference between red meat and white meat is the content of myoglobin. Chicken breast meat has no myoglobin and no red hue, but the legs and wings have myoglobin. Pork is often mislabeled as white meat, but it does have myoglobin, only in smaller amounts than beef.
Purge in a package of pork or chicken indicates the same conditions as that of beef.
Fish is generally a white meat, but tuna, shark, and swordfish are among the more common varieties containing myoglobin. Salmon, however, does not have myoglobin. It is red or pink due to carotenoids, the same chemical group that makes carrots orange.
The Most Important Thing to Remember About Purge
Purge is a sign of the condition of a piece of meat. It is a combination of water and the protein myoglobin. When a package of meat has a lot of purge in it, the meat has lost flavor and tenderness. The more purge, the less moisture in the meat, and the less tasty it will be.
That's why we let meat rest after cooking – it allows the juices to reabsorb into the meat. As the meat cools, it draws the moisture, fat, and myoglobin back into the muscle tissue, giving you a more tender and more flavorful steak.