What is the red juice in rare steak, and why isn't it blood?

For some red meat lovers, a rare steak offers the best flavor and an extra juicy texture. For others, seeing the meat dripping what looks like a pool of blood is quite unpleasant.

Myoglobin can be observed both before and after cooking a steak. About three-quarters of meat is water, so if a raw steak freezes, the water forms ice crystals that damage muscle cells. Upon thawing, the resulting liquid contains some of that iron-rich myoglobin, which can resemble blood. These juices are often called "purge" or "exudate," and virtually all of the animal's blood is removed during slaughter and processing.

Several factors affect the color of a raw steak, from the age of the animal to how the meat has been stored. When myoglobin comes into contact with oxygen, it forms oxymyoglobin and changes from a dark purple to a brighter blood red. This is why vacuum-packed meat often appears dark and turns redder upon exposure to air.

When cooking, the myoglobin content influences the color of the meat and its juices, and rare meat appears redder because it has more myoglobin. The common terms (rare, medium-rare, medium, medium-well, and well-done) refer to the internal temperature. This temperature changes the appearance and juiciness, as heat breaks down and darkens the myoglobin.

Beef appears red inside when cooked to 60 degrees Celsius (140 degrees Fahrenheit) because myoglobin doesn't denature much at that temperature. However, color isn't a reliable indicator, so it's best to use a meat thermometer to ensure the steak reaches the USDA's recommended minimum internal temperature of 63 degrees Celsius (145 degrees Fahrenheit).

Regardless of the cooking method, the key to a juicy steak is retaining the juices. Letting it rest for five to seven minutes before serving or slicing allows the juices to redistribute throughout the meat. Anthony Bourdain considered resting to be the most important tip for a perfect steak.