The juice that emerges from raw meat - it is not blood

Quite a common misconception that raw red meat (ie meat from animals) contains blood, as it implies a red liquid. When you are cooking meat, the liquid forms a surface "skin" of gray.

In fact, it does not blood. Almost all the blood flows from the meat when the animal is slaughtered, so that the liquid you see is composed mainly of water. The reddish hue gives it the presence of the protein myoglobin. The more myoglobin, the red meat, which is why the meat of animals called red. Fish and poultry have little of the protein, and are therefore classified as "white meat».

Cooked red meat turns brown for the same reason. When a piece of meat is heat treated, i.e. heated, every iron atom in the myoglobin molecule loses an electron passes and 2 to 3 degrees of oxidation. These chemical changes and explain the change in color from reddish-pink to dark brown.

via factroom.ru