Doneness

[6]: 165 As meat is cooked, it turns from red to pink to gray to brown to black (if burnt), and the amount of myoglobin and other juices decreases.

Before cooking, the iron atom is in a +2 oxidation state and bound to a dioxygen molecule (O2), giving raw meat its red color.

Searing raises the meat's surface temperature to 150 °C (302 °F), yielding browning via the caramelization of sugars and the Maillard reaction of amino acids.

Note that searing (cooking the exterior at a high temperature) in no way "seals in the juices", since water evaporates at the same or higher rates as it does in unseared meat.

[8] It recommends an internal temperature of at least 145 °F (63 °C) for cuts of beef, veal, and lamb in order to prevent foodborne illness, and warns that color and texture indicators are not reliable.