Meat Colour and Shelf Life
When meat is sliced, the surface is exposed to oxygen and will change in colour from dark purple to bright red. This is because the colour of meat depends mainly on the pigment myoglobin. Myoglobin exists in 3 different chemical forms and colours, deoxymyoglobin (purple), oxymyoglobin (red) and metmyoglobin (brown).
Blooming is the oxygenation of the myoglobin at the meat surface and is represented by the colour changing to red. This takes approximately 15–30 minutes.