Development of colour at the surface of meat

The colour of meat is determined by the concentration of myoglobin and its chemical state. Myoglobin is the primary meat pigment existing as:

Myoglobin (Mb, purple-red) – myoglobin is favoured by zero oxygen concentration. Mb predominates as no O2 is present. This is the case with vacuum packing	Metmyoglobin (MMb, brown) – metmyoglobin is favoured by low oxygen concentration MbO2 predominates at the meat surface, MMb layer forms at lower levels where O2 is low, Mb predominates at meat centre where no O2 is present	Oxymyoglobin (MbO2, bright red) – oxymyoglobin is favoured by high oxygen concentration With time, MMb layer thickens and extends to the meat surface, ‘browning’ and discolouring it
No O2	21% O2	70% O2
Surface of meat
		MbO2 MMb Mb

• myoglobin (Mb) a principle haem containing pigment in muscle tissue responsible for storing oxygen in muscle and associated with muscle colour
• haem the chemical group that contains iron. A greater haem concentration in the muscle will cause meat to look redder or darker and is likely to be an indication of more red oxidative fibres in the muscle which is characteristic of red meats

Source: Meat and Livestock Commission