Biochemical parameters, such as oxygen consumption rate by muscle post mortem (OCR), depth of
oxygen penetration into meat, rates of
myoglobin oxygenation and deoxygenation and
myoglobin content and
succinic dehydrogenase activity, were determined for muscles of differing colour stability.
Metmyoglobin reduction, in
anoxia following oxidation with
ferricyanide (MRA) and aerobically following oxidation with low pO(2) (ARA), were also determined. M. psoas major (poor colour stability) has higher enzymic activity than M. longissimus dorsi (good colour stability). This difference, together with the low
myoglobin content in M. psoas major, results in relatively high OCR with consequent low
oxygen penetration and rapid conversion of
oxymyoglobin to
myoglobin in M. psoas major, disposing it to rapid formation of
metmyoglobin.
Metmyoglobin reduction occurs both under anaerobic and aerobic conditions but no significant correlation is found between actual
metmyoglobin reduction and rate of discoloration of different muscles. The most significant factor affecting colour stability of beef muscles appears to be their enzymic activity which determines the rate of
myoglobin oxidation.