Changes in the content of MetMb, OxyMb and DeoxyMb during
storage are shown in Fig. 3. Generally the content of MetMb increased
during storage, but was always lower in steaks stored directly at
3 days postmortem (V0M0) or after vacuum ageing (V5M0 or V15M0)
compared with steaks aged in MAP (V0M5 or V5M10). This indicates
formation of MetMb already during ageing in MAP before storage in
air. Steaks aged for a total of 15 days in vacuum (V15M0) or vacuum
followed by MAP (V5M10) had the highest content of MetMb after
5 days of storage. The development of OxyMb during storage
corresponded closely with that of the a* value (Fig. 2). The most
marked change in OxyMb during storage was the large decrease from
day 4 to day 5 in steaks aged for a total of 15 days irrespective of
ageing system. The DeoxyMb content was constant and at the same
level for all the ageing systems during storage except for steaks stored
directly 3 days postmortem (V0M0). The content of DeoxyMb was
higher than that in the aged steaks after only 1 h of storage, but
decreased to the same level after 3 h.