The freeze–thaw process used for beef muscle accelerated color
deterioration during cold storage. The oxidation of Mb was not
related to lipid oxidation. It is possible that the damage to cellular
and sub-cellular compartments produced from physical disruption
by ice crystals during freezing and thawing could release enzymes
into sarcoplasm, and the enzymes could potentially be involved in
MetMb formation in the final thawed meat. The MetMb reductase
activity in mitochondria intermembrane space was decreased by
freeze–thaw process.