Differentiation of Fresh and Frozen Meat

The isoenzyme patterns of cell organelles, for instance mitochondria and microsomes, differ often from those of C34oplasm When the organelle membranes are damaged by a physical or chem- 

The enzyme P-hydroxyacyl-CoA-dehydrogenase (HADH, EC 1.1.1.35) is also suitable for the detection of frozen meat or fish. In the oxidation of fatty acids, HADH catalyzes the reaction shown in Formula 12.29. This enzyme is bound to the iimer membrane of mitochondria and is liberated in the freeze/thaw process. Its activity can then be measured in the issuing sap with acetoacetyl CoA or with the artificial substrate N-acetylacetoacetylcysteamine. 

Such membrane damage has been observed by freezing and thawing of tissue, for example, of muscle tissue, in which the isoenzymes of glutamate oxalacetate transaminase (GOT) bound to mitochondrial membranes are partially released and found in the sarcoplasm. The pressed sap collected from fresh unfroze meat has only sarcoplasm enzymes, while the frozen and thawed meat has, in addition, the isoenzymes derived from mitochondria. The GOT isoenzymes can be separated by electrophoresis (Fig. 12.41). This procedure is also apphcable to fish. 

Pigment analysis is carried out for the evaluation of meat freshness. The individual pigments, such as myoglobin (purple-red), oxymyoglobin (red) and metmyoglobin (brown), are determined. 

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