Protein denaturation in frozen fish. X.—changes in cod muscle in the unfrozen state, with some further observations on the principles underlying the cell fragility method

A study was made of the changes in the muscle proteins that occur when cod are kept in ice, using both protein extractability in salt solution and ‘cell fragility’ values as criteria. The results by the two methods did not agree, and the reason for this is discussed with the aid of photomicrographs of homogenates of cod muscle. It appears that changes in extractability are the consequence of a binding together of structural protein molecules and perhaps myofilaments, while a binding together of myofibrils is the agent causing changes in cell fragility readings. Cold storage changes the fragility of the cells (breakdown to fibril level), while bacterial action during stowage in ice changes the fragility of the myofibrils.