On the Nature of Altered Protein in Cod Muscle Stored at −29°c After Aging in Ice

SUMMARY Additional protein, inextractable with the usual technique, was extracted from cod muscle which had various free fatty acid contents and had been stored at −29°C after aging in ice. Ultracentrifugal patterns showed that the extracted protein was aggregated and polydisperse. Sedimentation behavior was similar to that of aggregated protein in extracts of muscle in which protein‐free fatty acid interaction occurred during prolonged aging in ice. Conditions under which altered protein was extracted, overnight exposure of homogenized muscle to neutral salt solution followed by rehomogenization; phase contrast micrographs of residues of homogenates before and after rehomogenization; and ultracentrifugal patterns of extracts containing aggregated protein that had been stored in extractant suggested that some of the linkages resulting from reactions in the frozen state were salt‐sensitive. The association that occurred in the muscle after storage at −29°C appeared to be more stable in a neutral salt environment than that occurring in muscle aged in ice.