EFFECT OF IN SITU FORMALDEHYDE PRODUCTION ON SOLUBILITY AND CROSS-LINKING OF PROTEINS OF MINCED RED HAKE MUSCLE DURING FROZEN STORAGE

Publisher Website
Google Scholar
Abstract
Three forms of minced red hake muscle representing whole-mince, mince with the low molecular weight fraction removed (reconstituted-minced) and mince with low and high molecular weight soluble fractions removed (washed-minced) were stored frozen with added Fe+2 and ascorbate (trimethylamine oxide (TMAO) was added when necessary). The production of DMA and free formaldehyde was measured as were the decreases in water-soluble and salt-soluble proteins and TMAO as a function of increasing concentrations of ascorbate. Dimethylamine (DMA) production and loss of overall protein extractability were greatest in minced muscle, followed by reconstituted-minced muscle, and least in washed-minced muscle. The minced muscle lost water-soluble proteins, however, less rapidly than the reconstituted-minced muscle. The percentage of formaldehyde that was bound was highest in the minced, next in the reconstituted-minced and least in the washed-minced muscle. This supports earlier data and indicates that formaldehyde reacts with both the small molecular weight fraction and the water-soluble proteins as well as the contractile proteins. Loss of protein extractability in all samples appeared to be heavily dependent on hydrophobic interactions. Disulfide interactions appeared to occur to some extent in the reconstituted-minced and washed-minced muscle but were a minor factor with the minced muscle samples. Surface hydrophobicity of the proteins was inversely related to their extractability. In the sample of minced muscle with the highest concentration of added ascorbate where approximately 79% of the proteins became inextractable, some 2% of the muscle proteins were covalently linked in polymers with molecular weights greater than that of the myosin heavy chains. The data indicate that cross-linking of protein components occurs as well as hydrolysis of a considerable amount of the protein.