The effect of brine composition and pH on the yield and nature of water-soluble proteins extractable from brined muscle of cod (Gadus morhua)

Fillets of Atlantic cod (Gadus morhua) were held for 36 h in brines of pH 6.5 and 8.5, respectively, containing various combinations of NaCl, KCl, MgCl2 and CaCl2. Proximate analyses and chloride content were determined. Soluble muscle protein extracted in distilled water and protein released into the brine following salting was determined by SDS-PAGE. The soluble fraction was not affected by the presence of divalent salts or KCl in the brines, but it was affected by the initial pH. Both actin and myosin heavy chain (MHC) were released in pH 6.5 brines after immersion of the fish. On the other hand, an initial pH of 8.5 did not favour the release of these proteins. There was a smaller variety of remaining soluble proteins in salted muscle with an initial pH of 6.5, than with 8.5. However, this effect of the lower pH was offset to the extent that the ionic strength of the brine was higher.