Effect of brine salting at different pHs on the functional properties of cod muscle proteins after subsequent dry salting

Fillets of Atlantic cod (Gadus morhua) were wet-salted in brines of pH 6.5 and 8.5 containing different combinations of NaCl, KCl, MgCl2 and CaCl2, then dry-salted in NaCl. Proximate analyses, functional properties (water holding capacity and protein solubility) and hardness were determined in the dry-salted cod. The compositions of the protein fractions soluble in water and in 0.86 M sodium chloride were determined by SDS–PAGE. The composition and pH of the brines slightly affected the protein composition of the major extract constituents and the functional properties of the muscle after dry-salting. Brining at alkaline pH produced a larger variety of water-soluble proteins, particularly actin, than at pH 6.5. Furthermore, the compositions of the protein fractions extracted with 0.86 M NaCl were very similar for both pHs, irrespective of the composition of the brine; in this case, myosin heavy chains were absent in both extracts due to aggregation caused by a massive uptake of salt by the muscle.