Water uptake, protein solubility, and protein changes of cod mince stored on ice as affected by polyphosphates

Water uptake ability (WUA) and protein solubility of cod mince were higher with sodium hexametaphosphate (SHMP) than with sodium tripolyphosphate (STP) or untreated controls during ice storage. WUA increased significantly with SHMP concentration up to 0.7% SHMP but above that WUA decreased, although protein solubility continued to increase. The SDS-PAGE results showed that extraction of a specific amount of water-soluble protein, perhaps including some myosin heavy chain (MHC, 200 kd), correlated with high WUA. However, excess extraction of MHC may cause destruction of the structural matrix of the insoluble protein network, preventing it from holding water