Applications of Polarography for Assessment of Fish Freshness

Fish freshness was assessed with an enzymatic method using a polarographic probe at 0.7 volt (platinum vs silver) to monitor degradation of inosine monophosphate (IMP), inosine (H × R), and hypoxanthine (Hx). The K‐value, a ratio of H × R + Hx/IMP + H × R + Hx, was determined in Sockeye salmon, Pacific cod and Pacific herring in ice and at 12°C. Results were compared with those from HPLC and sensory scores. K‐values by polarography correlated well with HPLC. Loss of freshness accompanied rise in K‐value in all studies. Sensory scores correlated relatively well with K‐values in Sockeye salmon and Pacific herring but less with Pacific cod. K‐value did not reflect eating quality of Pacific cod.