Autolytic degradation and microbiological activity in farmed Coho salmon (Oncorhynchus kisutch) during chilled storage

Two deteriorative pathways (autolysis and microbiological activity) were studied in farmed Coho salmon (Oncorhynchus kisutch) for 24 days during chilled storage. These changes were assessed by nucleotide degradation (determination of adenosine 50-triphosphate and its degradation compounds) and biochemical (pH; content of total volatile base-nitrogen; trimethylamine-nitrogen, TMA-N; histamine) and microbial (total aerobe mesophiles, TAM; coliforms) indices related to bacterial activity. An important nucleotide degradation could be assessed according to the fast inosine 50-monophosphate formation, followed by degradation into inosine and hypoxanthine; the K value was found to be an accurate tool for the measurement of quality loss throughout the whole experiment. Regarding bacterial activity, contents of TMA-N and histamine and TAM counts assessment showed sharp increases after the end of the microbial lag phase (12– 17 days); however, values obtained for histamine content and TAM growth remained below acceptable security limits throughout the whole experiment.