Effects of dietary fishmeal levels on adenosine triphosphate-related compounds and freshness of raw and cooked muscle in large yellow croaker Larimichthys crocea

A comparative study on the adenosine triphosphate (ATP)-related compounds and freshness of raw and cooked muscle in wild and farmed large yellow croaker (Larimichthys crocea) was performed. The two groups of farmed fish (189.87 +/- 0.89 g) were fed two diets containing 44% (CF) and 25% (LF) of fish meal (FM) for 82 days, respectively. Results showed that the contents of ATP, adenosine diphosphate (ADP), adenosine monophosphate (AMP) and inosine 5'-monophosphate (IMP) were highest in raw and cooked muscle of wild fish, while these values were lowest in raw and cooked muscle of fish fed LF. Conversely, wild fish had the lowest inosine (Ino) and hypoxanthine (Hx) contents in raw and cooked flesh, while the LF group had the highest levels of Ino and Hx in raw and cooked flesh. Fish fed CF had significantly higher amounts of ATP, ADP and IMP in raw muscle, ATP and AMP in cooked muscle than those in the LF group (P < 0.05). The above results allowed wild fish to have the lowest K and K-i values, closely followed by fish fed CF, and the LF group have the highest values in raw and cooked muscle (P < 0.05). Meanwhile, cooking significantly decreased ATP, ADP and IMP contents, while increased AMP and Ino levels, inducing significantly higher K and K-i values in cooked muscle of all the treatments (P < 0.05). In conclusion, lower dietary FM level could decrease the contents of IMP and its precursors, and increase the degradation products of IMP in muscle, leading to the declines in umami and freshness. The stronger umami of wild large yellow croaker could be related to the higher precursors and lower degradation products of IMP in fillets.