Fillet colour correlates with biochemical status in Australasian snapper (Pagrus auratus) during storage in refrigerated seawater

We demonstrate that two commonly used chilled storage temperatures (4.15 and 0.3 °C) differ in their effects on whole rested harvested Australasian snapper (Pagrus auratus) stored in refrigerated seawater (RSW) with respect to white muscle biochemistry and skin and fillet colour. White muscle pH decreased from 7.64 to ca. 6.4 over 48 h at both temperatures, but remained significantly (P < 0.05) elevated at 4.15 °C compared to 0.3 °C until 24 h post-mortem. This corresponded with significantly elevated potential energy and concentrations of ATP, ADP and glycogen. Depletion of these metabolites occurred by 24 h at both temperatures and was mirrored by rises in lactate and inosine monophosphate (IMP). At 24 h snapper stored at 4.15 °C remained in partial rigor, whereas animals at 0.3 °C were in firm rigor. After 72 h significantly higher inosine and hypoxanthine concentrations were present in the 4.15 °C group, demonstrating temperature related mass action. Tissue biochemistry significantly correlated with changes in fillet colour, particularly redness and yellowness, and we propose that fillet colour can be used as a non-destructive indicator of muscle biochemistry. We link these data with muscle ultrastructure and translucency through histology and with use of a novel laser penetration method.

► Storage of snapper in RSW at 4.15 °C extended time to firm-rigor until after 24 h.
► From 72 h storage at 0.3 °C reduced inosine and hypoxanthine concentrations.
► Fillet CIEL*a*b colours correlated with post-harvest fillet biochemistry.
► Laser penetration can be used to monitor opacity in fish fillets..
► As harvested skin colour was not preserved by RSW storage at either temperature.