Mitochondrial activity as an indicator of fish freshness.

Highlights • Mitochondria function as reliable indicator of fish freshness. • Several ultrastructural post mortem damages visible in fish fillets mitochondria. • Mitochondrial respiration altered in fish fillets from 96 h stored at +4 °C. • Mitochondrial potential (ΔΨ m) significantly disrupted after 96 h of storage at +4 °C. Abstract The current methods used to routinely assess freshness in the fishing industry reflect more a state of spoilage than a state of freshness. Mitochondria, the seat of cellular respiration, undergo profound changes in post mortem tissues. The objective of this study was to demonstrate that mitochondrial activity constitutes a putative early fish freshness marker. The structure of gilthead sea bream (Sparus aurata) muscle tissue was evaluated over time by transmission electron microscopy. Respiration was assessed in mitochondria isolated from sea bream fillets using oxygraphy. Membrane potential (ΔΨ m) was determined by fluorescence (Rhodamine 123). Mitochondrial activity of fillets stored at +4 °C was studied for 6 days. Changes in mitochondrial cristae structure appeared from Day 3 highlighting the presence of dense granules. ΔΨ m and mitochondrial activity were significantly disrupted in sea bream fillets after 96 h of storage at +4 °C. Mitochondrial activity constituted a reliable and early indicator of fish freshness. [ABSTRACT FROM AUTHOR]