Characterization of Quality Deterioration in Yellowfin Tuna

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Abstract
The spoilage pattern of thawed yellowfin tuna carcasses was examined. After five days storage at 10° and 18°C, bacterial counts were low (< 103) although visible softening of the flesh was apparent. Direct measurement of ethanol as an indicator of pre‐process spoilage also failed to reflect differences among carcasses which were aged for up to five days. Analysis of nucleotides by high performance liquid chro‐matography suggested that the ratio of inosine monophosphate (IMP) to other nucleotides may be a valuable indication of spoilage time where the IMP ratio decreased linearly with time after thawing. Average recoveries of adenosine monophosphate, inosine monophosphate, inosine and hypoxanthine were 50%, 75%, 64% and 92%, respectively, from spiked tuna which had been cooked at 122°C for 67 min.