This study was carried out to determine ATP in the muscle in olive flounder (Paralichthys olivaceus) content by using a luminometer, with the aim to facilitate field estimation of the postmortem interval of sliced raw fish, and establishing the extractant and extraction method to measure ATP content in fish muscle with a luminometer. In consideration of low variations in measurements and fewer dilutions, 0.5 M phosphate buffer (pH 6.8) was selected as the optimal extraction buffer for this method. As a proxy for ATP content, measurements from the luminometer in relative light units (RLU) in olive flounder muscle stored at 5°C resulted in 1,594 × 103 to 2,154 × 103 RLU from the fish muscle at 0 h postmortem, 922 × 103 to 1,616 × 103 RLU at 10 h postmortem, and 6.3 × 103 to 7.2 × 103 RLU at 24 h postmortem. Thus, increasing the time in storage reduced RLU values, and the ATP content rapidly declined after 24 h postmortem. ATP content measured by high-performance liquid chromatography (HPLC) ranged from 7.86 to 8.9 μmol/g and had almost disappeared after 24 h postmortem. The comparison between luminometer-measured RLU and HPLC-based ATP content showed a high correlation of r2 = 0.98 (600 g of fish), 0.96 (800 g), 0.97 (1,000 g), and 0.97 (1,200 g). Therefore, a luminometer can provide rapid and accurate field determination of the postmortem interval of sliced raw fish within 24 h.
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