ATP (adenosine triphosphate) in fish meat decomposes in a following process:
A parameter “K value” indicates freshness of fish meat and is defined as:
When K value is below 20 %, fish meat can be used for Sashimi (raw use) and 20% through 60% for cooked and processed use. We applied X-LC to an analysis of K value and evaluated its performance in comparison with results of conventional HPLC.
The chromatography system utilized in this experiment consists of JASCO X-LC series: two of 3185PU solvent delivery pump, 3080DG degasser, 3180MX high pressure mixing device, 3067CO column oven, 3070UV UV/Vis detector, 3159AS autosampler, and ChromNAV chromatography data system. Separation column used was a X-PressPak AQ-C18-W (3.0 mm ID x 50 mmL, 2µm). K value was obtained by a program calculation function in ChromNAV.
Pretreatment of fish meat was conducted in the following procedure:
- Add 0.4 M perchloric acid solution (20 mL) to fish meat (2.5 g) to homogenize.
- Centrifuge it at 3500 rpm for 10 min.
- Add 2 M potassium carbonate solution (1 mL) to the supernatant (5 mL) and centrifuge it at 3500 rpm for 5 min.
- Filter supernatant obtained at (3) with 0.45 µm membrane filter.
Figure 1 shows an X-LC chromatogram of standard mixture. X-LC succeeded in providing an analysis time eight times shorter than conventional HPLC. Figure 2 shows an X-LC chromatogram of tuna preserved for two days. As shown in this figure, six kinds of components provide a good separation without interfering with unknown components. K value of this sample was 8%. Figure 3 shows relationship between preservation days and K values of tuna and sea bream.