Validation of a K Value Method for Freshness Evaluation of Bony Fish Using High-Performance Liquid Chromatography: An Interlaboratory Study.

Background: Freshness is one of the most important qualities of fish and has a significant impact on the utilization and commercial value. As global production and trade volumes of fishery products increase, standardization of scientific methods for evaluating fish freshness is required.

Objective: K value based on the ratio of ATP derivative contents is widely recognized as a scientific freshness index of fish. The aim of this study was to standardize the K value analysis method that would be useful for fair commercial transactions of bony fish.

Methods: Conventional methods for analyzing K values of fish were modified. An interlaboratory study was conducted to evaluate the reproducibility of the method. The 11 participating laboratories analyzed 10 test samples (five pairs of blind duplicates of material) using high-performance liquid chromatography (HPLC).

Results: For five test materials with a K value of 6.12-83.4%, the range of reproducibility relative standard deviation (RSDR) was 1.3-3.5%. The reproducibility standard deviation (sR) was 0.21-1.2%.

Conclusions: Considering the rate of increase of K value in typical bony fish species and storage conditions, the target value of reproducibility standard deviation was set to sR ≤1.25%, so as detecting a difference of 5% in K values. The results of the interlaboratory study met this criterion.

Highlights: The precision of the method was found to be acceptable.