Determination of the fatty acids in fish tissue and feed — comparison of different methods and statistical evaluation

With the aim to reinforce laboratory competence in the field of testing the quality of fish from aquaculture, a study on the precision of fatty acid (FA) analyses in fish meat and fish feed was undertaken. Different methods were performed in laboratories. In situ transesterification method and extraction of lipids from the fish were followed by capillary gas chromatography with flame ionization detection. The reproducibility (R) values of the majority of FM were less than 3% of their absolute values. Differences in calculating ionization detector response factors and/or autoxidation caused by faulty sample-handling could lead to variation in quantification of FAs in fish, especially for FA C22:6n-3. Statistical analysis showed a significant correlation between the two laboratories quantifications of FM in fish and fish feed (Pearsons correlation coefficient; r = 0.987, r = 0.994, and r = 0.997; for fish Z [trout], fish g [rainbow trout], and fish feed, respectively). Overall, adequate accuracy was obtained in this study. The proposed method provides a fast and efficient means of identifying fish and feed for quality control purposes.