Beyond mislabelling: Chinese fish balls authentication by metabarcoding allows unveiling hidden mammal and avian species

In this study, 47 Chinese fish balls (FBs) sold on e-commerce platforms were collected and the ingredient of animal origin were identified using 16S rRNA metabarcoding. The sequencing results were compared to the FBs declared composition (DC) - obtained by combining the trade name and the ingredient list - to assess mislabelling. FBs were considered mislabelled if an ingredient not reported in the DC was detected molecularly, or if an ingredient in the DC was not detected. Excluding 14 FBs that only reported the generic term “fish" on the label, the DC mostly included eel (Anguilliformes), shark (Elasmobranch), and freshwater fish species. The presence of pork or chicken was also declared in a number of FBs. Overall, 65.9% of the FBs (n = 31) were mislabelled. The following cases were highlighted (the same FB could be included in more than one case, simultaneously): i) 21 FBs containing undeclared pork, chicken, or beef; ii) 9 FBs containing undelcared additional fish species; iii) 7 FBs not containing the fish reported in the DC. Threatened fish species were also detected. These mislabelling cases highlight the challenges consumers face in making ethical, religious, and sustainable choices. A more thorough evaluation of the quantitative potential of metabarcoding, as well as the possibility to combine this technique with quantitative methods (e. g. qPCR) should be considered for monitoring the surimi production chain.