Untargeted lipidomics for evaluating fish authenticity: the case of wild-caught and farmed species of Sparus aurata

Abstract

Aim: This study aims to develop sensitive and reliable analytical technologies to enable the distinction between wild-caught and farmed fish through appropriate molecular markers to protect consumers from fraudulent fish labelling. Gilthead sea bream, Sparus aurata L. (S. aurata L.), is a very common fish used as foodstuff worldwide and globally produced in aquaculture in the Mediterranean basin. Wild-caught and farmed species are very different in feed and lifestyle and the quality and safety of these products strongly depend on fish growth, processing history, and storage conditions. Methods: Hydrophilic interaction liquid chromatography (HILIC) coupled with electrospray ionization (ESI) and Fourier-transform mass spectrometry (FTMS; HILIC-ESI-FTMS) was employed to discriminate the phospholipidome profiles of fillets extracts of wild-caught from farmed gilthead sea breams. Results: The untargeted approach led to the annotation of a total of 216 phospholipids (PLs), namely 65 phosphatidylethanolamines (PEs), 27 lyso-PEs (LPEs), 61 phosphatidylcholines (PCs), 34 lyso-PCs (LPCs), and 29 sphingomyelins (SMs). Untargeted lipidomics data were investigated by principal component analysis (PCA) and K-means clustering. Lyso-PLs (LPLs) of PEs and PCs including ether-linked side chains were found as discriminating markers between the two types of fish samples. The PLs that were most responsible for distinguishing between the lipid extracts of farmed and wild S. aurata fillets were successfully characterized by tandem mass spectrometry (MS/MS). The analysis revealed that wild fillet lipid extracts contained some PE exhibiting ether bonds (PE P-), viz. 16:0, 18:0, 18:1, and 18:2 and polyunsaturated fatty acyl chains (i.e., 22:6 and 22:5). In farmed species, the estimated abundance ratios of fatty acyl chains 20:4/18:2 and 22:6/20:5 were 0.9 and 0.05, respectively. However, in wild-caught fish, these ratios were found to be two-fold higher and four-fold higher, respectively. Conclusions: This work demonstrates that the combination of HILIC-ESI-FTMS and chemometrics can serve as a valuable tool for evaluating fish authenticity and assessing quality concerns by monitoring specific lipid ratios.