Fatty acidomics: Evaluation of the effects of thermal treatments on commercial mussels through an extended characterization of their free fatty acids by liquid chromatography – Fourier transform mass spectrometry

•SPE on silica was exploited to collect free fatty acids from mussel lipid extracts.•Up to 191 different fatty acids were recognized distinctly by RPC-ESI-FTMS analysis.•Oxidized fatty acids, bearing hydroxylic, carbonylic or epoxylic moieties, were detected.•An increase in free fatty acids was found in frozen or long-term refrigerated mussels.•The FFA profile of 48 h-refrigerated mussels was comparable to that of fresh mussels. An unprecedented characterization of free fatty acids (FFA) in the lipid extracts of fresh or thermally treated mussels of sp. Mytilus galloprovincialis, including up to 128 saturated, mono- or poly-unsaturated and 63 oxidized (i.e., modified by hydroxylic, carbonylic and/or epoxylic groups) compounds, was achieved using reverse phase chromatography coupled to electrospray ionization-Fourier transform single and tandem mass spectrometry (RPC-ESI-FTMS,MS/MS). Subsequent Principal Components Analysis (PCA) evidenced several effects of thermal treatments on the mussel FFA profiles. In particular, death-inducing low temperature treatments (freezing at −16 °C or refrigeration at 4 °C for several days) induced a peculiar increase in the incidence of FFA, whereas the effect was absent in mussels undergoing death upon prolonged storage at room temperature (25 °C, 6 h) or fast cooking (100 °C, 5 min). Alive mussels, either fresh or resulting from short term (up to 48 h) refrigeration were actually indistinguishable by PCA, although subtle seasonal effects were observed.