Rapid and reliable species identification of scallops by MALDI-TOF mass spectrometry

Correct identification of scallop species is of crucial importance to the seafood industry to assess marketability of the product, as well as to prevent unintentional mislabeling and to comply with current legislative guidelines. However, various scallop species are virtually indistinguishable and to date there is no fast, reproducible, and inexpensive technique for species identification of scallops. A new promising tool in the identification of various organisms is the matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). In this study, we aimed to 1) evaluate the possibility of MALDI-TOF MS as a tool for rapid and reliable species identification of scallops and 2) assess the occurrence of mislabeled scallops sold in Switzerland. We therefore used 16 scallop reference samples, as well as scallops sampled at eight Swiss retail facilities and identified the scallop species both by 16S rRNA PCR and MALDI-TOF MS. For all tested scallop species, MALDI-TOF MS yielded reproducible and unique mass spectra profiles covering a wide molecular mass range of 3000–30,000 Da. Species-specific biomarker protein mass patterns were determined. Species identification of reference scallop samples using MALDI-TOF MS was in accordance with species identification using the established 16S rRNA PCR tool. Identification of the scallop samples purchased in Switzerland also yielded identical results for MALDI-TOF MS and the 16S RNA PCR approach. We were able to show that several of the scallop samples were labeled incorrectly. All mislabeled scallops belonged to the species Placopecten magellanicus, but were marketed as “Jacobsmuschel”, a commercial name reserved for Pecten spp. In this study, we show that MALDI-TOF MS allows for rapid, reliable, and highly accurate species identification of scallops.