Comparison of five preparatory protocols for fish species identification using MALDI-TOF MS
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Rapid and reliable methods for fish authentication are required to protect consumers against food fraud. Matrix-assisted laser desorption ionization time of-flight mass spectrometry (MALDI-TOF MS) is known as a fast and accurate method for microorganisms. In this study, the effect of five preparation protocols for fish samples on the quality and reproducibility of spectra using the MALDI Biotyper platform were evaluated. The suitability of the protocols for the identification of high-fat Atlantic mackerel (Scomber scombrus) and low-fat rainbow trout (Oncorhynchus mykiss) was examined in dependence on different storage temperatures and levels of food processing (fresh, refrigerated, frozen, cooked and smoked). The results of the present study showed that acquisition of reproducible and high quality main spectra projections for high-fat and low-fat fishes in fresh and frozen states was only possible by sample preparation with 25% formic acid followed by chloroform–methanol defatting. MALDI-TOF MS based identification was also possible after treating samples at 99 °C for 5 min but not for smoked fish. Furthermore, log score values for identification of frozen fish remained stable even after 14 months of storage at −20 °C.
KeywordsMatrix-assisted laser desorption ionization time-of-flight mass spectrometry Fish species identification MALDI Biotyper Sample preparation
We thank Dr. Jörg Rau (CVUA Stuttgart, Germany) for permission to quote his private communication. We are also grateful to Dr. Azuka Iwobi for critically reading our manuscript. Furthermore, we would like to acknowledge the financial support of the Bavarian State Ministry of the Environment and Consumer Protection.
Compliance with ethical standards
Conflict of interest
The authors declare that there is no conflict of interest regarding the publication of this paper.
Compliance with ethics requirements
This article does not contain any studies with human participants by any of the authors. All institutional and national guidelines for the care and use of animals were followed.
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