Application of direct analysis in real time ionization-mass spectrometry (DART-MS) in chicken meat metabolomics aiming at the retrospective control of feed fraud

Abstract

Metabolomic fingerprinting enabled by ambient mass spectrometry employing a direct analysis in real time (DART) ion source coupled to a medium-high resolution/accurate mass time-of-flight mass spectrometer (TOFMS) was used as a tool for differentiation between chickens fed by feed that contained 5-8 % (w/w) of chicken bone meal (a banned component) and those representing a reference group, i.e. grown otherwise under the same conditions. In the first step, the sample extraction and DART-TOFMS instrumental conditions were optimized to obtain the broadest possible representation of ionizable compounds occurring in the extracts obtained from chicken muscle and feed on which experimental animals were grown. To this end, a simultaneous (all-in-one) extraction procedure was developed employing water and cyclohexane mixture as the extraction solvents. Under these conditions both polar as well as non-polar metabolites were isolated within a single extraction step. In the next step, metabolomic fingerprints of a large set of chicken muscle and feed extracts were acquired. In the final phase, the experimental data were statistically evaluated using principal component analysis and orthogonal partial least squares discriminant analysis. In general, differentiation of chicken muscle according to diet (feed with and without the addition of chicken bone meal) was feasible. Additional experiments conducted after 6 months confirmed applicability of this approach. Correct classification was obtained based on the assessment of polar as well as non-polar extracts fingerprints. However, the analysis of non-polar extracts showed that the pattern of triacylglycerols is more prone to seasonal variability and/or type of raw materials used during feed preparation which obscures the bone meal impact to some extent. © 2013 Springer Science+Business Media New York.