Analysis of French Spirit Barrels (Oak Wood) Metabolites by LDI-MSI

Insight into the composition, migration, degradation, and external interactions of compounds within oak is fundamental to the wine and spirits industry, given their direct impact on the organoleptic properties of aged spirits. The characterization of oak extracts has traditionally relied on HPLC-MS and GC-MS. However, (MA)LDI-MS imaging is a technique that could give newinformation about wood metabolite distribution.IntroductionCognac barrels are primarily made of oak wood (Quercus spp.), a genus within the Fagaceae family that includes approximately 500 species. Understanding the composition, migration, degradation, and external interactions of compounds in oak is essential for the wine and spirits industry, as these processes directly influence the organoleptic properties of aged spirits. Oak extracts have been widely studied using techniques such as HPLC-MS1 and GC-MS2, while more recent work has used TOF-SIMS3 to analyze small surface regions of barrel staves. Although TOFSIMS offers high spatial resolution, it is limited in mass range and mass resolution.(1) Glabasnia, A.; Hofmann, T. Identification and Sensory Evaluation of Dehydro- and Deoxyellagitannins Formed upon Toasting of Oak Wood (Quercus alba L.). J. Agric. Food Chem. 2007, 55 (10), 4109–4118. DOI: 10.1021/jf070151m.(2) Flamini, R.; Panighel, A.; Marchi, F. de. Mass spectrometry in the study of wood compounds released in the barrel‐aged wine and spirits. Mass Spectrometry Reviews 2023, 42 (4), 1174–1220. DOI: 10.1002/mas.21754.(3) Cournut, A.; Vanbellingen, Q. P.; Demaye, A.; Ochs, M.; Römpp, A.; Touboul, D.; Eparvier, V.; Brunelle, A. Multimodal Analysis of Oak Wood Metabolites for a Comprehensive Understanding of the Aging Process in Typical French Spirit Barrels. Journal of mass spectrometry : JMS 2025, 60 (9), e5170. DOI: 10.1002/jms.5170.MethodsWe analyzed the transversal surface of oak staves, from the inner to the outer barrel wall, enabling the observation of gradual chemical changes across the entire wood section. We compared freshly cut, freshly toasted, and historical (100-year-old) staves. For our studies, we utilized a MALDI source equipped with autofocus and large sample holders, allowing the direct analysis of intact samples (2.0×0.3×0.5 cm).ResultsPreliminary results revealed a decrease in ion signal intensity in the inner and/or outer regions of the barrel. Several experimental strategies (including changes in acquisition direction, the use of internal standards, and optimization of instrumental parameters) were tested to determine whether this effect reflected true chemical variation or methodological limitations. Colocalization analysis using MZmine proved particularly effective for identifying spatially correlated compounds. Notably, compounds such as cyclotene, methylbutyric acid, and 1-(2-furanyl)ethanone seem to have higher intensities in toasted regions, consistent with previous reports based on barrel wood extracts. Additionally, previously unreported signals were observed in localized wood areas. Several compounds were tentatively identified using data-dependent acquisition (DDA) andMS/MS library matching.ConclusionAlthough this work at a preliminary stage, it demonstrates the feasibility of analyzing intact barrel staves by MALDI-MSI and establishes methodological strategies that will support comprehensive future studies of compound behavior in cognac barrels.