Impact of heat treatment on database recall and metabolomic fingerprints used for timber identification employing direct analysis in real time time-of-flight mass spectrometry

Illegal logging is a profitable transnational crime, prompting the development of global reference databases to support tools for identifying wood species and harvest location. While these tools are effective for raw timber, they have not been systematically evaluated for manufactured wood products which undergo high temperature, pressure, and steam treatments. Although it is known that these treatments alter wood's chemical composition, no chemical technique has demonstrated its ability to generalize measurements from raw wood to its manufactured form. This paper examines the impact of heat treatments and plywood manufacturing on metabolomic fingerprints and database recall for timber species identification. Processes included plywood manufacturing of Betula pendula and lab-based heat treatments (72 °C to 250 °C) for Cedrela odorata and Dalbergia nigra (both CITES-listed), as well as Diospyros crassiflora and Araucaria cunninghamii. The database recall for D. crassiflora and D. nigra, both dark woods, were largely unaffected by temperature whereas the database recall decreased with increasing temperatures for C. odorata (species-level database recall dropping below 30% after 24 h at 200 °C and continuing to decline with longer treatments) and A. cunninghamii (species-level database recall dropping below 10% after 24 h at 150 °C and continuing to decline with longer treatments) and due to manufacturing processes of the B. pendula plywood (manufacturer, using a single tree for each plywood batch. The logs were soaked and pressed at 120–135 °C). The findings underscore the need for (1) complementary identification methods for manufactured wood products and (2) further research into how manufacturing processes impact the effectiveness of identification and traceability methods under development.