Analysis of medieval organic remains: Incense in SE Spain

• Types of medieval incense and their botanical origins in religious contexts. • GC–MS and FT-IR analysis for identifying organic residues in archaeological settings. • Southwestern European incense: materials and uses in religious rituals. • FE-SEM and EDS applications in analyzing archaeological organic remains. • Chemical and physical deciphering of the ingredients and their botanical origin in medieval adhesive substances. The medieval organic materials recovered from Visigothic strata (8th century CE) at El Tolmo de Minateda (Hellín, Albacete, Spain) and from 11th century CE strata at La Graja (Higueruela, Albacete, Spain) were initially identified as incense remains used in religious ceremonies. Utilizing SEM, EDS, FT-IR, and GC–MS techniques, we have refined our understanding of these samples. The El Tolmo materials contain aromatic compounds from various botanical sources, especially conifer resins, indicating a local origin. In contrast, the La Graja samples, dating from the Muslim period, show a predominance of benzaldehyde and benzyl alcohol, differing significantly from the El Tolmo findings. The El Tolmo remains, which still emit an incense and smoke aroma, represent a local formulation of ritual incense using nearby botanical species. Conversely, the La Graja remains appear to have undergone intense pyrolysis. The presence of iron on the surface of these samples suggests they may have been in contact with iron, either in containers made of this material or in wooden-handled iron tools as plant-based adhesives.