Wine economy in Picton territory (IInd century BC – Ist century AD) 2. Archaeometrical study of content
Résumé
In Picton territory, in the western center of Gaul, the existence of local productions of amphorae have been highlighted by several studies (Durquety et al., 2012; Lemaître, 2012). Local workshops copied the forms of imported amphorae produced in the north of Spain (Pascual 1 and Dressel 2 – 4), or in the Narbonnaise province (Gauloise 4 and 5) (Durquety et al., 2012b). To determine for what purpose these amphorae were manufactured in Picton territory, we undertook the chemical study of the organic residues that were preserved in the vessels. After extraction, these residues can be characterized by mass spectrometry coupled with gas phase chromatography (GCMS). This technique enables the analysis of a wide range of compounds, in particular coming from grapes and wine, such as tartaric, malic, fumaric, succinic acids. Alongside, it can allow the determination of red wine markers (tannins, anthocyanins), and even permit to obtain data on their conservation via the detection of resins. As part of this research, we used a technique developed in the 1960s, pyrolysis, to study organic macromolecules that cannot be directly analyzed by GCMS due to their low volatility. With pyrolysis, the extraction step, which is by definition restrictive since the chemical composition of the residues has to be known to choose the extraction solvent, can be avoided. The analytical method that we developed was applied on amphorae discovered in production sites (Gourgé) that were never used. First, to identify the observable molecules by pyrolysis with GCMS, amphorae shards were soaked in a wine of known composition. Then, archeological residues from amphorae discovered in Limonum were analyzed.