Characterization of thermally assisted hydrolysis and methylation products of polyphenols from modern and archaeological vine derivatives using gas chromatography–mass spectrometry

Abstract

If some ceramics, such as vinary amphorae attest the consumption and trade of wine in the Roman world, the first wine productions in Occident often stay undocumented. Chemical analysis of organic materials preserved in archaeological vessels is the only way to bring new lights about the elaboration and the consumption of this fermented beverage. To determine the preservation state of wine and other grape derivatives residues, we proceeded to in situ tetramethylammonium hydroxide (TMAH) treatment followed by thermally assisted hydrolysis and methylation—gas chromatography—mass spectrometry (THM–GC–MS). The objectives of the study were (i) the understanding of the pyrolytic mechanisms of proanthocyanidins and (ii) the assessment of the usefulness of thermochemolysis for the identification of phenolic markers from polymeric solid deposit in modern wine bottle and Roman amphorae. THM–GC–MS was revealed to be an efficient method for the characterization of fruit derivatives even if mixed with another organic material, such as pitch used to ensure the watertightness of the ceramic container. The preservation of tannins during millennia in archaeological context is here enlightened for the first time by using analytical pyrolysis. The proposed identification of vinary residues is now based on the detection of the association of more than 30 pyrolytic markers derived from di- and trimethoxylated benzenoid compounds. THM–GC–MS represents a new method for the rapid detection of wine traces in ancient ceramics, adapted to tiny samples (<0.1 mg), allowing to precise the role and function of pottery during antiquity.