Alfa-cyclodextrin MS-signals from Danish Golden Age paintings

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Beer has been used in the cleaning and restoration of paintings: Danish literature specifically reports its use as adhesive, paint binder and for painting lining. Ten, approximately 200-year old paintings from C. W. Eckersberg and C. S. Købke were investigated in a study reported in Science Advances (Fabiana Di Gianvincenzo et al. , Proteomic identification of beer brewing products in the ground layer of Danish Golden Age paintings. Sci. Adv. 9, eade7686(2023). DOI:10.1126/sciadv.ade7686; ).

Application of mass spectrometry (MS)–based proteomics to artworks was aimed to reconstruct the artwork’s history focusing on yeast proteins in the ground layer. This proteomic profile points to a (by-)product of beer brewing, in agreement with local artists’ manuals.

To the surprise of the researchers, alfa-cyclodextrin (as well as maltopentaose and maltotetraose) was also found in the samples of four paintings, but unfortunately alfa-cyclodextrin has also been identified in some of the blanks. The authors postulate that the presence of cyclodextrin is rather likely due to environmental contamination.

The readers of this blog might be well aware of the fact that beer does contain cyclodextrins as minor components (Szente, L., Harangi, J., Greiner, M., Mandel, F. CYCLODEXTRINS FOUND IN ENZYME AND HEAT-PROCESSED STARCH-CONTAINING FOOD Chemistry & Biodiversity, Vol 3 1004-1014 (2006)). Consequently the presence of alfa-cyclodextrin would not be considered unlikely at all in well-reserved, dry paintings created with beer as an auxiliary material.

The research is worth further conducting experiments to seek unequivocal evidence for the presence of alfa-cyclodextrin, since this carbohydrate can be considered as a highly important, relevant, stabile tracing compound of beer. It might be anticipated that cyclodextrins have been well preserved in the matrix of further, even more ancient artworks even dating back to the pharaohs or beyond….

Image: one of the studied paintings: Eckersberg, CW – To russiske linjeskibe som saluterer – 1827 (Source: wikimedia commons)

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