Description

Research carried out at the UMR SPO has led to the creation of a unique database of oxidation markers for tannins produced naturally during product processing and preservation. However, characterising the ‘hidden side’ of tannins remains an analytical challenge at present. In particular, high-molecular-weight polymers – i.e. advanced (oxidised) tannins – cannot be directly analysed using traditional analytical methods (LC-MS). However, characterising the structures and quantifying the oxidised fraction of tannins would make it possible to optimise their use in existing industrial applications and to develop new ones. In order to overcome this obstacle, this PhD project – a collaboration between the UMR SPO and IATE research units – is based on the development of an innovative, multimodal analytical approach, combining ion mobility and mass spectrometry, to determine the oxidation state of tannins both qualitatively and quantitatively. This approach offers an alternative to current depolymerisation methods, which are difficult to apply. Indeed, this new approach will involve studying the oxidation state of tannins by exploiting the structural differences between oxidised and non-oxidised units through modulation of the voltages at the source and/or within the ion-mobility cell. The development of this approach will be based on the analysis of model solutions whose composition illustrates, on the one hand, the structural diversity of tannins and, on the other, the complexity of the compositions of natural products and extracts. Monitoring these solutions over time will enable us to characterise the progression of their oxidation in both qualitative (structures) and quantitative (proportion of oxidised units) terms.

Skills required

- Master’s degree in analytical chemistry, biomolecular chemistry or related disciplines - Experience of, or an interest in, mass spectrometry and structural analysis - Skills in data processing and spectrum interpretation - An analytical mind, scientific curiosity and the ability to work independently

Bibliography

1. Mouls, L. and H. Fulcrand, UPLC-ESI-MS study of the oxidation markers released from tannin depolymerization: toward a better characterization of the tannin evolution over food and beverage processing. Journal of Mass Spectrometry, 2012. 47(11): 1450-1457. DOI: org/10.1002/jms.3098
2. Mouls, L. and H. Fulcrand, Identification of new oxidation markers of grape-condensed tannins by UPLC–MS analysis after chemical depolymerization. Tetrahedron, 2015. 71(20): 3012-3019. DOI: org/10.1016/j.tet.2015.01.038
3. Engstrom, M.T., Pälijärvi, M., Fryganas, Grabber, J.H., Mueller-Harvey, I., Salminen, J-P., Rapid Qualitative and Quantitative Analyses of Proanthocyanidin Oligomers and Polymers by UPLC-MS/MS. Journal of Agricultural and Food Chemistry, 2014. 62(15): 3390-3399. DOI: 10.1021/jf500745y
4 . Dias A.L.S., et al. Improved analysis of isomeric polyphenol dimers using the 4th dimension of trapped ion mobility spectrometry – mass spectrometry. Molecules, 2022, 27(4176). DOI:10.3390/molecules27134176
5. S. Deshaies, F. Garcia, L. Suc, C. Saucier, and L. Mouls, Study of the oxidative evolution of tannins during Syrah red wines ageing by tandem mass spectrometry, Food Chemistry, 2021, 385, 132538, DOI: 10.1016/j.foodchem.2022.132538.
6 . Dias A.L.S., Fenger JA., Meudec E., Verbaere A., Costet P., Hue C., Coste F., Lair S., Cheynier V., Boulet JC., Sommerer N., Shades of Fine Dark Chocolate Colors: Polyphenol Metabolomics and Molecular Networking to Enlighten the Brown from the Black. Metabolites, 2023, 13(5), 667. DOI:10.3390/metabo13050667
7. Poncet-Legrand C., Cabane B., Bautista-Ortin AB, Carrillo S., Fulcrand H., Perez J., Vernhet A., Tannin Oxidation: Intra- versus Intermolecular Reactions. Biomacromolecules, 2010. 11(9), 2376-2386. DOI: org/10.1021/bm100515e

Keywords

polyphenol, mass spectrometry,, markers of oxidation, proanthocyanidin, ion mobility, tannin