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Updated: Jun 8, 2026
05:57
Quantitative 31P NMR Analysis of Lignins and Tannins
Published on: August 2, 2021
Tannin oxidation: intra- versus intermolecular reactions.
Céline Poncet-Legrand1, Bernard Cabane, Ana-Belén Bautista-Ortín
1INRA, UMR1083 SPO, F-34060 Montpellier, France. poncetc@supagro.inra.fr
Biomacromolecules
|September 14, 2010
Summary
Autoxidized grape and apple tannins form larger macromolecules through intermolecular reactions. Grape seed tannins form linear polymers, while apple tannins form branched structures due to differing reaction pathways.
Area of Science:
- Polymer Chemistry
- Food Chemistry
- Biomaterials Science
Background:
- Condensed tannins are complex polyphenolic polymers found in plants.
- Understanding tannin structure and reactivity is crucial for food and material applications.
- Autoxidation significantly alters tannin structure and properties.
Purpose of the Study:
- To investigate the structural changes in grape and apple condensed tannins upon autoxidation.
- To elucidate the mechanisms of intermolecular reactions during tannin oxidation.
- To compare the oxidation behavior of grape seed and apple tannins.
Main Methods:
- Autoxidation of tannin solutions at high concentrations (5 g/L).
- Thiolysis (depolymerization followed by HPLC) to analyze polymer structure.
- Small-angle X-ray scattering (SAXS) to determine macromolecular parameters.
Main Results:
- SAXS revealed structural parameters of native tannins (e.g., monomer length, statistical segment length).
- Oxidation introduced new, thiolysis-resistant bonds, some intramolecular.
- High concentration oxidation increased polymer size, indicating intermolecular reactions.
- Grape seed tannins formed longer linear polymers ('end to end' reactions).
- Apple tannins formed larger branched polymers ('end to middle' reactions).
Conclusions:
- Autoxidation leads to both intra- and intermolecular reactions in condensed tannins.
- The type of intermolecular reaction (linear vs. branched) depends on the tannin source and initial size.
- These findings have implications for tannin-based materials and food product stability.
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