Abstract
Various methods were used to characterize three kinds of lignin fractions from the heartwood of Quercus robur and Q. petraea. UV analysis and determination of the mean molecular mass showed that the first fraction, soluble in a hydroalcoholic medium and extractable with dichloromethane, is a mixture of oligomer lignins with a mass below 800 Da, highly enriched with free phenol aldehyde and lyoniresinol. The LE and LD fractions, extractable with ethanol and dioxane, respectively, are relatively pure lignins. LE and LD thioacidolysis products, and LE sine contains ellagic acid. IR and GC-MS analysis of their thioacidolysis products enabled us to demonstrate the heterogeneity of these two lignins. LE is characterized by an S/G close to 1, while LD has an S/G ratio between 1.41 and 1.67, characteristic of lignins rich in syringyl units.
- Received July 1996.
- Copyright 1998 by the American Society for Enology and Viticulture
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