Enzymatic hydrolysis of sugar‐beet pulp, and subsequent isolation of feruloylated oligosaccharides, has shown that ferulic acid groups are ester‐linked mainly on O‐2 of arabinose residues and on O‐6 of galactose residues in the pectin side‐chains. After saponification of sugar‐beet pulp enzymatic digests, dehydrodiferulic acids (0.14%, w/w) have also been identified and characterised as 8‐5′, 5‐5′, 8‐8′ and 8‐O‐4′ isomers, suggesting that covalent cross‐linking of pectic polysaccharides through diferulic bridges occurs in sugar‐beet pulp. Feruloylated oligosaccharides from the side‐chains of heteroxylans have been isolated from maize bran by acid hydrolysis. Ferulic acid is esterified on O‐5 of arabinofuranose residues. 8‐8′, 8‐5′, 8‐O‐4′ and 5‐5′ coupled dimers, which represent 2.5% (w/w) of the bran, have also been detected. It has been calculated that, in the cell wall, each heteroxylan macromolecule bore ∽75 esterified ferulic acid groups and could be cross‐linked through ∽30 diferulic bridges. This result suggests a high degree of cross‐linking of heteroxylans chains through ferulic acid in maize bran cell walls.

© 1999 Society of Chemical Industry