Diferulates as structural components in soluble and insoluble cereal dietary fibre

Abstract

Cell wall cross‐linking can have a substantial effect on the properties of the wall. To estimate cross‐linking (between arabinoxylans) in cereal fibres, dehydrodiferulate levels were measured in soluble and insoluble dietary fibre (SDF and IDF) isolated from whole grains of maize (Zea mays L), wheat (Triticum aestivum L), spelt (Triticum spelta L), rice (Oryza sativa L), wild rice (Zizania aquatica L), barley (Hordeum vulgare L), rye (Secale cereale L), oat (Avena sativa L) and millet (Panicum miliaceum L). After saponification of the cereal fibres the extracts were investigated for dehydrodimers of ferulic acid using GLC–MS and GLC–FID. From most cereal IDF the whole spectrum of dehydrodiferulic acids (DFAs) (8‐5′‐, 8‐8′‐, 5‐5′‐, 8‐O‐4′‐ and 4‐O‐5′‐coupled) could be identified. The absolute contents of total DFAs ranged between 2.4 and 12.6 mg g−1. With the exception of 4‐O‐5′‐coupled DFA, the whole range of DFAs was also detected from cereal SDF but only in amounts of 40–230 µg g−1. It was estimated that arabinoxylans of cereal IDF contain 8–39 times more diferulates than arabinoxylans of cereal SDF (where measurement of DFA levels in SDF was possible). In cereal IDF, 8‐5′‐coupled dimers dominated, whereas in cereal SDF, 8‐8′‐coupled dimers were relatively enhanced and often became the major dimers. © 2001 Society of Chemical Industry