ARS | Publication request: DIFERULATES AS STRUCTURAL COMPONENTS IN SOLUBLE AND INSOLUBLE CEREAL DIETARY FIBRE

Submitted to: Dietary Fiber Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 4, 2000
Publication Date: N/A

Technical Abstract: Physiological effects of cereal dietary fiber depend on their physicochemical properties. For example, the chemical structure, solubility and lignification exert an influence on hydration and viscosity properties as well as on fermentation and consequently on the physiological effects. Radical-mediated dimerization of ferulates linked to cereal cell-wall polysaccharides, particularly arabinoxylans, is a possible mechanism for cross-linking polysaccharides. Diferulates which have already cross-linked polysaccharide chains have at least one phenolic group free. Therefore diferulates can be incorporated into lignins. Consequently, diferulates represent important structural components of cereal dietary fibre. The insoluble and soluble dietary fibers of wheat, maize, oat, rye, millet, barley, spelt, rice and wild rice were investigated for diferulates. After saponification with NaOH, samples were acidified and diferulic acids extracted into diethyl ether. Trimethylsilylated derivatives of phenolic acids were separated by GLC and identified by comparison of their mass spectra and relative GLC retention times with those of the genuine compounds, which were synthesized and authenticated by NMR. Quantitative determination was carried out by GLC-FID. The entire spectrum of diferulates (8-8-, 8-5-, 5-5-, 8-0-4-, 4-0-5-coupled) could be identified from all insoluble fibers investigated. Amounts and patterns of diferulates vary between different cereals. Soluble cereal dietary fibers also contain diferulates, but only tiny amounts.