Dietary fibres (DF) are mainly plant cell wall constituents or plant materials resistant to hydrolysis catalysed by enzymes secreted from mammalian cells in the first part of the mammalian digestive tract. Our interest in DF is directed at physiological effects caused by DF; their effects on nutrients and non-nutrients including xenobiotics, and effects on the structure and composition of digesta including the microflora in the digestive tract. This means that DF have several both positive and negative effects on the quality of food and feed depending on the type of DF, and as DF are a necessary or important part of all high quality foods and feeds, focus should be placed on obtaining more exact structural information on DF. The chemical composition and structure of DF, their physico-chemical properties and physiological effects comprise therefore an area of increasing interest. In consequence thereof, we have placed specific focus on all parts of DF, not only the carbohydrates, but all DF constituents which give a contribution to the binding properties of DF toward nutrients and non-nutrients. These studies of DF have required investigations based on isolated DF, and it is found, that the unsolved problems, which also require a solution, are the questions of possible differences in effects in food/feed matrixes of isolated DF and indigenous DF. However, the research needs in all cases to be focused on the information required with respect to structure and properties of DF. Such investigations must be based on analytical methods, and the level of information obtainable therefrom can, as other systematic biochemical-natural product chemical research studies, be divided into 4 levels denoted as the 4 x C: 1. Composition: types of carbohydrates, lipids, proteins, phenolics and other compounds in DF; 2. Constitution: structure of the DF compounds and DF itself 3. Configuration: stereochemistry of DF/DF components: 4. Conformation: the actual or preferred spatial structure of the solvated DF. Part of this paper was presented at the Symposium: Dietary fibre-chemical composition and biological action, 24-25 April 1997, Radzików, Poland BJERGEGAARD CH. ET AL. In systematic DF studies of this type, the sequence needs to be from information level 1 to level 4, and the last three levels of information are important for an understanding of the binding properties or physiological effects DF may have.

Dietary fibres (DF) -their chemical composition and structure, physico-chemical properties, and physiological effects -comprise and area of increasing scientific interest. Progress in this research is, however, rendered somewhat difficult by the disagreement concerning demarcation of the DF concept. In the present study, a physiological based method of analysis for determination of total DF (TDF) corresponding to the sum of insoluble DF (IDF) and soluble DF (SDF) have been used as an initial step in studies of DF from different rape seed varieties and biorefined fractions of double low rape seed compared to DF from peas.A comprehensive characterization of DF from rape seed and peas have been performed, with determination of the neutral monosaccharide composition by different techniques as a first step. The yield of sugars, especially glucose, was found highly dependent on the procedure used for hydrolysis of the polysaccharides. The composition of the polysaccharide fractions also differed according to the type of plant material. This diversity was further emphasised by results from sequential extraction and separation of isolated DF leading to fractionation of DF into four groups: pectins, hemicelluloses, celluloses, and lignins. UV-VIS-spectroscopy of extracts from these groups provided useful information concerning the presence of material of non-carbohydrate origin. The hemicellulose fractions from peas and especially rape seed were shown to have the highest content of proteins and phenolics, possibly being present as strongly adsorbed or covalently bound components. The protein part of the DF fractions was further investigated by biochemical methods of analyses including affinity chromatography, electrophoresis as SDS IEF, and the presence of myrosinases was demonstrated in DF from rape seed. Peas also comprised DF associated proteins, although the level was considerable lower than found in rape seed DF. High performance capillary electrophoresis methods for determination of phenolics have been developed in order to provide an efficient tool for

Dark-seeded double improved Polish rape seed varieties (Brassica napus L.) (38 samples) were included in this study, with the main purpose of investigating their dietary fibre (DF) components. The chemical composition of unprocessed defatted seeds was determined, including analyses of neutral (NDF) and acid (ADF) detergent fibre, as well as insoluble (IDF), and soluble (SDF) dietary fibre. In eight samples (four spring type and four winter type rape seed) the prevalent DF fraction was IDF occurring in amounts from 27.6 to 34.0% of dry defatted matter (DDM), while SDF accounted for 3.8 to 6.1% of DDM. Arabinose and galactose were the prevalent monosaccharides in both fractions of DF. The DF fractions were associated with protein which was not digested by pepsin and pancreatin used in the isolation procedure. Protein associated with SDF ranged from 7.6 to 18.1% while protein associated with IDF ranged from 28.4 to 41.5% of the total protein content in rape seed. The amino acid composition of protein associated with IDF differed distinctly from that associated with SDF. Protein bound to IDF had an amino acid composition similar to that of whole rape seed, while protein associated with SDF had an extremely high content of lysine, cysteine, and serine, but a low content of methionine and phenylalanine.

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