Olof Theander

Aqueous, high-temperature transformation of carbohydrates relative to utilization of biomass

Publisher Summary This chapter discusses the aqueous, high-temperature transformation of carbohydrates. Over the past two decades, considerable interest has been directed toward the conversion of cellulosic biomass (materials such as wood wastes, bagasse, and straw) into useful products, notably fuels. Several procedures, including fermentation, gasification, liquefaction, and pyrolysis, have been commercially applied to carbohydrates with various degrees of success. To use the polysaccharides present in lignocellulosic materials as a substrate in fermentation processes, pretreatments are necessary, such as with steam (under slightly acid conditions) or alkali, followed by acid or enzymic hydrolysis. It is difficult to avoid some unwanted carbohydrate transformations in these pretreatments. Gasification is a rather direct and specific process. Liquefaction (hydrothermolysis) and pyrolysis are not so specific, as the mixtures obtained by these processes indicate that a complex series of mechanisms is involved. This chapter focuses on the transformation of monomeric saccharides the transformation of polysaccharides such as starch and cellulose. It also elaborates the concepts related to carbohydrate transformation in the presence of amino compounds.

The effects of various thermal processes on dietary fibre and starch content of whole grain wheat and white flour

The content of dietary fibre (DF) and starch in raw and processed materials obtained from wheat was evaluated. The processes studied were extrusion cooking, drum-drying, autoclaving, popping and steam flaking. The processing conditions were chosen to represent the limits that could be used commercially. The DF content was detennined using an enzymic-gravimetric method for soluble and insoluble DF components and a gas-liquid chromatographic method for complete characterisation of the constituent monosaccharides. Values for the total DF obtained by the two methods for a range of samples were closely correlated ( r = 0⁗99; P

Plant cell walls and monogastric diets

Abstract A brief summary is given of the recent and progressing research at the Swedish University of Agricultural Sciences in development of analytical methodology for plant cell wall components (dietary fiber) and mixed-linkage β-glucans. Applications of the methods for the chemical characterization of various types of human and monogastric animal foods will be presented, including heat-processed, starch-rich foods. In the latter group Maillard reaction products, “resistant starch” and chemically transformed starch increase the dietary fiber values. Nutritional studies on the role and properties of plant cell wall materials in connection with bile acid and cholesterol metabolism in hamster and with digestion of pig and poultry diets will be discussed.

Abietic acid, and activator of basidiospore germination in ectomycorrhizal species of the genus Suillus (Boletaceae)

Abstract Germination of basidiospores from four ectomycorrhizaforming Suillus species (S. granulatus, S. grevillei, S. luteus, and S. variegatus) was induced by exposing the spores to extracts or exudates from roots of Scotch pine (Pinus sylvestris L.). An active compound was contained in the lipophilic phase obtained by extraction of pine roots with chloroform/methanol. It was isolated and identified as abietic acid, a diterpene resin acid. With S. granulatus, the bioassay species, abietic acid caused germination at concentrations down to 10−7 M.

Seasonal variation of phenols, crude protein and cell wall content of birch (Betula pendula Roth.) in relation to ruminant in vitro digestibility

SummaryBirch twigs of diameter ≦1.5 mm exhibit seasonal trends in ruminant in vitro organic matter digestibility (IVOMD), and in the contents of crude protein, cell walls (neutral detergent fibre, NDF), and phenolic compounds. The IVOMD is low in winter twigs, increases in spring, and reaches a maximum in early summer. Crude protein behaves similarly. On the other hand, the proportion of hydrophilic phenols and cell walls (cellulose, hemicellulose, and lignin) to dry weight decreases dramatically in spring when leaves start emerging and growth is initiated. This reduction of phenols is reflected by concomitant changes in concentration of catechin, a major phenolic compound of birch. The concentration of phenolic acids are low in winter and spring but increase after leafing.The biological activity of an extract containing the phenolic compounds, measured as reduction of IVOMD, also decreases concomitantly with the decline of the total phenolic concentration and catechin. It is notable that catechin when tested alone at natural concentrations does not depress IVOMD. It is possible, however, that the amount of catechin reflects the level of condensed tannins, which may be responsible for IVOMD depression. The results strongly indicate that the decline of NDF and phenolic constituents is important for an improved food quality. Phenols may constitute the major chemical defense of birch in winter against browsing vertebrates by reducing digestibility and having toxic properties.

Chemical analysis of lignocellulose materials.

Abstract An improved methodology using 80% aqueous ethanol for effective and non-destructive removal from lignocellulosic materials of extractives for quantification (or prior to further analytical characterization) and for analysis of starch and fibre components in the residue is described, and some applications are given. Starch is removed or analyzed by an enzymatic system containing a thermostable α-amylase in combination with an amyloglucosidase. Sugar constituents in the non-starch polysaccharides are analyzed by gas liquid chromatography (GLC) (alternatively as alditol acetates or by a new direct acetylation procedure), uronic acid constituents by decarboxylation, and lignin gravimetrically. Acetyl and phenolic acid constituents on hemicellulose or other cell wall polymers are determined by GLC or high performance liquid chromatography (HPLC) after alkaline treatment.

CHEMICAL DEFENSE IN BIRCH. Platyphylloside: A Phenol from Betula pendula Inhibiting Digestibility

Extracts of Scandinavian birch (Betula pendula Roth) buds and internodes of varying twig diameters have been investigated for their inhibitory effect on ruminant digestibility in vitro. The predominant inhibitory effect was observed in extracts containing the phenol platyphylloside, 5-hydroxy-1,7-bis-(4-hydroxy-phenyl)-3-heptan-one-3-O-β-d-glucopyranoside. Isolation of the pure compound and incubation with rumen inocula showed that digestibility was negatively related to the concentration. Significant effect was measured below the concentration naturally occurring in birch (0.8% of dry matter). Another isolated compound, the closely related rhododendrin, 4-(4-hydroxyphenyl)-2-butanol-2-O-β-d-glucopyranoside, did not depress digestibility within the concentrations found in birch. An important phenol of buds, apigenin-4′,7-dimethylether, did not have any measurable effect on digestibility, while a nonphenolic fraction of bud extract had a slight inhibitory effect on digestibility. Implications for browsers feeding on birch are briefly discussed.

The formation of 2-furaldehyde and formic acid from pentoses in slightly acidic deuterium oxide studied by 1H NMR spectroscopy

The title reaction at 96°C and pD 1.5, 3.0, or 4.5 was followed by 1H NMR spectroscopy. The rate of pentose degradation increased in the order: arabinose ≈ xylose < ribose < 2-pentuloses. At pD 1.5, the rate of 2-furaldehyde formation increased in the same order. Increasing pD strongly accelerated the degradation of the aldoses but slightly retarded that of the ketoses. Increasing pD also retarded the formation of 2-furaldehyde, particularly from the ketoses, and increased its deuterium content at H-α (from 8–25 to 50–83 atom %) and H-3 (from 79–100 to 100 atom %). This is explained by assuming that 2-furaldehyde had formed mainly via acyclic intermediates, with reversible formation of a 3-deoxypentosulose. The formation of formic acid was slow and did not proceed via 2-furaldehyde. As evident from experiments with 1- or 5-13C-substituted aldopentoses, the formic acid was derived exclusively from the terminal pentose carbons, C-1 being somewhat more important than C-5.

Effects of baking on water-soluble non-starch polysaccharides in white bread fractions

Water-soluble non-starch polysaccharides were extracted from white flour and dough as well as from crumb, inner crust and outer crust fractions of white bread, baked at 210 °C for 22 or 35 min. Results from the two baking experiments were very similar. Extracted polysaccharides were fractionated on DEAE-cellulose and by different solubility properties in aqueous saturated ammonium sulfate. Fractions isolated were characterized by sugar- and 1 H-n.m.r. analysis, revealing the presence of arabinoxylan mixtures with widely different degrees of arabinose substitution. Arabinogalactanproteins isolated showed little variation in galactose/arabinose ratio (1·5–1·8). Highfield 1 H-n.m.r, of arabinoxylan fractions was particularly useful for estimating the ratios of terminal arabinofuranosidic residues linked to xylose residues at O -2 and O -3 or solely at O -3. Water-soluble arabinoxylans had a higher degree of arabinose substitution in bread fractions than in the flour and dough, probably due to increased solubilization of highly substituted arabinoxylans during baking.

Cis- and trans-dihydroquercetin glucosides from needles of Pinus sylvestris

Abstract (−)- cis -2,3-Dihydroquercetin (presumably as the 3′- O -β- d -glucopyranoside); the 3′- O - d -glucopyranosides of (+)- trans -2,3-dihydroquercetin, dihydromyricetin and eriodictyol; (+)-catechin and (+)-gallocatechin have been isolated from the needles of Pinus sylvestris . The dihydroquercetin aglycones interconvert in methanolic solution. Two chemotypes of Pinus sylvestris can be distinguished on the basis of their dihydroquercetin, dihydromyricetin and eriodictyol contents.