Xylan, beech

The foamability of the xylans tested [128] was low in comparison to a commercial whipping protein DIOO. Only the highly viscous beech wood xylan and the rye bran AX-protein complex exhibited remarkable foaming activity, which was similar to that of gum arable. As the MGX polymers contain considerable amounts of uronic acid side chains, this may play a role in their foaming activity together with the presence of low amounts of Ugnin. 

Fig. 7 Stabilization effect of various xylan types isolated from beech wood (GXl and GX2), corn cobs (AGXl), rye bran (AXRl and AXR3), and corn hulls (AXCl and AXC2) on the protein (BSA) foam against thermal disruption foam volume before (V1) and after (V2) heating at 95 °C for 3 min [128]...

Xylans from beech wood, corncobs, and the alkaline steeping liquor of the viscose process have been shown to be applicable as pharmaceutical auxiliaries [3]. Micro- and nanoparticles were prepared by a coacervation method from xylan isolated from corncobs [150]. The process is based on neutralization of an alkaline solution in the presence of surfactant, which was shown to influence both the particle size and morphology. They are aimed at applications in drug delivery systems. 

Partial etherification of the beech wood MGX with p-carboxybenzyl bromide in aqueous alkali yielded fully water-soluble xylan ethers with DS up to 0.25 without significant depolymerization the Mw determined by sedimentation velocity was 27 000 g/mol [400,401]. By combination of endo- 6-xylanase digestion and various ID- and 2D-NMR techniques, the distribution of the substituents was suggested to be blockwise rather than uniform. The derivatives exhibited remarkable emulsifying and protein foam-stabilizing activi-... 

Muller M (1980) Beitrag zum Einsatz der Curie Punkt-Pyrolyse Massenspektrometrie in der Analytik von Naturstoffen Dissertation ETH 6743, Zurich Obst JR (1983) Analytical pyrolysis of hardwood and softwood lignins and its use in lignin type determination of hardwood vessel elements J Wood Sci Technol 3 377-397 Pouwels AD, Boon JJ (1987) Analysis of lignin and chlorohgntn residues in a beech xylan fraction by pyrolysis gas chromatography mass spectrometry J Wood Sci Technol 7 197— 213... 

Samples from beech wood as well as from biomass components have been investigated using the same crucibles as for the temperature calibration. Microciystallinc cellulose (Avicel, Merck) lignin (Oiganosolv, Aldrich), and xylan... 

Table 7.7.2. Chemical constituents of the pyroly sate of holocellulose (A), a xylan fraction (B), and technical xylan (C) from beech wood [64], (The origin from lignin of certain compounds is also indicated in the table.)...

The phenomena which have been observed on extraction of wood with aqueous sodium hydroxide - also occur, albeit to a smaller extent, with holocelluloses the restriction to dissolution is, in this case, mostly due to the fiber structure itself. In a study of the extraction of a chlorine holocellulose from European beech with sodium hydroxide solutions of various concentrations, Corbett and Ewart found that 87% of the (4-0-methyl-glucurono) xylan could be removed under mild conditions, and another 10% by extraction with hot alkali, but that 1.3% remained associated with the cellulose. The same authors have also described an apparatus suitable for the alkaline extraction of wood or holocellulose in an atmosphere of nitrogen. 

Amylose and starch, both derived from potato, were commercial samples. Glucomannan and xylan were isolated from spruce and beech holocelluloses, respectively, and purified by the usual method (12). Pectin was isolated and purified from the midrib of Nicotiana taba-cum and kindly provided by Dr. Shigeru Eda at The Central Research Institute, Japan Tobacco Inc. ( ). 

Previous papers have investigated the suitable use of xylan in papermaking [10] and textile printing [21]. In the drug delivery field, xylan extracted from birch wood has been used for the production of nanoparticles after structural modification by the addition of different ester moieties, namely those with furoate and pyroglutamate functions [21]. On the other hand, the esterification of xylan from beech wood via the activation of the carboxylic acid with iV,iV -carbonyldiimidazole has been carried out in order to produce prodrugs for ibuprofen release [10, 21, 22, 37]. 

As already mentioned, there are differences in the content and the composition of polyoses in hardwood and softwood. While xylans (pentosans) are dominant in hardwood, mannans (hexosans) predominate in softwood. The xylans are so-called homopolymers, as the main chain consists of xylose only (Scheme 9.4.2), whereas the mannans present a heteropolymer consisting of glucose and mannose (Scheme 9.4.3). Furthermore, softwood has a higher content of polyoses as well as acetyl groups compared to softwood. The higher content of acetyl groups in hardwood can cause elimination of acetic acid in certain procedures e.g. steaming of beech or thermal modification. Section 9.4.5). 

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