Flexible oxygen barrier films from spruce xylan

• Published in: Carbohydrate polymers Vol. 87; no. 4; pp. 2381 - 2387
• Main Authors: Escalante, Alfredo, Gonçalves, Ana, Bodin, Aase, Stepan, Agnes, Sandström, Corine, Toriz, Guillermo, Gatenholm, Paul
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2012
• Subjects: Arabinoglucuronoxylan; arabinoxylans; barley; Characterization; dietary fiber; Film formation; Förnyelsebar bioenergi; Material; Material properties; oligosaccharides; properties; Renewable Bioenergy Research; spectroscopy; wood; Characterization; Arabinoglucuronoxylan; Film formation; Material properties
• ISSN: 0144-8617; 1879-1344; 1879-1344
• DOI: 10.1016/j.carbpol.2011.11.003

► Norwegian spruce xylan was used to prepare films by casting from aqueous solution. ► Xylan consisted of α-l-araf:4-O-Me-α-d-glucpA:β-d-Xylp in a ratio of 1:2:11. ► Films had stress and strain at break of 55MPa and 2.7% and Young's modulus 2735MPa. ► Films had 0.12cm3μmm−2d−1kPa−1 O2 permeability with potential for food packaging. ► Spruce xylan forms clear, flexible films with great oxygen barrier properties. Arabinoglucuronoxylan was extracted from Norway spruce and films prepared by casting from aqueous solution. The sugar analysis and NMR confirmed that the spruce xylan was composed of arabinose, 4-O-methyl-glucuronic acid and xylose in a ratio of 1:2:11 respectively. Substitutions of 4-O-methyl-α-d-GlcpA at O2 and of α-l-Araf at O3 on the xylose backbone were found by NOE analysis. NOE cross-peaks indicated as well that there is at least one free xylose on the main chain present between two substitutions. Whether the distribution of side chains was random or in blocks was uncertain. The average molecular weight of the sample was determined by size exclusion chromatography to be 12,780g/mol. Arabinoglucoronoxylan casting yielded transparent flexible films with an average stress at break of 55MPa, strain at break of 2.7% and a Young's Modulus 2735MPa. Wide-angle X-ray scattering analysis showed that the arabinoglucuronoxylan films were totally amorphous. Addition of sorbitol as plasticizer resulted in less strong but more flexible films (strain at break of 5%). Peaks of crystallinity could be seen in X-ray which corresponds to sorbitol crystallizing in distinct phases. The dynamic mechanical analysis showed that the arabinoglucuronoxylan film softened at a later relative humidity (80% RH) in comparison with plasticized films (60% RH). The films showed low oxygen permeability and thus have a potential application in food packaging.