Extraction, purification and characterization of wax from flax (Linum usitatissimum) straw

The chemical composition and selected physical parameters of wax extracted from flax straw with supercritical CO2 (SC-CO2) and hexane have been determined. From the GC/MS results, clear variations in composition and component distributions were observed between SC-CO2- and hexane-extracted samples. The major components of the SC-CO2 and hexane extracts from three flax cultivars were: fatty acids (36-49%), fatty alcohols (20-26%), aldehydes (10-14%), wax esters (5-12%), sterols (7-9%) and alkanes (4-5%). Purification of SC-CO2-extracted wax with silica gel chromatography yielded 0.4-0.5% (dry matter) and was composed primarily of wax esters (C44, C46 and C48) and alkanes (C27, C29 and C31). UVVis scans of the purified wax samples exhibited two main peaks indicating the presence of conjugated dienes and carotenoids or related compounds. Fourier transform infrared results showed prominent peaks at 2918 (-C-H), 2849 (-C-H), 1745 (-C=O), 1462 (-C-H), 1169 (-C-O) and 719 cm-1 (-(CH2)n-), with NorLin wax showing a slightly deviating pattern compared to the other samples. Thermal analysis by differential scanning calorimetry revealed a mean melting point of 55-56 °C and oxidation temperatures of 146-153 °C for purified wax from flax straw processed using different procedures. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.