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Title: CHEMICAL COMPOSITIONS OF COMPONENTS COMPRISING BAST TISSUE IN FLAX

Author
item Morrison Iii, Wiley
item Akin, Danny

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2001
Publication Date: 5/15/2001
Citation: Morrison III, W.H., Akin, D.E. 2001. Chemical compositions of components comprising bast tissue in flax. Journal of Agricultural and Food Chemistry; Vol 49(5), pp. 2333-2338.

Interpretive Summary: Flax is the source of line and is a commercially important crop in Europe; interest in flax/linen is gaining in the U.S. Flax fiber is released from the plant by a process called retting in which the action of microorganisms degrades the glue, which hold the fiber to the stalk. Retting can be carried out in the field, dew-retting, or in tanks, water-retting. Each method has advantages and disadvantages. Dew-retting is dependent on weather conditions and water-retting is less environmentally unfriendly. Water-retting produces a more uniform fiber but is environmentally unfriendly. The way in which the microorganisms degrade the plant differ and as a result, the chemistry of the fiber differs. If retting is not complete, tissues other than the fibers desired that can affect processing and quality often remain attached to the fiber. This study investigated the chemical composition of these other tissues to determine whatever individual compounds could be identified that could serve as indicators of presence of these tissues. Certain fatty acids were identified that were only found in the cuticle, the outer, protective layer of the flax plant. Our earlier work had shown that these fatty acids are present in higher amounts in fibers that were judged to be of lesser quality. These fatty acids should serve as indicators for retting efficiency and possibly quality.

Technical Abstract: Components from the bast region of flax (Linum usitatissium) were removed by hand from seed flax and fiber flax and analyzed by gas chromatography and mass spectrometry. Stems soaked in water were separated by hand into an outer layer, which consisted of epidermis with cuticle and parenchyma cells, and fiber bundles and evaluated for a chemical marker that could be used to predict the degree of retting and possibly fiber quality. The outer layer was subsequently treated with a mixed enzyme preparation to remove the carbohydrate portion, thus providing another fraction consisting primarily of cuticle. Four main constituent groups were investigated: dihydroxy fatty acids, long chain fatty acids and alcohols, sterols, and aromatics. Long chain fatty acids and alcohols located in the outer layer accounted for 80 92% of the total found in both fractions. Aromatics and sterols in the outer layer accounted for 29-72% and 27-67% respectively, of the total and do not appear to be a reliable marker for the degree of retting. The best markers for retting were the dihydroxy fatty acids of which 98-99% were accounted for in the outer layer. The main dihydroxy fatty acids were a mixture of 8,16- and 9,16-dihydroxyhexadecanoic acids and represented 87-89% of the total dihydroxy fatty acids measured. As a constituent of cuticle, this compound may serve as an excellent marker indicating the degree of retting as well as a possible measure of quality, since this compound is almost always exclusively associated with the outer layer and not the fiber.