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Title: SPECTROSCOPIC CHARACTERIZATION OF ENZYMATIC FLAX RETTING: FACTOR ANALYSIS OF FT-IR AND FT-RAMAN DATA

Author
item Archibald, Douglas
item HENRIKSSEN, G - ROYAL INST OF TECHNOLOGY
item AKIN, DANNY
item BARTON II, FRANKLIN

Submitted to: International Conference on Fourier Transform Spectroscopy Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/15/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Linen yarns are spun from the fibers which are extracted from flax stems. Flax 'retting', accomplished by chemical, microbial or enzymatic processing, is essential so that the fiber can be efficiently removed from the flax during subsequent mechanical processing. Flax retting must be monitored carefully because over-retted flax produces weak fiber. Conventional monitoring methods are subjective; often more of an art than technology. The lack of experience with flax retting can be a barrier for potential U.S. flax producers and processors. Lack of a good retting measurement method even limits laboratory research aimed at optimizing the retting process. The work reported here demonstrates that optical methods can be used to monitor the degree of enzymatic retting of flax samples, with very little sample preparation. Study of the technique indicates that it is measuring structural properties which are very likely to be the determinants of flax fiber quality. Consequently, there is promise that the technique will be useful for evaluating retted flax produced from other cultivars, and under other production and processing conditions.

Technical Abstract: Flax retting is a chemical, microbial or enzymatic process which releases the bast fibers from the stem matrix so they can be suitable for mechanical processing before spinning into linen yarn. This study aims to determine the vibrational spectral features and sampling methods which can be used to evaluate the retting process. Flax stems were retted on a small scale using an enzyme mixture known to yield good retted flax. Processed stems were harvested at various time points in the process and the retting was evaluated by conventional methods including weight loss, color difference and Fried's test, a visual ranking of how the stems disintegrate in hot water. Spectroscopic measurements were performed on either whole stems or powders of the fibers that were mechanically extracted from the stems. Selected regions of spectra were baseline and amplitude corrected using a variant of the multiplicative signal correction method. Principal component regression and partial least-squares regression with full cross-validation were used to determine the spectral features and rate of spectral transformation by regressing the spectra against the retting time in hours. FT-Raman of fiber powders and FT-IR reflectance of whole stems were the simplest and most precise methods for monitoring the retting transformation. Raman tracks the retting by measuring the decrease in aromatic signal and subtle changes in the C-H stretching vibrations. The IR method uses complex spectral features in the fingerprint and carbonyl region, many of which are due to polysaccharide components. Both spectral techniques monitor the retting process with greater precision than the reference method.