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Title: A NEW APPROACH FOR ESTIMATING PURITY OF PROCESSED FLAX FIBER BY NIR SPECTROSCOPY.

Author
item SOHN, MI RYEONG - USDA-FAS
item Barton Ii, Franklin
item Akin, Danny
item Morrison Iii, Wiley

Submitted to: Near Infrared Spectroscopy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2004
Publication Date: 11/5/2004
Citation: Sohn, M., Barton II, F.E., Akin, D.E., Morrison III, W.H. 2004. A new approach for estimating purity of processed flax fiber by NIR spectroscopy. Near Infrared Spectroscopy Journal. 12:259-262.

Interpretive Summary: The mechanical processing sequence of flax fiber has several steps that vary depending upon the desired product. The amount of 'shive' remaining in fiber during process can be used as an index for quality evaluation of the fiber. In the previous study, we reported that it is possible to measure the shive content in flax on a commercial processing line by NIR method. The shive index is, however, unavailable for very cleaned fiber because the shive is almost free from the fiber through extra cleaning process. This study shows a new index parameter and an establishment of a useful NIR-based procedure without recourse to calibration to estimate fiber purity in highly cleaned flax. These results will be used to decide the extent of cleaning required for particular applications.

Technical Abstract: Flax must be retted, in which bast fibers are separated from non-fiber components, and then mechanically processed to clean the fibers before industrial application. In the USDA Flax Fiber Pilot Plant, flax is first cleaned through four separate modules and then passed through a Shirley Analyzer to further clean fibers for high-value applications such as textiles. Often, multiple passages through the Shirley Analyzer are employed to obtain higher quality fibers, but it is difficult to determine when the limit for cleanliness is reached by this method. Further, it is clear that materials other than the woody shive components are being removed by Shirley-cleaning, and a method is needed to assess cleanliness beyond the measure for shives. In this study, we attempted to establish an index to determine the degree of purity of flax fiber during the secondary cleaning stage for high quality fiber. Dew-retted (DR) flax and enzyme-retted (ER) flax, which had been first processed through the USDA Flax Fiber Pilot Plant and assessed for shive content, were processed with 10 repetitions of cleaning through the Shirley Analyzer. For both flax samples, absorbances at 1730, 1766, 2312 and 2350 nm decreased with successive Shirley-cleaning steps. These wavelengths appeared to originate from the epidermal layer (EL) that was associated with the flax fiber, an index was calculated using 11 training samples and validated using 10 independent test samples from the same flax samples. Index values gradually decreased with successive Shirley-cleaning steps for both retted flax samples; a lower index value indicated cleaner fiber. Different curves were apparent for the two flax samples, suggesting variations in the cleanliness of the starting material or perhaps differences in fiber composition. The results suggest it is possible to determine the extent of cleaning of flax fiber using NIR spectroscopy beyond that for shive content based on the epidermal layer of the plant.