Characterizing the noncellulosics in developing cotton fibers

Surface wetting measurements and several analytical techniques including FT IR/ATR, Dsc, TGA, and pyrolysis-GC/MS are used to characterize the noncellu losic components of developing cotton fibers as intact components of the fi ber structure. Water contact angle measurements are most sensitive to the p resence of hydrophobic compounds on the surfaces of cotton fibers of all ag es and to their removal by alkaline scouring. In general, FTIR/ATR, DSC, TG A, and pyrolysis-GC/MS provide clear evidence of specific noncellulosic com ponents in developing cotton fibers through the onset of secondary cell wal l synthesis. Waxy compounds an evident by their melting endotherms in DSC t hermograms, carbonyl bands in FTIR spectra, and mass spectra in the untreat ed developing fibers between 12 and 17 dpa. Pectins are detected by FTIR in the 14 dpa and mature fibers. FTIR/ATR measurements indicate the presence of proteins in untreated fibers up to 16 dpa and water-rinsed fibers up to 18 dpa. The presence of proteins in 14 dpa fibers is also detected by pyrol ysis-GC/MS data. Among the analytical techniques, only pyrolysis-GC/MS can detect the presence of noncellulosic compounds in 27 dpa fibers. Detection of noncellulosics by the other techniques diminishes as the proportion of c ellulose rapidly increases with the onset of secondary cell wall synthesis.