In this work, two fractions of xylan, named xylan A and xylan B, were isolated from corncobs through three different processes using aqueous extraction, lipid removal, delignification, and alkaline extraction. The products obtained during the processes were analysed by thermogravimetry. The delignification step was responsible for the occurrence of an accentuated polymer degradation, evidenced by yield and thermal resistance decrease. Infrared spectra indicated the absence of uronic acids in the polymeric chains. Intrinsic viscosities obtained for xylan A (56 mL/g) and xylan B (75 mL/g), associated to the results from i.r. analysis, suggested a higher number of substituents, basically constituted of L-arabinose residues, in the case of xylan B.
Xylan; hemicellulose; polysaccharide; delignification
