Effect of ultrasound on the structural and physiochemical properties of organosolv soluble hemicelluloses from wheat straw

Effect of ultrasound on the yield and physiochemical properties of hemicelluloses from wheat straw using 0.5 M NaOH in 60% aqueous methanol has been comparatively studied. The results showed that applying sonication for 5, 10, 15, 20, 25, 30, and 35 min resulted in an increasing yield of hemicelluloses by 2.9%, 3.9%, 6.0%, 8.6%, 8.6%, 8.6%, and 9.2% of the original hemicelluloses, respectively, in comparison with the experiment performed without ultrasonic assistance. The hemicelluloses isolated by ultrasound-assisted extraction, showed a slightly lower molecular weight, associated lignin, and thermal stability during the first stage of decomposition, but slightly more linear as compared to the hemicelluloses obtained by classical method without ultrasonic irradiation. No substantial differences in the main structure features between the hemicellulosic preparations isolated by classical or ultrasound-assisted extractions were found. (C) 2002 Elsevier Science B.V. All rights reserved.