Aqueous treatments of Pinus pinaster wood were carried out in a pressurized reactor under non-isothermal conditions. The kinetics of the hydrolytic degradation of hemicelluloses has been studied. Hemicelluloses are formed by two major polymers (glucomannan and heteroxylan) made up of a number of structural components (chains of B-linked mannosyl, glucosyl, and xylosyl units, with acetyl, galactosyl, and arabinosyl substituents). The hydrolytic breakdown of polymers was assumed to proceed through a number of first order reactions. The backbones of the hemicellulosic polymers were split into oligomers, whereas substituents were hydrolyzed into the corresponding monomers. The resulting model provided a satisfactory interpretation of the experimental results. (C) 2013 Elsevier B.V. All rights reserved.