Five cereal (triticale, durum wheat, CPS wheat, feed barley, oats) and two oilseed (canola, mustard) straws were fractionated with pressurized low polarity water in a flow-through reactor at 165 degrees C with a flow rate of 115 mL/min and a solvent-to-solid ratio of 60 mL/g. The conversion and extraction of the major carbohydrates and lignin from the reactor system during hydrothermal treatment was largely completed within the first 20-30 min. Glucan content of all straws were enriched by the process. More. than 90% of the xylan and nearly 50% of the lignin were extracted and there was no effect on yield due to crop species. However, there were differences in solid residue and liquid extract composition. Cereal crops yielded a residue richer in glucan and lower in lignin. Oilseed crop residues contained very low levels of ash. Xylo-oligosaccharides from oilseed crops contain more acetyl and uronic acid substituents. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.