EFFECT OF STEAM TREATMENT ON THE CHEMICAL-COMPOSITION OF WHEAT-STRAW

A study was carried out on the effects of steam treatment at 120 degre es C/2 bar for different periods of time on the chemical composition o f wheat straw cell wall material. The contents of weakly acidic pectic polysaccharide (WAPP), 80% ethanol soluble material, lignin, hemicell uloses and a-cellulose were determined by successive extractions with 0.25% ammonium oxalate solution, 80% ethanol, acidic sodium chlorite s olution and 24% potassium hydroxide with 2% boric acid solution from t he residues of 15, 30, 60, 120, 180 and 300 min steam treated wheat st raw, respectively. The yields of WAPP, hemicellulose, cellulose and li gnin extracted from the treated straw ranged from 1.8 to 2.6%, 29.8 to 34.0%, 42.1 to 45.6% and 20.0 to 22.7%, respectively. The neutral sug ars in the extracts were measured by gas chromatography. The contents of phenolic acids and aldehydes resulting from alkaline nitrobenzene o xidation of lignin remaining in hemicellulose and cellulose extracted from steam treated wheat straw ranged between 0.14 and 0.33%. The resu lts showed that steam treatment removed some portion of pectic substan ces and hemicelluloses. In addition, for treatment periods greater tha n 120 min, the treated straw contained higher amounts of lignin and ce llulose than untreated straw.