Ammoniation of barley straw. Effect on cellulose crystallinity and water-holding capacity

The X-ray diffraction patterns of untreated and ammonia-treated barley (Hordeum vulgare L. cv. Klaxon) straws showed spectra typical of cellulosic materials, having the major peak at a diffraction angle (2θ) of 23° and a broader, secondary peak at 16°. Two measures of cellulose crystallinity calculated from the X-ray diffraction pattern indicated that treatment of barley straw with 30 g NH3 kg−1 straw produced a reduction in cyrstallinity index values of 14–24%. The water retention of ammonia-treated barley straw was approximately 25% greater than that of the untreated straw following centrifugation at 300 g and 3000 g. A slightly higher swollen volume was also observed for water-saturated ammonia-treated barley straw, although the difference was not significant. It is suggested that two major consequences of treatment, the effect of ammonia as a weak base on ester bonding within the cell wall and the ability of ammonia in an undissociated form to affect cellulose cystallinity, combine to increase the degradability of the treated straw.