Chemical and ultrastructural changes of ash wood thermally modified (TMW) using the thermo-vacuum process: II. Immunocytochemical study of the distribution of noncellulosic polysaccharides

Following structural and cytochemical studies (Part I) on thermally modified ash wood (TMW) by the thermo-vacuum (Termovuoto) process, changes in the distribution of noncellulosic polysaccharides have been investigated in TMW treated for 3 h at 220°C (TMW3 h, 220°C) by means of immunogold localization methods. Pectins (homogalacturonan, rhamnogalacturonan-I) and xyloglucan were significantly degraded in compound middle lamella (CML), including the middle lamella cell corner regions (CMLcc), of all xylem cells after thermal modification. Xylan and mannan degradation were also visible in fiber cell walls. In particular, degradation of mannan was very significant and showed variation between cell wall regions even within the same cell wall. The degradation of pectins was more significant than that of hemicelluloses. In summary, results suggest that each noncellulosic polysaccharide may have a different degradation process in ash TMWs.