The presence of acetyl groups were also observed in
the OS obtained from the roasting procedure at 220 ◦C, although in
very small amount (ESI-MS/MS spectrum similar to that presented
in Fig. 4c), confirming their resistance to temperature and alkali
reagents. A similar trend was observed by Pinto, Evtuguin, & Pascoal
Neto (2005) in hardwood glucuronoxylans from Eucalyptus globulus,
Eucalyptus urograndis, and Betula pendula after the kraft pulping
process, using temperatures of 160 ◦C and highly concentrated
solutions of sodium hydroxide and sodium sulphide.