Application of near Infrared Spectroscopy to Assessments of Colour Change in Plantation-Grown Eucalyptus Grandis Wood Subjected to Heat and Steaming Treatments

The relationships between colour parameters and chemical components of Eucalyptus grandis wood under a steaming and a heating process were examined by near infrared (NIR) spectroscopy to assess the best drying conditions. The results indicated that: 1) under steaming conditions, the second derivatives of absorption bands due to OH in the crystalline region of cellulose and CH in hemicellulose presented statistically significant positive correlation values for L* or b* and a decrease in lignin might be the reason leading to the colour changes; 2) under heat-treated conditions, the colour darkening process in wood was often accompanied by a severe collapse phenomena, especially at the 100°C condition. It was found spectroscopically that the concentrations of cellulose and hemicellulose were increased relatively by the collapse occurring and that lignin decreased with the elevated drying temperature. The crystalline regions in cellulose and hemicellulose were related to “blueness” (partial darkness) of E. grandis caused by the drying process.