Determination of lignin content in Acacia spp. using near-infrared reflectance spectroscopy

Abstract

Near infrared (NIR) spectroscopy method was introduced to measure the lignin content in Acacia species. Acid-soluble lignin, Klason lignin, and total lignin contents from 78 wood meal samples of Acacia spp. trees grown in Guangxi province with different ages, height, and families were measured by wet chemistry. NIR spectra were also collected using a Bruker MPA spectrometer within 4000-12500cm-1 of wavenumbers using a standard sample cup and split into calibration and prediction sets. Equations were developed using partial least squares (PLS) regression and cross validation for multivariate calibration in this study. High coefficients of determination (R2) and low root mean square errors of cross-validation (RMSECV) were obtained for Klason lignin (R2=0.94, RMSECV=0.398), acid-soluble lignin (R2=0.87, RMSECV=0.144), and total lignin (R2=0.91, RMSECV=0.448) from wood meal. High correlation coefficients were found between laboratory and predicted values for Klason lignin, acid-soluble lignin, and total lignin contents, with R2 and RMSEP values ranging from 0.67 to 0.94, and 0.19 to 0.526, respectively. The study showed that NIR analysis can be reliably used to predict lignin content in Acacia spp.