Estimation of Acacia melanoxylon unbleached Kraft pulp brightness by NIR spectroscopy

  • António J.A. Santos Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa, Lisboa.
  • Ofélia Anjos Instituto Politécnico de Castelo Branco, Escola Superior Agrária, Castelo Branco.
  • Helena Pereira Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa, Lisboa.


Aim of the study: The ability of NIR spectroscopy for predicting the ISO brightness was studied on unbleached Kraft pulps of Acacia melanoxylon R. Br.

Area of study: Sites covering littoral north, mid interior north and centre interior of Portugal.

Materials and methods: The samples were Kraft pulped in standard identical conditions targeted to a kappa number of 15. A Near Infrared (NIR) partial least squares regression (PLSR) model was developed for the ISO brightness prediction using 75 pulp samples with a variation range of 18.9 to 47.9 %.

Main results: Very good correlations between NIR spectra and ISO brightness were obtained. Ten methods were used for PLS analysis (cross validation with 48 samples), and a test set validation was made with 27 samples. The 1stDer pre-processed spectra coupling two wavenumber ranges from 9404 to 7498 cm-1 and 4605 to 4243 cm-1 allowed the best model with a root mean square error of ISO brightness prediction of 0.5 % (RMSEP), a r2 of 99.5 % with a RPD of 14.7.

Research highlights: According to AACC Method 39-00, the present model is sufficiently accurate to be used for process control (RPD ≥ 8).

Key words:  Acacia melanoxylon; unbleached Kraft pulps; ISO Brightness; NIR; RPD.


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How to Cite
SantosA. J., AnjosO., & PereiraH. (2015). Estimation of Acacia melanoxylon unbleached Kraft pulp brightness by NIR spectroscopy. Forest Systems, 24(2), eRC03.
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