Modelling of pH effects and CIE L*a*b*colour spaces of beech wood-inhabiting fungi by NIRS

ABSTRACT

A combination of statistical techniques of analyses were used to evaluate the potential of International Commission on Illumination (CIE) lightness (L*), redness (a*) and yellowness (b*) colour space system and near-infrared spectroscopy (NIRS) to assess surface changes in relation with progressive decay of beech (Fagus grandifolia Ehrh.) by wood-inhabiting lignicolous fungi Inonotus hispidus, Trametes versicolor and Xylaria polymorpha. pH effects based modelling predictions of beech earlywood and latewood tissues were also included. Multivariate analysis techniques included response surface optimization, sample-specific standard error of prediction (SEP) method and projection to latent structures partial least squares (PLS) regression. Strong statistical relationships were derived for pH predictions with R² values ranged: from 0.77 to 0.84 for I. hispidus; from 0.77 to 0.84 for T. versicolor and from 0.83 to 0.91 for X. polymorpha. R² values for CIE-based L*a*b* colour space measurements ranged: from 0.43 to 0.69 (L*), 0.66 to 0.76 (a*), 0.42 to 0.53 (b*) for I. hispidus; from 0.59 to 0.69 (L*), 0.69 to 0.79 (a*), 0.64 to 0.79 (b*) for T. versicolor; and from 0.51 to 0.75 (L*), 0.89 to 0.94 (a*), 0.85 to 0.89 (b*) for X. polymorpha. Multivariate technical analysis (response surface analysis, sample-specific SEP, PLS regression) of CIE L*a*b* system and NIRS results should be able to characterize pH effects and surface changes of wood spalted by lignicolous fungi as a quick and reliable non-destructive method relevant to wood-spalting concerns and the forest products industry.

KEYWORDS:

• Beech (Fagus grandifolia Ehrh.)
• CIE L*a*b* colour space system
• earlywood zones
• Inonotus hispidus
• latewood zones
• NIR spectroscopy
• pH effects
• response surface analysis
• Trametes versicolor
• wood-spalting
• Xylaria polymorpha

Acknowledgements

The authors greatly appreciate the input of Dr Sara Robinson, Dr Sally Krigstin, Vicktoriya Pakharenko, Latchmi Raghunanan, Nicolas Tanguy, Catalin Tudor and Andra Tudor from the Faculty of Forestry (U of T, Toronto), and Dr Delphine Dufour from the Faculty of Dentistry (U of T, Toronto), for their support with the technical laboratory assistance.

Disclosure statement

No potential conflict of interest was reported by the authors.