Evaluation of the Process Thermal Treatment of Maple Wood Saturated Water Steam in Terms of Change of pH and Color of Wood

Changes in maple wood's pH and color (Acer pseudoplatanus) were evaluated before and after thermal treatment process with saturated water steam. Maple wood was thermally treated at temperatures: t(I) = 105 +/- 2.5 degrees C, t(II) = 125 +/- 2.5 degrees C, and t(III) = 135 +/- 2.5 degrees C for tau <= 12 hours. Direct pH measurement of maple wood with a moisture content above the fiber saturation point (FSP) was performed using a pH-meter SI 600 with a Lance FET + H puncture probe. The polynomial dependence of pH and total color difference Delta E* on temperature t time tau was calculated by statistical processing of measured results. The correlation between the total color difference Delta E* of maple wood in the process of thermal color modification and the pH value is expressed y the equation: Delta E* = 4.5516.(pH)(2) - 48.405.(pH) + 134.35. This dependence is a suitable tool for assessing the achieved color change based on the change of wood pH in the technological process.