2.4 Color measurement
Color was measured with a colorimeter (Hunter Associates Laboratory, Inc., model MiniScan XE Plus,
VA, USA). The equipment was calibrated before the measurement with white tile (X = 79.9, Y = 84.4, Z
= 90.4). The color system used was the CIE (Commission International de I’ Eclairage) where L*
represents lightness or darkness, a* represents redness or greenness and b* represents yellowness or
blueness. In addition, the total color difference (