Color of samples was measured using a Hunter-Lab DP-9000 colorimeter (Hunter Associates Laboratory, Virginia, USA)
fitted with a 25 mm aperture diameter.
The instrument was calibrated with a white reference tile.
Color was expressed in Hunter-Lab units L⁄ (whiteness/brightness), a⁄ (redness/greenness) and b⁄ (yellowness/blueness). Three replicates were measured.