2.2. Colour measurement
The colour of orange juice was analysed using a Hunterlab ColorQuest
colorimeter (Hunterlab, Reston, VA). The instrument (45/
0 geometry, Illuminant D65, 10 observer) was calibrated with a
black and white ceramic tile (X = 78.66, Y = 83.31, Z = 88.40) before
the measurement. Subsequently, samples were placed in a glass
cell and covered with a white plate. Colour measurements were
carried out in triplicate with five readings for each sample. The
recorded XYZ tristimulus values were then converted to CIE L⁄
, a⁄
and b⁄ colour values. The L⁄ values represent lightness, ranging
from 0 (black) to 100 (white). The a⁄ values indicate greenness
(negative) to redness (positive) and the b⁄ values quantify blueness
(negative) to yellowness (positive). In CIELAB, three other parameters
were determined by the following equations:
D