Colorimetric parameters
Colour changes in sample were determined by a Minolta
CR-300 Chroma Meter (Minolta, Osaga, Japan) in L*,
a* and b* colour scales. Parameters L*, a* and b*
determine a three-dimensional colour space, in which L*
represents brightness (on a lightness–darkness scale),
whereas positive and negative a values determine the
redness and greenness and positive and negative b values
determine yellowness and blueness, respectively. The
instrument was calibrated against a white standard.
Measurements were individually taken for ten samples
per treatment, and the average of ten readings was
calculated. The colour difference DE was calculated
from the L*, a* and b* parameters using the Hunter–
Scotfield equation: