Colour assessment
Cut apple surface colour was measured with a handheld tristimulus reflectance colorimeter . Three replicates of10 apple cubes were used for each storage time. Colour
was recorded using a CIE––Lab uniform colour space(Lab), where L indicates lightness, a indicates chromaticity
on a green to red (þ) axis, and b chromaticity on a blue to yellow (þ) axis. Numerical
values of a and b were converted into hue angle and chroma [Chroma ¼ ða2 þ b2 Þ1=2] . The L value is a useful indicator of darkening
during storage, either resulting from oxidative
browning reactions or from increasing pigment concentrations.
The a value is a measure of greenness is
highly correlated with colour changes of apple flesh. A decrease in L value and an
increase in a value are indicative of browning . also suggested that enzymatic
browning at the cut surfaces of apples could be monitored
by measuring changes in reflectance L and a
values, and that b values seemed to be unrelated to the
extent of browning. The H is an angle in a colour wheel
of 360, with 0, 90, 180 and 270 representing the
hues red-purple, yellow, respectively, while chroma is
the intensity or purity of the hue.