(p < 0.05) than those recorded for fruit harvested later. Fruit picked
on the fifth and sixth harvest dates (1.25 m) exhibited L values significantly
higher than those obtained on the first harvest day, but
lower than those recorded for fruit harvested at 1.75 m, thus highlighting
the influence of height-on-tree on ripening.
Results for parameter a (green–red) increased significantly
during the harvesting period. Similarly, values for parameter b
(blue–yellow) rose significantly over the course of the study, fruit
displaying higher positive values (yellow) as ripening progressed;
higher-placed fruits also recorded significantly higher values
(p < 0.05) for this parameter.
These changes in a and b during ripening are due mainly to the
conversion of chloroplasts to chromoplasts, and to an increase in
carotenoid levels which give the mandarin skin its characteristic
color (García-Luis et al., 2002).
Color saturation (C) and the color index increased significantly
during ripening, due also to higher carotenoid levels. By contrast,
values for the parameter h rose significantly (p < 0.05) from the
first harvest day to the second, but thereafter displayed no significant
change (p > 0.05). These changes in mandarin skin color, from
green-yellowish tones (negative a and positive b) to orange-reddish
tones (positive a and b) typically occur in the course of ontree
ripening.
Firmness and maximum penetration force declined significantly
throughout ripening, each parameter decreasing by around 50%
from the first harvest day (13.77 N and 52.57 N, respectively) to
the last (6.78 N and 27.89 N, respectively).
Pericarp thickness remained fairly constant throughout the harvesting
period.
Juice weight rose significantly (p < 0.05) during ripening,
increasing by 70% between the start and the end of the study. An
equally significant increase (22%) was recorded for juice content
throughout ripening. Both parameters are of particular interest to
the citrus-fruit industry, minimum juice content for mandarins
being set at 33% (Arias and Toledo, 2000).
Mean values for SSC showed a slight but significant increase
(6%) during ripening, whereas TA decreased significantly from
about 1.33% citric acid at the beginning of the period to about
1.0% citric acid at the end. Since the decrease in TA was accompanied
by a slight change in SSC, a 47% increase was recorded in the
SSC:TA ratio. As a result, a significant (p < 0.05) rise in pH values
was detected over the study period.