As mentioned before, eggplant fruit cv Money Maker
No. 2 have different intensity of skin colour: dark purple in
the central section and light purple in upper section. At
harvest, 15 fruits were analysed and they shows that upper
section presents higher positive values of a* (Fig. 5) and lower and negative values of b* than the central section.
Therefore, Hue values (H1) for the upper section are always
negative while Chroma (C*) values are higher than of
central section. Values of L* were higher in upper than in
the central section (data not shown).
During storage, visual changes in colour were well
reproduced by C*, H1 and L* values. Central section
showed less colour variations than upper, probably due to
dark purple colouration present in the first section. Thus, in central section (Table 2), values of C* were essentially
constant at all temperatures. In this section, the other
parameter, H1, showed an increase at day 2 and decreased
from day 6 on, at either 10 or 01C. These changes were
higher at 01C than at 101C. On the other hand, in central
section values of L* kept mostly unchanged throughout the
storage time of fruits at 101C. In turn, lightness slightly
decreased after 2 days at 01C, then remained virtually
constant until day 13 and finally increased at day 15 to
recover the initial value.
In the upper section, changes in colour parameters
during fruit storage were more important than in the
central section (Table 2). At harvest, C* values in the upper
section were 14 times higher than in the central section.
This ratio showed little variations along storage. C* values in upper section were generally lower than the initial during
storage, regardless of temperature. C* decreased at day 2 at
both temperatures and then began to increase at 01C up to
a maximum at day 9, comparable to the initial value. The
parameter H1, in upper section, did not vary in practice
during storage at 101C. At 01C, it kept rather constant
until day 13 and then experienced a sharp increase to a
positive value at day 15. Finally, parameter L* in the upper
section showed slight variations along the entire storage
time at 101C. However, at 01C this parameter gradually
increased until the end of storage, attaining a value 30%
above the initial. In general, lightness in the upper section
(L*) and saturation (C*) were higher than in the central
section at harvest and throughout storage at both
temperatures tested.
Results indicate that only those fruits stored at 01C
showed significant changes in colour parameters especially
in the upper section. In general, surface CI symptoms were
related to variation in colour parameters. For example,
discolouration observed mainly in the upper skin after day
2 was related to a decrease of C*, whereas the evolution of
yellow-brown colouration owing to scalds was related to a
C* decrease and to increases of H1 and L*. Colour changes
were used to indicate evolution of CI symptoms in several
fruits. Thus, in cucumber (Martı´nez-Romero, Serrano, &
Valero, 2003), the occurrence of browned spots on the skin
surface was associated with a strong reduction in the H1
angle.