RESULTS AND DISCUSSION
Fruit ripening is associated with
important biochemical changes that
modify colour, texture, taste and
other quality traits. The changes of
some physico-chemical characteristics
of Maoluang fruit used in this
study are presented in Table 2. The
values reported are means of tree assays
of each group performed in triplicate.
The colour change of skin was
reflected by the variation of the L*,
a* and b* values determined in
Maoluang fruit. The L* value decreased
with fruit ripening as colour
became deep/dark. The Maoluang
fruit’s skin colour is green at the beginning
of ripening and becomes red
in conjunction with chlorophyll degradation
and anthocyanin accumulation
During ripening, a slight and insignificant
increase in the total soluble
solids (TSS) content occurred at
the immature and mature stages. But
at the ripe stage, the change in TSS
was significant (p < 0.05) and the
final TSS content was 18.40% (Tab.
2). The pH is becoming increasingly
recognized for its important contribution
to product quality. This is
especially true about red wine because
it plays a key role in prevention
of microbial spoilage, malolactic
fermentation occurrence and colour
stability of wines. The pH
slightly increased from about 2.20 to
3.95 during fruit development and
ripening. In contrast, the titratable
acidity (TAc) showed a gradual
decrease from about 1.40 to 0.75%. Acidity was inversely correlated to
pH. The ripe fruit sample which had
a low acid content, had a correspondingly
high pH. Evolution of TAc and
the pH of Maoluang recorded above,
agree with published data on strawberries
(Voća et al., 2008). Organic
acids usually decline during ripening
as they are respired or converted to
sugars. The maturation index is regarded
as the most reliable measure
of fruit quality such as fruit flavour.
The maturation index relates TAc
(sourness) and sugar level (sweetness)
and should be 30 to 32 (Gallander,
1983) for wine production.
The maturation index is an important
quality factor. One can predict from
the finding of this study that the mid
ripe stage is of less quality than those
of the ripe and over ripe stages, respectively.
In the over ripe stage, the
high ratio of 32.28% may be regarded
as low acid and would have a
sweet taste.