Postharvest Biology and Technology of Fruits, Vegetables, and Flowers

CHANGES IN NUTRITIONAL QUALITY OF FRUITS AND VEGETABLES 461
contents was observed, while the levels of sucrose decreased (Torija et al., 1998). The
explanation is due to hydrolysis of the sucrose to glucose and fructose by invertase.
A decline in sucrose content was also observed in pears during storage, while the levels
of fructose and glucose increased during 5 months of storage at 0 ◦ C (Chen et al., 2006). A
similar trend was also observed in apples. The contents of glucose, fructose, and sucrose
changed in apples during the storage at low temperature. The levels of glucose, fructose,
and sorbitol increased and sucrose decreased during storage at 1 ◦ C for 90 days in air (Drake
and Eisele, 1999). On the other hand, there was no difference found in TSSs of apples stored
in air and CA.
21.6.2 Controlled atmosphere storage and sugars
Sweet cherries are more tolerant of high CO 2 concentration than other temperate fruits. In
addition, high-soluble solids containing cherries have a lesser risk of low O 2 concentration
damage. “Stella” and “Van” cherries stored at high CO 2 concentrations (>10%) exhibited
less decay than cherries stored at lower CO 2 concentrations. In contrast, CO 2 concentration
in CA (15% CO 2 + 21% O 2 ) did not show any significant effect on soluble solids of
cherries (Wang and Vestrheim, 2002). Similar results were also found in “Burlat,” “Bing,”
and “Sweetheart” cherries stored in CA and MA (Remòn et al., 2004).
Holcroft and Kader (1999) reported that strawberry storage at high CO 2 concentration
(20 kPa CO 2 ) in CA showed a decline in sucrose, fructose, and glucose at 5 ◦ C for 10 days
storage period. Nevertheless, these concentrations were higher in 0.5 kPa O 2 . Overall, the
concentration of sucrose decreased, and the concentrations of glucose and fructose increased
during 10 days of storage in 0.5 kPa O 2 atmosphere. However, TSS content was decreased
with storage time. This could be due to the fact that TSS measures the levels of sugars,
organic acids, and soluble pectins.
21.6.3 Growth regulator treatments and sugars
Natural volatile compounds, including methyl jasmonate and jasmonic acid, have positive
effects on sugar content of fruits. Raspberry fruits treated with methyl jasmonate had highersoluble
solids content than the control fruits. Treated fruits contained higher levels of
fructose, glucose, and sucrose than the control fruits (Wang and Zheng, 2005). A combined
treatment of methyl jasmonate and ethanol also increased the soluble solids content in
strawberries (Ayala-Zavala et al., 2005). Similar results were also found in jasmonic acid–
treated apples (Wang and Zheng, 2005). Low respiration may be the cause of high sugar
contents in treated fruits, while high metabolism in control fruits may justify the depletion
of carbohydrate contents.
Postharvest treatment with 1-MCP has been explored to enhance the carbohydrate contents
in apples (Perera et al., 2003), peaches (Liu et al., 2005a), nectarines (Bregoli et al.,
2005), and pears (Fu et al., 2007). However, none of these studies has shown any significant
effect of 1-MCP on fruit sugar levels. This may suggest that ethylene does not affect free
sugar levels in fruits. On the other hand, an increase in soluble solids has been noticed
during ripening (Perera et al., 2003).
Thus, it is apparent that the postharvest quality of fruits may change during storage
depending on several preharvest and postharvest factors. Therefore, it is essential to optimize