Agriculture Reference
In-Depth Information
antioxidant activity (Sluis et al., 2001). An increase in antioxidant activity during storage
has been observed in apples stored in CA (2% CO
2
+
2% O
2
) or cold storage for 4 months
(Leja et al., 2003).
Off-flavor compounds such as ethanol and acetaldehyde start to accumulate during long-
term storage of pears in high CO
2
atmosphere that promotes progression of physiological
disorders including core browning (CB). It has been noticed that pears stored in CA with
high CO
2
concentrations developed rapid injury. In CA-stored pears, H
2
O
2
accumulated
rapidly indicating that fruits undergo stress from changes in O
2
and CO
2
concentrations.
Short-term storage of “Conference” pears under CA (2% O
2
and 5% CO
2
) exhibited an
increase in SOD and APX activities and a decrease in CAT activity (Larrigaudiere et al.,
2001). Higher lipoxygenase enzyme activities were also reported in CA-stored pears, which
induced membrane lipid peroxidation.
Broccoli has health-promoting compounds such as flavonoids, indole-3-carbinol, and
vitamin C that provide antioxidant capacity to freshly harvested broccoli. Reports suggest
that these antioxidant compounds degrade during storage. Broccoli, packed in MAP using
microperforated and nonperforated films, maintained the levels of total antioxidant activity
and phenolic content even after 28 days of storage, whereas a rapid decline in these health-
promoting compounds was monitored in control broccoli after 20 days of cold storage
(Serrano et al., 2006).
A significant decline in total antioxidant activity was observed in ready-to-eat shredded
purple carrots stored under MAP (95% O
2
+
5% CO
2
), while carrots stored at 90% N
2
+
5% CO
2
maintained antioxidant activity for 10 days (Alasalvar et al., 2005).
Therefore, CA storage can preserve health-promoting components in some cultivars, while
high CO
2
concentration may reduce the ascorbic acid content and antioxidant activity in
some fruits including strawberry and pears.
5% O
2
+
21.5.9 Growth regulator treatments and antioxidants
The application of several pre- and postharvest treatments have been investigated to reduce
the oxidative stress and to increase the nutritional value of the products. Antioxidant chem-
icals as dips or coatings have been used in several studies to prevent the oxidative reactions
(Sapers, 1993). An increase in ascorbic acid content was observed in 1% CaCl
2
dip-treated
kiwifruit slices. A further increase in ascorbic acid content was noticed when 1% CaCl
2
-
treated slices were kept in an ethylene-free atmosphere (Agar et al., 1999). An increase in
vitamin C content was also found in CaCl
2
-treated apples (Lee and Kader, 2000). In a study,
2% CaCl
2
treatment of apples maintained higher amount of ascorbic acid content after 60
days of storage than 1.5 and 1% CaCl
2
treatment (Hayat et al., 2005). Calcium dips have
also shown delayed membrane deterioration and senescence (Lester, 1996; Picchioni et al.,
1998). Calcium induces tolerance to tissue injury by enhancing antioxidant activity.
Pre- and postharvest treatments of fruits and vegetables with plant growth regulators and
natural volatile compounds have shown positive effects on antioxidant activity. Methyl jas-
monate, a natural volatile compound, increased the contents of ascorbate, dehydroascorbate,
and phenolics in raspberries during storage compared to control fruits. Moreover, methyl
jasmonate-treated raspberries showed higher activities of SOD, POX, APX, MDHAR, and
DHAR (Chanjirakul et al., 2006). Methyl jasmonate-treated strawberries and blueberries
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