Postharvest Biology and Technology of Fruits, Vegetables, and Flowers

458 POSTHARVEST BIOLOGY & TECHNOLOGY OF FRUITS, VEGETABLES, & FLOWERS
0 to 10, 20, and 30 ◦ C (Kalt et al., 1999). Storage temperatures did not show any effect
on the ascorbate content in strawberry and high-bush blueberry. Connor et al. noticed an
increase in antioxidant activity in blueberry during cold storage (Connor et al., 2002).
Higher antioxidant activity was directly related to the anthocyanin and phenolic contents
of blueberry during storage. In contrast, no difference in antioxidant capacity was found
in fresh, frozen, and cold-stored raspberries (Mullen et al., 2002). Sweet cherry storage
at −23 ◦ C for 6 months exhibited 58% decline in antioxidant activity, while fruits stored
at −70 ◦ C for 6 months showed 45% increase in antioxidant activity (Chaovanalikit and
Wrolstad, 2004).
An increase in the level of GR was observed in apples during storage for 1–3 months at
2 ◦ C. However, no change in ascorbate POX activity was noticed during storage (Barbara
and Marzenna, 2002). It has been indicated that CAT activity was reduced in apples during
freezing. Frozen apples showed 70–80% lower CAT activity than fresh apples (Gong et al.,
2000). Apple tissues kept at −25 ◦ C showed higher loss in CAT activity than tissues kept
at −70 ◦ C. It appears that if the freezing process is slow, the degradation in CAT activity
is higher. The freezing process did not show any significant effect on activities of other
enzymes including SOD and POX (Gong et al., 2000).
Low-temperature storage shows chilling injury in chilling-sensitive horticultural crops.
Cucumber stored at 5 ◦ C showed low ascorbic acid content, while no reduction in ascorbic
acid was noticed at 20 ◦ C (Lee and Kader, 2000). Low-temperature storage of chillingsensitive
mandarins increased chilling injury of fruits and decreased antioxidant enzyme
(POX, APX, and CAT) activities. However, chilling-tolerant fruits exhibited lower chilling
injury and higher antioxidant enzyme activities. It indicates that chilling-tolerant cultivars
have more efficient antioxidant system than chilling-sensitive cultivars (Sala, 1998).
21.5.8 Controlled atmosphere storage and antioxidants
Controlled atmosphere, with elevated CO 2 concentrations, is widely used to maintain the
shelf life and nutritional quality of several fruits and vegetables. In general, high CO 2
concentrations have shown a reduction in ascorbic acid content in the products. During
storage in CA with high CO 2 concentrations (20 and 30%), strawberries displayed a decrease
in ascorbic acid and vitamin C contents, while air-stored strawberries did not show any
reduction in the ascorbic acid and vitamin C contents (Agar et al., 1997). Similar patterns
were also found in red currants and blackberries. The strawberries with reduced ascorbic
acid showed an increase in DHA level, which might be due to the stimulation of ascorbic
acid oxidation by APX in the presence of high CO 2 . Moreover, it is believed that high
CO 2 may inhibit MDHAR and (dehydroascorbate reductase) DHAR activities (Agar et al.,
1997). Apples kept at a high CO 2 atmosphere also showed a loss in ascorbic acid content.
A reduction in vitamin C content in kiwifruit slices has been noticed with increasing CO 2
concentrations. Slices kept in air + 5, 10, or 20 kPa CO 2 accelerated the loss of vitamin C
by 14, 22, or 34%, respectively (Lee and Kader, 2000).
The antioxidant activities of air-stored cranberries increased by 50% from their harvest
levels in 2 months, while CA-stored fruits (21% O 2 + 30% CO 2 ) prevented this increase
(Gunes et al., 2002). This may result from an impediment in the release of bound phytochemicals
during the CA storage, which contribute to antioxidant activity. However, one
study reported that apples stored in cold or CA did not show any effect of storage on