Changes in Nutritional Quality of Fruits and Vegetables During Storage - Postharvest Biology and Technology of Fruits, Vegetables, and Flowers - page 454

70 ◦ C. In frozen and phenolic contents of cherries decreased during storage at − 23 and −

23 ◦ C during storage
for 6 months (Chaovanalikit and Wrolstad, 2004). A reduction in total phenolic content
was also found in frozen cherries, but it was not as high as in anthocyanins. The severe
reduction in anthocyanin content could be due to the presence of PPO activity. This enzyme
plays an important role in deterioration of quality of the most fruits and vegetables. At
freezing temperature, solute concentration is increased that helps in catalysis of chemical
reactions. Moreover, freezing increases membrane decompartmentalization and induces
enzyme-substrate contact (Cano et al., 1995). Similar patterns were also noticed in frozen
papaya (Cano et al., 1995). Therefore, long-term storage of fruits at freezing temperature
decreases the nutritional quality of the fruits.
Storage of some fruits at low temperature induces chilling injury characterized by re-
duced fruit quality, increased browning, and off-flavor development in fruits. Different fruits
show chilling injury at different temperatures. In general, fruit skin is more sensitive to de-
velop chilling injury than fruit flesh. It has been observed that the chilling injury is positively
correlated with the activities of PAL (Martınez-Tellez and Lafuente, 1997; Lafuente et al.,
2001) and PPO enzymes (Nguyen et al., 2003). However, no association between chilling
injury and changes in PPO and POX has been found in some mandarin (Martınez-Tellez and
Lafuente, 1997) and orange (Martınez-Tellez and Lafuente, 1993) cultivars. It is found that
chilling also increases ethylene production. Exogenous or endogenous ethylene produced
during stress conditions may provoke PAL activation (Lafuente et al., 2001). An inverse re-
lationship between free phenolics and chilling injury was also noticed (Nguyen et al., 2003).
This relationship may be because of membrane damage during chilling. In a recent report,
it has been reported that the antioxidant activity and phenolics levels remained relatively
stable in several fruits during room temperature storage or refrigerated storage at 4 ◦ C. In
some cases, an increase in anthocyanin levels was also observed (Kevers et al., 2007).

Bing cherries, ∼ 75% anthocyanin content was lost when stored at −

21.5.3 Controlled atmosphere storage and phenolic compounds

Since oxygen plays a pivotal role in oxidation of phenolics at normal atmosphere, the
complete removal of oxygen may control the phenolic oxidation. However, due to the risk
of anaerobic respiration, it is not a practical approach. The storage of fruits under CA with
reduced O 2 and increased CO 2 can be a favorable method in order to preserve the quality of
fruits. Controlled atmosphere in conjunction with low temperature can be a crucial factor
to regulate respiratory and metabolic activities of perishable commodities.
Several studies have evaluated the effect of CA on fruits and vegetables. It has been
observed that browning in fruits and vegetables was decreased by increasing the CO 2 level
in storage atmosphere (Buescher and Henderson, 1977; Siriphanick and Kader, 1985). CA
storage of “Delicious” apples for 7-14 weeks showed a major reduction in PPO activity and
browning (Barrett et al., 1991). During CA storage, lower PPO activity was also noticed in
minimally processed apple slices. All CA-stored apples exhibited lower PPO activity than
air-stored ones. Furthermore, it has been observed that the higher CO 2 concentrations had
the maximum effect on PPO activity inhibition (5-30%) (Awad and Jager, 2003). At high
CO 2 concentrations, higher phenolic content and lower browning index were also found,
probably, due to lower PPO activity. In several fruits, the CO 2 levels above 5% inhibited
PPO activity and finally reduced browning.