Postharvest Biology and Technology of Fruits, Vegetables, and Flowers

THE ROLE OF POLYPHENOLS 269
3'
OH
HO O + O-Sugar
5'
OH
Anthocyanin
Pelargonidin
Cyanidin
Delphinidin
Peonidin
Petunidin
Malvidin
Substituents
3′-OH
3′-OH, 5′-OH
3′-OCH 3
3′-OCH 3 , 5′-OH
3′-OCH 3 , 5′- OCH 3
Color
Orange red
Purplish red
Bluish purple
Rosy red
Purple
Pink/red
Fig. 12.5 Chemical structures of selected anthocyanins of fruits. The major sugars of C-3 glycosylation include
glucose, galactose, arabinose, rhamnose, and rutinose.
activity of PAL, which in turn is regulated by ethylene (Blankenship and Unrath, 1988;
Gomez-Cordoves et al., 1996). Exposure of fruit to UV light in combination with low-night
and high-day temperatures can also regulate anthocyanin biosynthesis (Reay, 1999). For
example, it was found that both UV light and advancing maturity promoted anthocyanin
biosynthesis in “Jonathan” apple (Reay and Lancaster, 2001). It has been found that the
concentration of anthocyanins was higher on the blush side than on the shaded side of
“Elstar” and “Jonagold” apples, and in fruit at the top and sides of the apple tree canopy
(Awad and de Jager, 2000). Fine regulation of the PAL activity may be dependent on the
extent of light exposure to the fruit (tree position) and climatic conditions during fruit
maturation. It has also been demonstrated that UV light and low temperatures can induce
the production of other flavonoids and phenolic acids (Lancaster et al., 2000). During
cold storage of apple (“Granny Smith,” “Crofton,” and “Lady Williams”), flavonoid levels
have been shown to remain constant (Golding et al., 2001), although some studies have
reported minor fluctuations in levels. A similar study using “Jonagold” and “Elstar” cultivars
found that most flavonoids and hydroxycinnamic acid derivatives were stable throughout
cold or controlled atmosphere storage (Awad and de Jager, 2000). In “Delicious” and
“Ralls” apple fruit, flavan-3-ols and flavonols were generally stable during storage; however,
an increase in anthocyanin concentration with a concomitant decrease in simple phenols
has also been reported (Ju et al., 1996). Others have reported a proportional decrease in
anthocyanin concentration in storage (Lin et al., 1989). It seems that anthocyanin content
remained constant during storage, while the carotenoid levels increased and chlorophyll
levels decreased (Reay, 1998). It has also been suggested that factors other than the level
of ethylene in the tissue contribute to the de novo biosynthesis of anthocyanins, including
low temperature (Arawaka, 1991), fruit maturity (Murphey and Dilley, 1988), and storage