62 Produce Degradation: Reaction Pathways and their Prevention
stage (Jiménez et al., 2003). Levels of antioxidant capacity also increased in storage
for both immature (green) and mature (red) fruit. The antioxidant constituents
responsible for the water-soluble antioxidant capacity were considered to be ascorbic
acid and glutathione. Ascorbic acid and glutathione (both endogenously produced
antioxidants) declined with more advanced maturity in pears (Lentheric et al., 1999).
This decline in antioxidant capacity was related to the increased susceptibility of
the fruit to internal browning of the pears in storage. Phenolic acids and flavonoids
are also components of antioxidant capacity in fruits and vegetables. Phenolic acids
decline in apple peels as the fruit matures and ripens, whereas flavonoids increase
(Awad et al., 2001). Tomatoes show a slight decline in phenolic acid content during
on-the-vine ripening; however, if fruits are harvested at the mature-green stage, they
show significant increases in phenolic acid content with ripening off-the-vine (Gio-
vanelli et al., 1999). In carrots, phenolic acid contents increase with advancing
maturity (Chubey and Nylund, 1970).
3.2.4 SHELF LIFE
The shelf life of fruits and vegetables can be determined by a number of factors,
including dehydration, development of disorders, and senescence. The following
discussion focuses on the influence of maturity on the development of visible changes
in fruit and vegetables that signal the end of useful shelf life.
Disorders associated with fruit maturity that lead to shortened shelf life are well
documented for tree fruits. Generally, the more mature an apple is when harvested,
the greater susceptibility it will have to incurring injuries from controlled atmosphere
storage conditions (Ferguson et al., 1999). Late-harvested ‘Fuji’ apples having water-
core at harvest were more susceptible to internal browning than fruit harvested at a
less mature state and not having visible symptoms of watercore (Fan et al., 1997a).
Similar findings have been reported for internal browning disorder in ‘Braeburn’
apples; later harvests showed greater incidence of the disorder in storage (Elgar et
al., 1997; Lau, 1997). Late-harvested ‘Conference’ pears stored in controlled atmo-
sphere conditions have been shown to have a greater incidence and severity of
internal flesh browning (Roelofs and deJager, 1997).
The previous paragraph indicated that more advanced maturity leads to greater
flesh browning. In contrast to flesh-related disorders, skin-related disorders tend to
decline as fruit matures (Toivonen, 2003). More advanced maturity in apples has
been shown to be associated with significantly lower incidence of superficial scald
(Toivonen, 2003). In a specific case, breaker fruit of ‘Fuji’ was found to be less
susceptible to scald than mature-green fruit (Fan et al., 1997b).
Water loss can be a significant determinant of shelf life, and if maturity influences
the water loss characteristics of a fruit, this has to be considered in the storage
strategy. Late-harvested apples were found to have greater water permeance than
early-harvested apples, suggesting that water loss control measures must be more
important for late-harvested fruit than for early-harvested fruit (Maguire et al., 1997).
The same has been found to be the case in tomatoes (Díaz-Pérez, 1997).
Senescence, expressed as visible yellowing, can be an important determinant of
shelf life, and the maturity of the fruit or vegetable at harvest can often have an