66 Produce Degradation: Reaction Pathways and their Prevention
ammonia lyase and tyrosine ammonia lyase activities, and these increases were, in
turn, related to the total anthocyanin content in the fruit (Montero et al., 1998).
Preharvest GA treatment of persimmons resulted in improved firmness retention
during storage (Monterde et al., 2001); this has been found to be due to inhibition
of cell wall dissolution normally experienced during ripening in that fruit (Ben-Arie
et al., 1996). Postharvest application of GA resulted in improved shelf life, reduced
weight loss, reduced fruit decay, and improved retention of chlorophyll and vitamin
C in green chile peppers (Arora et al., 2000). Similar positive responses were found
for mangoes treated with GA (Jain and Mukherjee, 2001). GA application appears
to have several different effects that lead to improved quality and its retention in
some fruits and vegetables.
3.3.2.4 Methyl Jasmonate
Jasmonates are classed as naturally occurring, growth-regulating oxylipins (Sembd-
ner and Parthier, 1993) that are generally applied as gaseous methyl jasmonate.
Methyl jasmonate applied postharvest enhanced the retention of total antioxidant
capacity of stored blueberry fruits (Wang, 2001), accelerated ripening (ethylene
production and respiration) in mangoes (Lalel et al., 2003b), and also enhanced
flavor volatile production in fruit stored at 20°C. Results obtained with mangoes
suggest that treated fruit should exhibit accelerated softening, but this point remains
to be demonstrated. In papaya, methyl jasmonate treatment increased firmness and
resistance to chilling injury at 10°C (Gonzaléz-Aguilar et al., 2003). Holding papaya
at 10°C normally leads to premature softening and other disorders (Gonzaléz-Aguilar
et al., 2003). Reduction in chilling injury with postharvest methyl jasmonate appli-
cation has also been demonstrated in avocados, grapefruits, and bell peppers (Meir
et al., 1996). Postharvest methyl jasmonate applications increased levels of β-caro-
tene in tomatoes and apple peel (Saniewski et al., 1987; Perez et al., 1993) and
inhibited sprouting in radishes, thus extending their shelf life (Wang, 1998).
On the negative side, methyl jasmonate has been shown to promote chlorophyll
degradation, ethylene production, and senescence in tomatoes and apples (Saniewski
et al., 1987; Perez et al., 1993; Fan et al., 1997c). However, unlike in the case of
ethylene, which produces similar effects on chlorophyll, ethylene production, and
senescence, methyl jasmonate does not appear to enhance softening or soluble solids
loss in apples (Fan et al., 1998). In addition, methyl jasmonate application can
suppress production of aroma volatiles (both alcohols and esters) in apples (Fan and
Mattheis, 1999), which, again, is the opposite of the effect of exogenous ethylene
application.
3.3.2.5 1-Methylcyclopropene
The compound 1-methylcyclopropene (1-MCP) is a recently discovered, man-made
gaseous inhibitor of ethylene action (Blankenship and Dole, 2003) and is considered
to be an anti-ethylene agent. Postharvest application of 1-MCP has been shown to
produce effects that depend on the particular fruit or vegetable, the cultivar, and the
specifics of the treatment and/or handling conditions. Blankenship and Dole (2003)