Agriculture Reference
In-Depth Information
mango cultivars. The optimum ripening temperatures for
different cultivars as suggested by various workers are
25°C for 'Alphonso'(Thomas 1975), 22°C for 'Tommy
Atkins' (Medlicott
et al
. 1986b), 20-22°C for 'Haden',
'Irwin', 'Keitt', 'Kent' (Vazquez-Salinas & Lakshminarayana
1985) and 18-23°C with optimum of 20°C for 'Kensington
Pride' (Lalel 2002, O'Hare 1995) mangoes. Ripening
temperatures below or higher than optimum result in
retention of more acids, less sugars, reduced carotenoid
development in skin and pulp, poor aroma and flavour qual-
ity in ripe fruit (Lalel 2002; Medlicott
et al
. 1986b; O'Hare
1995; Singh & Janes 2001; Thomas 1975; Vazquez-Salinas
& Lakshminarayana 1985). Thus, optimum ripening condi-
tions in a temperature range of 20-23°C are congenial for
the eventual appearance and flavour quality of mango fruit.
fruits treated with 250, 500 and 1000 ppm ethylene released
from ethrel, compared with untreated fruits (Mohamed &
Abou-Goukh 2003). The Queensland Department of
Primary Industries, Australia recommended the exposure of
'Kensington Pride' and 'R2E2' mangoes to ethylene
concentration of either 10 ppm (trickle system) or 100 ppm
(shot system) for 2-3 days at 18-20°C coupled with high
humidity 85% to obtain completely uniform ripe fruit.
Ethylene biosynthesis and action inhibitors
Aminoethoxyvinylglycine (AVG) is a potent inhibitor of
1-aminocyclopropane-1-carboxylic acid (ACC) synthase
activity, a key enzyme in the ethylene biosynthesis pathway.
The post-harvest application of AVG (100, 500 and
1000 ppm) inhibited the biosynthesis of ethylene in a dose-
dependent manner and also reduced the respiratory activity
of mango fruit during ripening under ambient conditions
(Lalel
et al
. 2003e). However, the aroma volatile production
of AVG-treated fruit is affected as ethylene influences the
metabolic pathways inducing volatile compounds produc-
tion (Lalel
et al
. 2003e). The use of 1-methylcyclopropene
(1-MCP), an ethylene action inhibitor, blocks the ethylene
receptors irreversibly and thus delays ripening. In mango,
the post-harvest application of 1-MCP to delay ripening has
been reported by many researchers (Hofman
et al
. 2001;
Jiang & Joyce 2000; Lalel
et al
. 2003e; Penchaiya
et al
.
2006). The treatment of mangoes with 1-MCP at 100 μl L
−1
for 12 hours delayed the fruit softness and skin colour
changes (Jiang & Joyce 2000). The post-harvest application
of 1-MCP at 25 μl L
−1
for 6 or 14 hours reduced the rate of
ethylene production drastically and delayed ripening by 5.1
days in 'Kensington' mangoes (Hofman
et al
. 2001; Lalel
et al
. 2003e). The application of 1-MCP in mango also
retarded the biosynthesis of aroma volatile compounds lead-
ing to lower aroma quality in ripe fruit (Lalel
et al
. 2003e).
The post-harvest life of 'Nam Dokmai' mangoes treated
with 1-MCP (1 μl L
−1
) for 24 hours could be extended to 15
days at 20°C (Penchaiya
et al
. 2006). A significant variation
has been observed among results from 1-MCP treatments at
differing doses and exposure durations in mango. To achieve
success of 1-MCP on commercial scale in mango, cultivar
and harvest maturity specific investigations are required.
Regulation of ripening
Ethylene, a ripening hormone, is directly involved in the
onset of ripening in climacteric fruits such as mango. Even
traces of ethylene in the storage environment can induce
the autocatalytic production of ethylene and promote
ripening. Thus, the ripening process can be regulated either
with exogenous application of ethylene or by inhibiting the
biosynthesis and action of ethylene in mango fruit.
Promoting ripening
The promotion of ripening is usually carried out keeping in
view the market demand and fruit supply. Special ripening
treatments are also required after long term storage at low
temperature either in ambient air or controlled atmospheres.
Mango fruit harvested at commercial maturity can be
ripened artificially with ethylene treatment. Exogenous
application of ethylene in the form of ethrel (200 to
2000 ppm) stimulates the biosynthesis of ethylene and
triggers respiration, carotenoid synthesis and chlorophyll
degradation in mango (Kulkarni
et al
. 2004; Medlicott
et al
.
1987; Nair & Singh 2003; Pal 1998a, 1998b; Singh & Janes
2001). The ethrel-treated fruit ripen uniformly with good
colour development and flavour and better overall sensory
scores. Ethrel treatment not only accelerates the ripening
process but also alleviates chilling injury and improves the
fruit quality (Nair & Singh 2003; Nair
et al
. 2004b). Dipping
fruit in ethrel solution is the most common method of exog-
enous application of ethylene. But the exposure of fruit to
ethylene released from ethrel in alkaline medium has been
found more advantageous than aqueous dip as it is more
effective and reduces an extra step in post-harvest operations
(Mohamed & Abou-Goukh 2003). Depending on concentra-
tion and cultivar, ripening was 1-3 days faster in fruits
dipped in 500 and 1000 ppm ethrel and 1 to 5 days earlier in
POST-HARVEST HANDLING AND STORAGE
Cool storage
Mango is a seasonal tropical fruit unlike many other
tropical fruits that are available throughout the year. Its sea
freight to importing countries may involve the transit
