Mango - Crop Post-Harvest: Science and Technology - page 121

skin and flesh discolouration was correlated with the
irradiation-induced increased polyphenoloxidase activity
in mango (Thomas & Janave 1973). Mature green pre-
climacteric 'Kensington Pride' mangoes irradiated with a
dose of 75 Gy showed delayed ripening, but higher dose
levels of 300 and 600 Gy caused lenticel damage and minor
losses of vitamin C (McLauchlan et al . 1990). However, a
recent study has shown that skin and flesh colours of 'Nam
Dokmai' and 'Chok Anan' mangoes were not affected by
gamma irradiation at a dose level of 400 to 600 Gy
(Uthairatanakij et al . 2006). Recently, it has been reported
that 'Tommy Atkins' mangoes can be irradiated with
electron beam at 1 k Gy dose without having any adverse
effect on biochemical and sensory attributes (Moreno et al .
2006). The stage of maturation of mango fruit decides the
rate of success as partially ripe fruit and those in their
climacteric phase are largely unaffected by irradiation
(Boag et al . 1990). Although, ripe fruit are more tolerant to
higher doses of irradiation with regard to appearance of
external injury symptoms, their limited shelf life may not
allow much time for marketing and distribution. Therefore,
treating mature green pre-climacteric fruit with lower doses
of radiation is the appropriate alternative for maximising
the benefits. In addition to lenticel damage and skin scald,
higher doses of irradiation may also result in excessive
softening of fruit (Moreno et al . 2006; Uthairatanakij et al .
2006). Utthairatanakij et al . (2006) also reported varietal
variation in the response of mango to irradiation and found
that higher doses of irradiation (400 or 600 Gy) resulted in
more softening of 'Chok Anan' than 'Nam Dokmai'
mangoes harvested at either 70% or 90% maturity.
Irradiation influences respiratory behaviour of mangoes
(Boag et al . 1990; Dharkar et al . 1966). Thomas (1993)
reported that there was a transient increase in the respiration
rate of mangoes immediately after irradiation which could
possibly be an implication of stress response. However, the
actual respiratory climacteric was delayed as well as
suppressed by the irradiation treatment in mangoes (Boag
et al . 1990; Dubery et al . 1984). Irradiation treatment of
'Haden' mangoes with a 750 Gy dose suppressed the
respiratory climacteric to a greater extent and also reduced
the peak activity of malic enzyme during ripening (Dubery
et al . 1984). Similarly, 'Kensington Pride' mangoes had
reduced respiratory activity when these were treated with a
200 Gy dose of gamma irradiation (Boag et al . 1990). The
application of other sources of radiation like UV-C in
enhancing the storage life and quality has also gained
momentum in fresh fruits including mango. The exposure
of ripe 'Tommy Atkins' fruit to UV-C irradiation for 10 min
was most effective in suppressing the decay symptoms and

maintaining firmness during storage at 5°C or 20°C for 14
days and did not affect sugars and organic acids levels
(Gonzalez-Aguilar et al . 2001). Irradiation did not have
much detrimental effect on nutritional quality of mangoes.
The changes in carotenoids, sugars, acids and vitamin C
were more strongly influenced by the post-irradiation
storage conditions than irradiation dose (Thomas 1993).
Moy and Wong (2002) found that 'Haden' mangoes
irradiated with 750 Gy did not differ from non-irradiated
fruit with regard to TSS, titratable acidity, ascorbic acid
and firmness. However, a minor decrease in ascorbic
acid was observed when mangoes were irradiated with a
generic irradiation dose of 150 Gy (Bustos et al . 2004). It is
evident from the literature that the results of various studies
were often contradictory with regard to optimum irradiation
doses and their resulting effects in mango. The major factors
that might have influenced the results included genotype,
ripeness stage, time interval between harvesting and irradia-
tion and post-treatment storage conditions. In conclusion,
mango fruit showed delayed ripening if irradiated with the
optimum dose and at the right stage of maturity.

Post-harvest application of calcium
Calcium (Ca), an important mineral nutrient, has a
profound effect on the post-harvest life and physiological
disorders in fresh fruits (Poovaiah et al . 1988). Low levels
of Ca have been associated with poor textural quality, short
post-harvest life and high incidence of physiological
disorders in many fruits including mango (Poovaiah et al .
1988; Wainwright & Burbage 1989). Therefore, post-
harvest application of Ca is of special interest in mango as
it undergoes accelerated softening during post-harvest
handling and storage. In order to increase Ca content in
fruit, pre-harvest sprays (Singh et al . 1993), post-harvest
dipping (Mootoo 1991; Santos et al . 2004; Singh et al .
2000; Yuniarti & Suhardi 1992) and vacuum infiltration
(Joyce et al . 2001; Shorter & Joyce 1998; Tirmazi & Wills
1981; Yuen et al . 1993) of calcium salts, mainly CaCl 2 ,
have been investigated by several researchers on mango.
Two consecutive sprays of 0.6% Ca 2+ as CaCl 2 , 20 and 10
days before commercial harvesting of 'Dashehari' mangoes
resulted into higher Ca levels in skin and flesh of fruit and
also reduced weight loss and restricted ripening changes
during storage under ambient conditions for 10 days (Singh
et al . 1993). Post-harvest CaCl 2 dips in either 4% (Tarmizi
et al . 1988) or 8% (Mootoo 1991; Santos et al . 2004;
Singh et al . 2000; Yuniarti & Suhardi 1992) have been
found to delay ripening in mature green mangoes. Calcium
treatment suppressed the respiration of mango fruit (Joyce
et al . 2001; Mootoo 1991; Singh et al . 1993) which resulted