Papaya - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 294

generally does not degreen when fruit ripens (Sommer and
Arpaia, 1992).

stage at harvest. Individual packaging of 'Solo' papaya
in low density polyethylene (LDPE) or Pebax-C film pre-
vented CI at 13 ◦ C for 30 days and maintained the ac-
ceptable levels of dietary antioxidants (Singh and Rao,
2005). Exposure of 'Sunrise' papaya fruit to methyl jas-
monate (MJ) vapors reduced CI development and loss of
firmness and inhibited fungal decay during 14-32 days at
10 ◦ C and 4 days shelf life at 20 ◦ C storage. Even more,
the postharvest quality of papaya was enhanced signifi-
cantly by combining the MJ treatments and the modified
atmosphere (MAP) created inside the LDPE film package
(3-5 kPa O 2 and 6-9 kPa CO 2 ) (Gonzalez-Aguilar et al.,
2003). O 2 levels below 2% and/or CO 2 levels above 8%
should be avoided because of the potential for development
of off flavors and uneven ripening.
Heat injury occurs when papayas are exposed to tempera-
tures above 30 ◦ C for longer than 10 days, or to temperature-
time combinations beyond those needed for decay and/or
insect control. The symptoms are uneven ripening, blotchy
ripening, poor color, abnormal softening, surface pitting,
and accelerated decay. Quick cooling to 13 ◦ C after heat
treatments minimizes heat injury. Paull (1995) observed
that disruption of the softening process and fruit heat sen-
sitivity correlated to harvest date, the mean of the rain-
fall, evaporation, and the minimum and maximum tem-
peratures in the three days before harvest. Thus when
3-day mean minimum temperature was higher than 22.4 ◦ C,
fruit injury did not occur. Moreover, the fruit with low meso-
carp calcium was less sensitive to heat treatments.
Skin freckles (SF) are a papaya skin disorder that depre-
ciates the fruit appearance and hampers its marketing. The
SF are gray or brown in color, ranging from very small
points to 10 mm diameter dark halos. They have been ob-
served in fruits over 40 days after anthesis, being more
apparent as the fruits become more developed, closer to
harvesting stage (Ventura et al., 2003). The SF is reported
to occur mainly on fruits developing in those months with
soil water deficiency and lower temperature. In the papaya
tree, fruits more exposed to sun radiation presented higher
intensity of SF (Kaiser et al., 1996). Even more, high cal-
cium contents associated with high temperature and large
diurnal temperature fluctuations contribute to greater cell
wall rigidity, facilitating increased turgor pressure, result-
ing in the rupture of the latex vessels and latex leaking
(Campostrini et al., 2010).
Pulp gelification is a disorder that is difficult to iden-
tify because the external appearance of the fruit does not
change while the pulp turns darker, rigid, and translucent
looking, like an overripe fruit. Schripsema et al. (2008) re-
vealed through a methabolonic investigation that affected

Packinghouse operations
Papaya skin fragility requires careful handling to prevent
skin blemishes and bruising during postharvest operations.
The occurrence of “green islands” areas of skin that remain
green and sunken when the fruit is fully ripe are induced
by mechanical injury (Quintana and Paull, 1993). First, pa-
payas are washed to remove latex and debris and sorted to
separate cull and ripe fruits, off size, and defective fruits.
Then papayas are treated to control postharvest decay and
to increase the shelf life of the product. Depending on the
volumes of fruits, washing, treatment, and grading can be
carried out using mechanized or manual systems. Grading
in each carton is required in terms of size, sex (shape),
and stage of ripeness. Fruits are packed in a single layer
cardboard or polystyrene carton and then protected from
damage with poly socks or paper wraps and with shredded
paper in the base of the carton. Individual labels can be
attached to the fruit for appearance and recognition. Carton
net weight is dependent on the importer, ranging from
3.5 to 5 kg, and must not be overfilled.
The best storage and transport conditions for mature-
green to 1/4 yellow papaya are 13 ◦ C; for partially
ripe papaya (1/4-1/2 yellow) 10 ◦ C; and for ripe ( 1/2

yellow) 7 ◦ C combined with 90-95% relative humidity
(O'Hare, 1993).

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Physiological disorders and their control
Chilling injury (CI) symptoms include pitting of the skin,
scald, hard lumps in the pulp around the vascular bundles,
water soaking of the flesh, abnormal ripening with blotchy
discoloration, skin scald, hard core (hard areas in the flesh
around the vascular bundles), water soaking of tissues, and
increased susceptibility to decay (Thompson and Lee, 1971;
El-Tomi et al., 1974; Chan et al., 1985; Chen and Paull,
1986; Ali et al., 1993). Temperatures below the best storage
and transport conditions negatively affect fruit ripening and
therefore the development of the sensorial characteristics
expected by consumers. Thus 1/2 yellow papaya developed
CI symptoms as pitting on the peel when stored 15 days at
5 ◦ C (Wongs-Aree et al., 2005) or 21 days if the maturity
was 3/5 yellow (Chen and Paull, 1986). Proulx et al. (2005)
observed that CI symptoms developed faster and were more
severe at color break stage than further ripe.
CA have been used to increase the shelf life and to pre-
vent from CI development in some fruits. Thus posthar-
vest life potential at 13 ◦ C was 2-4 weeks in air and
3-5 weeks in CA, depending on cultivar and ripeness