Agriculture Reference
In-Depth Information
are sometimes used. The harvesters stand on the platform, which is adjusted
to be at fruit height, as an operator slowly drives it down the rows.
The degree of ripeness for harvesting depends upon distance to markets.
Fruits may be one-quarter to one-half ripe for local markets. Fruits to be
transported long distances or exported are harvested at colour break to one-
quarter ripe, depending upon the cultivar's ripening characteristics and
season. Colour assessment is based upon the judgement of pickers. The Hawaii
grade standard requires fruits to have 11.5% total soluble solids with the
colour-break stage normally meeting this standard. Green immature fruit do
not ripen well and have a total soluble solids value that is frequently less than
10%, giving a bland taste.
Postharvest treatment
The need for postharvest treatments depends upon the importing countries.
Overseas markets require disinfestation treatments to eradicate fruit fl y larvae
and eggs from the fruit before shipment. The vapour heat method was the
fi rst disinfestation treatment used in the 1950s, and after the banning of the
fumigant ethylene dibromide in 1984, vapour heat and forced heat treatment
again became the industry standard. The fruit core temperature in these
heat treatments reaches at least 47.2°C and the total treatment time is about
7 h (Paull and Chen, 1990). The alternative method is irradiation at a dose
of about 250 Gy. This low irradiation dose sterilized the fruit fl y larvae and
eggs, preventing them from completing their life cycle. Irradiation at 250 Gy
does not provide postharvest disease control and needs to be coupled with a
postharvest disease control programme.
A fungicide-wax combination is recommended prior to packing (Paull and
Chen, 1990). Incidence of storage diseases can be reduced by fi eld spraying
and proper care in harvesting and handling to avoid wounding and bruising.
Skin injury is a major problem and is caused mostly by impact and abrasion
during harvesting (Quintana and Paull, 1993). The latter is mainly caused
when harvested fruits are being dropped into fi eld bins with rough side walls
and bottom. Careful handling is essential to avoid these unsightly blemishes,
which provide an invasion site for postharvest rots.
Following the disinfestation treatment, papayas are packed into cartons in
a screened area to prevent re-infestation by fruit fl ies. Defective fruits are culled
before and/or after disinfestation and fruits are graded for size and colour
and hand-packed into cardboard cartons with a capacity of about 4.5-10
kg. Cartons from areas requiring insect disinfestation are fully sealed to meet
regulatory requirements, while fruits from other areas can be in open-topped
cartons. Count size ranges from 6 to 18, depending upon fruit and carton size.
Fruits are marketed as colour break, one-quarter ripe, half-ripe and three-
