Agriculture Reference
In-Depth Information
loss and facilitate special treatments. Most tropical fruits are hand-packed
either by weight or by a fi xed number per container.
Postharvest cooling is carried out to reduce the rate of respiration and
ethylene ef ects. Cooling also reduces water loss from the fruit, rot organism
growth and the development of mechanical injury symptoms. The most
common method used is room cooling, where fruits are placed in a refrigerated
room that is above the chilling injury threshold for the fruit. Room cooling
is slow and, if the cartons are stacked on a pallet, can take days to reach the
room temperature setting. Forced air cooling draws refrigerated cold air
through the cartons themselves and thereby increases the rate of cooling.
Another less frequently used method for tropical fruit is hydro-cooling, where
cold water is used as the coolant instead of air and is faster.
POSTHARVEST INSECT DISINFESTATION
Postharvest treatments are required to disinfest economically important host
fruit, vegetables, dried fruits and vegetables, nuts, fl owers and ornamentals
of insect pests before they are moved through marketing channels to areas
where the pests do not occur (Paull and Armstrong, 1994). Examples of these
pests are various tephritid fruit fl ies and mango seed weevil. Alternatively, the
importing country has a 'zero tolerance' for all live insects, whether or not they
are economically important. While there are many insects and arthropods of
quarantine importance, fruit fl ies represents a major group of destructive pests
that attack a wide range of fruit, including most tropical fruit. Disinfestation
treatment technologies and strategies include pest-free zones, non-host status,
fumigation, irradiation, insecticides, heat and cold treatments, controlled
or modifi ed atmospheres, and combinations of these treatment methods.
Inspection by regulatory personnel is required to ensure quarantine treatment
procedures and regulations, including handling requirements to preclude
reinfestation after treatment, are followed.
Many of these disinfestation treatments cause damage to the commodity
that limits postharvest life and reduces quality (Paull and Chen, 2000).
Research ef orts are directed to the use of physical disinfestation treatments,
such as heat, cold and irradiation. Such physical disinfestation treatments
are non-polluting and they leave no toxic residues. No single quarantine
treatment or system can be expected to work equally against all insects
or for all host fruits, and the response to any treatment can vary greatly
between commodities.
POSTHARVEST DISEASE
During growth and development fruits are continually being attacked by
pathogens. However, disease is only seen when the fruit is injured and the
