Agriculture Reference
In-Depth Information
to the destruction of chlorophyll with
subsequent yellowing; and (iv) it promotes
senescence (Salveit, 2003b).
A change induced by ethylene can be
beneficial for one species (ripening of
tomato fruit) or harmful for another species
(yellowing in broccoli).
The application of ethylene must be
done at a proper temperature and at the
proper time of development. Field applica-
tion of ethylene is usually done by applying
products that release ethylene (such as
ethephon), whereas in the store, pure ethyl-
ene or ethylene generated from alcohol, is
used in sealed chambers.
In order to avoid the action of ethylene
in greenhouses or in closed environments
(store chambers, transport vehicles) proper
ventilation is required to prevent the accu-
mulation of biologically active levels of
this gas (Photo 15.3). Other ways of avoid-
ing the effects of ethylene are: (i) to prevent
its contact with plant tissues; (ii) storage at
low temperature; or (iii) using inhibitors of
the perception of ethylene, such as CO
2
,
silver thiosulfate (used for flowers) and
MCP (methylcyclopropane) (Salveit,
2003b). In the same way, it is possible to
block the response of the plant tissues to
ethylene using controlled atmospheres or
modified atmosphere packaging (MAP; see
section 15.5).
In the storage and transport of fruits
and vegetables it is essential to properly
combine the horticultural products that
will be mixed in the same enclosure, to
avoid undesired effects caused by ethyl-
ene generated by some of them (climac-
teric fruits) on the others and, if ethylene
is produced, to prevent its accumulation
by means of ventilation, absorption or
blockage.
15.5
Postharvest Handling
The ideal management of vegetables starts
with proper handling at harvest, an opera-
tion that should be done preferably in the
morning, when the ambient temperature is
lower. The harvested product must be pro-
tected from the sun, and whenever possi-
ble, to proceed immediately to their
pre-cooling (fast cooling before processing)
if such facilities are available.
The most popular pre-cooling proce-
dure is by forced air, which circulates air at
low temperature (Tompson, 2003).
Many vegetables are sensitive to cool-
ing (chilling), that is they get damaged if
Photo 15.3.
Handling and packaging buildings must be ventilated to avoid the action of ethylene.
