Agriculture Reference
In-Depth Information
Figure 8.5
Avocado in consumer packages.
Courtesy of Dr Mary Lu Arpaia, University of
California, Riverside, CA.
Figure 8.4
Packed avocado. Courtesy of Dr Mary Lu
Arpaia, University of California, Riverside, CA.
can be more accurate for uniform package and presentation
in the market place, but requires higher capital cost. The
calibre is the number of fruit that can be packed in a single
box. Once the fruit size is selected, and the defects have
been discarded, it is packed. The packaging material varies
according to the origin and the destination market, being
cardboard, plastic or wood (wood is not used in Europe).
The most common containers used for avocado are single
wall corrugated fibreboard (Figure 8.4) or wooden boxes.
The first usually have a capacity of 4 kg with one layer of
fruit, while the second usually contain 10 kg, and the fruit is
placed in bulk. In California, avocados are packed in a sin-
gle layer of 5.6 kg flats or trays, or a double layer of a total
of 11.3 kg lugs and 11.3 kg volume-fill boxes. Returnable
plastic containers (RPCs) are being increasing used in parts
of the United States and Europe. In some European
supermarkets 100% of the avocado is delivered in RPCs.
There is also increased usage of pre-packed units such as
polyethylene containers (clam shells) (Figure 8.5) or mesh
bags. For Florida avocados, the common packages used
are: single-layer, 6.1 kg flats; two-layer, 12.5 kg lugs;
15.9 kg cartons and 4.5 kg natural packs.
Individual boxes are then palleted, where boxes are
stowed and tied together. Pallets should comply with the
measurements established by the containers they will be
carried in. The number of boxes per pallet varies, but is
commonly 264 boxes of 4 kg each and less number of
boxes when package weight is 6 kg, with a total of 5280
boxes (4 kg) per container. Pallets are then immediately
pre-cooled, and then refrigerated until they are loaded into
the transport containers.
COOLING AND STORAGE
Pre-cooling
Pre-cooling soon after harvest is recommended to remove
field heat. Removal of excess heat prior to, or immediately
after packing reduces the refrigeration required during
shipment to maintain fruit at recommended temperatures and
to provide better control of the ripening process. This is criti-
cal where long storage periods or long transport shipments
are required or where field temperatures are high (>25°C).
Pre-cooling diminishes or slows down the metabolic rate,
ethylene synthesis and its action on the fruit, loss of texture,
fruit ripening, and fungal infections. Ideally, there should not
be more than six hours from harvest to pre-cooling, and
when this is not possible, the harvested fruit should not be
allowed to reach an internal temperature higher than 26°C in
the field and during transportation to the packinghouse.
Forced-air cooling is the method best suited for avocado
pre-cooling. It is carried out until the temperature in the fruit
reaches 6-7°C for 'Fuerte' and 'Hass' avocados. The time
required to achieve these temperatures varies according to
the initial temperature of the fruit, temperature and velocity
of the air, and the final temperature of the fruit. Hydro-cooling
of 'Hass' is also used commercially. It is of prime importance
to assure that temperature will not be lower than that
established for the fruit, otherwise CI can occur.
Refrigeration
Temperature is no doubt the single most important factor in
fruit storage. All biological processes are controlled by
temperature, including fruit quality and ripening. The rate
