Avocado - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 424

since it affects pulp firmness, turning it brown and soft;
(2) avocados should never fall onto the ground or be exces-
sively exposed to the sun; and (3) a portion of the peduncle
should remain attached to the fruit to avoid the entry of
pathogens.

cation of ethylene-inhibiting products, for example,
1-methylcyclopropene (1-MCP), which block the action of
ethylene in the cell and therefore prevent the reactions that
lead to ripening such as tissue softening, cell wall disinte-
gration, and pigment degradation (Osuna-Garcıa, 2005).

Quality grades
The Codex Alimentarius (CSA; 1995) states several dis-
positions regarding the quality of avocado fruits, such as
that avocados must be whole, healthy, clean, free of pests
that affect general appearance, free from abnormal external
moisture, and free from chill injury. Additionally, it recom-
mends that the fruits have a cleanly cut peduncle no larger
than 10 mm. The absence of a peduncle is not considered
a defect, as long as its point of detachment on the fruit
is dry and whole. Avocados are classified into three main
categories: Extra, Category I, and Category II. The Extra
classification does not permit any defects, while Category
I and Category II allow defects such as suberosity, healed
lenticels, and sunburn. However, in any case, the pulp must
be free of defects. When the peduncle is present, minor
damage is accepted in Category I, and visible damage in
Category II. For all the classifications the minimum weight
specified for individual fruits must be fulfilled, within a
tolerance of 10%.
The Codex also recommends that avocados should be
prepared and handled according to the corresponding sec-
tions of the International Code of Practices—General Prin-
ciples of Food Hygiene (CIPR, 2003) and the Code of Hy-
giene Practices for Fresh Fruits and Vegetables (CPHFH,
2003).

Current storage and shipping practices
Considering that pests may be controlled, but in most of
the cases are difficult to eliminate completely, the detection
and elimination of affected fruits must precede the current
storage of avocados.
Postharvest diseases of the fruits are normally suppressed
by dry brushing, washing, low-temperature storage, avoid-
ing high levels of humidity, creating modified atmospheres
with lower oxygen and elevated carbon dioxide levels, and
applying some treatments that delay the tissue senescence
(Maftoonazad et al., 2007).
When the fruits are intended for the fresh market, dry
cleaning is preferred to avoid excess moisture that favors
fungus growth. The fruit is cleaned with rotating brushes
and goes to the grading lines, where the selection is carried
out manually or with the help of machines, while consid-
ering the shape, size, and sanitary characteristics of the
fruit as well as all the defects caused by insects, rodents,
mechanical mishandling, and illness. Once the fruit size is
selected and the defective pieces have been discarded, the
fruit is packed. The packaging material varies according to
the market, being cardboard, plastic, or wood. The number
of boxes per pallet varies according to the packinghouse.
Pallets pass immediately into refrigerated chambers, where
they first undergo precooling. The temperature during stor-
age is the most important factor that helps maintain the
quality and extends the shelf life of avocado (Dorantes-
Alvarez et al., 2004).
The optimum storage temperature for the quality preser-
vation of avocado is in the range of 5 ◦ -13 ◦ C for green-
ripe fruit, with physiological or harvest ripeness (the exact
temperature depends on the type of cultivar), and 2 ◦ -4 ◦ C
(36 ◦ -40 ◦ F) for ready-to-consume avocados (Avalos, 2008).
Usually the shipping practices may last from 2 to 17 days,
depending on the destination. In the case of Mexico, export
fruit travels 2 days from Michoacan State to the Gulf of
Mexico in trucks with refrigerated containers, and from
there 15 days more to Europe in cargo ships. Transporta-
tion to Europe represents 30% of the final cost of avocado
(Dorantes- Alvarez et al., 2004).
A new technique that increases postharvest life and
helps

Innovative postharvest technologies
Avocado is a climacteric fruit characterized by a surge in
ethylene production at the onset of ripening. As ethylene
plays an important role in regulating fruit ripening, inhibit-
ing ethylene biosynthesis or its action should slow the ripen-
ing process and extend the postharvest storage life. These
objectives can be accomplished by using coatings or edible
films as well as the combination of ethylene inhibitors and
edible films. Any innovative technologies must be based
in the combination of factors (hurdle technology) to pre-
vent fast ripening and growth of pathogens. The examples
given below demonstrate attempts at developing innovative
postharvest technologies.
Saucedo-Pompa et al. (2009) combined ellagic acid
into candelilla wax matrix and coated avocados. All
samples were inoculated with a concentrated suspen-
sion of Colletotrichum gloeosporioides spores , the main maintain the quality of avocados is the appli-