Agriculture Reference
In-Depth Information
available, beyond the use of cherry pickers and other
elevated platforms (Menzel 2002).
Fruits are left on the cluster during harvesting because
removing single fruits causes damage to the stem end. To
preserve freshness the clusters are cut leaving a portion of
the stem with a few leaves attached. Individual fruits are
later removed with a piece of stem attached but removal
of the stalks is necessary when the fruits are packed indi-
vidually. Mechanical destalking using stiff bristle brushes
is sometimes done in Australia but these methods often
cause damage, particularly when fruit are wet. Lychee is
frequently sold on the panicle in Asia, but loose fruit are
more common in Australia, Europe and North America.
Over-ripe fruit are sweet, but bland (Menzel 2002). Fully
turgid fruit can be mechanically damaged quite easily and
should not be dropped more than 30 cm on to a hard surface
or 60 cm on to other fruit (Bryant
et al
. 2001).
Harvesting takes place every three to four days over a
period of three to four weeks, always during dry periods
since wetting of the fruits at harvest leads to quick decay.
Experienced pickers can collect about 25 kg per hour
(Morton 1987). Average yields range from 1 to 15 T ha
−1
; in
Taiwan yield is about 9.4 T ha
−1
(Anon. 2000) compared with
7.63 in India, 3.83 in Thailand, 2 in Viet Nam (Ha Min Trung
2000), 1.8 in China and 1.66 in Australia (Mitra 2002).
turn-around is necessary, freshly stung fruit can often be
identified by leakage of juice when they are gently
squeezed. Some buyers will not accept cosmetic defects
and so fruit of this type are usually downgraded and not
sent to the central markets, but can be processed or sold at
roadside stalls (Menzal 2002).
Most buyers have at least two grades of fruit but
ultimately grading systems depend on market requirements.
There are no international standards (Paull
et al
. 2002).
Grades are normally based on the colour and size of the
fruit size and the size of any blemish (Paull
et al
. 2002).
There are three grades in Australia; extra, first and second.
Fruit diameter should be larger than 20-25 mm for standard
or second class, and larger than 33 mm for extra class fruit.
Extra class lychees should be defect-free; first class can
have some defects but skin marks must not exceed 60 mm
2
in total on any one fruit (Menzel & McConchie 1998).
All fruit should weigh within 20% of the mean fruit weight
in the container (Fintrac 1994). Soluble solids content
should be greater than 18%, and sulphur residue in the flesh
should not exceed 10 mg/kg (Menzel 2002). As with other
perishable produce, fruit for export has higher standards
than that for domestic markets (Menzel 2002). FAO CODEX
export standards for fresh lychee stipulate a predominantly
red skin, with only a small area of green allowed.
Sorting and grading
These operations should be done in a cool, shady area,
either indoors in a packhouse or shed as in Australia and
the United States or outdoors as is common in Asia. Since
pathogens can accumulate in debris on surfaces and in
waste fruit, good hygiene is needed such that crates and
shelving should be washed with chlorinated water on a
daily basis and damaged fruit removed. Inferior fruit must
be removed during sorting to maintain overall quality. In
Asia sorting may be done on tables or as fruits move along
a series of rollers, as in Australia. Because even small areas
of damage can lead to rapid decay, the whole surface of
every lychee must be examined. This requires good lighting
and close attention to detail. Immature fruit and mature
fruit with mechanical damage from pulled stems, splits,
cracks and insects must be rejected (Menzel 2002).
In Australia, piercing moths such as
Othreis fullonia
(Clerk) and
Eudocima salaminia
(Cramer) may attack fruit
the night before harvest (Menzel & McConchie 1998).
Little damage will be apparent initially but signs of
weeping and tissue darkening are revealed within 24 h.
Therefore, fruit may be kept overnight in high humidity
cool-rooms. This ensures that the stung fruit are detected.
Conversely, if cool-rooms are unavailable or a quick
Disinfestation for quarantine purposes
Sale of lychee from Australia to Japan and the United
States is limited because of plant health concerns about
fruit flies. Holcroft and Mitcham (1996) reported several
methods of killing the insects. However, the fruit may be
damaged in the process and there are residue and consumer
concerns regarding, for example, fumigation with ethylene
dibromide or irradiation with gamma rays (Menzel 2002),
though in the United States, irradiation at 0.25-0.3 kGy
has been used without causing damage to the fruit (Follett
et al
. 1998; Kader 2000b). Hot air has also been tested as a
quarantine disinfectant but is not recommended for lychee
because of the damage the fruit sustains at temperatures
needed to disinfest them of quarantine pests (Sharp 1994;
Kerbel
et al
. 1987).
Lychee for export from Israel to the United States may
be disinfested at low temperature for different periods
depending on the temperature e.g. 10 days at 0°C, 11 days
at 0.55°C, 12 days at 1.11°C, 14 days at 1.65°C or 16 days
at 2.22°C (Fintrac 1992).
Transport to markets
Square or round and padded bamboo baskets are used for
carriage to markets in much of Asia. Rapid water loss
