Agriculture Reference
In-Depth Information
are culled. Similar mechanical injury to litchi tubercles leads to a site for skin
browning. Soluble solids should be greater than 15% and acid levels low.
Longan pre-cooling is carried out by room or forced air cooling. Longan
in plastic baskets can be hydrocooled, though hydrocooled longan should not
be treated with sulfur dioxide. Sulfur dioxide fumigation damages hydrocooled
fruit skin, producing brown spots on both the inner and outer skin surface and
greater SO
2
residues remain on the fruit. Sulfur dioxide treatment of fruit to be
sold as fresh is not approved in the USA and restricted in Europe.
The storage recommendation for longan is 4-7°C and 90-95% RH. Fruit
can be held for 2-3 weeks, though the skin losses it yellowish coloration and
becomes brown. At lower temperatures, there is a rapid loss of eating quality.
At storage temperature less than 5°C, fruits develop a slight of -fl avour after
about 1 week. Peel colour of longan stored at 0°C turns dark brown, while
SO
2
-fumigated longan remain yellowish-brown. The dark brown peel of
longan that develops at very low temperatures is regarded as chilling injury.
When fruits are stored above 10°C, postharvest disease is of concern.
Controlled atmosphere studies have been reported, though modifi ed
atmosphere storage in 0.03 mm polyethylene bags has been tested for 7 days
at room temperature, then 35 days at 4°C. A modifi ed atmosphere of 1-3%
oxygen delays browning and maintains soluble solids and vitamin C content
in litchi. With 1% O
2
treatment and at carbon dioxide greater than 10-13%
an of -fl avour develops and a build-up of ethanol occurs.
Irradiation studies have shown that litchi and longan for export can be
irradiated at 250 Grays. Hot-cold disinfestation protocols and cold treatment
for fruit fl y disinfestation can be used for litchi and longan (Paull
et al.
, 1995).
UTILIZATION
Important producing areas are China, India, Thailand, Taiwan, South Africa,
Mauritius and Australia. Proximate composition of litchi and longan indicates
they are a poor source of calcium, iron, thiamine and ribofl avin and a fair
source of phosphorus, and do not have provitamin A. They are a good source
of niacin and ascorbic acid (Table 9.7). Both fruits are usually eaten fresh
and can be preserved in a variety of ways. Dried litchi and longan, popularly
known as a 'nut', and canning are the most common. Peeled litchi fruit may
be canned in a 40% syrup, containing 0.2% citric acid. Hand-peeling of the
skin is the usual method, though a hot-lye dip and mechanical peeling are
used. The canned litchi, if fresh fruit are not available, are added to rare and
dainty dishes, and restaurants serve delicious litchi dishes with meat or with
syrup dressings.
