Agriculture Reference
In-Depth Information
large trees is dii cult and time-consuming. The trend of the last 20 years is
to maintain tree height at less than 3 m. This height allows all management
practices and harvesting to be carried out from the ground, which is faster and
more ei cient.
Harvesting is not done in the afternoon in China, as fruit colour is said to
become dull more rapidly, or on rainy days, as wet fruit is said to break down
rapidly. Panicles of fruit are packed in straw baskets or cartons containing
15-20 kg of fruit. Green leaves are also packed with the fruit, to reduce
damage in transit and assist in providing moisture and preserving fruit colour.
Harvested fruit are never exposed to sun, to prevent rapid drying.
Longan fruit maturity is judged by fruit shape, skin colour and the fl avour
of each cultivar. Most fruit can be picked from a tree with one harvest, unless
multiple fl owerings have occurred. No defi nite harvest index exists for longan,
but growers usually note the changes in skin appearance: mature fruit develop
a smooth and darker skin. Fruits are clipped from the stem, as hand removal
often leads to some of the skin being removed. One-piece fi breboard crates,
either 4.5 kg or 2.25 kg, with a plastic liner, are used, if not already packed in
polystyrene punnets.
Postharvest treatments
The major problem in marketing these two fresh fruits is the rapid skin
browning, which makes them unattractive, although the aril remains edible
(Paull and Chen, 1987). In many Asian countries fruits are sold still attached
to the panicle in bunches, while in western countries individual fruits in
punnets are marketed. Much of the postharvest research has been directed
towards the prevention of pericarp browning in storage and marketing of
fresh fruit. The fi eld skin colour of both litchi and longan can be retained by
a sulfur dioxide acid treatment applied before insect disinfestation. All longan
exported from Thailand are so treated, as are much of the litchi from some
other countries. The sulfur dioxide treatment is not approved in the USA.
Retention of litchi red pericarp colour for longer periods has been
demonstrated by wrapping fruit in PVC fi lm or bagging in polyethylene bags
and placing in storage temperatures of 0-10°C (Paull and Chen, 1987).
Commercial quantities (5.4 kg) of litchi and longan packaged in large
polyethylene bags and twisted closed, or individual fruits in punnets placed
in cardboard cartons and sealed are best stored at 2°C for up to 32 days. At
the retail level, all fruit not on display should be kept under refrigeration,
preferably as close as possible to 0-2°C. If surface transportation is used
instead of air freight, properly packaged fruit should be shipped at 0-2°C. Skin
colour and fl avour of fruit is retained for about a month.
Grade standards are similar for both species and are generally set between
the shipper and buyer. Small, poorly coloured, immature or damaged fruit
