Longan and Carambola - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 216

Table 12.2. Production and export of longan in Thailand in 2005-2009.

Export Amount (tons)

Area Production

Year (hectares) (metric tons) Fresh Dried Canned Frozen

2005 131,358 712,178 113,651 133,646 12,669 787

2006 139,220 471,892 119,430 78,390 11,206 354

2007 150,245 495,457 160,013 112,752 13,484 371

2008 154,693 476,930 168,285 91,567 26,130 346

2009 154,995 598,872 220,400 142,800 43,160 210

Source: OAE (2010).

by fruit weight, skin color, sugar content (total soluble
solids; TSS), titratable acidity (TA), sugar to acid ratio
(TSS/TA), flavor, and/or days after anthesis (Jiang et al.,
2002). Usually, longan is harvested when the skin becomes
smooth and the color changes to yellowish brown or light
brown, depending on the cultivar (Wong, 2000). In 1994,
Wara-Aswapati et al. recommended using the total solu-
ble solids as a maturity index, and established a minimum
maturity standard of 15.5 ◦ -16 ◦ Brix. Kader (2009a) recom-
mended a minimum of 20% soluble solids may be used as
a maturity index for longan. Li and Li (1999) investigated
maturity standards for 'Shixia' longan fruit and reported
the optimal harvest period as 75-78 days after anthesis due
to the highest sugar to acid ratio.

CONSUMPTION TRENDS, SIGNIFICANCE
IN HUMAN HEALTH
An increase in the consumption of longan fruit and its
processed products could be expected, based on an increas-
ing export amount of longan and processed products from
Thailand (Table 12.2). In China, longan is traditionally used
to treat palpitation due to fright, insomnia, and poor mem-
ory (Wu, 2005). An extract of longan with adenosine active
principle was tested for its anxiolytic-like (or antianxiety)
effect by application of the anticonflict method in mice
(Okuyama et al., 1999). The extract indicated significant
positive activity and also contributed to an analgesic ef-
fect observed through writhing. Three unusual amino acids
have been isolated from the longan seeds and identified as
antimutagens against spontaneous mutation of Salmonella
typhimurium TA100 (Minakata et al., 1985). Soong and
Barlow (2005) identified several phenolic compounds in
longan seeds that could be health-beneficial bioactive
compounds.

Harvesting
Longan fruits are harvested by removing the whole clus-
ter together with one or two leaves using knife or scissors.
Fruit should be harvested early in the day to minimize water
loss and fruit-heating from the sun (Holcroft et al., 2005).
Harvesting during rainy weather should be avoided due
to the increasing risk of breakdown after harvest (Wong,
2000). Unless there is a great variation in maturity on
a tree, all fruits are usually harvested at once. Posthar-
vest quality could be maintained by shading after harvest
and minimizing any delay between harvesting and cool-
ing facility (Tongdee, 1997; Lin, 2002). After harvesting,
the panicles should be handled carefully without dropping.
In Thailand, longan fruits are packed with approximately
15-cm stalk intact in round woven bamboo baskets lined
with longan leaves. For export and further processing, fruits
are clipped from the panicles; sorted for size, insect dam-
age, and skin blemishes; and then placed in corrugated
boxes or plastic baskets or bulk trays (Huang, 1995; Wong,
2000; Ratanachinakorn and Sukwiboon, 2004).

POSTHARVEST PHYSIOLOGY AND
STORAGE TECHNOLOGIES

Respiration and ethylene production
Longan has a nonclimacteric respiratory pattern. The res-
pirationrateof3.5-11.3mgCO 2 /kg/hr at 5 ◦ C, 16-25 mg
CO 2 /kg/hr at 10 ◦ C, and 30-53 mg CO 2 /kg/hr at 20 ◦ Cwere
reported by Liao et al. (1983). Zhang et al. (2002) mea-
sured respiration rates of 8 mg CO 2 /kg/hr at 3 ◦ C, 12 mg
CO 2 /kg/hr at 7 ◦ C, 54 mg CO 2 /kg/hr at 10 ◦ C, and 86 mg
CO 2 /kg/hr at 25 ◦ C. Kader (2009b) reported longan res-
piration rates of 8-12 ml CO 2 /kg/hr at 10 ◦ C(50 ◦ F) and
15-25 ml CO 2 /kg/hr at 20 ◦ C.
Longans produce relatively low concentrations of ethy-
lene after harvest. The low ethylene production rate of
longan as < 0.1 μ lC 2 H 4 /kg/hr at 20 ◦ C was report by