Longan and Carambola - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 219

and 5% CO 2 had less browning and higher TSS and ascor-
bic acid content compared with those stored in air. Zhang
et al. (2002) showed that 'Chike' longan packed in 0.06-
mm-thick PE film bags flushed with N 2 andstoredat5 ◦ C
had extended storage life, better fruit quality, and reduced
browning compared with unpackaged fruit. However, an
increasing of ethanol content and off flavors are detected
when CO 2 concentrations exceed 10-13% (Lu et al., 1992;
Lin et al., 2001a, 2002b).

the fumigation chamber (Ratanachinakorn and Sukwiboon,
2004). According to Codex standards, the SO 2 in aril should
not exceed 10 μ g/g (ppm) (Codex Alimentarius Commis-
sion, 1999). In Thailand, it is recommended that longan be
fumigated with 200-250 ml SO 2 /kg fruit so that the SO 2
residues of 1,500-2,200 mg/kg and < 10 mg/kg are detected
in the pericarp and in aril, respectively (Ratanachinakorn
and Sukwiboon, 2004). Since many importing countries are
concerned about sulfur residues in fresh fruit, hazard analy-
sis critical control point (HACCP) and good manufacturing
practices (GMP) have been introduced as safety assurance
systems (Tongdee, 1997).
Owing to increasing concerns about SO 2 residues in the
fruit, particularly for people who are sensitive to sulfites
(Tongdee, 1994), many researchers have investigated SO 2 -
alternative chemicals/methods to prevent postharvest loss
of longan during storage such as citric acids, acetic acid, ac-
etaldehyde, surface coating, irradiation, and heat treatment
(Lu et al., 1992; Peng and Cheng, 1999; Ratanachinakorn
and Sukwiboon, 2004).

Sulfur dioxide fumigation
Sulfur dioxide fumigation is an effective treatment for
preventing decay (fungal growth) of longan during stor-
age. Short-term SO 2 fumigation combined with low stor-
age temperature is currently considered to be the prac-
tical method of storage of longan fruit (Wong, 2000).
Sulfur dioxide fumigation generally extends shelf life of
longan to 4-6 weeks at storage temperature of 0 ◦ -2 ◦ C
(Ratanachinakorn and Sukwiboon, 2004). 'Shixia' longan
fumigated with sulfur dioxide for 20 min could maintain
good quality after 28 days of storage at 4 ◦ C without chill-
ing injury (Han et al., 2000). In addition to decay control,
SO 2 helps inhibiting browning and helps bleach longan
skin to a bright yellow color (O'Hare and Prasad, 1991b;
Tongdee, 1994). However, SO 2 injury of the fruit may oc-
cur when excessive concentrations and exposure times are
applied. The symptom of injury usually appears as irreg-
ular rusty-brown circles or lines on the underside of the
pericarp a few days after fumigation (Tongdee, 1997). Ap-
plication of high concentration of SO 2 could result in a
dull white color of the aril (Tongdee, 1994). Although
after the first few days after fumigation, sulfur residues
decrease rapidly, sulfur residues in the aril occasionally
still exceed national and international limits. For effec-
tive SO 2 fumigation, it is necessary to consider many
factors, including the concentration of SO 2 , fumigation
chamber size, quantity of fruit, absorptivity of the fruit,
the volume of free space in the chamber, the absorptivity
of the containers, the type of packaging materials, and
potential losses through leakage (Holcroft et al., 2005).
Gaseous SO 2 can be derived from burning sulfur pow-
der, vaporizing liquid SO 2 held in a pressurized cylinder,
or dissociation of sulfite compounds (Neamprem, 1992).
Metabisulfite pads have been used on longan, but at the high
concentration, the pulp was tainted (O'Hare and Prasad,
1991b). Slow-release systems of metabisulfite pads also
cause high SO 2 levels to build up and are more difficult
to control than SO 2 fumigation (Huang, 1995). A forced
air-gas mixing and diffusing system is usually recom-
mended to ensure good mixing and distribution of SO 2 in

Fungicides
The application of fungicides before packing helps ex-
tending the shelf life of longan to 5-7 days at ambient
temperature by controlling browning and fungal contam-
ination. Fungicides commercially used include benomyl,
thiabendazole, and iprodione (Wara-Aswapati et al., 1989;
Lu et al., 1992; Zhou et al., 1997b; Pan and Zhang, 1999).
Benomyl fungicide efficacy was enhanced by application
in a hot-water bath at 52 ◦ C (Peng and Cheng, 1999). Al-
though benomyl is a very effective fungicide, it is no longer
registered as a postharvest chemical in many countries due
to potential oncogenic risks (National Research Council,
1987). Thiabendazole could be effectively used as a beno-
myl alternative (Su and Yang, 1996; Zhou et al., 1997a).
Treatment with 0.1% thiabendazole in combination with
0.05% iprodione gave even more effective control of lon-
gan fruit decay (Zhou et al., 1997b).

Disinfestation
Longan is a fruit fly host, and thus disinfestation is required
by many importing countries, especially the United States
and Japan (Jacobi et al., 1993; Armstrong, 1994; Campbell,
1994; USDA, 1996; McGuire, 1998). Cold, heat, and
gamma irradiation treatments are acceptable for use in lon-
gan (McGuire, 1998; Follett and Sanxter, 2001).
Cold treatment at 1.1 ◦ C for 15 days has been suggested
as a method for insect disinfestation of longan. However,
storage at this condition resulted in chilling injury mani-
festing as patches of bronze discoloration on the pericarp