- Mrs Sing Ching Tongdee
-
Thailand Institute of Scientific and Technological Research
196 Phaholyothin Road, Chatuchak, Bangkok, Thailand 10900
Paper presented at the Lychee Post-harvest Workshop
held on 8 - 9 January 1998, organized by the South African Litchi Growers' Association
- 1998
The lychee or litchi (Litchi chinensis Sonn) is one of the most highly praised fruits in Asia. The flesh or aril of a mature fruit is firm or turgid and has a delicate aromatic flavour. The sweet taste, with a tinge of sourness, is exotic yet easily liked once tried. Its appeal also lies in the attractive colour befitting the Chinese empress.
Summary:
- Lychee (Litchi chinensis) is a highly prized fruit in Asia, with a firm, aromatic, sweet, and slightly sour taste, and its appeal is enhanced by the attractive red color of its rind, which is important for consumer acceptance.
- Thailand produces mostly the Hong Huai cultivar (over 90%) mainly in the northern region, with the bulk for domestic consumption and canning, and a smaller portion exported fresh primarily to Hong Kong and neighboring countries.
- Major challenges in export include high fruit perishability, rapid browning of the rind post-harvest due to dehydration and enzymatic browning, and losses during long sea transit as well as high airfreight costs leading to a preference for maintaining rather than expanding market share.
- The rind color comes from anthocyanins formed under the influence of sugar concentration and light; however, the color fades quickly after harvest due to oxidation and enzymatic browning, accelerated by fine cracks in the rind that cause dehydration.
- Sulphur dioxide (SO2) fumigation is widely used in Thailand and other export countries to control browning and fungal decay, but it has drawbacks such as off-flavors, bleaching of fruit color, risk of residue exceeding market limits, and injury symptoms on certain cultivars or maturity stages.
- Alternatives to SO2 fumigation like heat-acid treatments and liquid sulphating agents have been explored; however, challenges remain including pulp browning, rind degradation, pigment staining, and variability between cultivars.
- Post-harvest handling practices include harvesting in cool conditions, hydrocooling before transport to reduce heat damage, and maintaining a cold chain to prolong shelf life, although lychee is susceptible to chilling injury below 4-7°C.
- Packaging innovations including wax coatings, modified atmosphere, and ventilation control are under investigation, but optimal solutions balancing moisture retention and fungal control are still needed.
- SO2 residue detection and regulation are critical issues internationally, with some markets enforcing strict residue limits or zero tolerance, prompting ongoing research and regulatory discussions for safe, acceptable treatment levels.
- The article emphasizes the need for continued research into incremental improvements, reliable information, and careful management to enable sustainable lychee export markets using a blend of practical technologies and good management.