| Dimocarpus longan|
Dimocarpus longan, commonly known as the longan (UK: //; US: //, //), is a tropical tree that produces edible fruit. It is one of the better-known tropical members of the soapberry family (Sapindaceae), to which the lychee also belongs. It is native to Southern Asia.
The longan (simplified Chinese: 龙眼; traditional Chinese: 龍眼; pinyin: lóngyǎn; Pe̍h-ōe-jī: Lêng-géng; literally: "dragon eye"), is so named because it resembles an eyeball when its fruit is shelled (the black seed shows through the translucent flesh like a pupil/iris). The seed is small, round and hard, and of an enamel-like, lacquered black. The fully ripened, freshly harvested fruit has a bark-like shell, thin, and firm, making the fruit easy to peel by squeezing the pulp out as if one is "cracking" a sunflower seed. When the shell has more moisture content and is more tender, the fruit becomes less convenient to shell. The tenderness of the shell varies due to either premature harvest, variety, weather conditions, or transport/storage conditions.
The Dimocarpus longan tree is a medium-sized evergreen that can grow up to 6 to 7 metres (20 to 23 ft) in height. It is somewhat sensitive to frost. Longan trees prefer sandy soil. While the species prefers temperatures that do not typically fall below 4.5 °C (40 °F), it can withstand brief temperature drops to about −2 °C (28 °F). Longans usually bear fruit slightly later than lychees.
The wild longan population have been decimated considerably by large-scale loggings in the past, and the species used to be listed as Vulnerable on the IUCN Red List. If left alone, longan tree stumps will resprout and the listing was upgraded to Near Threatened in 1998. Recent field data are inadequate for a contemporary IUCN assessment.
The fruit is sweet, juicy and succulent in superior agricultural varieties. The seed and the shell are not consumed. Apart from being eaten fresh and raw, longan fruit is also often used in Asian soups, snacks, desserts, and sweet-and-sour foods, either fresh or dried, and sometimes preserved and canned in syrup. The taste is different from lychees; while longan have a drier sweetness, lychees are often messily juicy with a more tropical, sour sweetness.
Dried longan are often used in Chinese cuisine and Chinese sweet dessert soups. In Chinese food therapy and herbal medicine, it is believed to have an effect on relaxation. In contrast with the fresh fruit, which is juicy and white, the flesh of dried longans is dark brown to almost black.
A peeled longan fruit
|Nutritional value per 100 g (3.5 oz)|
|Energy||251 kJ (60 kcal)|
|Dietary fiber||1.1 g|
|Aspartic acid||0.126 g|
|Glutamic acid||0.209 g|
Link to USDA Database entry
Vitamin B6/Folate values were unavailable
Percentages are roughly approximated using US recommendations for adults. |
Source: USDA Nutrient Database
Potassium chlorate has been found to cause the longan tree to blossom. However, this causes stress on the tree if it is used excessively, and eventually kills it.
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Notes and references
- "Dimocarpus longan". IUCN Red List of Threatened Species. IUCN. 1998: e.T32399A9698234. 1998. doi:10.2305/IUCN.UK.1998.RLTS.T32399A9698234.en. Retrieved 5 Sep 2016.
- "Dimocarpus longan". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew. Retrieved 5 Sep 2016 – via The Plant List.
- "USDA GRIN Taxonomy".
- Boning, Charles R. (2006). Florida's Best Fruiting Plants: Native and Exotic Trees, Shrubs, and Vines. Sarasota, Florida: Pineapple Press, Inc. p. 125.
- Fruits of Warm Climates: Longan
- Teeguarden, Ron. "Tonic Herbs That Every Qigong Practioner Should Know, Part 2". Qi Journal.
- Manochai, P.; Sruamsiri, P.; Wiriya-alongkorn, W.; Naphrom, D.; Hegele, M.; Bangerth, F. (February 12, 2005). "Year around off season flower induction in longan (Dimocarpus longan, Lour.) trees by KClO3 applications: potentials and problems". Scientia Horticulturae. 104 (4): 379–390. doi:10.1016/j.scienta.2005.01.004. Retrieved November 28, 2010.
- Yang B, Jiang YM, Shi J, Chen F, Ashraf M (2011). "Extraction and pharmacological properties of bioactive compounds from longan (Dimocarpus longan Lour.) fruit – A review". Food Research International. 44: 1837–1842. doi:10.1016/j.foodres.2010.10.019.
- Fruits of Warm Climates: Longan
- Longan Production in Asia from the Food and Agriculture Organization of the United Nations