Longan Fruit
Longan fruits are similar to lychees but come from a
different family of plants, Sapindaceae.
They are known in Chinese as “dragon eyes” and in Indonesian as “cat’s
eyes,” as they are a perfectly round fruit.
When their light brown shell (husk) is removed, they reveal translucent
skin and a dark seed that shows through, appearing like the dark pupil/iris,
which is what gives them their name.
Longan crops are grown in southern China, Taiwan, Thailand, Malaysia,
Indonesia, Cambodia, Laos, Vietnam, India, Sri Lanka, Philippines, Australia,
United States, Mauritius and Bangladesh.
Longan trees can produce thousands of ping-pong ball
sized fruits that are eaten fresh or dried. They look a bit similar to
‘langsat’ and ‘longkong’. The fruits (also called Dragon Eye fruit) can be
eaten fresh, but can also be dried. Dried fruits have a dark colour and are
eaten as snacks or can be used in cooking.
Longan is native to South and Southeast Asia. A lot of fruits are produced
in Thailand, China and Taiwan.
It is a subtropical tree but it grows well in the
tropics. It needs a prominent change of
seasons for satisfactory flowering. A cool season of 2-3 months results in
abundant flowering. Round fruits with a
thin, brown-coloured inedible shell. The flesh of the fruit is translucent
white, soft, and juicy. It surrounds a big, black seed. That’s why it is called
"Dragon’s Eye."
This is a symmetrical, evergreen tree with dense dark
green foliage. Depending upon climate and soil type the tree may grow over 100
ft tall. However, in south Florida, trees typically grow to 30-40 ft in height
and width. Longan is tolerant of dry soil conditions. Withholding or reducing
watering during the late summer/early fall through winter is recommended to
stop or reduce excessive vegetative growth and enhance subsequent flowering
during the spring. However, for optimum fruit production and quality, regular
irrigation is recommended from flowering through harvest.
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 were "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 leaves are oblong and blunt-tipped, usually 4–8
inches (10–20 cm) long and 2 in (5 cm) wide. The leaves are pinnately
compounded and alternate. There are 6 to
9 pairs of leaflets per leaf and the upper surface is wavy and a dark,
glossy-green. Depending upon climate and
soil type the tree may grow to over 100 feet (30 m) in height, but it typically
stands 30–40 ft (9–12 m) in height and the crown is round. The trunk is 2.5 ft (0.8 m) thick with corky
bark. The branches are long and thick,
typically drooping.
The Longan tree produces light-yellow inflorescences at
the end of branches. The inflorescence
is commonly called a panicle and are 4–18 in (10–46 cm) long, and widely
branched. The small flowers have 5 to 6
sepals and petals that are brownish-yellow. The flower has a two-lobed pistil
and 8 stamen. There are three flower types, distributed throughout the
panicle; staminate (functionally male),
pistillate (functionally female), and hermaphroditic flowers. Flowering occurs
as a progression.
The longan is believed to originate from the mountain
range between Myanmar and southern China. Other reported origins include India,
Sri Lanka, upper Myanmar, north Thailand, Kampuchea (more commonly known as
Cambodia), north Vietnam and New Guinea.
Its earliest record of existence draws back to the Han Dynasty in 200
BC. The emperor had demanded lychee and longan trees to be planted in his
palace gardens in Shaanxi, but the plants failed. Four hundred years later,
longan trees flourished in other parts of China like Fujian and Guangdong,
where longan production soon became an industry.
Despite its long success in China, the longan is
considered to be a relatively new fruit to the world. It has only been
acknowledged outside of China in the last 250 years. The first European acknowledgement of the
fruit was recorded by Joao de Loureiro, a Jesuit botanist, in 1790. The first
entry resides in his collection of works, Flora Cochinchinensis.
Longan fruit with flesh, seed, and peel visible. The fruit hangs in drooping clusters that are
circular and about 1 in (2.5 cm) wide. The peel is tan, thin, and leathery with
tiny hairs. The flesh is translucent,
and the seed is large and black with a circular white spot at the base. This gives
the illusion of an eye. The flesh has a
musky, sweet taste, which can be compared to the flavour of lychee fruit. The Longan tree 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 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 similar to dates, lychees are often messily
juicy with a more tropical, grape-like sour sweetness.
Dried longans 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.
During harvest, pickers must climb ladders to carefully
remove branches of fruit from longan trees. Longan fruit remain fresher if
still attached to the branch, so efforts are made to prevent the fruit from
detaching too early. Mechanical picking would damage the delicate skin of the
fruit, so the preferred method is to harvest by hand. Knives and scissors are
the most commonly used tools.
Fruit is picked early in the day in order to minimize
water loss and to prevent high heat exposure, which would be damaging. The
fruit is then placed into either plastic crates or bamboo baskets and taken to
packaging houses, where the fruit undergo a series of checks for quality. The
packaging houses are well-ventilated and shaded to prevent further decay. The
process of checking and sorting are performed by workers instead of machinery.
Any fruit that is split, under-ripe, or decaying is disposed of. The remaining
healthy fruit is then prepped and shipped to markets.
It is found commonly in most of Asia, primarily in China,
Taiwan, Vietnam and Thailand. China, the
main longan producing country in the world, produced about 1,300 million tonnes
of longan in 2010. Vietnam and Thailand produced around 600 million and 500
million tonnes, respectively. Like
Vietnam, Thailand's economy relies heavily on the cultivation and shipments of
longan as well as lychee. This increase in the production of longan reflects
recent interest in exotic fruits in other parts of the world. The longan industry is very new in North
America and Australia. Commercial crops have only been around for twenty years.
Many companies add preservatives to canned longan.
Regulations control the preserving process. The only known preservative added
to canned longan is sulfur dioxide, to prevent discoloration. Fresh longan that is shipped worldwide is
exposed to sulfur fumigation. Tests have shown that sulfur residues remain on
the fruit skin, branches, and leaves for a few weeks. This violates many
countries' limits on fumigation residue, and efforts have been made to reduce
this amount. Potassium chlorate has been
found to cause the longan tree to blossom. However, this stresses the tree if
used excessively, and eventually kills it.
The nutritional profiles of longan and lychee are
similar. Both fruits are low in calories and carbs and have zero fat. One ounce
of fresh longan has just 17 calories and 4 grams of carbs. One ounce of fresh
lychee has 18 calories and 5 grams of carbs.
Both dried longan and dried lychee are higher in calories and carbs than
their fresh counterparts. One ounce of dried longan has 80 calories and 21
carbs. One ounce of dried lychee has 78 calories and 20 carbs.
Longans have high levels of polyphenols. The polyphenolic
compounds like gallic acid eliminate the stress-causing free radicals and toxic
intermediates that can cause cancer. The fruit, flower, and the seed are
equally potent antioxidants. Traditional
Chinese medicine has used longan seed extracts that interfere with DNA
synthesis and suppress the undesirable oncoproteins in the tumors, in turn,
destroying them. Hence, consuming longan fruits or seed extract powders can
systematically inhibit breast, colorectal, liver, lung, and cervix cancer cells.
The Asians used longan fruit pulp to heal wounds,
allergies, flu, and other inflammatory diseases. The pericarp (outer layer), pulp, and seeds
have anti-inflammatory phytochemicals like gallic acid, epicatechin, and
ellagic acid. These compounds inhibit the production of pro-inflammatory
chemicals like prostaglandins, histamines, nitric oxide, and tissue necrosis
factor (TNF) in your body. Also, because
of the abundance of vitamins B and C, longans promote healing and treat chronic
inflammatory conditions like edema and irritable bowel disease (IBS).
Longan extracts, along with other native herbs, are used
in Chinese traditional medicine to cure intractable anemia, thrombocytopenia,
and other blood-related disorders. It was identified that urban women who did
not maintain WHO recommended level of iron in their diets (<5 servings of
fruit or vegetables per day) were at a higher risk of moderate and severe
anemia. Dried longans contain 1.5 mg of
iron per ounce. This fruit will boost the platelet count and hemoglobin
concentration – especially in menstruating and expecting women. Phytochemicals
have always been the best solution to treat various disorders, and longan has
them in abundance.
Bioactive compounds like corilagin, gallic acid, and
ellagic acid in dried longans possess the highest free radical scavenging
activity. The fruit also has antityrosinase activity and hence can prevent the
onset of cancers. Consuming such a
potent antioxidant can give clean, bright, and spotless skin with reduced risk
of developing photosensitivity or skin cancer.
Commercially available drugs to treat insomnia that
target the GABA receptors, histamine receptors, and other active centers of brain
have temporary benefits and long-term side effects. The leaves and pulp of
longan have bioactive compounds that suppress the levels of neurotransmitters
that cause anxiety, insomnia, and stress.
Longan can help eliminate wrinkles, age spots, as well as
blemishes and the appearance of scars. The flesh of the fruit contains vitamins
B and C as well as antioxidants, which have anti-aging properties and minimize
dryness, as well as the cracking and peeling of the skin.
Longan is a delicious tropical fruit which contains
anti-aging properties, improves skin health, nourishes the blood, increases
circulation, and enhances memory. The fruit’s amazing health benefits also
include boosting the nervous system, improving immunity, lowering blood
pressure, calming the body, and improving sleep quality. In Chinese traditional
medicine, it is used to increase the energy of the heart, and as a sexual and
beauty tonic.
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