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Edible bird's nests, also known as swallow nests ( zh, c=燕窝, p=yànwō), are
bird nest A bird nest is the spot in which a bird lays and Avian incubation, incubates its Bird egg, eggs and raises its young. Although the term popularly refers to a specific structures built by animals, structure made by the bird itself—such as th ...
s created from solidified
saliva Saliva (commonly referred as spit or drool) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which ...
by edible-nest swiftlets, Indian swiftlets and other
swiftlet Swiftlets are birds from the four genera ''Aerodramus'', ''Collocalia'', ''Hydrochous'' and ''Schoutedenapus'', which form the tribe (biology), tribe Collocaliini within the swift (bird), swift family (biology), family Apodidae. The group contain ...
s of the genera ''
Aerodramus ''Aerodramus'' is a genus of small, dark, cave-nesting birds in the swiftlet, Collocaliini tribe (biology), tribe of the Swift (bird), swift family. Its members are confined to tropical and subtropical regions in southern Asia, Oceania and north ...
'', '' Hydrochous'', '' Schoutedenapus'' and '' Collocalia'', which are harvested for human consumption. Swiftlet nests have been used as a
delicacy A delicacy is a rare food item that is considered highly desirable, sophisticated, or peculiarly distinctive within a given culture or region. A delicacy may have an unusual flavor or be expensive compared to everyday foods. Delicacies va ...
for over 400 years, most often as
soup Soup is a primarily liquid food, generally served warm or hot – though it is sometimes served chilled – made by cooking or otherwise combining meat or vegetables with Stock (food), stock, milk, or water. According to ''The Oxford Compan ...
. They are particularly prized in
Chinese cuisine Chinese cuisine comprises cuisines originating from Greater China, China, as well as from Overseas Chinese, Chinese people from other parts of the world. Because of the Chinese diaspora and the historical power of the country, Chinese cuisine ...
due to the rarity, high
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
content and rich flavor, and are among the most expensive animal products consumed by humans, with prices up to about depending on grading. The type or grading of a swiftlet nest depends on the bird species, as well as the shape and colour of the bird's nest. It is usually white in colour, but there also exists a red version that is sometimes called 'blood nest' ( zh, c=血燕, p=Xuě Yàn). According to
traditional Chinese medicine Traditional Chinese medicine (TCM) is an alternative medicine, alternative medical practice drawn from traditional medicine in China. A large share of its claims are pseudoscientific, with the majority of treatments having no robust evidence ...
, it promotes good health, especially for the
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...
.


Etymology

The Chinese name for edible bird's nest, (), translates literally as 'swallow's (or swiftlet's) nest'; in Indonesia often serves as a synonym for bird's nest soup. In English, "swallow" refers to an ecologically-similar but unrelated group of songbirds ( Hirundindae) whose nests are not used in soup, whereas "swift(let)" refers to aerial insectivores in the order Apodiformes, which are more closely related to hummingbirds.


Culinary use

The best-known use of edible bird's nest is bird's nest soup, a
delicacy A delicacy is a rare food item that is considered highly desirable, sophisticated, or peculiarly distinctive within a given culture or region. A delicacy may have an unusual flavor or be expensive compared to everyday foods. Delicacies va ...
in
Chinese cuisine Chinese cuisine comprises cuisines originating from Greater China, China, as well as from Overseas Chinese, Chinese people from other parts of the world. Because of the Chinese diaspora and the historical power of the country, Chinese cuisine ...
. When dissolved in water, the bird's nests have a flavored gelatinous texture utilized in
soup Soup is a primarily liquid food, generally served warm or hot – though it is sometimes served chilled – made by cooking or otherwise combining meat or vegetables with Stock (food), stock, milk, or water. According to ''The Oxford Compan ...
or sweet soup ( tong sui). It is mostly referred to as () unless references are made to the savory or sweet soup in
Chinese cuisine Chinese cuisine comprises cuisines originating from Greater China, China, as well as from Overseas Chinese, Chinese people from other parts of the world. Because of the Chinese diaspora and the historical power of the country, Chinese cuisine ...
. According to the
Qing dynasty The Qing dynasty ( ), officially the Great Qing, was a Manchu-led Dynasties of China, imperial dynasty of China and an early modern empire in East Asia. The last imperial dynasty in Chinese history, the Qing dynasty was preceded by the ...
manual of
gastronomy Gastronomy is the study of the relationship between Human food, food and culture, the art of preparing and serving rich or delicate and appetizing food, the cooking styles of particular regions, and the science of good eating. One who is well ver ...
, the '' Suiyuan shidan'', bird's nest was regarded as a delicate ingredient not to be flavored or cooked with anything overpowering or oily. While it is rare and expensive, it must be served in relatively large quantities; otherwise its texture cannot be fully experienced and enjoyed. In addition to their use in soup, edible bird's nests can be used as an ingredient in other dishes. They can be cooked with rice to produce bird's nest
congee Congee ( , derived from Tamil language, Tamil ), is a form of savoury rice porridge made by boiling rice in a large amount of water until the rice softens. Depending on rice–water ratio, the thickness of congee varies from a Western oatmeal ...
or bird's nest boiled rice, or they can be added to egg tarts and other desserts. A bird's nest jelly can be made by placing the bird's nest in a ceramic container with minimal water and sugar (or salt) before double steaming.


Production and harvest

The most heavily harvested nests are from the edible-nest swiftlet or white-nest swiftlet (''Aerodramus fuciphagus'') and the black-nest swiftlet (''Aerodramus maximus''). Previous studies conducted by Lee et al. have reported that the nutrient composition of edible bird's nest is dependent on the country of origin, food intake of the birds, climate and breeding sites. Most nests are built during the breeding season by the male swiftlet over a period of 35 days. They take the shape of a shallow cup stuck to the cave wall. The nests are composed of interwoven strands of
saliva Saliva (commonly referred as spit or drool) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which ...
ry cement. Both nests have high levels of calcium, iron, potassium, and magnesium. The nests were formerly harvested from caves, principally the enormous
limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
caves at Gomantong and Niah in
Borneo Borneo () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...
. With the escalation in demand these sources have been supplanted since the late-1990s by purpose-built nesting houses, usually
reinforced concrete Reinforced concrete, also called ferroconcrete or ferro-concrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ...
structures following the design of the Southeast Asian shop-house (). These nesting houses are normally found in urban areas near the sea, since the birds have a propensity to flock in such places. It has become an expanding industry as is evident in such places as the province of
North Sumatra North Sumatra () is a Provinces of Indonesia, province of Indonesia located in the northern part of the island of Sumatra. Its capital and largest city is Medan on the east coast of the island. It borders Aceh to the northwest, Riau to the sou ...
or the Pak Phanang District in Thailand. From those places the nests are mostly exported to the markets in Hong Kong, which has become the center of the world trade in bird's nests; the industry is valued at around HK$4.3billion per year, although most of the final consumers are from mainland China. China is the world's largest consumer of birds' nests, accounting for more than 90 percent of consumption. In some places, nest gatherers (known in the Philippines as busyadors) have seen a steep decline in the number of birds and a rise in unexplained fatalities.


Colour

Although bird's nest is usually white, there also exists a red version, called 'blood nest' (), which is significantly more expensive and believed to have more medicinal value. In the market, a kilogram of white bird's nest can fetch up to , and a kilogram of red nests up to . The reason for its characteristic redness has been a puzzle for centuries. Contrary to popular beliefs, red bird's nest does not contain
hemoglobin Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. Hemoglobin ...
, the protein responsible for the colour of human blood. Researchers reported in 2013 that 'bird soil' containing guano droppings from bird houses were able to turn white edible bird's nests red, and that edible bird's nests' colour is likely caused by environmental factors in cave interiors and bird houses. Subsequently, a research team at Nanyang Technological University, Singapore has found that its redness is caused by the
vapor In physics, a vapor (American English) or vapour (Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is a substance in the gas phase at a temperature lower than its critical temperature,R ...
of
reactive nitrogen species Reactive nitrogen species (RNS) are a family of antimicrobial molecules derived from nitric oxide (•NO) and superoxide (O2•−) produced via the enzymatic activity of inducible nitric oxide synthase 2 (Nitric oxide synthase 2A, NOS2) and NADPH ...
in the atmosphere of the bird house or cave reacting with the mucin glycoprotein of the initially formed white bird nest. Red bird's nest contains tyrosine that has combined with reactive nitrogen species to form 3-nitrotyrosine. At high concentrations, 3-nitrotyrosine produces a distinctively rich red colour, while at lower concentrations, it produces the characteristic yellow, golden and orange colours seen in other varieties of bird's nest products. The researchers also note that the bird nest also readily absorbs
nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...
and
nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...
from the process' vapor which explains why the red bird's nest contains a high concentration of nitrite and nitrate, which are known to lead to carcinogenic compounds. This may mean that non-white bird's nests are harmful to human health.


Market

Indonesia is the largest bird's nest producer in
Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...
, exporting around per year, followed by Malaysia at , and Thailand, . The Philippines, producing roughly per year, is the smallest producer. The bird's nest industry in 2014 accounts for 0.5 percent of the Indonesian GDP, a GDP percentage equivalent to about a quarter of the country's fishing industry. In Thailand, the trade value of bird's nests, both wild and "farmed", is estimated at around 20 billion
baht The baht (; , ; currency sign, sign: ฿; ISO 4217, code: THB) is the official currency of Thailand. It is divided into 100 ''satang'' (, ). Prior to decimalisation, the baht was divided into eight ''fueang'' (, ), each of eight ''at'' (, ). The ...
per year. The industry globally is an estimated . Hong Kong and the United States are the largest importers of nests. In Hong Kong, a bowl of bird's nest soup costs to .


Counterfeiting

Besides the natural colouration process, the white nests can be treated with red pigment to defraud buyers, but methods have been developed to determine an adulterated nest. Natural red cave nests are often found in limestone caves in Pak Phayun District, Thailand. The high returns and growing demand have attracted counterfeiters, leading to the halt of Malaysian nest exports to China. The Malaysian government has since employed
RFID Radio-frequency identification (RFID) uses electromagnetic fields to automatically identify and track tags attached to objects. An RFID system consists of a tiny radio transponder called a tag, a radio receiver, and a transmitter. When tri ...
technology to thwart counterfeiting by micro-chipping nests with details about harvesting, packaging, and transport. Industrial quality-control techniques such as
failure mode and effects analysis Failure is the social concept of not meeting a desirable or intended Goal, objective, and is usually viewed as the opposite of success. The criteria for failure depends on context, and may be relative to a particular observer or belief system ...
have been applied to bird's nest processing at nesting houses in Sarawak, Malaysia, and reported by a research team at Universiti Malaysia Sarawak.


Authentication

The high demand for edible bird's nest has garnered the attention of counterfeiters to defraud buyers. Fake edible bird's nest or edible bird's nest with adulterants may be harmful to those who consume it. Hence, there is an urgent need to find a solution to the issues regarding the authenticity and quality of the edible bird's nest. Numerous sophisticated techniques have been used for the detection of adulterants in edible bird's nest such as energy disperse X-ray microanalysis, electronic microscopy and spectroscopy. Some other methods including DNA-based polymerase chain reactions, protein-based two-dimension gel electrophoresis and genetic identification based on mitochondrial DNA have found applications in the authentication of edible bird's nest. Previous studies used gel electrophoresis in combination with liquid chromatographic methods to identify some common adulterants in edible bird's nest. In this study, gel electrophoresis and liquid chromatography were used for protein profiling and amino acids studies of cave and house nests, and others samples such as white fungus, fish swimming bladder, jelly and egg white. Each of the samples had a unique protein profile which will be reflected on the protein gel and these results were supported by the chromatographic analysis. Gel electrophoresis also was used to identify and differentiate the edible bird's nests based on their geographical origins.


Import restrictions

Because a bird's nest is an animal product, it is subject to strict import restrictions in some countries, particularly with regard to
H5N1 Influenza A virus subtype H5N1 (A/H5N1) is a subtype of the influenza A virus, which causes the disease avian influenza (often referred to as "bird flu"). It is enzootic (maintained in the population) in many bird populations, and also panzoo ...
avian flu. In Canada, commercially prepared, canned, and sterile bird's nest preparations are generally acceptable, but may be subject to import restrictions.


See also

*
Traditional Chinese medicine Traditional Chinese medicine (TCM) is an alternative medicine, alternative medical practice drawn from traditional medicine in China. A large share of its claims are pseudoscientific, with the majority of treatments having no robust evidence ...
* List of Chinese soups * List of delicacies * List of soups


References


Bibliography

* * * * * * * * . *


Further reading

* *Ting Hun, Lee., Wassem, A. Wani., & Eddie, Tan Ti Tjih (2015)
Edible bird's nest: An Incredible salivary bioproduct from swiflets.
LAP LAMBERT Academic Publishing. .


External links

* {{Guangdong topics Chinese soups Cantonese cuisine Hong Kong cuisine Bird breeding Bird products Apodidae