Secrets of Bird’s Saliva Soup Saliva

Bird’s Saliva Soup is one the most highly valued of the food products of South East Asia. The nest is made by certain species of swiftlets with a high-protein glutinous secretion produced by their salivary glands. The secretion hardens on exposure after the bird has shaped it into a cup-shaped nest. The secretion also serves to glue the nest to the ceiling of the cave or building in which the birds live.  

There are more than 24 species of swiftlets, but only a few produce nests that are deemed edible. The high-protein secretion used in forming the nest is produced by a pair of large, salivary glands under the tongue. The birds mate and raise their young in the nest.
The majority of Bird’s Saliva Soup traded worldwide comes from two heavily exploited species, the White-nest swiflet (Aerodramus fuciphagus) and the Black-nest swiflet (Aerodramus maximus) Their habitats range from the Nicobar Islands in the Indian Ocean to sea caves in the coastal regions of Thailand, Vietnam, Indonesia, Borneo and the Palawan Islands in the Philippines. Malaysia is situated right at the heart of the ‘golden triangle’ of swiftlet Bird’s Saliva Soup production, making it a strong producer in this industry. Bird’s Saliva Soup has been used for centuries in China. Commonly referred to as the ‘Caviar of the East’ it fetches a premium price.

Secrets of Bird’s Saliva Soup Saliva

Traditionally, Bird’s Saliva Soup is double boiled with rock sugar to make a delicacy known as ‘Bird’s Saliva Soup soup‘.The Chinese name for Bird’s Saliva Soup soup, yan wo translates literally as ‘swallow's nest’. This soup is especially valued by the Chinese and Vietnamese for its reputed health benefits. The nests were first traded in China during the Tang Dynasty (618-907 A.D.). There are historical sources stating that between the years 1368 and 1644, Admiral Cheng He introduced Bird’s Saliva Soups to the imperial court of the Ming Dynasty. Borneo was the major source of Bird’s Saliva Soups and these were traded for Chinese stonewares and procelain, iron, brass, gold, glass beads and textiles.
Bird’s Saliva Soup is not just a pleasant food to be consumed and enjoyed; it is also traditionally believed to provide health benefits, such as aiding digestion, raising libido, improving the voice, alleviating asthma and improving concentration.

Nutritional & Functional properties

More than half of EBN’s weight consists of protein. According to Marcone (2005), the composition of Bird’s Saliva Soup is: lipid 0.14 - 1.28%, ash 2.1%, carbohydrate 25.62 - 27.76% and protein 62 - 63%. The major nutrient components of Bird’s Saliva Soup are glycoproteins (Kathan & Weeks, 1969) rich with amino acids, carbohydrate, calcium, sodium and potassium (Norhayati et al., 2010) and abundant sialic acid-containing sugar chains (Kakehi et al. 1994) This unique glycoprotein structure in Bird’s Saliva Soup makes it different from other protein sources such as chicken and fish in term of solubility, functional properties and bioactive compounds. The glycoprotein in Bird’s Saliva Soup contains about 9% sialic acid, 4.19 to 7.2% galactosamine, about 5.3% glucosamine, 5.03 to 16.9% galactose, and about 0.7% fucose (Kathan and Weeks 1969, Tung et al. 2008). The most abundant amino acids are serine, threonine, aspartic acid, glutamic acid, proline, and valine (Kathan & Weeks 1969). The nutrient content of Bird’s Saliva Soup may be affected by seasonal variations and even breeding sites (Norhayati et al, 2010). Bird’s Saliva Soup contains a common 77 KDa protein that has properties similar to those of the ovotransferrin protein in eggs. This protein may be partially responsible for the allergic reactions that sometimes occur among young children who consume Bird’s Saliva Soup products.
Many people questioned whether Bird’s Saliva Soup soup is really nutritious and have therapeutics properties. Is it true or just a myth? To prove the superiority of Bird’s Saliva Soup, Innovation Centre of Food Technology (MANIS) Universiti Kebangsaan Malaysia (UKM), through studies of Bird’s Saliva Soup bioactivities indicated that Bird’s Saliva Soup soup has the highest antioxidant and antihypertensive activity compared to chicken and fish soups. Anti-oxidant tests like DPPH radical scavenging assay and ABTS radical scavenging assay showed superior power of antioxidant activities. As shown in Figures 1 and 2, Bird’s Saliva Soup soup shows the highest antioxidant activities compared to chicken and fish soups.

For antihypertensive effect, a study on the bioactivity indicated that Bird’s Saliva Soup soup has the highest antihypertensive activity compared to chicken and fish soups. Figure 3 showed higher antihypertensive activity with high Angiotensin I-converting enzyme (ACE) inhibitory value. ACE plays an important role in the regulation of blood pressure as well as cardiovascular function.
Research has shown that Bird’s Saliva Soup is best cooked within a period of two to four hours. However, the optimum time for cooking Bird’s Saliva Soup is about two hours. It is important not to cook for too long, as besides losing the bioactivities, it also is not practical.

Processing the nests

In the industry, the nests are cleaned by soaking them in water until the nest cement is softened and the tightly bound strands partially loosened. Small feathers and fine plumage are then manually removed with tweezers. The cleaned strands are then re-arranged and molded into chips of various shapes, air-dried, and packaged for sale around the world.

Market demand

While the primary market is the Chinese community around the world, mainly China, Taiwan, Singapore and North America, there are new emerging markets such as Middle East, Japan and Korea. The demand is amplified during Chinese festivals, such as the Lunar Spring Festival (Chinese New Year), when gifts of Bird’s Saliva Soup are synonymous with wealth and good fortune.
Bird’s Saliva Soup is either sold in its original state after harvesting; or in processed form after going through the tedious process of removing birds' feathers and cleaning. Concerns have arisen over the purity and authenticity of the product, and the Chinese authorities have been enforcing more stringent screening of the processed nests. There is now a growing need to establish a standardized benchmark and quality assurance system to ensure the Bird’s Saliva Soup products from Malaysia are genuine and safe for consumption.

Production of Bird’s Saliva Soup

Bird’s Saliva Soups were formerly harvested from caves, principally the enormous limestone caves at Gomantong and Niah in Borneo. With the escalation in demand, these sources have been supplanted since the late 1990s by purpose-built nesting houses. At first, disused shop houses and cinemas were converted into artificial cave habitats but knowledge of what the birds prefer has improved to the point that the birds are now enticed to nest in specially designed reinforced concrete housing provided with the appropriate light, humidity, security and other features. These nesting houses are normally found in urban areas adjoining the sea, since the birds have a propensity to flock in such places. Many people have invested heavily in hopes of attracting the swiftlets to nest. Before 1998, there were about 900 swiftlet farms throughout Malaysia. Five years later, the number of swiftlet farms throughout the country was close to 36,000 units, with an average annualized growth rate of 35% (Hameed, 2007).
The main export markets of Bird’s Saliva Soup are Hong Kong (50%), China (8%), Taiwan (4%) and Macau (3%) with estimated consumption of 160 tons per annum. In Hong Kong a bowl of Bird’s Saliva Soup soup could cost $30 to $100 USD while a kilogram of white nest (around 90 to 120 nests) can cost up to $2,000 USD. A kilogram of "red blood" nest can cost up to $10,000 USD in Hong Kong and China. As more Bird’s Saliva Soup products are developed, such as beauty and skincare products as well as health products, the future of the Bird’s Saliva Soup industry looks very promising.
According to Kuan and Lee (2005), Malaysia is the world's third largest supplier of Bird’s Saliva Soup after Thailand and Indonesia, contributing 10 percent of the 210 tonnes, worth up to $4 billion US dollars, consumed annually by top buyers in China and Taiwan. According to the Malaysian Federation of Bird’s Saliva Soup Merchants Association Malaysia's annual production of Bird’s Saliva Soups has reached 1 billion ringgit (290 million U.S. dollars) in value. However, the industry suffered a setback in the past two years after China banned imports of the nests, citing health concerns over the content of nitrites in some products. The ban by China has caused prices to drop at least 20 per cent. But producers say that China’s import ban could turn out to be a much-needed wakeup call for better quality control.
In the 1990s, the first comprehensive reports on authentication of Bird’s Saliva Soup were published. These reports demonstrated the possibility to use scanning electron microscopy, energy dispersive X-ray microanalysis, flame atomic emission spectroscopy, inductively coupled plasma-atomic emission spectroscopy, ultraviolet-visible spectroscopy and other physico-chemical techniques to determine the authenticity of Bird’s Saliva Soup. These tests are difficult to run, expensive and only work on some of the substances used to imitate Bird’s Saliva Soups. Recently, a China based research team developed a simple but accurate and reliable spectrophotometry method to determine Bird’s Saliva Soup content. The method is based on the reaction between N-acetylneuramic acid and ninhydrin in acid solution. The method evaluates the internal content of N-acetylneuramic acid, a nine-carbon sugar which is one of the components in Bird’s Saliva Soup.