Bird’s Nest – Food Safety and Authenticity
Bird’s Nest – Food Safety and Authenticity
YY TSANG
(CMA Testing and Certification Laboratories)
Many countries have implemented stringent import control of high risk foods. For example, a food establishment in an exporting country is required to register with the relevant authorities in an importing country, and pass an assessment before she is allowed to export food to that country. It is noted that all foreign establishments exporting bird’s nests to China shall register since 1st Jan 20161.
1 Source of Information：http://www.aqsiq.gov.cn/xxgk_13386/jlgg_12538/zjgg/2015/201512/t20151207_455697.htm
Bird’s Nest and Nitrite
In 2011, high level of carcinogenic “nitrite” was detected in imported bird’s nests by Mainland authority. Nitrite can either occur naturally in a bird’s nest, or come from bird droppings which contain high level of nitrate. For example, illegal traders might “colorize” a cheap bird’s nest by smoking bird’s dropping, and then sell it as a “counterfeit” of blood-red bird’s nest.
Image Source：Baidu, 2012
http://tieba.baidu.com/p/1561006281
Excessive intake of nitrite can lead to adverse health effects such as methemoglobinemia and cancers. Currently, China and major bird’s nest producing countries (including Malaysia and Thailand) already specify that the nitrite content in dried bird’s nests cannot exceed 30 mg/kg.
Thoroughly washing and soaking of dried bird’s nests for a few hours can indeed remove substantial amount (up to 90%) of nitrite in bird’s nests. Since nitrite will dissolve into the soaking water, water used for soaking bird’s nests should be replaced once or twice during the soaking process, as well as be discarded after soaking.
Bird’s Nest and Microbes
Bird’s nests were also once found to contain the bacteria Staphylococcus aureus. Although bird’s nests shall be heat treated before consumption, Salmonella spp. or avian influenza viruses present in a bird’s nest can directly infect a person in contact with it.
To date, countries including Malaysia, Indonesia and Thailand have specified the tolerance levels of different microbes in raw bird’s nests. For example, Malaysia stipulates that Staphylococcus aureus in bird’s nests cannot exceed 100 MPN/g; while other microbes with specified limits include total bacterial count, coliform bacteria, E. coli, Salmonella spp., yeast and mold.
Bird’s Nest and Heavy Metals
Although excessive heavy metals in bird’s nest are rarely reported, it is noted that many years ago the bird’s nest of a particular brand from Singapore was detected with excessive arsenic.
Environmental conditions of a bird’s nest production site can be a critical factor. For example, cave nest can be contaminated with heavy metals inside the walls of a cave. In Malaysia, tolerance levels of several heavy metals (arsenic, lead, mercury and cadmium) in a bird’s nest are specified.
Bird’s Nest and Authenticity
Apart from food safety, consumers also concern about the authenticity of expensive bird’s nests.
Image Source：Appledaily, 2011
http://hk.apple.nextmedia.com/news/art/20110923/15639033
Indeed, from time to time, bird’s nests and their derived products sold in the market are found lacking of natural bird’s nest ingredients. “Fake Bird’s Nest” can be composed of materials including fungus, pork skin, agar, pectin, etc.
In order to differentiate a real bird’s nest from the fake one, one of the authenticity indicators is sialic acid. In China, the industry standard specifies the sialic acid content in bird’s nests must be equal to or exceed 5%. On the other hand, Malaysia also stipulates that bird’s nests must contain sialic acid (though the minimum content of sialic acid is not specified).
Moreover, analysis of DNA sequences present in a bird’s nest sample can accurately identify the origin of the sample (i.e. species of the bird producing the nest). Another authentication method is analysis and comparison of the amino acid fingerprints of a sample with that of the real bird’s nests.