Edible bird’s nests, made from the saliva of several Swiftlet species, have been used in Chinese cooking for over 400 years, most commonly in bird’s nest soup. This is an expensive delicacy in China and is believed to provide many health benefits. Now, the nests have become big business, with Hong Kong and the United States being the largest importers of these nests, and China being the highest end user.
Last summer, when this story broke, China’s Zhejiang Provincial Administration for Industry and Commerce found nitrite levels in the rare red bird’s nest imported from Malaysia averaged 4,400 mg/kg, far above the allowed maximum of 70 mg/kg. The administration said that the contamination was the result of adulteration—dying white bird’s nests and selling them as the rare and more expensive blood-red bird’s nests.
This contamination is of concern because nitrite can react with secondary amines in food products or in the digestive system to form nitrosoamines (link to a Wikipedia page), a class of carcinogenic compounds. Nitrate, although more stable than nitrite, can act as a reservoir for nitrite. Also, nitrate can readily be converted into nitrite by microbial reduction. Thus, both nitrate and nitrite must be monitored to ensure the quality and safety of meat products.
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A few months later, it was reported on China.org.cn that the Chinese government was mulling over chemical standards for edible bird nest. Then, as recently as December of 2011, the CHINADAILY.com.cn reported that again nitrite had been found in bird nests originating from Malaysia.
With vast experience with nitrite and nitrate analyses, we offer the following three methods as solid starting points for the analysis of nitrites and nitrates in edible bird’s nests and other food products.
- Application Note 154, Inorganic Anions in Environmental Waters Using a Hydroxide-Selective Column (downloadable PDF)
- Application Note 131, Nitrite and Nitrate in Drinking Water Using Chemically Suppressed Ion Chromatography (downloadable PDF)
- Application 132, Nitrite and Nitrate in Drinking Water Using Ion Chromatography with Direct UV Detection (downloadable PDF)
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