This week Chinese scientists funded by the Chinese Ministry of Health announced in the peer-reviewed Talanta journal that they have developed a quick and simple color change test to detect melamine in milk products.

Scientists began working on developing a test after the contaminated milk scandal in 2008, when milk powder tainted with melamine sickened an estimated 300,000 people and killed six children.

In the article, scientists explained that they developed a colorimetric testing method that uses gold nanoparticles to determine whether or not the product is tainted. The test is designed so that when the nanoparticles approach each other and aggregate, their color changes from wine red to purple or blue.  When melamine is present in the tested product, the aggregate approach process commences.

The new test can be used to test for melamine in infant formula and liquid milk with a detection limit of 1.0 ppm for liquid milk and 4.2 ppm for formula.  The use of UV-vis-spectroscopy improves the sensitivity to 0.15 ppm in liauid milk and 2.5 ppm in infant formula.

The test can be completed within 30 minutes and does not require pretreatment.  Study authors said, “The proposed method is promising for on-site screening of melamine adulterant in milk products.”

The new testing method is praised by the scientists as faster, less costly than existing methods, and does not require advanced instruments or solid phase examination, but it is less sensitive than other tests.  

Despite sensitivity issues, scientists claim that the test is sufficiently sensitive to detect melamine in milk-based products at levels desired by regulatory bodies.

In Europe and the US, melamine safety limits are 2.5mg kg-1 while the limit in China is 1mg kg-1 for infant formula and 2.5mg kg-1 for other dairy products.