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  • Test makes light work of contaminant detection


Researchers have developed a quick and simple test that detects if food is contaminated by melamine, the industrial chemical implicated in the recent scandal of tainted milk in China.   

The test gives reliable results in 15 minutes and could be developed into a simple kit to detect melamine in human and animal food products in developing countries, they said.

The researchers detected contaminated milk with the new method. First they removed casein, a protein that can interfere with melamine detection from milk. They then added gold nanoparticles, which react with melamine and change the colour of the solution from red to blue if it is contaminated.

"Our method enables sensitive detection of melamine directly from milk within minutes," said Na Li, lead author and director of the Integrated Nano-Bio Systems Laboratory at the University of Miami, United States.

The technique uses readily available low-cost reagents and equipment, he added, avoiding more expensive methods such as chromatography and mass spectroscopy, and could be carried out by laypeople.

Melamine — which can be misused to increase food's apparent protein content — has been found to be a widespread contaminant, extending well beyond dairy products in China (see also Tainted milk blamed on 'pressure to innovate' in China).  

"For some developing countries where the food safety regulations are less efficient and the expensive analytical equipments for food safety monitoring are less accessible, melamine-contaminated dairy products could pose a serious issue," said Li.

"A simple, rapid and accurate detection method for food safety is critical for society," he added.

Such a test would be very useful as a quick screening test,Angelika Tritscher, an official atthe WHODepartment of Food Safety and Zoonoses, told SciDev.Net.

But she said that researchers developing such tests need to take into account that small, safe amounts of melamine end up in food from packaging and other approved uses of the chemical, and only illegally and intentionally adulterated foods lead to the high levels that are of health concern.

Tritscher added that other laboratories should validate the results of this study before they can be turned into accepted tests.

Huanwen Chen, a chemist at the East China Institute of Technology, Fuzhou, said this new method could be developed into a commercial test in as little as 3–6 months. But he added that "there are similar methods being developed in China to detect melamine in liquid milk in less than 5 minutes" and will cost less than three US cents per test.

The method was described in a paper in Applied Physics Letters last month (March 2010).

Link to abstract in Applied Physics Letters


Applied Physics Letters doi: 10.1063/1.3373325 (2010)

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