Detecting melamine

Melamine is the compound found in contaminated pet food and in tainted dairy products from China in 2007 and 2008 respectively. The laced dairy products were responsible for sickening thousands of people, especially children. The situation caused recalls of Chinese dairy products all over the world.

Monitoring melamine-tainted products continues to be a worldwide concern. Melamine is an industrial substance commonly used in plastics and fertilizers. Since melamine is high in nitrogen, when added to foods it can make the products appear higher in protein value during standard testing. However, when ingested, the chemical can cause serious health problems and in some cases death.

’Current methods of melamine detection in milk are costly and time consuming,’ said University of Miami assistant engineering professor Na Li. ’Our work represents a significant step towards the rapid detection of melamine, which addresses a critical global issue.’

The new detection method can be completed in less than 15 minutes.

The researchers first step is to separate the casein-based milk component, which can interfere with melamine detection. Next, they add gold nanoparticles to the solution. The interaction between the gold nanoparticles and melamine causes a dramatic colour change indicating the presence of melamine.

When melamine is present, the colour of the solution changes from red to blue within seconds and can be measured both by visual inspection and spectrophotometry. Cyanuric acid, which has a specific reaction with melamine, is introduced sequentially to increase specificity. If melamine is present, a precipitant is formed, which can also be assessed both visually and by spectrophotometry.

’This method provides a unique opportunity to use the highly sensitive detection properties of nanoparticles to prevent people from being harmed by melamine ingestion,’ said Dean Ho, assistant professor in the Departments of Biomedical and Mechanical Engineering at Northwestern University.

In the future, the researchers hope to develop a commercial simple kit that can be used by the layperson, at home or in the field, to detect melamine contaminant in food.