Researchers find easy way to detect melamine in milk

Thanks to the advances of nanotechnology, a rapid, simple and affordable way to detect the milk adulterant melamine is just around the corner.

Researchers from the Indian Institute of Science have been able to demonstrate that they can quickly and easily detect melamine with the aid of the synthesis of silver nanoparticles.

The research - which could be used to develop a simple, handheld device for detecting adulteration in the field - could be a boon for the food industry given that the incidence of adulterated milk with melamine is a serious concern.

Melamine is a nitrogen rich crystalline compound and is often added to milk to increase the apparent protein content. Normally used in the plastics industry, it can cause kidney problems in those who consume it.

In 2008, there was a widespread scandal in China where melamine was added to infant milk formula. More than 54,000 children were hospitalised and at least four died as a result of drinking the contaminated milk.

Authorities in India suggest more than 1 part per million (ppm) of melamine in infant formula and more than 2.5 ppm in other foods should be considered possibly contaminated.

In the current study, the researchers found that melamine interacts with a reducing agent while forming nanoparticles at room temperature, which can be picked up as a colour change. Caffeic acid, a major constituent of leaf extract from the noxious weed Parthenium was used as a reducing agent alongside silver nitrate.

"If melamine is present then it interferes with the synthesis [of the nanoparticles] and there is abrupt formation of nanoparticles leading to colour change," the researchers said.

The researchers used UV-vis spectroscopy and high resolution transmission electron microscopy (HR-TEM) to detect the spectral surface plasmon resonance (SPR) and morphological changes of the synthesised silver nanoparticles both in the presence and absence of melamine.

The colour change depended on the amount of melamine present. When melamine was present there was almost no colour versus a reddish yellow in the absence of the compound.

In the past prepared nanoparticles have been used to detect melamine but it took around 30 minutes to sense the synthesised nanoparticles. Meanwhile, current techniques are lab based requiring technology such as gas chromatography-mass spectrometry (GC-MS), which can be laborious and requires samples to be taken to the lab.

In contrast, the researchers were able to use a handheld device and detect melamine in seconds from just 1ml of milk.

"Biosynthesis along with sensing reported here has made possible the realisation of a robust integrated sensor for field applications," said the researchers, who are in the process of commercialising the product. Furthermore, the technique could now be used as a platform to sense other adulterants, they added.

The results are published in the journal Sensors and Actuators B: Chemical.