IISc develops low-cost method to trace adulterants in milk

Researchers at the Indian Institute of Science (IISc) have developed a low-cost and effective method to detect adulterants in milk.

Their method analyses deposition patterns after evaporation.

In the study, which was published in ACS Omega, the researchers used the method to test for the presence of urea and water – the most common adulterants. They looked at evaporative deposition patterns.

These patterns emerge when a liquid mixture like milk completely evaporates, causing volatile components to dissipate, and solids or non-volatile components to arrange themselves in distinctive patterns.

Milk with and without water or urea showed very different evaporative patterns.

In unadulterated milk, the evaporative pattern consisted of a central, irregular blob-like pattern. Water was found to cause distortion or complete loss of this distinctive pattern, depending on how much is added.

Current techniques such as using a lactometer and looking for changes in the freezing point of milk can be used to detect the presence of water, but they have certain limitations.

For example, the freezing point technique can detect water only up to 3.5 per cent of the total milk concentration.

In addition, although biosensors with high sensitivity are available to test for urea, they are expensive, and their accuracy tends to decrease with time.

The IISc team was able to detect water concentrations as high as 30 per cent and urea concentrations in diluted milk as low as 0.4 per cent using this type of pattern analysis.

The researchers said that this technique can potentially be extended to test for adulterants in other beverages.

“The pattern you get is highly sensitive to what is added to it. So, I think this method can be used to detect impurities in volatile liquids,” explained Dr Susmita Dash, assistant professor in the department of mechanical engineering and co-author of the study.

The simplicity of this method lends itself to easy automation, once the patterns for all adulterants and their combinations are standardised, explained Virkeshwar Kumar, a postdoctoral researcher and another co-author of the study.

“These could be fed into an image analysis software, for example, which would compare a photo – even one taken with a mobile phone – of the sample’s evaporative pattern with other standard patterns to accurately detect the adulterants present,” IISc said in a statement.

The problem

Adulteration of milk is a pressing concern in developing countries like India, where a majority of supplied milk fails to comply with the standards set by the Food Safety and Standards Authority of India. Water is frequently added to increase the volume of milk, along with urea, which makes the watered-down version whiter and foamier – this can potentially endanger the normal functioning of the liver, heart and kidneys.