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India’s milk production has increased by 51 per cent in the last eight years with the country contributing to 24 per cent of the world’s total production in 2021-22. However, adulteration of milk may still be a cause of concern for many consumers. As an answer to this, the researchers at the Indian Institute of Technology Madras (IIT Madras) and the Indian Institute of Science Education and Research (IISER) Bhopal have jointly developed a method to detect milk adulteration using only a drop and evaporation technique.
This technique can be used to detect starch adulteration in milk up to 0.005 percent weight by volume of starch. The researchers have come up with a simple technique to detect starch in milk and other liquids by analyzing what is known as a ‘sessile drop’ of milk under a portable microscope.
This method is economical, more effective, and accurate compared with conventional techniques and can be deployed in the field. India’s total milk production has increased from 146.31 million tonnes in 2014-15 to 221.1 MT in 2021-22, owing to various schemes that the Centre had initiated. While some industry estimates indicate that more than 70 per cent of this is adulterated, the last nationwide National Milk Safety and Quality Survey conducted by FSSAI indicated that only 0.19 per cent of the total 6,432 milk samples were found adulterated.
“This concept is based on the evaporation of the drop. As of now, we have tested our hypothesis in terms of adulteration with starch. Starch is one of the cheapest available forms of adulteration in India,” said Madivala G Basavaraj, Department of Chemical Engineering, IIT Madras. “Starch as an adulterant can be very dangerous. If added in large concentrations, it can cause diarrhea due to its undigested remains in the intestinal tract. Accumulation of starch in the body can lead to death in diabetic patients. This makes the study of starch adulteration in milk and ways to detect it very important in the context of global health and nutrition,” he added.
The existing method for checking the adulteration of starch in milk is the iodine test. Through that only beyond a certain level, it can be identified. However, our test can detect starch adulteration in milk up to 0.005 percent weight by volume of starch,” said Padma Ishwarya S, who was an Institute Postdoctoral Fellow in the Department of Chemical Engineering, IIT Madras.
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The drop of the milk under the microscope is allowed to evaporate, and by measuring the width and height of the deposit, the amount of starch adulteration can be detected. There have been grave concerns over how recent adulteration strategies are escaping conventional adulteration detection methods which include the iodine test. The limit of detection (LOD) for the iodine test is 0.02 percent weight by volume of starch. Moreover, the iodine test is qualitative and does not provide an accurate estimate of starch concentration.
Other methods to detect starch concentration in milk which include iodine titration and near-infrared spectroscopy require sophisticated instruments and skilled personnel. These methods also use chemical reagents.
“Milk is one of the most important food items in the world to the point that it is almost a necessity for most of us. To manage the high demand of milk, milk suppliers may resort to unethical techniques and adulterate the milk in order to match the demand and get a huge profit. This is a major problem, especially in emerging economies,” Ishwarya said.
“The growing problem of milk adulteration requires efficient and cost-effective methods for detection and control. Our research has shown that the sessile drop method is a promising technique for detecting starch in milk. This method not only offers a cost-effective solution but also has a higher sensitivity of detection compared to existing methods,” said Venkateshwar Rao Dugyala, Department of Chemical Engineering, IISER Bhopal.
