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. Adulterants in milk can be classified into 4 categories, namely:
1. Protein-based adulterants (e.g.: whey protein isolate, soy protein isolate, pea protein isolate)
2. Nitrogen-based adulterants (e.g.: urea, melamine)
3. Carbohydrate-based adulterants (e.g.: sucrose, glucose, lactose, starch)
4. Chemical preservatives (e.g.: formaldehyde, hydrogen peroxide)
In a research article, the authors, Dr. Padma Ishwarya S and Dr. Madivala G. Basavaraj from the Department of Chemical Engineering, Indian Institute of Technology (IIT) Madras, Chennai, India, Dr. Venkateshwar Rao Dugyala from the Department of Chemical Engineering, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal, India, and Dr. Shantanu Pradhan from the Department of Biotechnology, Indian Institute of Technology (IIT) Madras, Chennai, India, have focused their attention on starch as an adulterant.
Dr. Padma Ishwarya S 
Dr. Madivala G. Basavaraj 
Dr. Venkateshwar Rao Dugyala 
Dr. Shantanu Pradhan
Starch as an adulterant can be very dangerous. If added in large concentrations, it can cause diarrhoea 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.
Iodine test is the most commonly used technique to identify starch adulteration in milk. But there have been grave concerns over how recent adulteration strategies are escaping conventional adulteration detection methods which include the iodine test.
Also, the range of detection of starch using the iodine test is very limited. 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 have also not been entirely reliable as these methods require sophisticated instruments and skilled personnel. These methods are tedious and complicated. They also use harmful chemicals.
Keeping these problems in mind, the authors of the article (published in Food Control), have come up with a simple technique for detection of starch in milk and other liquids by analyzing what is known as a sessile drop of milk under a portable microscope. This method is cheaper, more effective, more accurate, and can be used in the field.
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. This technique can be used to detect starch adulteration in milk up to 0.005 percent weight by volume of starch.
Although this technique has been found to be effective to detect starch adulteration in milk, future studies are required to understand the influence of a wide-range of parameters such as starch concentration, substrate types, and temperature/humidity conditions on the efficacy of this novel sessile drop evaporation based adulterant detection approach.
Prof. Rajneesh Bhardwaj from the Department of Mechanical Engineering, Indian Institute of Technology (IIT) Bombay, Mumbai, India, acknowledged the extensive research into the sessile drop phenomenon by giving the following comments: “The evaporation of sessile droplets on a solid surface containing colloidal particles, also known as the coffee-ring effect (CRE), has been a much-studied problem in the field of interfaces in the last two decades. After its proposition by Deegan et al. in 1997, significant research has been reported on the effect of different problem parameters, such as thermophysical properties of the substrate, particle size, etc.”
He further goes on to say that in spite of the extensive research done, there have been very few practical applications of the same: “While several fundamental insights are known now about the CRE, there are very few reports on applying CRE in technical applications.” He lauds the work done by the authors for utilizing the CRE to study milk adulteration by giving the following comments: “In this paper, Basavaraj and co-workers employed CRE to evaluate the milk’s adulteration. They showed that the distinct differences between the dried deposits of pure and adulterated milk might act as valuable markers to determine adulteration. This method also works for low values of starch, a common milk adulterant. In the Indian context, the proposed technique by IIT Madras researchers is vital due to a debilitated milk distribution in many states, prone to adulteration at several points in its supply chain.”
Article by Akshay Anantharaman
Here is the original link to the paper:
https://www.sciencedirect.com/science/article/abs/pii/S0956713522004650
