Researchers at the Indian Institute of Technology (IIT) Guwahati have developed a paper-based sensor that can accurately asses the quality and freshness of milk within minutes by changing its colour.
The quality and freshness of milk are decided by the invasion and presence of microbes in the milk, the researchers explained in the study published in the journal Biosensors, and Bioelectronics.
They noted that bacteria and other microbes that grow in milk can not only affect its taste and freshness, but also result in health issues. Pasteurisation is commonly used to kill the microbes in milk and various tests are used to ensure the effectiveness of the process, according to the researchers led by Pranjal Chandra, an assistant professor at IIT Guwahati.
Commonly used tests such as the methylene blue test, are time-consuming, and could take many hours for colour changes to indicate the presence and absence of microbes.
The team, including scholar Kuldeep Mahato, developed the simple visual detection technique to asses the quality of milk, without the need for special equipment and instruments.
“It would be useful if the quality of milk can be tested at the point of collection of milk or even in the home kitchen,” Chandra said, adding that such testing requires easy-to-operate and portable detection kits.
Chandra explained that Alkaline Phosphatase (ALP) is a metalloprotein found naturally in raw milk samples, and is considered an important biomarker in the quality control of milk. Detection of ALP in milk can thus point to inadequate pasteurisation and perhaps contamination.
The researchers used simple filter paper, chemically modified it, and loaded it with a recognition element — anti-ALP — which captures the ALP present in the milk.