Photo: iStock
Photo: iStock

IIT-Guwahati scientists develop paper based sensor to check milk quality at home

  • The researchers at IIT-Guwahati have used simple filter paper, chemically modified it, and loaded it with recognition element to detect the quality of milk
  • The takes merely 13 min to detect ALP, and hence it can be applied for quick onsite analysis

NEW DELHI : Indian scientists have developed a paper based sensor to instantaneously check freshness of milk. Researchers at Indian Institute of Technology (IIT) Guwahati have developed this simple visual detection technique to detect the quality of milk, without the need for special equipment and instruments.

The research has also published in the journal of Biosensors, and Bioelectronics which was done by a team led by Pranjal Chandra, Assistant Professor, Department of Biosciences and Bioengineering, IIT Guwahati along with Kuldeep Mahato, research scholar.

The quality and freshness of milk are decided by the invasion and presence of microbes in the milk. Bacteria and other microbes that can grow in milk, not only affect the taste and freshness, but also result in health issues.

Pasteurization is commonly used to kill the microbes in milk and various tests are used to ensure the effectiveness of pasteurization. Commonly used tests such as the methylene blue test, are time consuming; it could take many hours for colour changes to indicate presence and absence of microbes. Commercial phenol-based tests require sophisticated spectrophotometers and involve multistep procedures, which necessitates dedicated testing centres and skilled personnel. 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.

“Alkaline Phosphatase (ALP) is a metalloprotein found naturally in raw milk samples and is considered an important biomarker in quality control of milk. It is found in raw milk and is destroyed during pasteurization. ALP is also found in higher amounts in the case of milk derived from animals with infection in the mammary glands. Detection of ALP in milk can thus point to inadequate pasteurization and perhaps contamination," Chandra said.

“Despite ALP’s recognizable detection potential in native milk, the multistep nature, and requirement of sophisticated bulky analytical instruments and trained personnel, to detect ALP, limits their use as a sensor of milk quality in remote settings and in home kitchens," Chandra said.

The researchers have used simple filter paper, chemically modified it, and loaded it with a recognition element anti-ALP, which captures the ALP present in the milk. Upon treatment of the colour forming compound BCIP (a chemical compound) to the captured complex of ALP forms a blue-green coloured precipitate, that otherwise does not gives any colour in the absence of ALP. The intensity of the colour indicates the amount of ALP present. The team used a smartphone to capture the image of the colour and used the RGB (Red Green Blue) filter in the phone to profile the colour obtained, which could be co-related to the concentration of ALP present in the test sample.

The takes merely 13 min to detect ALP, and hence it can be applied for quick onsite analysis. The researchers successfully tested milk obtained from villages and commercially available milk samples using their paper-based sensor kit, and found that they could detect down to 0.87 units of ALP per millilitre of milk to about 91–100% accuracy. This detection limit and accuracy make it possible to discriminate raw milk (often contains as high as 191 U/mL ALP) from pasteurized/boiled milk which contains ALP in ultra-trace amount.

Based on the detection principle, the team has also developed a miniaturized detection kit and demonstrated the instrument-free, in-kitchen applicability of the kit for milk monitoring.

New sensor has been developed by Kuldeep Mahato, Ashutosh Kumar, Buddhadev Purohit. “We plan to extend the sensing platform/principle we have developed for ALP towards the detection of various molecules in different matrices. In fact, we have developed another sensor for ALP detection using a label-free bio-electronic chip," said Chandra.

“The developed bio-electronic chip is an advanced version of the paper-based kit with improved accuracy. We have plans to commercialize both the variants of milk pasteurization testing kits." he also added on future plans," Chandra added.

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