GUWAHATI, Nov 14 - A team of researchers from Indian Institute of Technology (IIT) Guwahati have developed a paper-based sensor that can assess the freshness of milk by a simple visual detection technique without the need for using any special equipment and instrument.
The IIT-G team’s research findings have been published in scientific journal Biosensors & Bioelectronics.
The research team was led by Dr Pranjal Chandra, assistant professor in the Department of Biosciences and Bioengineering at IIT-G, along with research scholar Kuldeep Mahato.
“Alkaline Phosphatase (ALP) is a metalloprotein found naturally in raw milk samples and is considered an important biomarker in quality control of milk. Though found in raw milk, ALP gets destroyed during pasteurization. Detection of ALP in milk can thus point to inadequate pasteurization and perhaps contamination,” said Dr Chandra.
He said there were lots of advantages if the quality of milk can be tested at the point of collection of the product or even at kitchens in home.
Despite ALP’s recognisable detection potential in native milk, the multistep nature and requirement of sophisticated bulky analytical instruments and trained personnel to detect the metalloprotein limit its use as a sensor of milk quality in remote settings and in home kitchens. “That is why there is a need for developing better ALP detection kits,” said Dr Chandra.
The researchers used simple filter paper, chemically modified it, and loaded it with a recognition element which captures the ALP present in the milk.
“Upon treatment of the colour forming compound known as BCIP to the captured complex, the presence of ALP results in formation of a blue-green coloured precipitate. In the absence of ALP, it does not produce any colour. The intensity of the colour indicates the amount of ALP present. Our team used smart-phone 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,” said Dr Chandra. “Our sensor takes merely 13 minutes to detect ALP. Hence it can be applied for quick onsite analysis,” he added.
The researchers successfully tested milk obtained from villages and also commercially available milk samples using their paper-based sensor kit. The team found that they could detect down to 0.87 units of ALP per ml of milk to about 91-100 per cent accuracy. “This detection limit and accuracy makes it possible to discriminate raw milk, which often contains as high as 191 units per ml of ALP, from pasteurized and boiled milk which contains ALP in ultra-trace amount,” said Dr Chandra.
Based on the detection principle, the team has also developed a miniaturised detection kit and demonstrated the instrument and its applicability for milk monitoring. “We plan to extend the sensing platform and the 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. The developed bio-electronic chip is an advanced version of the paper-based kit with improved accuracy. We have plans to commercialise both the variants of milk pasteurization testing kits,” said Dr Chandra.