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IIT Guwahati Scientists Invented Paper-Based Biosensor For Confirmation Of Milk Pasteurization

A research group from the Indian Institute of Technology, Guwahati, have developed a paper-based kit that can evaluate the pasteurization of milk based. The developed kit can discriminate the pasteurized and raw milk based on the determination of intrinsic indicator present in milk. The duo team, led by Prof. Pranjal Chandra, department of biosciences and bioengineering at Indian Institute of Technology, Guwahati with Ph.D. research scholar Kuldeep Mahato has published the recent innovation in biosensor and bioelectronics journal.

As per the authors “Milk being a widely consumed stable food, its safety has become a prime concern to consumers due to the inevitable microbial invasion making it a pool for the various type of food born infections. Therefore, milk is boiled in households and before consumption and in dairies a rapid heat & cold shock is given technically called pasteurization for killing the microbial forms.  The available confirmatory for this the tests are based on various high-end instruments which limits the test in many ways, thus, the requirement of low cost easy to handle kit based detection is of the need of the hour especially in the third world countries”. Prof. Chandra the lead author also added that “in context to the third world countries the availability of quality controls are rare or nonfunctioning at the point of collections. Thus, using our developed portable testing kit, the reportedly greater mass spoilage of milk at collection points due to the microbial invasion can be prevented from such quality deteriorations”.

To develop the kit researchers used ordinary filter paper and cut to small disc using the office punch machine. Thereafter, the paper discs were chemically impregnated with the sensing probe consisting the antibody of the ALP an indicator molecule for the pasteurization and target molecule in this case. When ALP comes into contact with the probe, it turns white paper disc into a colored one.

As per the authors “, the paper was functionalized with the 4-carboxybenzene diazonium solution followed by chemical treatment which eventually exposes the COOH flanking groups. On which the NH2 groups of the anti-ALP was coupled by means of covalent bioconjugation techniques on the paper surface. When a drop of milk is dispensed on the paper disc, the present ALP reacts with probes, gives the color change. The appearance of the greenish blue color at the paper sensor was then captured using smartphone camera and the image was processes using the digital image colorimetric technique. The technique tells the correlation of the  ALP content on the basis of color change. Using this generated data from standard conditions, one can estimate the amount of ALP in the milk and tell the state of freshness.

" The kit have been assessed using the milk of different sources collected from the nearby villages and the commercial outlets form the IIT-G campus following the spike-recovery method of analysis" said Prof. Chandra. In most cases, close to 94% of the ALP have been determined using the probe. The authors also confirmed the greenish blue color appearance is explicitly due to the ALP, not due to the interference of vitamins, other proteins, and minerals in the milk. The handy kit is merely of 2 square centimeter in size made up of the paper biosensor and the support of cellulose acetate film. The biosensor is covered from outside using the O-ring and the centrally holed cellulose acetate circular lid, which prevent the probe from the mechanical distortion. Since ALP is also tested in various body fluids, the kit can also be utilized in clinics. Fabrication in the laboratory at present costs around Rs. 80 to Rs 125 per kit and could come down when mass manufactured, researchers said.

 "As of now, our developed kit is capable of discriminating the raw from pasteurized milk based on the ALP determination, which is correlated with the present microbial forms or microbial contamination in milk. We are considering that in future we will address the determination of chemical-based contaminations in milk as well," Kuldeep Mahato, a Ph.D. scholar, who worked on this project along with Prof. Chandra told during an interaction.

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