Research Highlight

Portable device to detect adulteration of milk

doi:10.1038/nindia.2020.22 Published online 6 February 2020

Using paper, wax and a chemical reagent, scientists have fabricated a portable lab-on-a-chip for the detection of starch contamination in milk1. The handy detectors would cost less than a dollar for 100 strips, they say.

Adulteration of milk with starch to increase its density poses a major health concern. Excess starch in milk has been reported to cause diarrhoea in children and is harmful for diabetic patients.

The paper-based device can replace existing iodine-based starch detection tests that need to be conducted in a chemical laboratory, its makers from SRM Institute of Science and Technology (SRMIST) in Tamil Nadu, India, say.

The portable device uses a standard filter paper selectively impregnated with paraffin wax to create a circular hydrophilic (water friendly) 'test zone' within a hydrophobic (water repelling) region to ensure that the sample does not flow out of the detection region.

Colours on the strip show: (a) pure milk on uncoated paper, (b) pure milk on paper coated with chemicals and (c) starch contaminated milk on paper coated with chemicals.
They coated the test zone with potassium iodide and iodine — chemical reagents that can detect starch in milk. Potassium iodide contains iodide ions that combine with iodine molecules to form soluble tri-iodide ions. These ions interact with starch in the test zone resulting in a colour change that can be imaged by a smart phone camera.

A colour change from light brown to brownish blue indicates the presence of starch, the authors say. Integration of this detection procedure with smart phone imaging allows portability and affordability, making the device commercially promising.


References

1. Govindarajalu, A. K. et al. Cellulosic paper-based sensor for detection of starch contamination in milk. Bull. Mater. Sci. 42, 255 (2019) doi: 10.1007/s12034-019-1958-2