Indian Institute of Technology, Guwahati has developed a paper kit to test freshness of milk. The simple paper kit will work with aid of smartphone app and comes handy to test milk quality before it turns sour. Several industries in dairy, confectionery units, milk collection centres are worried about milk freshness. Testing for freshness is a time consuming effort and needs sophisticated equipment line spectrometers.
The paper kit works on the principle of detecting Alkaline Phosphatase which present even after pasteurization means microbes. The paper kit coated with 4-carboxybenzene diazonium solution and then chemically treated to expose-COOH groups on the diazonium. When milk drops are added it attaches to NH2 groups on anti-ALP probe molecules and changes in color. The changes in color is read by smartphone camera which is calibrated to decode the freshness of milk.