Development and validation of paper-based strip method for the detection of formalin in milk

Formalin has been reported to be added to milk to prolong the shelf life of milk. The present study was conducted to develop and validate liquid-phase and paper-based strip methods for the rapid detection of formalin in milk using four different procedures i.e., A, B, C and D. Among all the procedures, procedure A worked successfully both in the liquid-phase and paper-based assays. The developed strip-based method involved the dipping of the strips in milk followed by visualization of change in colour. Formalin adulterated milk gave yellow colour to the strip, while for normal milk, it remained colourless. Limit of detection of developed strips was 0.05% with a response time of 7-8 min. Shelf life of the strips was a minimum of 6 months at both room (30-37 °C) and refrigeration (4 ℃) temperature. The strips can be used both at field as well as household levels for rapid detection of formalin presence in milk with greater sensitivity and hence can contribute in supplying authentic milk to the consumers.