A novel paper/plastic-based hybrid strip test for rapid and multiplexed colorimetric detection of milk adulterants

Milk adulteration remains a major concern for food safety and consumer protection, as it can compromise nutritional quality and pose health risks. This study presents a low-cost hybrid paper/plastic strip test for the simultaneous detection of seven common adulterants in cow milk: urea, hydrogen peroxide, starch, formaldehyde, antioxidants (e.g., ascorbic acid), sodium hypochlorite, and neutralizers/detergents, using a pH-based colorimetric sensing without sample pretreatment. The device was fabricated using a craft cutter and combined paper and plastic substrates, allowing multiplexed detection on a single strip. Analytical performance was optimized, yielding recovery rates between 86% and 112% for key adulterants. The test strips remained stable for up to 30 days under refrigeration (2-5 °C). In a case study of 50 milk samples, the device accurately identified adulterants with minimal interference, and results showed no significant deviation from reference methods (validated by Tukey's test). With a fabrication cost of only $0.25 per unit, the proposed platform provides a reliable, affordable, and scalable solution for routine milk quality monitoring, representing a promising tool for enhancing quality control in the dairy industry.