eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2026-10-10 23 3 59994 article Priyanka Gaikwad 1 Roma Sharma 1 Tanvi Kisan Dond 1 Bushra Sayyed 1 Snehal Dhananjay Jadhav 1 Department of Pharmacognosy, Pravara Rural Education Society's College of Pharmacy (for Women), Savitribai Phule Pune University, Nashik, India Milk adulteration represents a critical global food safety issue, as illegal additions of synthetic chemicals and neutralizers compromise nutritional quality and pose severe human health risks. Among common adulterants, urea and alkaline neutralizers (such as caustic soda, sodium bicarbonate, or carbonate) are added to artificially inflate apparent protein content and prevent souring. To address the need for simple, low-cost point-of-care testing, this study developed a plant-based dual-zone colorimetric paper strip for the simultaneous screening of urea and alkaline adulterants in milk. The screening device utilizes Whatman filter paper partitioned by a paraffin wax barrier to prevent cross-contamination. Zone A is functionalized with crude soybean (Glycine max) extract as a natural source of urease enzyme integrated with turmeric-derived curcumin (Curcuma longa), while Zone B contains curcumin alone as a pH-responsive indicator. Enzymatic hydrolysis of urea in Zone A generates ammonia, causing local alkalinization and a distinct visual color change from yellow to reddish-brown. Zone B responds directly to elevated pH (> 8.0) resulting from alkaline adulteration. Under optimized conditions, the test strip exhibited a rapid visual response within 30–60 seconds using a sample volume of 20–30 µL. Evaluation across 30 field and commercial milk samples demonstrated presumptive positive screening in 13 samples (43.3%), with no false-positive color changes observed in negative pure milk controls. While the curcumin indicator effectively screens for alkaline conditions, it does not distinguish specific sodium hydroxide from other basic adulterants. This eco-friendly, equipment-free paper strip provides a promising preliminary screening platform for dairy quality monitoring, though quantitative validation against gold-standard laboratory methods (such as HPLC/FTIR) and broader matrix interference testing remain necessary before field deployment. https://www.biotech-asia.org/vol23no3/development-of-a-plant-based-dual-zone-colorimetric-strip-for-rapid-screening-of-urea-and-alkaline-adulteration-in-milk/ Alkaline adulteration; Curcumin pH indicator; Dual-zone colorimetric sensor; Milk adulteration screening; Paper-based analytical device; Soybean urease