Natural Dye Detects Spoiled Milk: Is This the Future of Safety

Scientists at Christ University have developed an innovative plant-based pH-responsive sensor to monitor milk freshness, a pressing concern for India's massive dairy market, which produces over 239 million tonnes of milk annually. This method, based on traditional Asian plant extracts—specifically, Caesalpinia sappan L., commonly used as a dye—transforms the heartwood into a color indicator for milk spoilage detection. The effectiveness of this sensor lies in its sensitivity to pH changes: as milk spoils and acidity increases, the indicator shifts from bright orange-red (fresh milk, pH ≈ 7.0) to yellow (spoiled milk, pH ≈ 3.5).

The active compound, brazilein, is renowned for its dyeing and medicinal properties, providing stability under light and heat,—key advantages for practical applications in intelligent packaging. This not only offers consumers a real-time visual alert but also fits seamlessly into supply chains. The practical usability is enhanced by the ability to analyze pH changes using a smartphone camera and RGB analysis, which detects the “green chromatic shift”, making sophisticated laboratory tools or trained personnel redundant.

This scientific innovation blends traditional plant chemistry with digital accessibility, posing significant potential for food safety improvements and waste reduction across the global dairy supply chain. The findings have been published in the journal Food Analytical Methods and are patent-pending in India.