Non-destructive colorimetric detection of milk freshness by starch–alginate sensor beads stabilized by nanoemulsions

The study presents the development of Ca²⁺-crosslinked starch-alginate beads encapsulating ternatin-loaded nanoemulsions (SAB) for rapid detection of milk spoilage. The beads exhibited strong, stable colorimetric responses (Δ<i>E</i> > 50) across the pH range (5-7), shifting from light blue in fresh milk, dark blue in spoiling milk and blue-grey in spoiled milk. Encapsulation of the nanoemulsion within the bead effectively prevented the leaching of ternatin, while structural integrity was confirmed by FTIR and TGA analyses. Dry SAB showed superior stability in liquids and 87% cell viability, confirming its non-toxic nature. Unlike conventional techniques, SAB enabled fast, non-destructive on-site spoilage monitoring, highlighting its potential for real-time food safety applications.