A novel use of purple tulip petal anthocyanins in pH-sensitive polyvinyl alcohol films for the real-time monitoring of shrimp freshness.

BACKGROUND Shrimp is among the most perishable seafood commodities, and its freshness is still largely assessed through time-consuming laboratory methods. pH-responsive colorimetric films have received growing attention as they allow visual, real-time quality monitoring without specialized equipment. To date, anthocyanins from several floral sources have been tested in such systems, but purple Tulipa gesneriana petals, which are rich in anthocyanins and widely available as ornamental waste, have not been evaluated. In this study, tulip petal extract (TPE) was incorporated into polyvinyl alcohol (PVA) films to develop a smart indicator system for monitoring shrimp freshness.

RESULTS Incorporation of TPE (7.5-20 g kg-1, film basis) into PVA films significantly enhanced pH sensitivity and ammonia responsiveness while modulating structural and functional properties. X-ray diffraction and differential scanning calorimetric analyses indicated reduced crystallinity and thermal stability due to disruption of hydrogen bonding within the PVA matrix. Mechanical testing revealed a dose-dependent decrease in tensile strength (21.8 → 16.9 MPa) and a corresponding increase in elongation at break (213% → 286%), confirming a plasticizing effect. In addition, water solubility and water vapor permeability decreased, improving barrier performance. The films exhibited progressive color transitions from red to yellow-brown in response to increasing pH and total volatile basic nitrogen levels (112-616 mg kg-1) during refrigerated shrimp storage, demonstrating their effectiveness as real-time freshness indicators.

CONCLUSION TPE-enriched PVA films represent sustainable and cost-effective visual indicators for seafood freshness and show strong potential for broader intelligent food packaging applications. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.