Eco-friendly polylactic acid/modified thermoplastic starch films enhanced with clove essential oil and cochineal for dual-functional active and intelligent food packaging

Abstract

This study introduces a novel, industrially viable, eco-friendly packaging film based on polylactic acid (PLA) and thermoplastic starch (TPS), incorporated with cochineal dye and clove essential oil (CEO), to simultaneously monitor spoilage and preserve high-protein foods, such as shrimp. Citric acid-modified TPS showed significant improvements in particle dispersion, interphase adhesion, and size reduction when blended with PLA. Incorporating 20 % modified TPS into PLA significantly enhanced ammonia sensitivity, achieving faster and more uniform color changes, while improving tensile strength by 32.6 % to 28.48 ± 1.25 MPa and increasing water vapor resistance by 11 % compared to standard PLA/TPS film. The engineered composite films effectively indicated shrimp freshness by transitioning from orange to purple, exhibiting a 117 % higher total color change (ΔE) compared to the unmodified film, reaching 69.54 ± 2.36. This color change demonstrated a strong correlation with shrimp spoilage indices within 24 h of storage at 28 °C.The films demonstrated antibacterial efficacy, with inhibition zones of 16.1 mm and 12.3 mm against L. monocytogenes and E. coli, respectively. CEO's moisture-sensitive release mechanism maintained total viable count (TVC) levels below the 7 log CFU/mL threshold for 15 days under 4 °C storage, extending shrimp shelf life by 10 days compared to control samples.