Smart and active packaging based on thermoplastic starch and gelatin blends with curcumin, micro/nanocellulose, and tea tree oil.

Abstract

Biodegradable materials with active and intelligent functionalities have attracted increasing interest as sustainable alternatives to conventional food packaging. This study developed and characterized thermoplastic starch (TPS)/gelatin films containing curcumin (Cur) as a pH-sensitive indicator, tea tree essential oil (TTO) as an active agent, and kombucha bacterial cellulose (KBC) as a natural emulsifier. KBC was purified, dried, and ultrasonicated, producing a heterogeneous micro/nanocellulose suspension (39.1-139.9 nm). The addition of gelatin substantially increased film stiffness, with Young's modulus increasing from 1.06 to 69.10 MPa and elongation at break decreasing from 583.94% to 25.93%, whereas the incorporation of KBC partially restored tensile strength to 2.88 MPa. KBC also improved water resistance by reducing solubility from 23.0% to 10.7% and increasing the water contact angle from 64.4° to 70.6°. The films exhibited a transparency index of approximately 4.0%, intense yellow coloration, and color transition from yellow to orange at pH ≥ 9. Although antimicrobial activity against Escherichia coli was limited, TTO increased DPPH radical scavenging activity from 44.75% to 52.55%, and storage tests with chicken samples showed color changes after 7 days of refrigerated storage.