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

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.