Fabrication of cellulose nanofiber-based functional color indicator film incorporated with shikonin extracted from Lithospermum erythrorhizon root

Cellulose nanofiber (CNF)-based functional films were prepared by adding shikonin extracted from dried roots of gromwell (Lithospermum erythrorhizon) using a solution casting method. The shikonin added CNF film showed distinctive color changes depending on the pH in the range of 2–12. The shikonin was evenly dispersed in the CNF matrix to form a compatible red colored film. The addition of shikonin (10%) improved the mechanical properties of the CNF film without significantly affecting the crystal structure, water vapor barrier, and thermal stability properties of the film. The CNF/shikonin composite film showed remarkable ultraviolet blocking properties without much-sacrificing transparency. Besides, the composite film showed potent antimicrobial and antioxidant activities. The CNF-based color indicator films with improved physical and functional properties have a high potential for active and intelligent food packaging applications.