Design and fabrication of anthocyanin functionalized layered clay/poly (vinyl alcohol) coatings on poly(lactic acid) film for active food packaging

Biodegradable polymers (poly(lactic acid) (PLA), etc.) have been severely limited in their practical applications due to their inherent limitations in performance. Surface coating technology can effectively improve the active packaging function for food packaging. In this study, anthocyanin (ACY) functionalized layered double hy-droxides (LDHs@ACY-Cu) was synthesized for the first time by adsorption and complexation of ACY with Cu(II) on the LDHs. Further, ACY (5 wt%)/poly(vinyl alcohol) (PVA) coatings as the first layer and LDHs@ACY-Cu (1-7 wt%)/PVA coatings as the second layer were successively coated on the PLA base film to fabricate active multilayer films. The results showed that ACY-Cu(II) complexes were loaded on the LDHs successfully with a thickness of 4 nm. With the increase of LDHs@ACY-Cu content, UV barrier, antioxidant, antibacterial and gas barrier properties of active multilayer films were improved significantly. When the addition of LDHs@ACY-Cu increased to 7 wt%, UV barrier (at 280 nm) and oxygen barrier properties of active multilayer films were increased by 44.9% and 99.1% compared with PLA base film, and the antibacterial and antioxidant properties also reached 96.4% and 82.21%, respectively. Although the color of all films showed a tendency to brown, the light transmittance exceeded 89.0% in the visible light range (at 600 nm). The milk spoilage test indicated that active multilayer films can inhibit the rapid bacterial reproduction in the pasteurized milk and extend the shelf life of milk. Therefore, active multilayer films exhibit good potential for applications in the field of active food packaging.

Automated summary

In this study, active multilayer films were fabricated by synthesizing anthocyanin functionalized layered double hydroxides (LDHs@ACY-Cu) and coating them on a PLA base film. The active multilayer films showed improved UV barrier, antioxidant, antibacterial, and gas barrier properties, indicating their potential in active food packaging applications.