Poly (vinyl alcohol)/hydrothermally treated tannic acid composite films as sustainable antioxidant and barrier packaging materials

Antioxidant food packaging aids in prolonging the shelf life of foods by retarding the rate of oxidation. In this study, we newly developed poly (vinyl alcohol) (PVA)/hydrothermally treated tannic acid (HTA) composite films (PVA/HTA) using a solution casting method for use as sustainable antioxidant and barrier films. TA was first treated using a hydrothermal method and subsequently incorporated into the PVA film. HTA with numerous OH groups strongly interacted with PVA via a crosslinking reaction. Accordingly, the crystallinity and crystalline size of PVA gradually decreased with increasing HTA content (from 0 to 5 %) owing to the lower chain mobility and chain disordering caused by the crosslinking. A higher crosslinking density also reduced the free volume in the matrix and compromised the swelling properties, which improved the oxygen barrier properties and imparted some hydrophobicity to the composite film, respectively. Further, adding HTA increased the rigidity of the film while reducing the elongation at break. The antioxidant capacity of the PVA/HTA composite films also signif-icantly increased (4.2 % to 80.3 % in the DPPH assay and 4.6 % to 98.8 % in the ABTS assay) with increasing HTA content, owing to the radical scavenging ability of HTA. These results clearly indicate that the novel PVA/ HTA composite film with antioxidant properties can be used as an active packaging material.