Preparation and characterization of active gelatin-based films incorporated with natural antioxidants

A series of active gelatin films containing natural antioxidants (NAs) were used as food packaging in this paper. Five kinds of NAs [green tea extract (GTE), grape seed extract (proanthocyanidins, OPC), grape seed extract (grape seed polyphenols, GSP), ginger extract (GE), gingko leaf extract (GBE)] were added into gelatin-based films as antioxidant additive. The effects of these extracts on the antioxidant, physical and mechanical properties of the films were studied. The results suggested that addition of GBE made the gelatin-based film possess the highest DPPH radical scavenging activity at 1.0 mg/ml. The UV light barrier was also greatly improved when the film mixed with GBE and the value of light transmission was 23.242% at 400 nm. In addition, it was observed that the gelatin-based film blending of GTE resulted in significantly increased protection against moisture. As to the mechanical properties, the lowest tensile strength (14.64 ± 2.51 MPa) and percentage of elongation at break (30.86 ± 6.86%) were found in the gelatin-based film mixing of GSP. The moisture content and water solubility of films were not altered with addition of NA. Furthermore, the active gelatin films showed the heterogeneous surface and porous formation by scanning electron microscopy after blending of NA. At the same time, the FTIR-ATR spectra was used to investigate the interactions between gelatin and extracts. These results reveal that addition of GTE, OPC, GBE into gelatin film is an ideal choice to be developed into active food packaging for food preservation. The natural extracts increase the antioxidant activity of gelatin films by DPPH free-radical scavenging capacity. DPPH radical scavenging activity of gelatin films with extracts at 0.01 mg/ml, 1.0 mg/ml, 5.0 mg/ml. Control: no extracts added; GTE: film with green tea extract; OPC: film with grape seed extract (proanthocyanidins); GSP: film with grape seed extract (grape seed polyphenols); GE: film with ginger extract; GBE: film with gingko leaf extract. [Display omitted] •Functional gelatin-based films were prepared.•Five kinds of natural extracts were added to gelatin-based film as active additive.•The active gelatin-based films improved the barrier to UV light and moisture.•The natural extracts made the film possess the excellent antioxidant activity.