Incorporation of antioxidant borage extract into edible films based on sole skin gelatin or a commercial fish gelatin

An edible film plasticized with glycerol and sorbitol was successfully prepared from a sole skin gelatin. Some physico-chemical properties of the films (water vapour permeability, water solubility, opacity) were similar to those from a commercially acquired catfish skin gelatin, whereas the breaking force was significantly lower (11.4 ± 2.1 vs. 28.1 ± 3.1 N) and the breaking deformation significantly higher (18.1 ± 1.0 vs. 14.5 ± 2.1%). A borage extract was prepared and its antioxidant properties (total phenolics, reducing ability by the FRAP assay, radical scavenging capacity by the ABTS assay, iron (II) chelation activity) were determined. The incorporation of the borage extract into the films gave rise to a pronounced increase of their antioxidant properties irrespective of the gelatin origin, with minor modifications of their physico-chemical properties: decrease of the breaking force and increase of film opacity. The antioxidant properties of films incorporated with borage extract were higher than those of films incorporated with α-tocopherol and BHT.