Edible films made from tuna-fish gelatin with antioxidant extracts of two different murta ecotypes leaves (Ugni molinae Turcz)

The aqueous extract of two ecotypes of murta (Ugni molinae Turcz) leaves (Soloyo Grande “SG” and Soloyo Chico “SC”), were analysed for their antioxidant capacity, SC extract exhibiting a higher antioxidant capacity than SG extract. This difference affects physical properties of tuna-fish (Thunnus tynnus  ) gelatin-based edible films with incorporated murta leaves extract. Dynamic viscoelastic studies, scanning electron microscopy (Cryo-SEM) and SDS-PAGE denoted a certain degree of interference of polyphenolic compounds in the arrangement of gelatine molecules. The addition of the murta extracts leads to transparent films with increased protection against UV light as well as antioxidant capacity. The puncture test showed no significant differences (p>0.05)(p>0.05) between the Control film and the SG film, whereas puncture force and puncture deformation were significantly lower for SC ecotype. Water vapour permeability of tuna-fish skin gelatin films with SG was 2.87×10−8 g mm h−1 cm−2 Pa−1, significantly different (p⩽0.05)(p⩽0.05) to 1.83×10−8 g mm h−1 cm−2 Pa−1 of the film with SC.