Edible cassava starch films carrying rosemary antioxidant extracts for potential use as active food packaging

Polyphenols-rich rosemary extracts (RE) were successfully incorporated within cassava starch films in order to produce active food packaging with antioxidant properties. Films with similar thicknesses (about 200 μm) and water content (15–20%) were obtained (p > 0.05). The polyphenols content of the active films ranged between 4.4 and 13.6 mg of gallic acid equivalents per gram. As the polyphenols content increased, the films showed an increase in their antioxidant activity. Moreover, the films containing the greater extract concentration showed better barrier properties against UV light. Surface hydrophobicity of the films was affected by the extract presence; the active films showed about 40% higher contact angle values (about 51°) than the control ones (about 37°). Fourier transform infrared spectroscopy and thermogravimetric analysis suggested that RE presence inhibited the bonding between glycerol and starch molecules and as a result the water vapor permeability and mechanical properties of the active films were affected. Migration tests were carried out using water and ethanol 95% as food simulants for aqueous and fatty foods, respectively. After 7 days of film exposition, the total polyphenols content loaded in the films was migrated within the aqueous food simulant, while, only a negligible polyphenol amount was detected in the fatty food one. Finally, the bio-disintegration of the films was tested finding that as the RE content increased the integrity of the RE-containing films was better preserved along the composting.