Alginate/Lignosulfonate Blends with Photoprotective and Antioxidant Properties for Active Packaging Applications

Sodium alginate/ammonium lignosulfonate blend solutions and thin films with different compositions have been prepared and studied. The rheology of the film forming solutions was comparatively evaluated and was established the effect of lignosulfonate incorporation onto sodium alginate solution properties and partial compatibility of components was found. The shear-thinning behaviour of the ALG/LS solutions was better evidenced at high ALG content, suggesting that the time required for the reorganization of the network structure is longer for the samples containing predominantly ALG, because its structure is damaged by increasing shear rate. The structural, morphological, optical and antioxidant properties of the crosslinked ALG/LS blend films were investigated with the aim to identify their potential as new active materials with photoprotective and antioxidant properties. The ATR-FTIR spectroscopy revealed the hydrogen bonding interactions between the components and scanning electron microscopy showed the modified microstructure of the blend films depending on composition. The surface topography changes have been evidenced by atomic force microscopy, showing an increased average surface roughness when the increasing lignosulfonate amount was incorporated into ALG matrix. The optical properties measurements revealed the light barrier properties of the blend films and the antioxidant activity evaluation showed the enhanced radical scavenging activity of the films with higher lignosulfonate content.