Development of Dual Enzymatic-Ionic Crosslinked Alginate-Gelatin Films Enriched with Pelargonium sidoides Extract for...

Active biodegradable packaging materials capable of preserving fruit quality and reducing oxidative processes are promising alternatives to conventional petroleum-based plastics. In this study, alginate-gelatin composite films were developed using a dual crosslinking strategy combining microbial transglutaminase-mediated enzymatic crosslinking with Ca²⁺-induced ionic gelation. The films were then enriched with Pelargonium sidoides root extract as a natural antioxidant. The combined crosslinking approach resulted in a more compact protein-polysaccharide network, which was reflected in increased film density and reduced swelling. The highest density was observed for film 1.0F (ρ = 1.2004 ± 0.0151 g/cm³), while films containing Ca²⁺ showed lower swelling values, with SI₆₀ decreasing from 7655 ± 70 for 0F to 5853 ± 49 for 0Ca²⁺F. The addition of the extract promoted additional interactions within the polymer matrix and affected the swelling and barrier properties of the films. The WVTR values were 36.1 ± 0.9 g/m²·24 h for 1.0F and 49.8 ± 1.5 g/m²·24 h for 1.0Ca²⁺F. The incorporation of P. sidoides extract also significantly increased the antioxidant activity of the films, particularly at higher extract concentrations. Furthermore, films containing Ca²⁺ and the extract contributed to the preservation of anthocyanins in Flame Seedless grapes during 14 days of storage, with the anthocyanin content reaching 0.208% ± 0.019 for the 1.0Ca²⁺F treatment. Overall, the results indicate that dual-crosslinked alginate-gelatin films enriched with P. sidoides extract have favorable physicochemical and functional properties and may be suitable for the development of sustainable active packaging materials for anthocyanin-rich fruits.