Design and characterization of biodegradable curcumin-loaded active agar-based composite film packaging from Gelidium elegans seaweed for extending the shelf life of fish fillets

An agar-based biodegradable film was developed from Gelidium elegans seaweed by integrating curcumin and chitosan into an agar matrix, and its potential as a replacement for petroleum-based food packaging was analyzed. The agar–chitosan–curcumin (AG–CS–CUR) films exhibited significantly higher ( p < 0.05) opacity and notable antioxidant activity, with 2,2-diphenyl-1-picrylhydrazyl and hydroxyl radical scavenging activity score of 68.83% and 60.33%, respectively. The AG–CS–CUR films exhibited good mechanical strength and enhanced barrier properties, with reduced water-vapor and oxygen permeabilities of 2.99 × 10 −10 g/m·s·Pa and 6.62 × 10 −7 g/m·s compared to AG films (3.88 × 10 −10 g/m·s·Pa and 8.48 × 10 −7 g/m·s), respectively. Although the moisture content was not significantly different, the swelling degree decreased markedly to 161.90% from 686.31% of AG, attributed to changes in hydrogen bonding indicated by Fourier-transform infrared peak shifts (3200–3400 cm −1 ) toward lower wavenumbers. Overall migration from AG–CS–CUR occurred at a low rate (<2.6 × 10 −4 mg/dm 2 ) under pH lower or higher than 4.5 and fatty food media. The films were biodegradable, reaching up to 32.14% degradation within 28 days. Scanning electron microscopy confirmed a dense matrix with no visible pores. In summary, the AG-CS-CUR films exhibited active preservation by delaying fish color changes (ΔE = 7.89–9.38) compared to plastic films (ΔE = 17.41–20.00). Although AG-CS-CUR films showed higher weight loss (9.30–23.27%) than plastic films (5.88–8.60%), they outperformed pure agar films (6.64–28.67%) during one week of storage, demonstrating promising potential for advancement in active packaging technology.