Fabrication and characterization of chitosan-based films incorporating DES-extracted astaxanthin from shrimp shells for antimicrobial shrimp packaging applications

This study investigates the enhancement of chitosan-based films by incorporating polyethylene glycol (PEG), deep eutectic solvents (DES), and a DES formulation containing astaxanthin extracted from shrimp shells (DES-Ast). The films were evaluated for visual, structural, mechanical, and functional properties. Neat chitosan films (Ch) exhibited brittleness, high crystallinity (crystallinity index - CrI ∼77.78 %), and rough surfaces (root mean square roughness - R_q = 27.82 nm). The incorporation of PEG and DES reduced surface roughness and crystallinity, with DES demonstrating a stronger plasticizing effect. The optimal formulation, DES-Ast-Ch (1,5, 14.89 μg/g astaxanthin), improved film structure (R_q = 2.63 nm; CrI ∼50.00 %) and mechanical properties, including tensile strength (TS: 3.80 MPa) and elongation at break (EAB: 52.33 %). Antioxidant capacity was significantly enhanced, with ABTS and DPPH values reaching 3.16 and 4.90 μmol Trolox equivalent (TE)/mL, respectively. The DES-Ast-Ch films exhibited antimicrobial activity against Staphylococcus aureus (Gram-positive), Salmonella enterica serovar Typhimurium (Gram-negative), and Candida albicans (yeast), with inhibition zones up to 15.42 mm and minimum inhibitory concentration (MIC) values as low as 1.35 μL/mL for S. typhimurium. In shrimp preservation tests, DES-Ast-Ch coatings (1,5) reduced weight loss (3.76 %), microbial load (4.3 log CFU/g), and total volatile basic nitrogen (TVB-N - 22.76 mg/100 g). These results suggest that DES-Ast-Ch films are promising candidates for sustainable food packaging, particularly for perishable products like seafood, where enhanced antioxidant and antimicrobial properties are crucial for maintaining freshness and safety.