Shelf-life extension of marinated trout (Oncorhynchus mykiss) fillets using chitosan-thymol nanocomposite coatings

Rainbow trout ( Oncorhynchus mykiss ) is highly perishable, necessitating effective preservation strategies. This study evaluated chitosan/nanoclay nanocomposite coatings enriched with thymol (CH/NC-THY), applied alone and in combination with marination, on the quality of trout fillets quality during refrigeration (4 °C for 12 days). Increasing thymol concentration enhanced bioactivity; the 20 mg/mL (2 %) concentration exhibited the highest antioxidant capacity (DPPH: 69.7%; TPC: 29.97 mg GAE/g). The marinated CH/NC-THY treatment yielded the lowest microbial counts (TAMB: 4.8 log CFU/g), minimal lipid oxidation (TBA: 0.36 mg MDA/kg), stable pH (∼5.8), and TVB-N values (21.5 mg/100 g) below the acceptability limit throughout storage. Sensory evaluation confirmed superior overall acceptability after 12 days, while control samples spoiled by day 6. Nanoclay enhanced thymol stability and dispersion, while marination provided complementary pH control and antimicrobial effects. These findings demonstrate that CH/NC-THY coating combined with marination is an effective multi-hurdle preservation strategy for fatty fish.