Chitosan Edible Coating, Vacuum Packaging, and Their Synergistic Effects on the Refrigerated Shelf Life of Pangas Fish (Pangasianodon hypophthalmus) Fillets

Fresh fish fillets are highly perishable even under refrigerated conditions due to psychrotrophic microbial growth, enzymatic activity, and lipid oxidation. This study evaluated the individual and combined effects of chitosan edible coating and vacuum packaging on the quality and shelf life of Pangasianodon hypophthalmus fillets stored at 4 ± 1 °C for 15 days. Four treatments were applied: uncoated aerobic (U-A), uncoated vacuum (U-V), chitosan-coated aerobic (Ch-A), and chitosan-coated vacuum (Ch-V). Quality changes were assessed through chemical, physical, microbiological, and sensory analyses. Total volatile base nitrogen (TVB-N) increased rapidly in U-A (3.5–22.4 mg N/100 g), whereas lower values were observed in Ch-V (13.3 mg N/100 g). Peroxide value (PV) increased to 1.43 meq O2/kg fat in U-A but remained lowest in Ch-V (0.77 meq O2/kg fat). Total plate count (TPC) exceeded the acceptability limit in U-A by day 15, while Ch-V remained within safe limits (6.03 log CFU/g). Coated treatments maintained more stable pH, and chitosan coating reduced moisture loss under aerobic storage. Sensory quality declined rapidly in U-A but was best preserved in Ch-V. The combined application of chitosan coating and vacuum packaging exhibited a clear synergistic effect, extending the refrigerated shelf life of fillets to at least 15 days compared with 9–12 days in uncoated samples. This approach represents an effective and eco-friendly strategy for maintaining the quality and safety of fresh fish products.