Plasma activated water (PAW) - gelatin coatings: moderate oxidation of gelatin and controlled release of PAW for preservation of snakehead (Channa argus) fillets

Abstract

Plasma-activated water (PAW) was utilized to dissolve gelatin for the preparation of antibacterial coatings aimed to preserve snakeheads (Channa argus) fillets at 4 °C. PAW significantly enhanced the transparency and viscosity of the gelatin solutions. Specifically, PAW treated for 10 min (PAW₁₀) induced the densest network structure of gelatins with decreased α-helix and increased β-sheet. The antibacterial activity against Escherichia coli and Pseudomonas aeruginosa was enhanced dependently on the preparation time of PAW (P < 0.05). Furthermore, PAW-gelatin coatings decelerated the release of H₂O₂, which favored to reduce the total viable count (TVC) and total volatile base nitrogen (TVB-N) during the storage of fillets (P < 0.05) and extended the shelf life from 6 days to 9 days. Essentially, G-PAW₁₀ reduced the crude protease activity of fillets from 102.25 nkat/mL to 7.16 nkat/mL (P < 0.05), suggesting the suppression in protein degradation and autolysis. Consequently, the muscle fibres of FG-PAW₁₀ remained intact, smooth and tightly packed, with the shear force increasing from 230.36 g in the control to 839.67 g and the poriness of tissue structures decreasing from 44.97 % to 31.58 % (P < 0.05), indicating effective structural preservation.