In this study, the bactericidal effect and mechanism of plasma activated water (PAW) against Shewanella putrefaciens, a common microorganism found in aquatic products, were investigated by plate counting, fluorescence staining and scanning electron microscopy (SEM). The impact of PAW on cell morphology, cell membrane permeability, cell membrane potential and cell content leakage was examined. The results showed that the count of Shewanella putrefaciens was significantly decreased by PAW (P < 0.05). After 6.0 min of treatment with activated water from plasma discharge 120 s (PAW120), the colony count decreased by 7.44(lg (CFU/mL)), the cell morphology showed shrinkage and rupture, and the permeability of the inner and outer membranes increased by 989.31% and 474.51%, respectively. Moreover, intracellular macromolecules such as nucleic acids and proteins leaked out of the cells, and the electrical conductivity increased significantly (P < 0.05). The results of Fourier transform infrared (FTIR) spectroscopy showed that the structures of intracellular lipids and proteins were changed after PAW120 treatment. In conclusion, PAW could destroy the cell wall, and increase the permeability of the cell membrane, thereby leading to the leakage of intracellular nucleic acids and proteins and eventually cell death. This study provides a theoretical basis for the application of PAW in the preservation of aquatic products.

In this study, the effects of high-intensity ultrasound (HIU, frequency 20 kHz, amplitude 60%, power 450 W) for 0, 6, and 9 min on the emulsifying properties of chicken myofibrillar protein (MP) under different NaCl concentrations (0.2, 0.3, 0.4, and 0.5 mol/L) were investigated. The results showed that the increasing NaCl concentration and prolonged HIU treatment time significantly enhanced the emulsifying activity, the emulsifying stability and storage stability of MP emulsion were increased significantly (P < 0.05), and the particle size of MP emulsion were decreased significantly (P < 0.05). HIU pretreatment decreased the interfacial tension, and increased the apparent viscosity and the absolute zeta-potential of reduced-NaCl MP emulsions. Compared with the non-HIU group at 0.5 mol/L NaCl, the emulsions stability was significantly improved when the HIU time was extended to 9 min under 0.3 mol/L NaCl (P < 0.05). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis result of interfacial MP showed that the band strength of myosin heavy chain and actin significantly increased after 9 min-HIU treatment at both 0.3 and 0.5 mol/L NaCl. Circular dichroism analysis showed that the random coil relative content of interfacial MP was decreased significantly (P < 0.05), and the relative content of α-helix and β-sheet were increased (P < 0.05) after HIU. Extended HIU time could partially alternative the effect of NaCl on the emulsification properties of MP, and improve the stability of the interfacial protein structure and MP emulsion in reduced-salt conditions, which facilitated the processing of lower salt emulsion-based meat products.