低温等离子体活化水发生设备设计与试验 .

Plasma-activated water (PAW) has been proven to have broad-spectrum bactericidal properties, and can effectively kill microorganisms on fresh foods and inhibit their spoilage. Low-temperature PAW sterilization is viewed as an emerging cold sterilization technology, presenting great potential for the application in food production and safety control, which has attracted wide attention from scholars at home and abroad. However, there are few research reports on PAW generating equipment, and its design basis is still lacking. In order to improve the level of PAW equipment development and application, the equipment for producing low-temperature PAW was developed in this study based on the basic principle of plasma generation by dielectric barrier discharge. The system of this equipment included dielectric barrier discharge components, ventilation channels of heat dissipation, flow channels of activated water, the high voltage alternating current power supply, and so on. The dielectric barrier discharge components were composed of a cylindrical high-voltage discharge electrode and a flat-shaped low-voltage discharge electrode in an upper-down parallel configuration with the uniform gas gap, in which the stainless-steel plate for water flow and the flowing water film was integrated to be used as the low-voltage electrode, realizing uniform plasma generation and continuous and stable production of activated water. The heat dissipation of the high-voltage discharge electrode employed two bidirectional-countercurrent ventilation channels inside and outside the electrode tube, which effectively improved the heat dissipation effect and working stability of the equipment. A structure of alternating current-direct current-alternating current was designed as the power circuit of the high-voltage alternating current power supply to realize the energy supply of dielectric barrier discharge. And the control circuit could be realized the monitoring and adjustment of parameters such as frequency, voltage, and current, etc. To meet the diversified requirements for the application of plasma-activated water, some structural parameters and working parameters of this equipment were designed to be continuously adjustable within a certain range, which included the inclination angle of guide plate, the air gap between the high-voltage discharge electrode and the guide plate, water flow rate, supply power, working voltage, working current, and so on. To verify the effect of plasma-activated water treatment from this equipment on the vegetables, the fresh-cut potato slices were simulated to be infected with Escherichia coli, and sterilization cleaning and preservation by using the plasma-activated water was performed. The conditions for the sterilizing of plasma-activated water on Escherichia coli in the potato slices were optimized to result in the optimal sterilization rate (98.65±0.59) %, in which the water flow was 600 mL/min, the air gap was 10 mm, the mass ratio of material to activated water was 1∶20, the power supply voltage was 137.4 V, and the sterilization time was 4.72 min. Compared with the treatment without cleaning and the treatment with distilled water cleaning, the treatment of cleaning with the plasma-activated water by using the above-optimized conditions contributed to relatively higher hardness, lower color difference, lower relative conductivity, lower soluble solid content, and lower decay rate in the bacteria-contaminated potato slices during storage. After 24 d of storage, the bacteria-infected potato slices without cleaning, with distilled water cleaning, and with PAW cleaning achieved a hardness of (3.01±0.84), (3.54±0.81), (4.70±0.48) N, respectively, a color difference of 22.08±1.05, 13.21±1.43, 7.35±0.81, respectively, a relative conductivity of (28.00±6.43) %, (26.72±2.07) %, (17.19±2.26) %, respectively, a soluble solid content of (6.850±0.120) %, (5.430±0.006) %, (3.080±0.006) %, respectively, and a decay rate of (87.04±1.63) %, (76.32±1.60) %, (52.09±1.41) %, respectively, showing good advantages of sterilization and preservation. This study could provide a reference for the development and the industrial application of the sterilization technology of plasma-activated water [ABSTRACT FROM AUTHOR]