AU2021101811A4

AU2021101811A4 - Device for preparation of high-throughput plasma-activated liquid

Info

Publication number: AU2021101811A4
Application number: AU2021101811A
Authority: AU
Inventors: Long Xu; Wenjing YAN; Jianhao ZAHNG
Original assignee: Nanjing Agricultural University; Suzhou Yirun Food Technology Co Ltd
Current assignee: Nanjing Agricultural University; Suzhou Yirun Food Technology Co Ltd
Priority date: 2020-12-31
Filing date: 2021-04-08
Publication date: 2021-05-27
Anticipated expiration: 2029-04-08
Also published as: CN112830544A

Abstract

DEVICE FOR PREPARATION OF HIGH-THROUGHPUT PLASMA-ACTIVATED LIQUID ABSTRACT The disclosure provides a device for preparation of high-throughput plasma-activated liquid. The device includes a pretreatment tank, at least two plasma jet devices, at least two high-voltage electric field generators, and at least two transformers. The pretreatment tank includes an input end and an output end. The input end is provided with a first water inlet valve. The output end is connected to a first plasma jet device. The at least two plasma jet devices are connected together, end to end, and a last plasma jet device is connected to a water outlet valve. Each of the at least two plasma jet devices is connected to a high-voltage electric field generator and a transformer. Each of the at least two plasma jet devices includes at least two plasma jet generators, a water tank, and at least two controllers. 12 1/3 Plasma jet generator Valve Water inlet Pretreat ing tank Backflow Water outlet Valve FIG. 1 2 4 6 3 FIG. 2

Description

1/3

Plasma jet generator Valve Water inlet Pretreat ing tank

Backflow

Water outlet Valve

FIG. 1

2

4 6

3

FIG. 2

DEVICE FOR PREPARATION OF HIGH-THROUGHPUT PLASMA-ACTIVATED LIQUID TECHNICAL FIELD

[0001] The disclosure relates to the field of plasma technology, and more particularly, to a device for preparation of high-throughput plasma-activated liquid.

BACKGROUND

[0002] Plasma-activated liquid has the characteristics of broad spectrum antibacterial activity, no chemical residues, environmental protection, food safety, etc., so it is suitable for use in the food industry. Traditional chemical fungicides such as sodium hypochlorite can be replaced with the plasma-activated liquid which may sterilize and preserve products. Chinese Patent Application No. 201911276662.0 (a device for highly efficient preparation of plasma-activated water) disclosed a device capable of treating water of 1-2.5 L, which cannot meet industrial needs and cannot achieve high-efficiency applications. Chinese Patent Application No. 201910196952.8 (a plasma-activated lactic acid and methods for use) discloses a device for sterilization of liquids by using a single spray gun. Having regard to the above, it is an aim of the disclosure to increase the amount of liquid to be sterilized. Current plasma-activated liquids mainly include deionized water, phosphate buffer, hydrogen peroxide solution, etc. The problems with prior art methods are as follows: 1) Small amounts of liquid may be sterilized. The liquid to be sterilized is generally loaded onto a 96-well plate, a petri dish or a 50 mL beaker. 2) Low-efficiency sterilization: the ratio of plasma-activated liquid to bacterial suspension is at 9: 1, and even at 99: 1. Accordingly, it is very important for the food industry to establish an efficient method for industrial preparation of plasma-activated liquids.

SUMMARY

[0003] The disclosure provides a device for preparation of high-throughput plasma-activated liquid.

[0004] The device comprises a pretreatment tank, at least two plasma jet devices, at least two high-voltage electric field generators, and at least two transformers. The pretreatment tank comprises an input end and an output end. The input end is provided with a first water inlet valve. The output end is connected to a first plasma jet device. The at least two plasmajet devices are connected together, end to end, and a last plasma jet device is connected to a water outlet valve. Each of the at least two plasma jet devices is connected to a high-voltage electric field generator and a transformer. Each of the at least two plasma jet devices comprises at least two plasma jet generators, a water tank, and at least two controllers. One end of the water tank is connected to an inlet pipe and another end is connected to an outlet pipe. The inlet pipe is provided with a second water inlet valve, and the outlet pipe is provided with a water dump valve. The inlet pipe and the outlet pipe each comprise a flow meter. The at least two plasma jet generators are embedded in an upper part of the water tank. Each of the at least two plasma jet generators comprises an electrode and a plasma jet nozzle, disposed on a top part and a lower part of each plasma jet generator, respectively. The electrode is connected to the high-voltage electric field generator, and the plasma jet nozzle is disposed below the liquid level in the water tank. Each of the at least two plasma jet generators is connected to one of the at least two controllers.

[0005] In a class of this embodiment, the water tank comprises an exhaust port provided with a pressure regulating valve.

[0006] Ina class of this embodiment, the plasma jet nozzle is immersed 3-10 mm below the liquid level in the water tank.

[0007] Ina class of this embodiment, the number of the at least two plasma jet devices is 3-5, and the number of the at least two plasmajet generators is 2-4.

[0008] In a class of this embodiment, the high-voltage electric field generator runs at the voltage of 10-30 k, the current of 0.01-0.1 mA, and the frequency of 20 kHz.

[0009] In a class of this embodiment, the volume of the water tank is 10-50 L.

[0010] The following advantages are associated with the device of the disclosure:

[0011] 1. The device of the disclosure achieves a production volume of 240 L/h plasma-activated lactic acid.

[0012] 2. The device of the disclosure exhibits a high sterilization efficiency over the prior art. Mixed with a bacterial suspension at a ratio of 1: 1, the plasma-activated liquid is inactive 106 CFU/mL bacteria.

[0013] 3. The device of the disclosure is configured to prepare the plasma-activated lactic acid having a 48-hour antibacterial activity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a perspective view of a device for preparation of high-throughput plasma-activated liquid according to one embodiment of the disclosure.

[0015] FIG. 2 is a perspective view of a plasma jet device according to one example of the disclosure.

[0016] FIG. 3 is a perspective view of a plasma jet generator according to one example of the disclosure.

[0017] FIG. 4 is a graph showing the stability of the antibacterial activity of the plasma-activated liquid in Example 2 of the disclosure.

[0018] In the drawings, the following reference numbers are used: 1. Plasma jet generator; 11. Electrode; 12. Plasmajet nozzle; 2. Water tank; 3. Controller; 4. Water inlet valve; 5. Water outlet valve; 6. Flow meter; and 7. Pressure regulating valve.

DETAILED DESCRIPTION

[0019] To further illustrate the disclosure, embodiments detailing a device for preparation of high-throughput plasma-activated liquid are described below. It should be noted that the following embodiments are intended to describe and not to limit the disclosure.

[0020] Referring to FIG. 1, a device for preparation of high-throughput plasma-activated liquid comprises a pretreatment tank, at least 3-5 plasma jet devices, at least two high-voltage electric field generators, and at least two transformers. The pretreatment tank comprises an input end and an output end. The input end is provided with a first water inlet valve. The output end is connected to the first plasma jet device. The 3-5 plasma jet devices are connected together, end to end, and the last plasma jet device is connected to a water outlet valve. Each of the 3-5 plasma jet devices is connected to a high-voltage electric field generator and a transformer. The high-voltage electric field generator runs at the voltage of 10-30 k, the current of 0.01-0.1 mA, and the frequency of 20 kHz.

[0021] Referring to FIG. 2, each of the 3-5 plasma jet devices comprises 2-4 plasma jet generators 1, a water tank 2, and 2-4 controllers 3. The 2-4 plasma jet generators 1 are disposed on the upper part of the water tank 2. One end of the water tank 2 is connected to an inlet pipe and another end is connected to an outlet pipe. The inlet pipe is provided with a second water inlet valve 4, and the outlet pipe is provided with a water outlet valve 5. The inlet pipe and the outlet pipe each comprise a flow meter 6. Referring to FIG. 3, each of the 2-4 plasmajet generators 1 comprises an electrode 11 and a plasma jet nozzle 12, disposed on the top part and the lower part of each plasma jet generator, respectively. The electrode 11 is connected to the high-voltage electric field generator, and the plasma jet nozzle 12 is immersed 3-10 mm below the liquid level in the water tank 2. Each of the 2-4 plasma jet generators 1 is connected to a corresponding controller 3. The water tank 2 further comprises an exhaust port provided with a pressure regulating valve 7. The volume of the water tank 2 is 10-50 L.

[0022] To increase the antibacterial activity of the plasma-activated liquid, 0-0.20% lactic acid was added to the water for preparation of plasma-activated lactic acid used in sterilization of livestock and poultry meat; or 0-1.5 mmol/L salicylic acid was added to the water for preparation of plasma-activated salicylic acid used in the sterilization of fruits and vegetables.

[0023] A method for preparation of plasma-activated liquid using the device of the disclosure is summarized as follows:

[0024] The plasma jet generator operates at the voltage of 10-30 kV and the current of 0.01-0.1 mA, at the same time, air flows through the plasma jet generator at a flow rate of 10-30 L/min and plasma can thus be generated. The plasma penetrates into -50 L of the water to be sterilized. 0.01-5% lactic acid may be added to the 10-50 L of the water to be sterilized, and sterilized by the plasma for 0-30 minutes, thereby obtaining a plasma-activated liquid with high antibacterial activity.

[0025] In the following examples, the plasma jet generator runs at the voltage of 19 k, the current of 0.0024 mA, and the frequency of 20 kHz, at the same time, air flowed through the plasma jet generator at a flow rate of 22.5 L/min and plasma can thus be generated. The plasma jet nozzle was immersed 10 cm below the surface of the liquid to be sterilized. The volume of the liquid to be sterilized was 40 L.

Example 1

[0026] Effect of treatment time on the antibacterial activity of the plasma-activated liquid.

[0027] Both of 40 L of 0.20% lactic acid and 40 L of water were sterilized for 0-30 minutes with a plasma jet device (comprising four plasma jet generators connected together), separately mixed with 108 CFU/mL of Salmonella enteritidis at a ratio of 1: 1, and allowed to react for 15 minutes. Referring to Table 1, the antibacterial activity of the two plasma-activated liquids was calculated by counting colonies forming units (CFUs) on a plate.

Table 1 Effect of sterilization time on the antibacterial activity of the plasma-activated liquid

Treatment 0 5 10 15 20 25 30 time (min)

Plasma-activated water Total number of bacterial 108 107-108 106 105 104 1200 50 colonies (CFU/mL) Plasma-activated lactic acid Total number of bacterial 108 1600 100 0 0 0 0 colonies (CFU/mL)

[0028] Referring to Table 1, within a given time period, the plasma-activated lactic acid displayed higher antibacterial activity than the plasma-activated water. The total number of bacterial colonies was reduced from 108 CFU/mL to 50 CFU/mL in the plasma-activated water after sterilization for 30 minutes, and reduced to 100 CFU/mL in the plasma-activated lactic acid within 10 minutes. The results indicated that the plasma-activated lactic acid was more efficient at sterilization than the plasma-activated water, minimizing the treatment time.

Example 2

[0029] Stability of antibacterial activity of the plasma-activated liquid.

[0030] Both of 40 L of 0.20% lactic acid and 40 L of water were sterilized for 0-30 minutes with a plasma jet device (comprising four plasma jet generators connected together) and stored at room temperature for 48 hours. The following steps were taken every six hours to measure the antibacterial activity of the plasma-activated liquids: at each time point, the plasma-activated liquids were separately mixed with 108 CFU/mL of Salmonella enteritidis and allowed to react for 15 minutes. Referring to FIG. 4, the stability of antibacterial activity of the two plasma-activated liquids was calculated by counting colonies forming units on a plate.

[0031] Referring to FIG. 4, the antibacterial activity of the plasma-activated water against Salmonella enteritidis gradually decreased with increasing storage time. After storage for 12 hours, the total number of CFUs was increased from initial value (0 hour after storage) of 1.7 logioCFU/mL to 5.4 logioCFU/mL. When the plasma-activated water was stored for 18 hours, its antibacterial activity almost completely disappeared. In a 24-hour storage period, the plasma-activated lactic acid was shown to effectively inhibit the growth of Salmonella enteritidis, and after storage for 48 hours, the total number of CFUs was reduced from 8.0 logoCFU/mL to 4.8 logioCFU/mL.

Example 3

[0032] Effect of the plasma-activated liquid on the quality of poultry meat.

[0033] Both of 40 L of 0.20% lactic acid and 40 L of water were sterilized for 0-30 minutes with a plasma jet device (comprising four plasma jet generators connected together). Chicken wings were submerged under the two plasma-activated liquids for

15 minutes. The chicken wings submerged under water and 0.05% sodium hypochlorite solution were used as the control groups. After treatment, the changes in total number of bacterial colonies, total number of Escherichiacoli (E. coli), pH, and lipid oxidation, as shown in Table 2.

Table 2 Effect of the plasma-activated liquid on the quality of poultry meat

of Total number of Total number of Total number bacterial colonies E. coli Pseudomonas TBARS Treatment liquid (logioCFU/g) (logioCFU/g) aerugosa (mg/kg) (logioCFU/g) Water 5.26 ±0.12 1.25 ±0.07 2.54 ±0.02 0.021 ±0.011 Sodium hypochlorite 4.84 ±0.11 1.08 ±0.11 2.18 ±0.14 0.019 ±0.009 Plasma-activated water 4.90 ±0.12 1.21 ±0.09 2.35 ±0.08 0.022± 0.014 Plasmid-activated 4.10 ±0.12 0.79 ±0.10 2.01 ±0.10 0.014 ±0.007 lactic acid

[0034] Referring to Table 2, after the chicken wings were submerged under different liquids, the total number of bacteria colonies was reduced to 0.42 logioCFU/g in the 0.05% sodium hypochlorite solution, reduced to 0.36 logioCFU/g in the plasma-activated water, and reduced to 1.16 logioCFU/g in the plasma-activated lactic acid. The results indicated that the plasma-activated lactic acid was more efficient at sterilization than the two control groups. The different treatment groups showed the same trend in the antibacterial activity against Pseudomonas aeruginosa and foodbome pathogenic E. coli. The plasma-activated lactic acid inhibited the lipid oxidation of the chicken wings at a certain degree.

Example 4

[0035] Effect of the plasma-activated liquids on the beef quality.

[0036] Both of 40 L of 0.20% lactic acid and 40 L of water were sterilized for 0-30 minutes with a plasma jet device (comprising four plasma jet generators connected together). The different plasma-activated liquids were separately sprayed on the slices of a beef leg (40 x 40 x 2 mm). The slices of a beef leg sprayed with water and 2.0% lactic acid were used as the control groups. After treatment, the changes in total number of bacterial colonies, pH, and lipid oxidation, as shown in Table 3.

Table 3 Effect of the plasma-activated liquids on beef quality

Total number of Total number of liquid bacterialcolonies Pseudomonas TBARS Treatment lqibatracones aerugi.nosa (mg/kg) (logioCFU/g) (logioCFU/g) Water 3.15 ±0.08 2.82 ±0.10 0.062 ±0.008 Lactic acid 2.58 ±0.04 2.01 ±0.08 0.057± 0.013 Plasma-activated water 2.61 ±0.10 2.13 ±0.05 0.061 ±0.015 Plasmid-activated lactic acid 2.04 ±0.12 1.98 ±0.12 0.066 ±0.007

[0037] Referring to Table 3, compared to the control groups, the slices of a beef leg sprayed with different plasma-activated liquids did not exhibit significant changes in pH and lipid oxidation. From the perspective of antibacterial activity, the number of bacteria colonies was significantly reduced by 0.57 logioCFU/g in the 2.0% lactic acid, reduced by 0.54 logioCFU/g in the plasma-activated water, reduced by 1.11 logioCFU/g in the plasma-activated lactic acid. The three treatment groups showed the same trend in the antibacterial activity against Pseudomonas aeruginosa, eliminating the food-borne pathogens in the fresh beef. The results indicated that the reactive oxygen species in the water did not cause significant lipid oxidation in the beef leg.

Example 5

[0038] Effect of the plasma-activated liquids on the quality of lettuce.

[0039] Both of 40 L of 0.20% lactic acid and 40 L of water were sterilized for 0-30 minutes with a plasma jet device (comprising four plasma jet generators connected together). Lettuce were soaked in different plasma-activated liquids for 10 minutes. The lettuce soaked in the water were used as the control group. After treatment, the changes in total number of bacterial colonies and chromaticity, as shown in Table 4.

Table 4 Effect of the plasma-activated liquids on the quality of lettuce

Total number of Treatment liquid bacterial colonies L* a* b (logioCFU/g) Water 5.07 ±0.15 68.90 ±1.21 -15.07 ±0.54 40.17 ±1.14 Plasma-activated 3.54 ±0.09 68.27 1.04 -15.80 0.87 40.75 2.01 water Plasmid-activated 2.74 ±0.14 67.60± 1.68 -15.31 ±0.69 43.09 1.57 lactic acid

[0040] Referring to Table 4, after the lettuce soaked in the plasma-activated water and the plasma-activated lactic acid, the total number of bacteria colonies was significantly reduced by 1.53 logioCFU/g and 2.33 logioCFU/g, respectively. Compared to the control group, the lettuce soaked in the different plasma-activated liquids did not exhibit significant color changes. The results indicated that the plasma-activated liquids were more efficient at sterilization of the lettuce without loss of the apparent quality.

[0041] It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications.

Claims

DEVICE FOR PREPARATION OF HIGH-THROUGHPUT PLASMA-ACTIVATED LIQUID CLAIMS

1. A device for preparation of high-throughput plasma-activated liquid, the

device comprising: a pretreatment tank, at least two plasma jet devices, at least

two high-voltage electric field generators, and at least two transformers;

wherein:

the pretreatment tank comprises an input end and an output end; the input end is provided with a first water inlet valve; the output end is connected to a first plasma jet device; the at least two plasma jet devices are connected together, end to end, and a last plasma jet device is connected to a water outlet valve; and each of the at least two plasma jet devices is connected to a high-voltage electric field generator and a transformer; and

each of the at least two plasma jet devices comprises at least two plasma jet generators (1), a water tank (2), and at least two controllers (3); one end of the water tank is connected to an inlet pipe and another end is connected to an outlet pipe; the inlet pipe is provided with a second water inlet valve (4), and the outlet pipe is provided with a water dump valve (5); the inlet pipe and the outlet pipe each comprise a flow meter (6); the at least two plasma jet generators (1) are embedded in an upper part of the water tank (2); each of the at least two plasma jet generators (1) comprises an electrode and a plasmajet nozzle, disposed on a top part and a lower part of each plasmajet generator, respectively; the electrode (11) is connected to the high-voltage electric field generator, and the plasma jet nozzle (12) is disposed below a liquid level in the water tank (2); and each of the at least two plasma jet generators (1) is connected to one of the at least two controllers (3).

2. The device of claim 1, wherein the water tank comprises an exhaust port

provided with a pressure regulating valve (7).

3. The device of claim 1, wherein the plasma jet nozzle is immersed 3-10 mm

below the liquid level in the water tank.

4. The device of claim 1, wherein a number of the at least two plasma jet devices

is 3-5, and a number of the at least two plasma jet generators is 2-4.

5. The device of claim 1, wherein the high-voltage electric field generator runs at

a voltage of 10-30 kV, a current of 0.01-0.1 mA, and a frequency of 20 kHz.

6. The device of claim 1, wherein a volume of the water tank is 10-50 L.