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Sterilization effect of pulsed light on microorganisms
pubdate：2016-10-12 Author： Click：
The pulsed light is a new technology which is expected to replace the traditional physical and chemical sterilization methods, it is a light energy pulsed high intensity using instantaneous, effectively killing exposed in the food and packaging material or surface water of bacteria, fungi, spores, viruses, and other types of dormant spore protoplasm, microbial and endogenous in food enzyme. Pulse strong light on all kinds of microbial sterilization effect is very obvious, and it is a kind of no mercury, low heat, no by-products of the new sterilization technology.
The mechanism of pulse light sterilization
Because of the genetic information of bacteria in the cells of the nucleic acid, when the nucleic acid is pulsed light exposure will absorb a large amount of ultraviolet light, resulting in the body to form a part of the inter - and two - two - nitrogen - benzene isomers. This substance can cause the bacteria's own metabolism dysfunction, and will lead to the genetic problems of bacteria, until death. In the light pulse part 200-280nm the most easily absorbed, actinism is mainly UVC.
2 Photo thermal effect
Although the actinism mainly comes from UVC, but the UVA and UVB part of light pulse also plays a certain bactericidal effect. When the radiation dose reaches a certain level, UVB and UVA can make the cell surface temperature rapidly increased to 130 degrees C, thereby destroying the cell wall of bacteria, so that the cell fluid evaporation, completely destroy the cell structure, resulting in death
Two, pulsed light on the bactericidal experiment of Escherichia coli
1 experimental apparatus and parameters
The device adopts a pulse strong light sterilization device, which adopts a capacitor type pulse generating circuit, which is used for manual control, a straight tube type pulsed strong light lamp is used as a pulse light source, and a semi cylindrical reflector is used for the light gathering of a pulsed light source. After testing, the device sends out the pulse strong light wavelength range is 200~1100nm, the pulse light pulse width is 20 s, the maximum input energy is 644J. The device can adjust the light intensity of the device, the flash frequency, the distance between the flash and the light source.
2 experimental methods
Preparation of 2.1 bacterial liquid
The Escherichia coli in the test tube was activated, and the sterile super net work was inoculated in the sterile water, and the inoculation amount was controlled in 106 ~ 107 /ml.
2.2 processing methods
Each diameter of 75 mm plate containing a certain volume of the treated bacteria liquid, placed in the center of the sterilization process room, with a light source distance of 2 cm, according to the set of process parameters for pulse light flash treatment, repeated test 3 times.
2.3 test parameter setting
Light intensity: 0.2, 0.25, 0.3, 0 375,0. 5, 0.625, 0.75 J /cm2; flash number: 1, 2, 4, 8, 16; thickness: 3.4, 6.8 bacteria, 10.2, 13.6, 17 cm; bacteria transmittance: 1, 2, 4, 8, 16. 32; the concentration of bacteria (dilutions): 10, 100, 1000 times.
2.4 Escherichia coli death test
The bacteria liquid processed by 1: 10 diluted, a total of 2 10-, 10- 3, 10- 4, 10 - 5, 10 - 6,5 dilution, each dilution 3 times repeated tests, when counting the average. Bacteria examination use peptone medium. Compared with the control group (without treatment).
Detection of viable bacteria count by plate counting method for treating bacteria.
The sterilization rate = [(the number of the control bacteria and the number of treatments) / control residual bacteria number] * 100%
The influence factors of light intensity, light intensity, liquid thickness, light transmittance and bacterial liquid concentration were selected.
3 experimental results
3.1 the effect of light intensity on germicidal efficacy
The light intensity and the sterilization rate is proportional to the rate of sterilization with light intensity increased, when the light intensity is 0.75J/cm2 of Escherichia coli completely to death.
3.2 the effect of lightning flash count on germicidal efficacy
The light intensity was 0.5J/cm2, the bacterial liquid thickness was 3.4 mm, the bacterial liquid transmittance was 100, and the different flash times were used for treatment. The flash frequency is directly proportional to the sterilization rate, and the sterilization rate increases with the increasing of the flash.
Effect of 3.3 bacteria liquid thickness on germicidal efficacy
In the case of light transmittance of 1, the thickness of the bacteria liquid is inversely proportional to the bactericidal rate, the lower the liquid layer is, the lower the bactericidal rate is. When the transmittance is 100, change the thickness of the bacterial liquid, the sterilization rate is basically no change. It is concluded that the bacterial liquid thickness and the liquid light transmission rate of each other, the thickness of a certain bacteria can only affect the bactericidal effect under a certain light transmission rate, and vice versa.
From the above analysis results can be seen that the pulse light sterilization is very significant for the bactericidal effect of Escherichia coli, in several pulse can be lethal, compared with traditional ultraviolet sterilization, the sterilization effect under the same sterilization time, the technology is a kind of sterilization technology has broad prospects, as for other microorganisms the effect of sterilization:
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