Pulsed light sterilization and other technologies

Introduction

The decontamination process is different depending on the industries field and on the decontamination levels required :

• Food industries use for example chemicals and continuous UV (amongst other technologies)
• Pharmaceuticals industries prefer Ebeam
• Water decontamination is often performed with continuous UV

This article is a short overview of the different decontamination systems used in industry compared to the pulsed light sterilization.

Chemicals

Solutions used to disinfect surfaces in industry are, generally, peracetic acid and hydrogen peroxide. Clean room or food company for instance, use this kind of disinfection.

Hydrogen peroxide is a colorless liquid substance having powerful oxidizing properties. This is a bactericidal, fungicidal, sporicidal and virucidal substance.This solution is appreciate by the industrial because its decomposition in water and oxygen is non‑toxic :

H2O2 ⇒ H2O + ½ O2

For a rapid and efficient disinfection, hydrogen peroxide is raised to high temperature and uses with high concentration. If the temperature and concentration were not strong enough, the disinfection time shall be increased.  

Peracetic acid is a powerful oxidizing agent that penetrates the cell walls of microorganisms and kills them. Peracetic acid is produced by reacting acetic acid and hydrogen peroxide. This product is more stable than hydrogen peroxide even after a long storage time. This chemical remains efficient, even at low temperature.

The risks are the following : inflammable vapour, explosion depending on the storage, irriting to the eyes and the skin (depending on the concentration). Nevertheless, it is explained in litteratures that peractic acid decomposes into acetic acid which is a weak acid and water, which minimize the environmental impact.  

E‑beam

E‑beam is a non‑chemicals technologies, it’s a physical treatment.

Most often used in pharmaceutical industry, this technology has been recently developed for the food industry, and more specifically for bottles disinfection. A study has been also published in 2007 by ANSES about the effect of E‑beam on foodstuffs. A maximum tolerated dose of 10 kGy would not cause negative effect.  

E‑beam is safe, cold method, there is no residue, no chemicals during the process. The control is very easy and can be made by the parameters of applied dose : voltage, current and exposure time. 

Principle : the electron rays pass through the material enabling a complete sterilization of the packaging. The maximum tolerated dose must be respected and controlled in order to not alter the structure of the material and create newly‑formed and toxic product.

Unfortunately, for the sterilization of the equipment, you need chemicals (hydrogen peroxyde) and several days of maintenance every years that requires an entire stop of the equipment. The weight of the equipment is definetely heavier than light technologies and the dimension is more imposing.

Continuous UV

Continuous‑UV uses principally a bulb with a wavelength of 254 nm. DNA has a broad absorption peak at 250‑280 nm, therefore, the UV‑bulb has the best performing wavelength for a germicidal effect. These bulbs are used for water disinfection but also, for surfaces in food industries.

The UV power is unfortunately insufficient for sterilization on surface and moreover, all micro‑organisms are not altered by these wavelengths. To maximize the decontamination, several seconds exposure are requested but temperature increases significantly the target and multiply the number of continuous‑UV modules. Some configurations are difficult to implement due to a high speed of the production line. Thus, this UV disinfection is sufficient for low decontamination, could be enough for preventive decontamination. Moreover, it remains a technology with mercury, at which we often point the finger, because of its toxicity.

Pulsed Light

Pulsed light sterilization is an emerging process with a broad‑spectrum from 180 to 1100 nm. The combination of intensity and UVC dose enables to get a high level of decontamination in just one flash (few hundreds of µseconds). It is faster and leaves no residues.

Inactivation of micro‑organism by Pulsed Light is due to DNA damages. There is a complete destruction of the double‑strands of the DNA, no replication is possible.

Depending on the decontamination target, parameters of Pulsed Light could be changed : Voltage, Number of lamps, number of flashes. Three flashes are enough to get the requested decontamination in industry. An increase of the number of flashes is possible but has an impact on the production cost and the temperature of the target. The technology is compact, and flexible, meaning that installation is easily performed.

Moreover, for material transparent to UV‑light, as uncolored plastic, the rays of pulsed light go through the material, killing germs inside and outside the target. And a complete sterilization could be reached!

Pulsed light technology is considered as surface decontamination, non‑aggressive, in comparison to E‑beam.

Cold method, low operating cost, no mercury, no residues, efficient for sterilization, but also, simple, cost‑effective and efficient solution, Pulsed Light has a lot of advantages compare to the other technologies.

Conclusion

References

https://www.dir.ca.gov/dosh/DoshReg/5155-Meetings/Peracetic-Acid-9-5-2017-draft.pdf
https://www.allamericanchemical.com/media/wysiwyg/documentdownloads/Sanitation%Presentation.pdf

https://www.anses.fr/fr/system/files/AAAT-Ra-ionisation.pdf
http://www.mercuryconvention.org/Minamata-Convention-booklet-fr-full.pdf