EP0045201A1

EP0045201A1 - A method of rendering material aseptic

Info

Publication number: EP0045201A1
Application number: EP81303417A
Authority: EP
Inventors: Catherine Jane Stannard; John Mathew Wood
Original assignee: Liquipak International BV
Current assignee: LIQUIPAK INTERNATIONAL B.V.
Priority date: 1980-07-29
Filing date: 1981-07-24
Publication date: 1982-02-03
Also published as: AU7352581A; JPS57110252A; DK338481A; JPS644468B2

Abstract

A method of rendering aseptic the interior surface of a polyethylene-coated aluminium or paperboard packaging carton comprises spraying into the cartons water or H₂0₂ to provide a layer of water or H₂0₂ about 2µ thick and then irradiating the interior surface with ultraviolet radiation to give a dosage of at least 5 mW sec./cm², the water or H₂0₂ and the radiation having a synergistic sterilizing effect.

Description

This invention relates to a method of rendering material aseptic.
United States Patent 3,566,575 discloses an aseptic packaging machine for forming, aseptically treating, filling and sealing containers while protecting them with a clear air atmosphere after they have been aseptically treated by a bactericide. The aseptic treatment is accomplished by a fogging system to provide for total contact by the bactericide with the internal sufaces of the container and includes a drying station for removal of the residual bactericide after the treatment.
The suggested bactericide is 35% hydrogen peroxide solution (H₂0₂). However, this could take a relatively long time, up to several seconds, to give a high kill of bacteria, such as a 1 in 10⁴ survival rate. Then the H₂0₂ is removed by drying, which is done by jetting hot air down through the open top of the container. Complete removal is desirable since it has been alleged that, even in small residual quantities, H₂0₂ has a toxic effect on human beings. However, the relatively large amount of H₂0 ₂ required is very difficult to dry away completely, especially since the drying is least effective at the bottom of the container, so that again a relatively long time is required. The total time delays involved therefore seriously jeopardize the commercial
of the machine.
cream or fruit juiceare inter sterilised before
by exposing them in an asepcic cnamber so a saccer-cidal radiation by elsochromagnetic baves or particles. The radiation source is directed with Its window inside the carton to cover all internal surfaces. The carton is designed so as to avoid any shadows on its inside. The radiation source is a gas discharge lamp with a power unit and emits ultraviolet rays cf 200-280 nm (esp. 254 nm) when a lifter has raised a carton around the quartz tube of the lamp. Addition UV lamps can be arranged in the chamber. If an electron beam is used instead of the UV lamps, lead screens are required to protect the personnel against X-rays, produced as a secondary effect. A preferred material for the cartons is polystyrene foam, strengthened by a surface coating of a homogeneous plastic.
The raising of the cartons one after another around the quartz tube results in either a very low speed of horizontal advance of the carton or a very short time of exposure of the carton interior to the radiation. Moreover, any carton made by folding sheet material is liable to have among its folds shadows where the bacteria are not exposed to the radiation.
In an article in the Journal of Applied Bacteriology 1979, 47, 263-269, entitled "The Combined Effect of Hydrogen Peroxide and Ultraviolet Irradiation on Bacterial Spores" by Bayliss and Waites, it is suggested that hydrogen peroxide solution combined with ultraviolet radiation be used to sterilize packaging for aseptic filling. This article particularly discloses that it is possible to obtain an especially strong bactericidal effect at low concentrations of H₂0₂ in the solution.
We believe that the action of killing microorganisms in this way is linked to the breakdown of hydrogen peroxide into hydroxyl radicals by the ultraviolet radiation.
According to one aspect of the present invention, there is provided a method of rendering material aseptic in which the material is contacted with a substance, and the material and the substance are irradiated with ultraviolet radiation, the substance and the radiation having a synergistic sterilizing effect, characterized in that said substance is not toxic in residual quantities,
The use of such substances has the advantages of obviating the risk of any toxic effects and thus of avoiding any need to remove any residual quantities of the substance from the material.
Such substance can be water, for example.
According to another aspect of the present invention, there is provided a method of rendering material aseptic in which the material is provided with a layer of a substance and the material and the substance are irradiated with ultravioler. radiation the substance and the radiation having a synergistie.sterilizing effect, characyterized in that said layer is relatively thin and the irradiation is relatively intensive.
The substance can be hydrogen peroxide solution or water, for example.
In a preferred embodiment, the layer consists of droplets of H₂0₂ or water. Particularly, the layer is less than 0.1 mm thick, for example about 2u thick. we believe that such a relatively thin layer has the advantage that the droplets do not shelter to a substantial extent from the ultraviolet radiation the organisms to be killed. The dosage of the irradiation is advantageously at least 5 mW sec./cm² over every part of the material desired to be rendered aseptic, so giving a relatively high dosage.
According to a further aspect of the present invention, there is provided a method of rendering material aseptic, in which the material is irradiated with ultraviolet radiation, characterized in that substantially no radiation the wavelength of which has been substantially changed by the material is reflected by the material.
We believe that such lack of change in the wavelength of the radiation is of importance, since there is a particular wavelength (usually 254 nm) at which the radiation is most lethal, so that if there is reflected radiation of a substantially different wavelength, the method is less effective.
In order that the invention may be clearly understood and readily carried into effect, examples thereof will now be described.
Experiments have been carried out to ascertain the effect of various treatments on microbial populations, particularly bacterial spores, on the interior surfaces
1 litre cartons of dimensions 245 mm. x 70 mm. x 70 mm., one interior surfaces of two of the cartons being of polyethylene-coated aluminium and of another two being of polyethylene-coated paperboard.
Ultraviolet radiation was provided by a hign intensity W-C germicidal lamp (UVC-13-70) produced by Brown, Boveri & Cie of Baden. The lamp was so situated relative to the carton that the lowest dosage of any part of the interior surface of the carton was 5 mW-sec./cm² with a 10 second exposure of the interior surface.
Prepared suspensions of the test organisms were sprayed into the cartons by means of an atomizing nozzle. An inoculum containing spores of Bacillus subtilis and of> 10⁷ cells/ml was sprayed for 0.5 sec. to produce uniform inoculation of the interior surface.
An atomizing nozzle was used to spray H_z0₂ solution into the cartons at ambient temperature. 0.1 ml of H₂O₂ in 1% w/v solution was sprayed for 0.6 sec., to give an H₂0₂ layer thickness of about 2µ. Water was also sprayed into the cartons in a similar manner.
The following data were obtained:
we believe that if reflection from the aluminium in the polysthylene-coated aluminim interior cartons is substantially prevented by some means. then the loss. of effectiveness in the treatment of such cartons is substanteally obviated.
Further experiments producec the following gata for
coated paperboard interior cartons:
The present invention is particularly usable in the machine of our Patent Application No. ₇9302970.3
The desired lethal effect'on bacteria of the combined use of H₂0₂ and UV has been found to be consistently achieved even at very low H₂0₂ concentrations e.g. down to 0.05% H₂0₂ solution. Thus residual H₂0₂ can in any case be made very low, without any serious detriment to the bactericidal effect.

Claims

1. A method of rendering material aseptic in which the material is contacted with a substance, and the material and the substance are irradiated with ultraviolet radiation, the substance and the radiation having a synergistic sterilizing effect. characterized in that said substance is not toxic in residual quantities.

2. A method according to claim 1, characterized in that said substance is water.

3. A method of rendering material aseptic in which the material is provided with a. layer of a substance, and the material and the substance are irradiated with ultraviolet radiation, the substance and the radiation having a synergistic sterilizing effect, characterized in that said layer is relatively thin and the irradiation is relatively intensive,

4. A method according to claim 3, characterized in that said substance is water.

5. A method according to claim S or 4, characterized in that said layer is less than 0.1 mm thick.

6. A method according to claim 5, characterized in that said layer is about 2µ thick.

7. A method according to any one of claims 3 to 6, characterized In that the dosage of the irradiation is at least 6 mW sec./cm² over every part of the material desired to be rendered aseptic.

A method of rendering material aseptic, in whish the material is irradiated with ultraviolet radiation, caracterized in that substantially no radiation the

length

which has been substantially changed by the material is reflected by the material.