Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using direct contact with electrical or electromagnetic...
Patent
1994-02-24
1998-04-28
Warden, Robert J.
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using direct contact with electrical or electromagnetic...
422 22, 422 28, 25045511, 2504921, 2504951, 426241, A61L 210, A61L 216
Patent
active
057440948
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the treatment of material, in particular the subjection of material to laser UV.
BACKGROUND OF THE INVENTION
It is known to sterilise packaging material, for example the inside surfaces of cartons, in a variety of ways, used together or separately. One is to use heat, for example in the form of hot air or steam, at a temperature above 100.degree. C. for several seconds. Another treatment is to use UV radiation of a bactericidal wavelength (for example 254 mm) giving an average power density at the treatment surface of the order of mW/cm.sup.2, for example 8 mW/cm.sup.2, for many seconds. A further treatment is to employ a relatively highly concentrated H.sub.2 O.sub.2 solution for several seconds. The combining of two or more of the treatments is conventional and enables certain parameters of the treatments, for example the temperature, the treatment time, and/or the H.sub.2 O.sub.2 concentration to be reduced. For example, WO-A-80/01457 discloses a sterilization method applicable to liquids, e.g. waste water and cannery cooling water, but particularly for the sterilization of surfaces, for example surfaces of walls and furniture in hospitals and the surfaces of food containers. The latter surfaces are treated with a concentration of H.sub.2 O.sub.2 no greater than 10% by weight, for example by passing the container or material from which the container will be fabricated through a tank containing the H.sub.2 O.sub.2 solution or by spraying the surfaces of the container or material with the solution. Irradiation is carried out by an UV-lamp so disposed that containers or materials which have emerged from the tank or spray are subjected to UV of wholly or predominantly below 325 nm., such that micro-organisms are rendered non-viable by synergism between the UV and the H.sub.2 O.sub.2.
The use of ultraviolet radiation as a physical agent for the reduction of micro-organisms is well-established. Cellular DNA absorbs the energy of radiation between 250 and 260 nm which leads to the formation of chemical bonds between adjacent thymine nucleotide bases. This change distorts the DNA strands, interfering with replication and transcription and thus expression of the genes. Fatality is inevitable if essential genes are blocked or DNA replication is hindered. The number of vegetative cells killed with UV radiation depends on exposure and dose in mW/cm.sup.2 and mJ/cm.sup.2, respectively, and UV is often ineffective in the killing of bacterial endospores, particularly because UV has poor penetrating power. The combined use of UV radiation, hydrogen peroxide (peroxide radical reacts with most chemical bonds) and heat, achieves sterilisation, but at a high price in terms of time and cost (for example at least 10 seconds treatment time per carton) to the packager. Also the use of a chemical, for example H.sub.2 O.sub.2, for the treatment of food packaging can be an ethical consideration and thus classed as less desirable. It is therefore very attractive to search for an alternative sterilisation system.
WO-A-88/03369 discloses a system for sterilizing such things as air, water, food and food packaging by means of intermittent, very intense, very short duration pulses of light in the visible and near visible frequencies, such light being produced by flashlamps, for example. The components of each pulse cover a broad spectral range and may include far and near UV for deactivation of micro-organisms through photochemical effects. Such UV-rich pulses have at least 15% and preferably at least about 30% of their energy at wavelengths shorter than 300 nm. Such UV-rich pulses may typically have relatively low total energy density, such as in the range of from about 0.01 to 15 J/cm..sup.2 and typically from about 0.1 to 3 J/cm..sup.2. However, for treating food product surfaces, it may be desirable to filter out portions of the spectrum, so that at least about 90% of their energy is distributed between 300 and 2500 nm. In such methods in which the UV-component of the pulsed light flashes is suppressed
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Bergmann Karin
Castberg Helge Bakketun
Hyde Peter John
Ness Karen Margaret Montgomery
Stanley Christopher John
Dawson E. Leigh
Elopak Systems AG
Warden Robert J.
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