GB2517022A - Apparatus and method of killing pathogens on the surface of a product - Google Patents
Apparatus and method of killing pathogens on the surface of a product Download PDFInfo
- Publication number
- GB2517022A GB2517022A GB1408521.1A GB201408521A GB2517022A GB 2517022 A GB2517022 A GB 2517022A GB 201408521 A GB201408521 A GB 201408521A GB 2517022 A GB2517022 A GB 2517022A
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- product
- support surface
- light source
- source
- ozone
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- 238000000034 method Methods 0.000 title claims abstract description 51
- 244000052769 pathogen Species 0.000 title claims abstract description 19
- 230000005855 radiation Effects 0.000 claims abstract description 20
- 230000001678 irradiating effect Effects 0.000 claims abstract description 8
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 42
- 238000011144 upstream manufacturing Methods 0.000 claims description 5
- 238000005086 pumping Methods 0.000 claims description 2
- 235000020639 clam Nutrition 0.000 claims 3
- 241000237519 Bivalvia Species 0.000 claims 1
- 241001665400 Coracias abyssinicus Species 0.000 claims 1
- 239000000047 product Substances 0.000 description 116
- 244000061456 Solanum tuberosum Species 0.000 description 31
- 235000002595 Solanum tuberosum Nutrition 0.000 description 31
- 235000012015 potatoes Nutrition 0.000 description 14
- 235000013305 food Nutrition 0.000 description 7
- 239000000428 dust Substances 0.000 description 5
- 230000001954 sterilising effect Effects 0.000 description 5
- 241000894006 Bacteria Species 0.000 description 4
- 239000003990 capacitor Substances 0.000 description 4
- 235000013399 edible fruits Nutrition 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000002123 temporal effect Effects 0.000 description 4
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 2
- 239000005977 Ethylene Substances 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
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- 235000013372 meat Nutrition 0.000 description 2
- 229940127554 medical product Drugs 0.000 description 2
- 244000005700 microbiome Species 0.000 description 2
- 230000005070 ripening Effects 0.000 description 2
- 230000001360 synchronised effect Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 241000219130 Cucurbita pepo subsp. pepo Species 0.000 description 1
- 235000003954 Cucurbita pepo var melopepo Nutrition 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 240000009088 Fragaria x ananassa Species 0.000 description 1
- 241000233866 Fungi Species 0.000 description 1
- 235000007688 Lycopersicon esculentum Nutrition 0.000 description 1
- 244000141359 Malus pumila Species 0.000 description 1
- 240000008790 Musa x paradisiaca Species 0.000 description 1
- 235000018290 Musa x paradisiaca Nutrition 0.000 description 1
- 208000035415 Reinfection Diseases 0.000 description 1
- 240000004808 Saccharomyces cerevisiae Species 0.000 description 1
- 240000003768 Solanum lycopersicum Species 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
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- 238000007796 conventional method Methods 0.000 description 1
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- 230000009849 deactivation Effects 0.000 description 1
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- 230000004345 fruit ripening Effects 0.000 description 1
- 235000012055 fruits and vegetables Nutrition 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 210000004394 hip joint Anatomy 0.000 description 1
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- 229910052743 krypton Inorganic materials 0.000 description 1
- DNNSSWSSYDEUBZ-UHFFFAOYSA-N krypton atom Chemical compound [Kr] DNNSSWSSYDEUBZ-UHFFFAOYSA-N 0.000 description 1
- 210000002414 leg Anatomy 0.000 description 1
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- 150000004032 porphyrins Chemical class 0.000 description 1
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- 230000000717 retained effect Effects 0.000 description 1
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- 238000001228 spectrum Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000004659 sterilization and disinfection Methods 0.000 description 1
- 235000021012 strawberries Nutrition 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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Classifications
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
- A23B7/00—Preservation or chemical ripening of fruit or vegetables
- A23B7/015—Preserving by irradiation or electric treatment without heating effect
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
- A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
- A23L3/26—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by irradiation without heating
- A23L3/28—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by irradiation without heating with ultraviolet light
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
- A61L2/02—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor using physical phenomena
- A61L2/08—Radiation
- A61L2/10—Ultraviolet radiation
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Polymers & Plastics (AREA)
- Food Science & Technology (AREA)
- General Chemical & Material Sciences (AREA)
- Wood Science & Technology (AREA)
- Zoology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Epidemiology (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Nutrition Science (AREA)
- Apparatus For Disinfection Or Sterilisation (AREA)
Abstract
A method of killing pathogens on the surface of a product 5 comprises the steps of providing a source of pulsed ultra-violet radiation 100 and irradiating the product with multiple pulses of ultra-violet radiation while rotating the product 5 in synchrony with the pulses. Monochromatic or polychromatic light with a wavelength in the range 200 to 380 nm may be used. The product 5 to be treated may be placed on a support surface 120 and the support surface 120 may be rotated by a calculated amount in order to rotate the product 5 as desired. Rotating the product 5 in synchrony with the pulses ensures that the entire product is irradiated efficiently, reducing costs. By rotating the product 5 a controlled amount it is possible to ensure none of the product is unnecessarily irradiated a second time. Apparatus for killing pathogens on the surface of a product is also disclosed.
Description
I
TITLE: APPARATUS AND METHOD OF KiLlING PATHOGENS ON TIlE SURFACE OF A PRODUCT
DESCRIPTION
TECHNICAL FIELD
l'he present invention relates to the killing of pathogens on the surFace ola product, in particular agricultural products, particularly but not exclusively seed potatoes and ware potatoes, and medical products, particularly but not exclusively medical prostheses.
BACKGROUND ART
US 5,489,442 discloses the exposure of a food product to intense (0.01 to 50 J/cm2, e.g., 0.5 J/cm2, energy density measured at the surface of the food product), short duration pulses of polycbromatic light in a broad spectrum (1 70 to 2600 rim; 1. 8xl 015 Hz to 1.2xI 014 Hz), referring to US 4,871,559, which discloses the deactivation of bacteria such as E-coli by flashes of polychromatic light including UV (e.g. from a pulsed Xenon-or Krypton-filled flash lamp). The food products are provided with a light-transmissive coating, applied in fluid form, to inhibit subsequent re-infection of the food product by microorganisms. The food product can be exposed to four pulses (or flashes) of the polycbromatic light, illumination of the entire surface of the food product being achieved by rotating (e.g. using rollers or a shaker apparatus) the food product between two or more flashes of the polychromatic lamp. The method is stated to be particularly useful with fruits and vegetables, such as strawberries, oranges, apples, tomatoes and zucchini. However, WOOl /85222 to the same applicant as US 5,489,442 notes that the method can he ineffective unless a large number of pulses are used while the product is moving within the treatment area to allow all of its surfaces to be exposed to the sterilizing light. Problems with increases in cost and energy are noted.
DISCLOSURE OF INVENTION
According to one aspect of the present invention, there is provided A method of killing pathogens on the surface of a product, the method comprising the steps of providing a source of pulsed ultra-violet radiation; irradiating the product with multiple pulses of ultra-violet radiation from the source while rotating the product relative to the source and in synchrony with the pulses.
By rotating the product in synchrony with the pulses, i.e. such that there is a predetermined temporal relationship between the pulsing of the source of ultra-violet radiation and the rotation of the product, the source is used efficiently, thereby reducing cost and energy wastage.
Specifically, the method may comprise applying a first pulse of radiation to the product, thereby irradiating the product over a segment thereof subtending an angle 0; and applying the next pulse of radiation to the product when the product has rotated through an angle a, where a is at least 50% of 0, preferably at least 75% of 0, and may even be about equal to 0. This ensures that the majority of the region of the product irradiated by the first pulse is not-unnecessarily -irradiated by the second pulse.
In other words, the frequency of the pulses of radiation is controlled in dependence on the speed of rotation of the product, or vice versa.
Specifically, the method may comprise the step of irradiating the product with multiple pulses at a frequency f Hz while rotating the product at w rotations per second, where w=f/n and n is an integer.
To avoid the same region of the product being exposed to consecutive pulses, n may be greater than one.
Given the inherent difficulty in properly illuminating a segment of angle 0 of 1800 by a single pulse, n is preferably greater than two.
In particular, n may equal 3, corresponding to a segment angle 0 of 1200, so that three pulses are applied for every one rotation of the product.
However, it is believed that there is unlikely to be any difficulty in illuminating a segment subtending an angle 0 of 400, so that n may be equal to or less than 9.
The method may comprise the step of ceasing inadiation of the product once the whole surface of the product is irradiated.
The predetermined temporal relationship between pulse application and product rotation is in contrast to the aforementioned prior art where a lack of synchronism between light pulses and the rotation of the product necessitates a large excess -number of pulses while the product is moving within the treatment area if confidence is to he had that all of the product surface has been sufficiently exposed to the sterilizing light.
According to another aspect of the present invention, there is provided a method o killing pathogens on the surface of a product, the method comprising the steps of providing a pulsed light source; actuating the light source to apply a first pulse of light to a first region of the surface facing the light source; thereafter, while the light source is deactivated, reorienting the product such that a second region of the surface faces the light source and the first region of the surface is substantially hidden from the light source; and thereafter actuating the light source to apply a second pulse of light to the second region.
By applying the second pulse of light only once the second region has been exposed to, and the first region substantially hidden from, the light source, little if any of the second pulse is wasted on the first region where pathogens have already bccn killed by the first pulse.
This reduction in waste results in reduced energy consumption overall.
I 0 For all aspects of the invention, the source may he monochromatic (i.e. radiation of a single wavelength) or polychromatic. In the latter case, the source may be 6ltered. the output of the source may he configured to maximise the most effective wavelengths of the polychromatic light, typically in the range 200 to 380nm. Each pulse may have an intensity for the 200 to 380nm wavelengths at the surface of the product in the range 0.05 to 0.2 J/cm2, in particular about 0.1 J/cm2.
The methods may comprise the step of placing the product on a support surface that is curved about an axis and rotating the support surface about the axis, thereby rotating the product. T he support surface may comprise a convex cylindrical surface. The support surface may be defined by a roller having a circular cross-section. The methods may comprise the step of placing the product on two adjacent parallel rollers. The product may sit in the vcc formed by two adjacent rollers.
Alternatively, the method may comprise the step of placing the product on a support surface and rotating the support surface about an axis perpendicular to that surface, thereby rotating the product.
The method may further comprise the step of receiving the nominal diameter of the product, calculating the amount by which the support surface must he rotated to achieve a predetermined rotation of the product, and controlling the relationship between the speed of rotation of the support surface and the frequency of actuation of thc light source accordingly.
As set out above, the predetermined rotation of the product may be chosen such that consecutive pulses of radiation do not substantially illuminate the same region of the product.
The nominal diameter of the product may be measured by an operator or a diameter sensor.
The invention also provides apparatus for killing pathogens on the surface of a product, the apparatus comprising: a pulsed ultra-violet light source; a product support surface that is rotatable; and a controller configured to control the rotation o the product support surface and the pulsed light source in accordance with the method steps outlined above.
The product support surface may be configured to rotatc about an axis substantially parallel to that surface. The apparatus may comprise a roller defining a convex cylindrical support surface. The apparatus may comprise two adjacent rollers each defining a support surface.
Alternatively, the product support surface may bc configured to rotate about an axis substantially perpendicular to the product support surface.
Thc controller may be configured to read the nominal diameter of the product and control the relationship between the speed of rotation of the surface and the frequency of actuation of the light source in accordance with one or more of the method steps outhned abovc. In particular, the controller may be configured to control the speed of rotation of a roller defining the product support surface.
The apparatus may also comprise a system configured to measure the nominal diameter of the product.
According to another aspect of the invention there is provided: apparatus for killing pathogens on the surface of a product, the apparatus comprising an ultra-violet light source configured to irradiate the surfaec of the product with ultra-violct radiation; the apparatus being configured to convey ozone generated adjacent the surface of the light source to the surface of the product.
The application to the product of ozone generated as a by-product of the irradiation process increases the efficacy of the pathogen killing process overall. Where the product is a fruit, ozone may additionally reduce ripening by destroying the ethylene emitted in the fruit ripcning process.
The apparatus may comprise a first enclosure containing the ultra-violet light source and having an inlet for air and an outlet for ozone generatcd adjacent the surface of the light source.
The apparatus may comprise a support surface for the product, the apparatus being configured to convey the ozone to that support surface.
The apparatus may be configured to convey the ozone to the surface of the product prior to any irradiation of the product by the source.
The apparatus may comprise a pump configured to convey the ozone to the surface of the product. The pump may he located downstream of the ozone flow to the product.
The pump maybe located upstream of the ultra-violet light source.
The apparatus may comprise an enclosure into which the ozone is conveyed for application to the surface of the product. The enclosure may be located upstream of the ozone flow to the product. The enclosure may be located downstream of the ozone flow to the product.
The above aspect of the invention may be implemented in combination with one or more of the other aspects set out above. The various aspects may include a pump configured to clean the product by pumping air over the product, in particular prior to any irradiation by the light source.
BRIEF DESCRIPTION OF DRAWINGS
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1A is a perspective view of a first embodiment of apparatus according to the present invention; Figure lB is a side view of figure IA; Figures 2A-D are detailed views of figure 1A illustrating the steps of the invention; Figure 3 is a detailed view of figure lA.
Figure 4A is a perspective view of a second embodiment of the invention; Figure 4B is a detailed view of figure 4A; Figure 5 is a side view of a third embodiment of the invention; Figure 6 is a side view of a fourth embodiment of the invention.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
Referring to figure IA, product -in this case potatoes S -are treated as they travel (in a direction indicated by arrow M) along a roller table 110 having rollers 120 driven by a motor indicated schematically at 140. The rollers on the table rotate, rotating the potatoes to allow a 3600 exposure of each potato as it travels horizontally along the roller table. As illustrated in the side view of figure 1 B, each potato 5 call be considered to be substantially circular in cross-section and to sit in the vee formed by adjacent rollers.
Mounted above the table is a lamp box or cartridge 100 containing one or more multidirectional lamps 101 that generate pulses (indicated by arrows 20) of multidirectional polychromatic light in the range 200 to I 000nm.
As is well known, ultraviolet (UV) radiation in the wavelength range of 200 to 400nm, and more specifically UVC radiation with a wavelength of 254nm, kills microorganisms such as yeasts, mould spores, bacteria and fungi. Certain chemicals within the cells of the pathogens are highly absorbent to the energy of these wavelengths and act as heat-sinks' which rapidly convert the UV cncrgy into thermal energy. I'hese small areas of intense heat cannot be quickly dissipated causing in'eparable or irreversible lethal damage to the organism.
Moreover, longer wavelengths (visible light) can produce a photo-dynamic effect, which is very aggressive to nearby molecules. Wavelengths of 405 to 420nm and 635nm produce a peak in porphyrin excitation in most cells. This can generate reactive oxygen species, such as singlet oxygen or free radicals, which can lead to necrosis of cells upon light exposure.
The emission spectrum and peak output from the lamps is dependent on several factors including the magnitude and pulse length of the driving voltage and the physical construction of the lamp. Typically, the spectral peak is in the ultra-violet range of 230 to 2SOnm and the drive voltage is in the range of 1500 to 4500 Volts, specifically 3500V.
Light pulse duration may be in the range of from about I x 106 seconds to about 1 x lO seconds but is typically about 10 milliseconds (10 x i03 seconds).
The lamp box 100 has a special glass on its bottom face 102 to transmit the frill spectrum of light onto the target. Alternatively, a filter may be used e.g. to filter out infra-red radiation that might otherwise cause undesired heating of the product The lamp box interior, sides and top are reflective so as to direct the light down though the glass and utilisc tile full output of the lamps. A UV sensor, not shown, may be placed below the lamp box window to monitor changes in output due e.g. to dust on the window or ageing of the window.
A control unit 130, such as a computer or programmable controller controls the pulsing of the lamps and the rotation of the rollers -and thus the product -such that they operate in synchrony, i.e. such that there is a predetermined temporal relationship between the pulsing of the lamps and the rotation of the product, the latter being effected by the rotation of the rollers on which the product is supported. The control unit may also control any safety deviccs and alarms of the kind typically required depending, inter alia, on the output of the UV sensor mentioned above and the output of the lamps as indicated by the charging of the capacitors that drive the lamps.
iS For example, where the lamps pulse at a fixed frequency f liz, the speed of rotation of the rollers is chosen such that the product rotates at w rotations per second, where wfIn, n being an integer greater than one (at n1, the product will complete one rotation between pulses, resulting in the same region of the product being exposed to every pulse while leaving other regions untreated -a clearly undesirable situation).
The value of n is chosen -either manually by the operator or automatically by computer -depending on the size of the product to be treated relative to the dimensions of the rest of the apparatus. Figure 2A shows the exposure of the surface 10 of the potato 5 to a first pulse of polychromatie light indicated by arrows 21. It will be evident that only that region 30 of the surface facing the tight source 100 (region 30 being delimited between radial lines 31 and 32 and covering the shaded sector 30') will receive sufficient exposure to kill pathogens to the required level, the relative dimensions of the product and the lamp relative to the product being such that region 30 subtends an angle 0 between radial lines 31 and 32 of approximately 1200, i.e. a third of the entire periphery of 3600.
It follows that, for complete 360° irradiation, the product must he rotated and irradiated a further two times, i.e. rotated in synchrony with thc pulses at a frequency that is one third that of the pulse frequency, i.e. n=3. In another embodiment, not shown, the relative dimensions of the product and the lamp relative to the product arc such that region 30 subtends around 400, corresponding to n9. Nine is typically the maximum number of steps required to achieve full illumination of a product.
Accordingly, as illustrated in figure 2B, and while the lamp is not activated, the product is rotated such that a second, substantially separate region 40 of the surface (region 40 being delimited by radial lines 41 and 42 and covering a 0 = 120° sector 40') faces the light source 100 and such that the first region 30 of the surface is substantially hidden from the light source. In the example shown, product 5 is rotated anti-clockwise by an angle 0 of approximately 120° (corresponding to n3), resulting in a second region that is substantially contiguous with the first region and with approximately 80% of the first region being hidden from the light source. Only once the product has been oriented in this way is the light source actuated, i.e. the product is rotated in synchrony with the pulse, the resulting second pulse 22 of polychromatie light primarily irradiating the second region rather than the first region which has already been irradiated in the previous step.
To achieve irradiation of the entire surface of the potato, the potato is rotated a further 120° such that a third region 50 of the surface (region 50 being delimited by radial lines 51, 52 and covering a sector 50' subtending angle 0 = 1200) is exposed to the lamp. Once this has been achieved, a third light pulse is applied as indicated by arrows 23 in figure 2D.
In contrast to the conventional techniques described above, this method allows the cntire surface of the potato to be irradiated without a large number of pulses. Not least, this results in reduced energy consumption.
The steps of figures 2A-D may be repeated so that each potato is exposed over two complete rotations and to six light pulses in total. This may allow the use of lower power light sources that would not be able to kill pathogens in a single exposure. It may also allow for differences in diameter and/or shape between products (as is typical with potatoes).
The rotation of each potato is typically continuous and is driven by the continuous rotation of the rollers 120 on which the potatoes sit, the actuation of the lamps being synchronised with the rotation of the rollers so as pulse only when each potato has rotated an appropriate amount as previously described. However, it will be appreciated that the product rotates very little, i.e. is effectively stationary, during the typical 10 millisecond duration of each light pulse.
As illustrated in figure 3, a potato 5 is supported by at least onc surface 121 of a roller 120, the surface being curved about an axis 122 about which the roller rotates. In thc particular roller table arrangement of figures 2A-D, support for each potato is provided by two adjacent parallel rollers 120 each having a circular cross-section providing a convex cylindrical surface. The present inventors have recognized that the rolling diameter of the potato or other product will influence the number of rotations achieved while on the roller table, with a small diameter potato rotating more times than a large diameter potato for a given rotation of thc roller. It follows that a rotation of the rollers sufficient to achicve a 120° rotation of a small potato will not be sufficient to achieve a similar rotation of a larger potato.
To compensate for this, the nominal diameter of the product is measured and input to thc controller 130 which calculates the amount by which thc curved surface, i.e. the roller 120, must be rotated to achieve an angular rotation oF' the product that exposes a second region of the surface and substantially hides the first region. The control unit then selects the synchronous relalionship between the speed of rotation of the curved surface and the frequency of actuation of the light source accordingly. In the example shown, this involves changing the pulse frequency of the light source for a given roller rotation speed. This frequency can typically alter between 0.1 and S second intervals, the minimum period being largely dependent on the charging capacity of the power supply. Alternatively, the roller speed may be changed for a given pulse frequency.
In the case of seed potatoes, these are often sized', for example they may be supplied as 45-55mm sized seed. This size' can be entered manually into the control unit 1 30 by a machine operator. Alternatively, the size of the potatoes can be measured by a product diameter sensor (indicated at 150 in figure 1A) and input into the controller.
In another embodiment, not shown,, the diameter of the rollers can be altered depending on the size of the product to be treated, so that changes to the pulse frequency and roller rotation speed are not necessary.
Figure 4A is a perspective view of a frirther embodiment in which all key components are integrated into a single table unit supported on legs. Rollers 120 are linked together in a recirculating loop 200 in the manner of a conveyor belt so that product deposited on to one end 210 of the upper side of the loop is transported to the other end 220 thereof, where it falls off and down as indicated by arrow 300. As shown in the detailed view of figure 4B, the rollers 120 on the upper side of the loop roll along a support surface 250 under the action of a linked chain 260 moving at a velocity V, which in turn results in the surface of each roller rotating with a tangential velocity V. As will be evident from the figure, this in turn results in the product rotating at V / IJD rotations per second, D being the diameter of the product 5.
In the embodiment shown, the rollers have a diameter of 60mm, suitable for operation with seed potatoes having a nominal diameter D in the range 45 to 65mm, and are pulled along the support surface at a speed V of approximately 0.1 metres per second.
Where the linked chain is driven by a fixed speed motor, so that V is also fixed, synchrony between product rotation and light pulses is achieved by altering the pulse frequency in accordance with the formula Vn / nD, where n is an integer greater than 1, i.e. a predetermined temporal relationship between the rotation of the product and frequency of application of the light pulses.
Referring to figure 4A, there is indicated at 230 a number of electrical capacitors and other components situated adjacent the lamp box 100 and are coimected to the lamps. The power for these capacitors will be supplied from a power supply unit mounted either adjacent to the capacitors on the machine or mounted on the floor nearby. A hood is provided to screen any electromagnetic emissions from these items.
The materials used for the roller table are variously chosen for their suitability for use with UV and ozone (stainless steel may he appropriate), for reflection of light to improve treatment and, near the product exit areas 220, for absorption of TJV light to reduce the exposure of operators to the light pulses, in particular the UV component thereof Referring to the embodiments of both figures lB and 4A, the lamps 101 produce a lot of heat and to this end are cooled by air forced into the lamp box 100 as indicated by arrow 103. When the lamps flash, air in the box and adjacent the lamps is converted into ozone. This by-product is exhausted from the lamp box and fed via conduit 104 onto the potatoes supported on the surface 121 of rollers 120, there having a sterilizing effect on bacteria and moulds as is well known and also sterilizing nearby surfaces that are not in the treatment area of the lamps. Alternatively/in addition, ozone will reduce ripening of fruit by destroying the ethylene emitted in the fruit ripening process. Alternatively / in addition, ozone can be supplied from a separate ozone generator.
Figure 5 shows more detail of a suction fan 400 that may be placed bclow the rollers to create a distinct ozone treatment zone, the fan pulling the ozone past the productS to aid ozone coverage. An under tray 410 to the conveying system may also serve as an ozone trap, creating an ozone enriched area for the product and reducing loss of ozone to operator areas. As with the hood mentioned above, such an under tray may be configured to screen electromagnetic emissions.
Similarly, a ceiling 420 above the product on the conveyor ioop or roller table 110 can create an enclosed tunnel 430 in which ozone would be applied and retained, the length of the tunnel being sufficient to allow time for the ozone to take effect, the zone of irradiation by lamps 101 having a typical length L oI400mm.
To increase the ozone immersion time, product may subsequently be placed in an ozone-enriched bath. Alternatively/in addition, product may be washed/sprayed with, or immersed in, ozone-enriched water created, e.g. by bubbling ozone through water.
By placing the ozone outlet 104 upstream of the lamps, some of the ozone will subsequently be destroyed by the ultra violet light of the lamps, thereby reducing ozone hazards to operators. Any remaining exhausted ozone may also be used to disinfect containers (trays, pumiets, boxes) for the treated product and/or exhausted to atmosphere or to an ozone killer' device.
The forced-air cooling can also used to blow dust off the potatoes to give a better treatment efficacy. Not only does dust carry pathogens, soil and dust act as an umbrella', hiding the pathogens on the underside from the treatment. Dust granules can also cause microscopic scratches on the potato surface to allow in' the harmful bacteria. A further option to improve the efficacy of the system is to clean the potatoes before treatment, e.g. by washing or dry-brushing.
Figure 6 is a schematic view of a second embodiment of the invention applied to a different product, in this case a medical prosthesis such as a hip joint, shown schematically at 5 and having a surface 10. Prosthesis 5 is supported on the surface 121 of turntable 150 rotatable (as indicated by arrow R) by an actuator such as a stepper motor 152 about axis 151 normal to the surface 121, pulses of light 21 from source 100 being applied in synchrony with the rotation under the control of a controller 160 as indicated by dashed lines.
It should be understood that this invention has been described by way of examples only and that a wide variety of modifications can be made without departing from the scope of the invention.
In particular, whilst the invention has been described with reference to the treatment of seed potatoes, it is also applicable to control pathogcns on a wide range of products in the agricultural, industrial and medical products. In the case of agricultural products, this may include ware potatoes (for consumption), foodstuffs, fruits and meats. In the case of banana hands or meat carcasses, rotation about a vertical rather than horizontal axis may be appropriate. In the case of industrial products, this could involve the sterilization of yoghurt pots before filling.
Nor is it restricted to the use with roller eonveyors: other products, especially small seeds and non-circular products may use another conveyor type to move and rotate for treatment, e.g. a vibratory conveyor or a conveyor that tumbles the produce to rotate. Nor must the product be supported during rotation: treatment may take place as the rotating product is free falling from the end of a conveyor or feed tank.
In another possible embodiment, the product could be transported in a pneumatic conveyor, with inlets br lamp cartridges to be attached. Such lamp cartridges may have a S reflective interior to improve performance, while interruptors or baffles may be placed in the air flow to scatter the product flow, thereby increasing the area of product exposed to the light pulses.
Nor is the invention restricted to the arrangement of lamps discussed above: lamps may be mounted above, below or adjacent to the target, in any directional position to suit that target.
Similarly, the invention is not restricted to continuous throughput of product but is also applicable to batch treatment systems in which product is moved under lamps, the horizontal movement of the product is stopped, the product is rotated and treated as set out above, and horizontal movement is started again.
Claims (3)
- CLANS1. Method of killing pathogens on the surface of a product, the method comprising the steps of: providing a source of pulsed ultra-violet radiation; irradiating the product vith multiple pulses of ultra--violet radiation from the source while rotating the product relative to the source and in synchrony with the pulses.
- 2. Method according to claim I and comprising the steps of applying a first pulse of radiation to the product, thereby irradiating the product over a segment thereof subtending an angle 0; and applying the next pulse of radiation to the product when the product has rotated through an angle cx, where cx is at least 50% of 0, 3 Method according to clam 2 wherem a s at least 7c% of 0 1 5 4. Method according to claim 3, wherein a is about equal to 0.5. Method according to any preceding claim and comprising the step of irradiating the product with multiple pulses at a frequency f Hz while rotating the product at w rotations per second, where w=f/n and n is an integer.6. Method according to claim 5, wherein n is greater than one.7. Method according to claim 6, wherein n is greater than two is 8. Method according to claim 7, wherein ii equals
- 3.9. Method according to any one of claims 5 to 8, wherein a is equal to or less than 9.10. Method according to any preceding claim and comprising the step of ceasing irradiation of the product once the whole surface of the product is irradiated.11. N'klhod of killing paihogens on the surface of a product, the method comprising the steps of providing a pulsed light source; actuating the ight source to apply a first pulse of light to a first region of the surthce facing the light source; thereafter, while the light source is deactivated, reorienting the product such that a second region of the surface faces the light source and the first region of the surface is substantially hidden from the light source; and thereafter actuating the light source to apply a second pulse of light to the second region.12. Method according to any preceding claim, wherein the source is monochromatic.13. Method according to any pneeding claim, wherein the source is polychromati.14. Method according to claim 13, wherein the source is filtered.15. Method according to claim 13 or claim 14, wherein the output of the source is eonflgured to maxinüse the most effective wavelengths of the polychromatic light.16. Method according to claim 15, wherein the output of the source is configured to maxirnise the wavelengths of the polychromatic light in the range 200 to 3SOnrn.1 7. Method according to any preceding claim, wherein each pulse has an intensity for the 200 to 3SOnni wavelengths at the surfhce of the product in the range 0.05 to 0.2 J/cm2.I.. Method according to claim 17, wherein each pulse has an. intensity for the 200 to 380nm wavelengths at the surface of the product of about 0.1 Fern2.19. Method according to any preceding claim arid comprising the step of placing the product on a support surface that is curved about an axis and rotating the support surface about the axis, thereby rotating the product.20. Method according to claim 19, wherein the support surface comprises a convex cylindrical surface.21. Method according to claim 20, wherein the support surface is defined by a. roller having a circular crosssection.22. Method according 10 claim 21 and comprising ie. step of placing the product on two adjacent parallel rollers. Method cioidmg to cairn 22 and eornpnsmg the step of plau g thc produc' in the 24. Method according to any one of cbixn.s Ito 18 and comprising the step of placing the product on a support surface and. rotating the support surface about an axis perpendicular to that surface, thereby rotating the product.25, Method according to any one of claims 19 to 24 and comprising the step of receiving the nominal diameter of the product, calculating the amount by which the support surface must be rotated to achieve a predetermined rotation of the product, and controlling the relationship between the speed of rotation of the support surface and the frequency of act uabon of the tght source accorthngl' 26. Method according to claim 25 and comprising the step of calculating the amount by which the support surface must be rotated to achieve a predetermined rotation of the product such that consecutive pulses of radiation do not substantially illuminate the same region of the I S product.27. Method according to claim 25 or claim 26 and comprising the step of measuring, the nominal diameter of the product by an operator or a diameter sensor.28. Apparatus fir killing pathogens on the surthee of a product, the apparatus comprising: a pulsed ultravioiet light source; a product support surface that is rotatable; and a controller configured to control the rorafton of the product support surface and t'ic.pulsed light source in accordance with any one of claims 11 to 27.29. Apparatus according to dam, 28, wherein the product support surfitce is configured to rotate about an axis substantially parallel to that surface.30 Apparatus accoiding to clam 29 and o.npnsrng a ro]er dcfining i coin cx cyimdncal support surface.3 1. Apparatus according to claim 30 and comprising two adjacent rollers each defining a support surface.32. Apparatus according to claim 28, tyherein the product support surface is configured to rotate about an axis substantially ptrpendicular to the product support surface.33 Apparatus according to any oe of clams 13 to 2, wherein the controller,s configured to read the nominal diameter of the product and control the relationship between the speed of rotation of tile surface and the frequency of actuation of the light source accordingly.34. Apparatus according to claim 33, wherein the controller is configured to control the speed of rotation of a roller defining the product support surface.35. Apparatus according to any one of claims 28 to 34 and conlpnsing a system configured to measure the nominal diameter of the product.LL36. Apparatus fhr killing pathogens on the surface of a product, the apparatus comprising ifl JltTcl-%IOlCt light soutce configurcd to niadiate the surface of the pioduct with ultia violet radiation; the apparatLs lx mg con li g ii ed to cor tVC ozone generated ad ac cut tile surface of the light source to tile surface of the product.37. Apparatus according to claim 36 and comprising a first enclosure containing the ultra-violet light source and having an inlet for air and an outlet for ozone generated adjacent the surface of the light source.38. Apparatus according to claim 36 or claim 37 and comprising a support surface for the product. the apparatus being configured to convey the ozone to that support surface.39.. Apparatus according to any one of claims 36 to 38 and configured to convey the ozone to the surface of the product prior to any irradiation of the product by the source.40, Apparatus according to any one of claims 36 to 39 and comprising a pump configured to convey the ozone to the surface of the product.41. Apparatus according to claim 40, where the pinrp is located downstream of the ozone flow to the product.42. Apparatus according to claim 40 or claim 41, wherein the pnnp is located upstream of the ultra-violet light source.43. Apparatus according to any one of claims 36 to 42 and comprising an enclosure into which the ozone is conveyed for application to the surface of the product.S 44 Apparatus acc.oidmg to cann 43, v.herem the enclosure is located upstream of the ozone flow to the product.4 Apparaws according to claim 43 wherein tie cnc1osure located downstream of the ozone flow to the product.46. Apparatus according to any one of claims 28 to 45 and comprising a pump configured to clean the product by pumping air over the product.47. Apparatus according to claim 46, wherein the pump is configured to clean the product prior to any irradiation by the light source.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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GB201309648A GB201309648D0 (en) | 2013-05-30 | 2013-05-30 | Apparatus and method of killing pathogens on the surfcace of a product |
GB201401138A GB201401138D0 (en) | 2014-01-23 | 2014-01-23 | Apparatus and method of killing pathogens on the surface of a product |
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GB201408521D0 GB201408521D0 (en) | 2014-06-25 |
GB2517022A true GB2517022A (en) | 2015-02-11 |
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GB1408521.1A Withdrawn GB2517022A (en) | 2013-05-30 | 2014-05-14 | Apparatus and method of killing pathogens on the surface of a product |
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Cited By (4)
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WO2016162511A1 (en) * | 2015-04-10 | 2016-10-13 | E.T.I.A. - Evaluation Technologique, Ingenierie Et Applications | Method and device for the continuous ozone-based treatment of particulate products, comprising means for conveying and vibrating said products |
US9801966B2 (en) | 2015-07-31 | 2017-10-31 | Hyper Light Technologies, Llc | Systems and methods of microbial sterilization using polychromatic light |
US9961927B2 (en) | 2015-07-31 | 2018-05-08 | Hyper Light Technologies, Llc | Systems and methods of microbial sterilization using polychromatic light |
WO2018167439A1 (en) | 2017-03-17 | 2018-09-20 | Université D'avignon Et Des Pays De Vaucluse | Method for decontaminating fresh vegetables, fresh fruits, living plants or vegetation the surface of which is contaminated by pesticides |
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WO1995028095A1 (en) * | 1994-04-18 | 1995-10-26 | Purepulse Technologies, Inc. | Prolongation of shelf-life in perishable food products |
WO2001085222A1 (en) * | 2000-05-05 | 2001-11-15 | Purepulse Technologies, Inc. | Transmissive conveyor for use in pulsed light sterilization |
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US4871559A (en) * | 1983-11-23 | 1989-10-03 | Maxwell Laboratories, Inc. | Methods for preservation of foodstuffs |
WO1995028095A1 (en) * | 1994-04-18 | 1995-10-26 | Purepulse Technologies, Inc. | Prolongation of shelf-life in perishable food products |
WO2001085222A1 (en) * | 2000-05-05 | 2001-11-15 | Purepulse Technologies, Inc. | Transmissive conveyor for use in pulsed light sterilization |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
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WO2016162511A1 (en) * | 2015-04-10 | 2016-10-13 | E.T.I.A. - Evaluation Technologique, Ingenierie Et Applications | Method and device for the continuous ozone-based treatment of particulate products, comprising means for conveying and vibrating said products |
FR3034674A1 (en) * | 2015-04-10 | 2016-10-14 | E T I A - Evaluation Tech Ingenierie Et Applications | PROCESS FOR OZONE CONTINUOUS DEBACTERIZATION WITH VIBRATED TUBE |
CN107529793A (en) * | 2015-04-10 | 2018-01-02 | 工程与应用评估技术公司 | Method and apparatus for continuous ozone-based treatment of particulate products, comprising means for conveying and vibrating said products |
US20180117199A1 (en) * | 2015-04-10 | 2018-05-03 | E.T.I.A. -Evaluation Technologique, Ingenierie Et Applications | Method and device for the continuous ozone-based treatment of particulate products, comprising means for conveying and vibrating said products |
US10632218B2 (en) | 2015-04-10 | 2020-04-28 | E.T.I.A.—Evaluation Technologique, Ingenierie et Applications | Method and device for the continuous ozone-based treatment of particulate products, comprising means for conveying and vibrating said products |
US9801966B2 (en) | 2015-07-31 | 2017-10-31 | Hyper Light Technologies, Llc | Systems and methods of microbial sterilization using polychromatic light |
US9961927B2 (en) | 2015-07-31 | 2018-05-08 | Hyper Light Technologies, Llc | Systems and methods of microbial sterilization using polychromatic light |
WO2018167439A1 (en) | 2017-03-17 | 2018-09-20 | Université D'avignon Et Des Pays De Vaucluse | Method for decontaminating fresh vegetables, fresh fruits, living plants or vegetation the surface of which is contaminated by pesticides |
FR3063974A1 (en) * | 2017-03-17 | 2018-09-21 | Universite D'avignon Et Des Pays De Vaucluse | PROCESS FOR DECONTAMINATING FRESH FRUITS, FRESH FRUITS, PLANTS OR VEGETABLE PLANTS WHOSE SURFACE IS CONTAMINATED BY PESTICIDES |
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