WO2018083471A1

WO2018083471A1 - Disinfection of foodstuffs

Info

Publication number: WO2018083471A1
Application number: PCT/GB2017/053294
Authority: WO
Inventors: Malcolm Robert Snowball
Original assignee: Ultra Biotecs Limited
Priority date: 2016-11-04
Filing date: 2017-11-01
Publication date: 2018-05-11
Also published as: GB2559946A

Abstract

An apparatus for disinfecting products is disclosed herein. The apparatus comprises a tank for holding a liquid for receiving microorganisms from the products, wherein the tank comprises a channel for the liquid to flow through and for receiving the products, at least one ultrasonic transducer for providing ultrasonic energy to the products in the channel via the liquid for forcing microorganisms off the products and into the liquid, and a flow provider arranged to provide a flow of liquid along the channel and arranged to recirculate the liquid through a liquid steriliser. The liquid steriliser comprises a liquid duct having a UV transmissive wall providing a surface area for irradiation and a source of UV radiation arranged to irradiate liquid flowing in the duct through the UV transmissive wall.

Description

Disinfection of foodstuffs

Field of the invention

The present disclosure relates to a method and apparatus for the sterilisation or disinfection of products, for example foodstuffs such as fruit and vegetables.

Background

The shelf life of food is substantially shortened due to the presence of micro-organisms in the food, which can cause the food to deteriorate. Not only does shelf life affect the economic viability of food producers but it has a direct effect on public health, since the presence of certain micro-organisms in food can be hazardous if the food is ingested. These problems can be exacerbated if the food is not kept sufficiently refrigerated or is undercooked, since the micro-organisms in the food can multiply rapidly. In order to overcome the above-mentioned problems, it has been proposed to pasteurise food. However, a disadvantage of pasteurisation is that the process is lengthy and can only be used on certain types of food. Furthermore, the pasteurisation process affects the taste of the food and is costly to perform, since it uses a substantial amount of energy, a great deal of which is discharged into the working environment.

Thermal disinfection processes such as steam or water scalding, for example at 100 °c seriously degrade the foodstuffs and are not acceptable to either the food manufacturers or the retailers. Strong chemicals and biocides are not acceptable because they impart objectionable tastes and or smells, and are banned for the processing of certain foodstuffs in Europe.

Summary of the invention

Aspects of the invention are as set out in the independent claims and optional features are set out in the dependent claims. Aspects of the invention may be provided in conjunction with each other and features of one aspect may be applied to other aspects.

Drawings Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a cross-section through an example apparatus for disinfecting products; Fig. 2A shows a plan view of an apparatus for disinfecting products such as the apparatus of Fig. 1 ;

Fig. 2B shows a side view of an apparatus for disinfecting products such as the apparatus of Figs. 1 and 2A;

Fig. 3 shows a cross-section through an example liquid steriliser for use with an apparatus for disinfecting products, such as the apparatus of Figs. 1 to 2B;

Fig. 4 shows a cross-section through another example liquid steriliser for use with an apparatus for disinfecting products, such as the apparatus of Figs. 1 to 2B;

Fig. 5 shows a cross-section through an example liquid steriliser for use with an apparatus for disinfecting products, such as the apparatus of Figs. 1 to 2B;

Fig. 6 shows an exploded view of an example mixing device of a liquid steriliser for use with an apparatus for disinfecting products, such as the apparatus of Figs. 1 to 2B; and Fig. 7 shows an exploded view of another example mixing device of a liquid steriliser for use with an apparatus for disinfecting products, such as the apparatus of Figs. 1 to 2B. Specific description

Embodiments of the claims relate to an apparatus for disinfecting products, such as the apparatus 100 shown in Fig. 1 . The products may comprise foodstuffs, such as fruit or vegetables. The apparatus 100 comprises a tank 101 for holding a liquid for receiving microorganisms from the products. The tank 101 comprises a channel 104 for the liquid to flow through and for receiving the products and at least one ultrasonic transducer 109 for providing ultrasonic energy to the products in the channel 104 via the liquid for forcing microorganisms off the products and into the liquid.

The apparatus 100 also comprises a flow provider 150 arranged to provide a flow of liquid along the channel 104 and arranged to recirculate the liquid through a liquid steriliser 155, wherein the liquid steriliser 155 comprises a liquid duct 157 having a UV transmissive wall 161 providing a surface area for irradiation and a source of UV radiation 159 arranged to irradiate liquid flowing in the duct 157 through the UV transmissive wall 161 .

Independent tests have shown that examples of the disclosure are particularly good at disinfecting the surface of foodstuffs such as fruit and vegetables without imparting any taste, change of texture or change of colour. Previous work done with ultrasonic wave energy has shown that there is a disinfection effect on micro-organisms due to the implosion effect of collapsing vacuum bubbles caused by the ultrasonic wave energy and the shear stresses caused by the implosion phenomenon. There is also evidence that in examples where water is used, this shearing effect causes the formation of free radicals stripped from the water.

Recirculating the liquid through the liquid steriliser 155, where the liquid steriliser 155 is arranged to irradiate the liquid with a source of UV radiation 159, may allow a faster and more efficient through-put of liquid through the apparatus 100. In contrast to other liquid sterilisation techniques (for example using chemicals), the use of UV radiation may allow a much faster disinfection of the liquid. This may also mean that the apparatus 100 as a whole uses a smaller total volume of liquid, thus preserving resources and improving the environmental impact of the apparatus 100. In addition, by not using chemicals, the environmental impact of the apparatus 100 is greatly reduced.

Apparatuses described herein may be configured to disinfect foodstuffs, for example meat such as chicken or beef, fruit and vegetables and nuts.

It will be appreciated from the discussion above that the embodiments shown in the Figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims.

An example apparatus is shown in Figs. 1 to 2B. The apparatus 100 comprises an elongate tank 101 . As shown in Fig. 1 , the elongate tank 101 is substantially rectangular in cross-section and comprises two barriers 103 extending substantially the whole length of the tank 101 and separating two regions 105, 107 of liquid in the tank 101 , although in other examples only one or no barrier 103 may be used. The barriers 103 define two sides of a channel 104 providing a flowpath for products through the tank 101 . The channel 104 corresponds to the first region 105, with the second region 107 being either side (or in some examples only to one side of) the channel 104.

In the example shown in Fig. 1 the channel 104 is in the middle of the tank 101 and is deeper than the region 107 to either side of the channel 104, although in other examples the channel 104 may have the same depth as the rest of the tank 101 . For example, the channel 104 may be 377 mm deep whereas the rest of the tank may be 317 mm deep. The length of the channel 104 may be 2865 mm. The width of the channel 104 may be 220 mm, whereas the width of the tank may be 654 mm.

The barrier 103 is coupled to a wall of the tank 101 along its bottom edge. The coupling and the barrier 103 are watertight, for example the barrier 103 may be made from an impermeable material such as glass or metal (such as stainless steel), so that the two regions 105, 107 of liquid are kept separate. In some examples, the liquid held in the second region 107 is different to the liquid held in the first region 105. For example, the liquid held in second region 107 may be deionised water while the liquid held in the first region 105 may be normal tap water.

The tank 101 comprises a plurality of ultrasonic transducers 109 arranged along the channel 104, although it will be understood that in some examples only one ultrasonic transducer 109 is used or a pair of opposing transducers 109 is used. The plurality of ultrasonic transducers 109 may be arranged either side of the channel 104, for example mirroring each other (as shown in Fig. 1 ), or along only one side of the channel 104. The plurality of ultrasonic transducers 109 are evenly spaced along the length of the channel 104. The plurality of ultrasonic transducers 109 may extend substantially the whole height of the tank 101 and/or channel 104. The plurality of ultrasonic transducers 109 may be phase linked and/or synchronised, for example synchronised in frequency.

Each ultrasonic transducer 109 is coupled to a wall of the tank 101 inside the tank 101 . In this way, each ultrasonic transducer 109 defines a boundary of liquid in the tank 101 , and in the example shown in Fig. 1 , each ultrasonic transducer 109 defines a boundary of the liquid in the second region 107. For example, each ultrasonic transducer 109 may form a wall of the tank 101 . As can be seen in Figs. 2A and 2B, the channel 104 comprises an upstream end 175 and a downstream end 177. The apparatus 100 is arranged in a plurality of stages (in the example show, two stages) along the length of the channel 104, from the upstream end 175 to the downstream end 177, wherein each stage comprises a respective liquid steriliser 155.

Arranging the apparatus 100 in stages, with each stage comprising a respective liquid steriliser 155, means that fresh, clean liquid (such as water) can be fed into the channel 104 in the tank at various points along the flowpath of the product through the channel 104 of the tank. It means that the product can be repeatedly washed with fresh, clean liquid as it progresses along the channel 104 of the apparatus 100. This may improve the disinfecting properties of the apparatus 100. Each respective liquid steriliser 155 is coupled to an outer wall of the tank 101 , level with the liquid in the channel 104. A flow provider 150 and a liquid steriliser 155 are coupled in series to the tank 101 via a pipe 151 . The flow provider 150 may comprise a pump, such as an impeller pump. In the example shown, the flow provider 150 is in-line with the pipe 151 coupling the liquid steriliser 155 to the tank 101 . Each liquid steriliser 155 has a liquid inlet 125 at an end of the pipe 151 upstream of a liquid outlet 127 at another end of the pipe 151 . The channel 104 in the tank 101 also has an upper surface 185 and a lower surface 187, the upper surface 185 having at least an exposed portion for receiving the products. Each liquid inlet 125 is arranged near the lower surface 187 of the channel 104, and each liquid outlet 127 is arranged near the upper surface 185. Each liquid inlet 125 also comprises a filter 129 for filtering debris from the liquid in the channel 104.

Each liquid steriliser 155 comprises two elongate tubular liquid ducts 157 running in parallel, each liquid duct 157 having a UV transmissive wall 161 providing a surface area for irradiation, and a source of UV radiation 159 arranged to irradiate liquid flowing in the duct 157 through the UV transmissive wall. The two elongate tubular liquid ducts 157 also run parallel to the direction of the channel 104 in the tank 101 , so that the longitudinal axis of each elongate tubular liquid duct 157 runs in parallel to a longitudinal axis of the tank 101 . The two elongate tubular liquid ducts 157 are coupled to the flow provider 150 via the pipe 151 in parallel, so that half the liquid that flows through the liquid steriliser 155 flows through one elongate tubular liquid duct 157, and half through the other.

Each elongate tubular liquid duct 157 has a hollow core and is arranged to form a tube. In the example shown, each elongate tubular liquid duct 157 has an elongate source of UV radiation 159 extending longitudinally inside each elongate tubular duct 157 through the hollow core, so that the elongate tubular liquid duct 157 is concentric with the source of UV radiation 159. Each elongate tubular liquid duct 157 has a UV transmissive wall 161 on its inside providing a surface area for irradiation, and an outer wall 163 forming the outer surface of the elongate tubular liquid duct 157. Each elongate tubular liquid duct 157 is therefore arranged to form a tubular sleeve 162 around the elongate source of UV radiation 159 for the flow of a liquid. Providing such a tubular sleeve 162 allows a thin film of liquid to flow therethrough, which may improve the sterilising effect of the UV radiation to the liquid.

The source of UV radiation 159 in the example shown is coaxial with each elongate tubular liquid duct 157 and extends along the central axis (corresponding to the longitudinal axis) of each elongate tubular liquid duct 157. The source of UV radiation 159 is therefore surrounded by the tubular sleeve 162 providing a flow passage for the flow of liquid to pass therethrough. The source of UV radiation 159 comprises an elongate lamp disposed inside the UV transmissive wall 161 which is preferably formed of quartz or another material which is a good transmitter of UV radiation. In some example, the UV transmissive wall 161 may be configured to substantially transmit germicidal wavelengths of UV radiation (220 nm to 280 nm).

The elongate tubular liquid ducts 157 of the liquid steriliser 155 each have a cross- sectional area for holding the liquid that is smaller than the cross-sectional area of the channel 104 of the tank 101 , and in the example shown in Figs. 1 to 2B, the total cross- sectional area for holding the liquid in both of the ducts 157 of a liquid steriliser 155 is smaller than the cross-sectional area of the channel 104. Each elongate tubular liquid duct 157 may have a cross-sectional area of at least 1 x10^"4 m² and less than 1 x10^"3 m² for liquid to flow therethrough. Having a cross-sectional area that is smaller than the cross-sectional area of the channel 104 may allow the UV radiation to more effectively penetrate through the liquid to help ensure that all of the liquid is exposed to UV radiation and that any microorganisms in the liquid are killed by the UV radiation.

Each elongate tubular liquid duct 157 has an interior diameter and an exterior diameter, where the interior diameter is formed by the interior surface of the UV transmissive wall 161 , and the exterior diameter is formed by the exterior surface of the outer wall 163, where the interior surface is a surface facing in towards the longitudinal axis of the elongate tubular liquid duct 157 and the exterior surface is a surface facing away from the longitudinal axis of the elongate tubular liquid duct 157. Each elongate tubular liquid duct 157 therefore has a radial extent defined by the distance between the exterior surface of the UV transmissive wall 161 and the interior surface of the outer wall 163. In some examples, the exterior surface of the inner, UV transmissive wall 161 has a diameter of at least 38.5 mm, for example at least 39 mm, at least 39.5 mm. In some examples, the interior surface of the outer wall 163 has a diameter of less than 54 mm, for example less than 52 mm, less than 51 mm, less than 50.5 mm. The distance between the exterior surface of the inner, UV transmissive wall 161 and the interor surface of the outer wall 163 defines the radial extent of the tubular sleeve 162 providing a flow passage for the flow of liquid to pass therethrough.

The ultrasonic transducers 109 are operable to provide ultrasonic energy to products in the channel 104 through the liquid in the second region 107, through the barrier 103, and through the liquid in the first region 105. The channel 104 is arranged so that products can be carried into, through and out of the liquid in the channel 104. The position of the ultrasonic transducers 109 may be selected to provide ultrasonic energy to the centre of the products when the products are submerged in the liquid of the channel 104. The degree of ultrasonic energy provided to the products by the ultrasonic transducers 109 is selected to dislodge or force microorganisms from the surface of the products into the liquid.

The flow provider 150 is configured to recirculate liquid flowing through the channel 104 of the tank 101 . The liquid steriliser 155 is configured to treat (for example disinfect) the liquid being circulated through the apparatus 100. The flow provider 150 is arranged to flow liquid along the channel 104 in a direction from the upstream end 175 to the downstream end 177. The flow provider 150 is configured to draw the liquid from a region near the lower surface187 of the channel 104 and recirculate it to a region near the upper surface 185 of the channel 104 upstream of the direction of liquid flow through the channel 104.

The flow provider 150 is also arranged to provide a flow of liquid through the elongate tubular liquid ducts 157 of the liquid steriliser 155 in a direction opposite to that through the channel 104 in the tank 101 . For example, the flow provider 150 may be configured to provide a pressure difference between the liquid inlet 125 and liquid outlet 127 of less than 0.4 bar and more than 0.005 bar. The flow provider 150, the velocity of the liquid in the liquid steriliser 155, and the selection and arrangement of the elongate tubular liquid ducts 157 may be configured to adjust the dwell time of liquid in the liquid steriliser 155 and thereby the treatment time of the liquid in the liquid steriliser 155. The flow provider 150 may be arranged to provide a flow of liquid in the liquid steriliser 155 at a velocity of between 0.6 and 1 .8 metres per second. Because the elongate tubular liquid ducts 157 of the liquid steriliser 155 each have a cross-sectional area for holding the liquid that is smaller than the cross-sectional area of the channel 104 of the tank 101 , the flow provider 150 may be arranged to provide a flow of liquid through the elongate tubular liquid duct 157 that is at a velocity greater than that through the channel 104 in the tank 101 . The volume flow rate through the channel 104, and the liquid steriliser 155, however, may be the same.

The flow provider 150 may also be configured to adjust the amount of UV energy delivered to the liquid. For example, the flow provider 150 may be configured to control the velocity of liquid flow through the liquid steriliser 155 based on the length of the elongate tubular liquid ducts 157 and the UV power density so that at least 300 Joules of UV energy per square metre of the surface area for irradiation is provided to the liquid during the dwell time of the liquid in the ducts 157. 300 Joules of UV energy per square metre of the surface area for has been found to be particularly effective at killing microorganisms.

The flow provider 150 may be adjusted to control the flow rate of liquid through the channel 104 based on the products being disinfected. For example, if the product is a soft fruit, the flow rate may be selected to be much slower, for example less than or equal to 0.1 m/s, less than or equal to 0.2 m/s, less than or equal to 0.5 m/s, whereas for harder vegetables the flow rate may be selected to be faster, for example at least 0.5 m/s, at least 1 m/s, at least 2 m/s, at least 3 m/s, at least 4 m/s, at least 5 m/s. Selecting the flow rate based on the products being disinfected may help maintain the integrity of the product and prevent damage to the products occurring through the apparatus 100.

In use, products are carried into, through and out of the channel 104 of the tank 101 . The ultrasonic transducers 109 provide energy to the products in the channel 104 via the second 107 and first 105 regions (and through the barrier 103) which act to dislodge and scrub the product to force microorganisms off the product and into the liquid in the channel 104. The liquid in the channel 104 is driven along by the flow provider 150 and, for each stage, is recirculated from the tank 101 , through the pipe 451 , through the liquid steriliser 155, and back to the channel 104 upstream of where the liquid was withdrawn. As the products pass through the channel 104, debris is removed from their surface by the ultrasonic scrubbing action of the ultrasonic transducers 109. The debris is drawn by a current downstream, and settle to the bottom of the channel 104 due to gravity. Drawing the liquid from the lower surface 187 of the channel 104 may therefore help to catch and filter (via filter 129) this debris from the liquid and may help to clean and sterilise the liquid.

The size and dimensions of the elongate tubular liquid ducts 157, the flow rate through the liquid steriliser 155 and the strength of UV radiation from the source of UV energy 159 are selected to disinfect the liquid and to kill any microorganisms forced off the product into the liquid. For example the dwell time may be selected to be at least 5 seconds, at least 10 seconds, at least 30 seconds.

As the products progress through the stages of the apparatus 100 along the channel 104, the products are exposed to fresh, clean liquid. In this way, the products may undergo a number of stages of cleaning. For example, in the first stage (the upstream stage) the products may undergo a first-pass cleaning, that removes the worst of the microorganisms and debris that may be accumulated to and attached onto the product. As the products pass along the channel 104 and reach a new stage, the products are exposed to fresh, clean liquid and may undergo a second-pass cleaning, which removes the rest of the microorganisms from the product. It will of course be understood that the apparatus need not be limited to only two stages and two-passes of cleaning, but that multiple stages may be used. Such multi-pass cleaning may result in improved disinfection of products.

Accordingly, other embodiments of the claims relate to a method for disinfecting products, the method comprising flowing a liquid for receiving microorganisms from the products along a channel in a tank, carrying products into, along, and out of the channel, delivering ultrasonic energy via the liquid to the products, for forcing microorganisms off the products and into the liquid, and sterilising and recirculating the liquid in the channel with a liquid steriliser, with the liquid steriliser comprising a liquid duct having a UV transmissive wall providing a surface area for irradiation and a source of UV radiation arranged to irradiate liquid flowing in the duct through the UV transmissive wall.

With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein. It will be appreciated however that the functionality need not be divided in this way, and should not be taken to imply any particular structure of hardware other than that described and claimed below. The function of one or more of the elements shown in the drawings may be further subdivided, and/or distributed throughout apparatus of the disclosure. For example, the function of the flow provider 150 may be distributed throughout the apparatus 100, for example at multiple stages along pipe 151 or in liquid steriliser 150. The source of UV energy 159 may also be provided in a number of different way to irradiate liquid flowing through the liquid steriliser 155. In some embodiments the function of one or more elements shown in the drawings may be integrated into a single functional unit. For example, the function of the flow provider 150, the liquid steriliser 155 and the filter 129 may be integrated into a single functional unit.

In the context of the above examples it will be understood that the feature of the barriers 103 in the tank 101 may be optional, and that some examples will not have a barrier 103 separating two regions 105, 107 of the tank 101 . In some examples the barrier 103 comprises a material having an acoustic impedance greater than that of water. For example, the barrier may comprise a material having an acoustic impedance of at least 12 x 10⁶ kg/m²sec, for example at least 35 x 10⁶ kg/m²sec. The barrier may be 3-6 mm thick, for example the barrier may be 18 to 22 gauge stainless steel.

In some examples, the barrier 103 (if present) may comprise a respective window for each ultrasonic transducer 109 for transmitting ultrasonic pressure waves from the second region 107 to the first region 105. The size of each window may be selected based on the size of the corresponding ultrasonic transducer 109. Each respective window may be acoustically insulated from the other windows, for example by a strip of insulating material such as rubber. The distance between a window in the barrier 103 and the corresponding ultrasonic transducer 109 may be greater than the wavelength of ultrasonic pressure waves produced by the ultrasonic transducer. For example, the distance between the at least one window and the ultrasonic transducer 109 may be greater than 35 mm, for example greater than 50 mm, preferably 63 mm. If the barrier 103 comprises a window, the window is configured to transmit ultrasonic energy from liquid on one side of the barrier 103 to liquid on the other side of the barrier 103.

In some examples, the tank 100 may also comprise a run-off weir along the top edge of the channel 104. The run-off weir may be configured to collect debris/oils/fats forced off the product 19 by the ultrasonic energy.

In some examples, the apparatus 100 also comprises a conveyor for carrying the products through the liquid in the channel 104. The conveyor may have baskets or hooks for carrying and dipping the products in the liquid in the channel 104. In the example show in Figs. 1 -2B, the channel 104 is open, although in other examples the tank 101 may comprise a lid covering at least a portion, for example a central portion, of the channel 104. The lid may be arranged to have openings for a conveyor to carry products into, through and out of the channel 104.

In examples where a conveyor is present, the flow provider 150 may be arranged to provide a flow of liquid through the channel 104 in the first region 105 at a velocity selected based on that of the conveyor carrying the products through the liquid. For example, the flow provider 150 may be configured to adjust the flow rate of liquid through the channel 104 to match the velocity of the products being carried by the conveyor. Matching the velocity of the liquid through the channel 104 to that of the products may help to reduce turbulence (and thereby the creation of undesirable bubbles in the liquid) and hence increase the efficacy of the transmission of ultrasonic energy to the product 19 from the ultrasonic transducers 109. In some examples, the flow provider 150 may have an output with a cross-sectional area that is selected or adjusted to provide a substantially laminar flow through the channel 104 at the velocity selected based on that of the conveyor.

The speed of the conveyor and/or the length of the channel 104 (and hence the dwell time of the product in the liquid of the channel 104) may be adjusted based on the ultrasonic energy applied to the products and/or the temperature of the liquid in the channel 104, but may be at least 5 seconds, for example at least 6.5 seconds. The conveyor may carry the products at a speed of, for example, 0.5 m/s, resulting in, for example, 12,000 products being processed per hour.

The flow of products through the channel 104 may draw liquid along with the products in the channel 104. This flow of products can create turbulence in the liquid. In some examples, the flow provider 150 is arranged to provide a flow of liquid through the channel 104 at a velocity selected based on that of the velocity of the products being carried through the channel 104. For example, the flow provider 150 may be configured to adjust the flow rate of liquid through the channel 104 to match the velocity of the products being carried through the channel 104, for example to match the velocity of the conveyor.

In some examples, the liquid outlet 127 of the pipe 151 coupled to the flow provider 150 has a cross-sectional area configured to provide a laminar flow through the channel 104 at the velocity selected based on that of the products being carried through the channel 104, for example the cross-sectional area of the outlet 127 may be sufficiently large to provide a laminar flow through the channel 104. The tank 101 may hold the liquid in the second region 107 (adjacent to the ultrasonic transducers 109) at a relatively stationary velocity. Because the liquid adjacent to the ultrasonic transducers 109 is relatively stationary, this may increase the efficacy of the transmission of ultrasonic energy to the products. In some examples, each liquid steriliser 155 comprises two elongate tubular liquid ducts 157 arranged in parallel, each liquid duct 157 having a UV transmissive wall 161 providing a surface area for irradiation and sharing a source of UV radiation 159 arranged to irradiate liquid flowing in both ducts through each UV transmissive wall 161 (instead of having their own respective sources of UV radiation 159). In such examples, the UV transmissive wall 161 may be on an outer surface of the elongate tubular liquid ducts 157, or on a portion of the outer surface of the elongate tubular liquid ducts 157 facing towards the source of UV radiation 159.

In some examples, the elongate tubular liquid duct 157 provides a linear path for substantially laminar flow of the liquid. This laminar flow of liquid is pumped along the duct 157 with a linear speed set by the flow provider 150 and based on the volume flow rate and the cross section of the duct 157. The substantially laminar flow is directed along a path which is substantially parallel with the axis of the tubular duct 157. Providing a laminar flow of the liquid in this way may provide a consistent thin film of liquid that is exposed to the UV radiation, which may improve the sterilising effect of the liquid steriliser 155.

In some examples, such as shown in Figs. 3 and 4, mixing devices 200 such as baffles are distributed at evenly spaced intervals along the duct 157 and are arranged substantially perpendicular to the direction of liquid flow. The liquid flow (along the duct 157 or elsewhere) need not be laminar and in some examples may be partially or fully turbulent. In some examples the liquid will have had many complete reversals of flow through the mixing devices 200 creating a thorough mixing of the liquid. For example, each liquid steriliser 155 may comprise a plurality of mixing devices 200 each sealingly fitted between adjacent longitudinal portions of the duct 157. The mixing devices 200 may be placed at intervals along the length of the liquid steriliser 155 forcing the recirculated liquid to change direction and ensuring constant and thorough mixing of the liquid as it flows through the liquid steriliser 155. For example, the mixing devices 200 may be arranged to provide a labyrinth-like path for the liquid to flow through.

In some examples, each liquid steriliser 155 may form different arrangements and need not run parallel to the channel 104, and may comprise a plurality of sources of UV radiation 159 and a plurality of elongate tubular liquid ducts 157. Similarly, the elongate tubular liquid ducts 157 need not be straight. For example the liquid sterilisers 155 and the elongate tubular liquid ducts 157 may form a serpentine path for the liquid to flow along, as shown in Fig. 5. In other examples, the elongate tubular liquid ducts 157 may form a spiral path, for example where the spiral is in the form of a corkscrew shape and wraps around a source of UV radiation 159.

In some examples a plurality of liquid sterilisers 155 may be coupled together in series and/or in parallel, for example to improve the sterilising efficacy of the apparatus 100. For example, a plurality of liquid sterilisers 155 may be coupled in series as shown in Fig. 5, to form a serpentine path. A plurality of liquid sterilisers 155 couples in this way may have portions where the liquid is directed to flow in a direction opposite to that of liquid flowing in the channel 104, and portions where the liquid is directed to flow in the same direction as the liquid flowing in the channel 104, for example as well as portions where the liquid is directed to flow in a direction transverse to that of liquid flowing in the channel 104. The respective liquid sterilisers 155 may be coupled together via an inlet manifold 250 and an outlet manifold 260. The liquid may be pumped around the manifolds 250, 260 and the liquid sterilisers 155 via one or more pumps 270, for example comprising an impeller 275 as shown in Fig. 5. In some examples, the pump(s) 270 may act in addition to the flow provider 150.

In some examples, for example as shown in Figs. 6 and 7, the mixing devices 200 may be arranged to divert all of the liquid flowing along the duct 157 through liquid mixing formations 220 in the mixing device 200 and to return the mixed liquid to the duct 157. For example, the liquid mixing formations 220 may be formed in opposing faces of plates 210 which are clamped together against a central plate 210 formed with apertures 215 that communicate between the formations 220. The central plate 210 and/or the opposing plates 210 may be manufactured from a material which transmits UV radiation 5 so that the flow path is sterilised by the radiation from the source of UV radiation 159. The mixing devices 200 may be made of a food grade standard material, such as stainless steel. The internal parts of the mixing devices 200 (such as the formations 220) may be made from PTFE, Teflon FEP.

10 In some examples, the flow path through the mixing devices 200, for example through the apertures 215 and/or formations 220, comprises one or more turns of 90 degrees and preferably the flow passage turns the liquid through at least 180 degrees between adjacent longitudinal portions of the duct 157. Good mixing of the liquid can be achieved by continually changing the direction through, for example, 90 degree bends or through

15 180 degree bends. The continual sudden velocity changes imparted to the liquid by this technique may help to ensure all constituents of the liquid are mixed. Preferably at least a portion of the flow path through a mixing device200 is arranged to be irradiated by UV radiation emitted by the source of UV radiation 159.

20 It should be noted that known static mixers do not create flow reversal i.e. 180 degree bend; instead they blend a liquid by manipulating it always in a forward direction and hence need a sizable longitudinal component to effect the mixing. The mixing devices 200 described herein may mix the liquid over a short distance by flow reversal and hence a plurality of mixing devices 200 can be employed over a short distance.

25

In some examples each liquid steriliser 155 comprises a flow control means arranged to control the velocity of liquid flow along the liquid duct based on the length of the liquid duct so that at least 300 Joules of UV energy per square metre of the surface area for irradiation is provided to the liquid during the dwell time of the liquid in the duct. The flow 30 control means may be configured to control the flow of liquid along the liquid duct such that the average velocity of the liquid flow between mixing stages of the liquid steriliser is between 0.5 and 4 metres per second, for example between 0.6 and 1 .6 meters per second. The flow control means may be provided, for example, by the mixing devices 200 mentioned above, and/or baffles arranged in the tubular sleeve 162 providing a flow passage for the flow of liquid to pass therethrough along the length of the elongate tubular liquid ducts 157. In some examples the UV transmissive wall 161 may be coated with a material such as Teflon® FEP that is arranged to maintain the integrity of the tube should it break, thereby preventing contamination of the liquid with potential harmful pieces of the tube material. The coating or covering material may comprise fluorinated ethylene propylene. The liquid steriliser 155 may have an additional feature in that after CIP (clean in place - the drinks industry standard cleaning process) it self-sterilises. The liquid steriliser 155 may self-sterilise, if, at the end of the cleaning cycle it is filled with water and the source of UV radiation 159 is switched on for a period of time, and there is enough radiation to reflect through the liquid steriliser 155 to disinfect it.

In some examples the liquid steriliser 155 may be adapted to operate at room temperature. In some examples the liquid steriliser 155 is adapted to withstand the industry cleaning pressures - for example, all parts are able to withstand pressures of at least 10 bar.

Operation of the ultrasonic transducers 109, the flow provider 150, the liquid steriliser 155, and where present the conveyor, may be controlled by a controller such as a programmable logic circuit, PLC. The PLC may be configured to control the temperature of the liquid (for example by controlling operation of a heater or a chiller), the flow rate and/or velocity of the liquid through the apparatus 100 and the velocity of the product through the apparatus 100. In some examples, the PLC may be configured to receive signals, for example from a temperature sensor for detecting the temperature of the liquid in the channel 104, in the liquid steriliser 155 and/or in pipe 151 , or a flow meter for detecting the velocity of the liquid in the channel 104, in the liquid steriliser 155 and/or in pipe 151 , and adjusting the outputs of a heater/chiller, or the flow provider 150, as appropriate.

The above embodiments are to be understood as illustrative examples. Further embodiments are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

In some examples, one or more memory elements can store data and/or program instructions used to implement the operations described herein. Embodiments of the disclosure provide tangible, non-transitory storage media comprising program instructions operable to program a processor to perform any one or more of the methods described and/or claimed herein and/or to provide data processing apparatus as described and/or claimed herein. The activities and apparatus outlined herein may be implemented with fixed logic such as assemblies of logic gates or programmable logic such as software and/or computer program instructions executed by a processor. Other kinds of programmable logic include programmable processors, programmable digital logic (e.g., a field programmable gate array (FPGA), an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM)), an application specific integrated circuit, ASIC, or any other kind of digital logic, software, code, electronic instructions, flash memory, optical disks, CD-ROMs, DVD ROMs, magnetic or optical cards, other types of machine-readable mediums suitable for storing electronic instructions, or any suitable combination thereof.

In the context of the present disclosure other examples and variations of the apparatus and methods described herein will be apparent to a person of skill in the art.

Claims

CLAIMS:

1 . An apparatus for disinfecting products, the apparatus comprising:

a tank for holding a liquid for receiving microorganisms from the products;

wherein the tank comprises a channel for the liquid to flow through and for receiving the products;

at least one ultrasonic transducer for providing ultrasonic energy to the products in the channel via the liquid for forcing microorganisms off the products and into the liquid; and

a flow provider arranged to provide a flow of liquid along the channel and arranged to recirculate the liquid through a liquid steriliser, wherein the liquid steriliser comprises a liquid duct having a UV transmissive wall providing a surface area for irradiation and a source of UV radiation arranged to irradiate liquid flowing in the duct through the UV transmissive wall.

2. The apparatus of claim 1 wherein the flow provider is arranged to provide a flow of liquid through the liquid duct of the liquid steriliser at a velocity greater than that through the channel in the tank.

3. The apparatus of claim 1 or 2 wherein the flow provider is arranged to provide a flow of liquid through the liquid duct of the liquid steriliser in a direction opposite to that through the channel in the tank.

4. The apparatus of any of the previous claims wherein the channel has an upper surface and a lower surface, the upper surface having at least an exposed portion for receiving the products; and

wherein the flow provider is configured to draw the liquid from a region near the lower surface of the channel and recirculate it to a region near the upper surface of the channel upstream of the direction of liquid flow through the channel.

5. The apparatus of any of the previous claims wherein the liquid duct of the liquid steriliser has a cross-sectional area for holding the liquid that is smaller than the cross- sectional area of the channel of the tank.

6. The apparatus of any of the previous claims wherein each liquid steriliser comprises a plurality of mixing stages configured to provide turbulent flow in the liquid.

7. The apparatus of claim 8 wherein the plurality of mixing stages are spaced apart along the length of the liquid duct, and wherein segments of the duct between the mixing stages are arranged to provide flow adjacent the UV transmissive wall.

8. The apparatus of claim 6 or 7 in which the mixing stages comprise UV transmissive material and the mixing stages are arranged so that UV light from the UV source can reach the interior surfaces of the mixing stages when the mixing stage is filled with a UV transmissive liquid.

9. The apparatus of any of the previous claims wherein the liquid duct comprises a cylindrical outer wall and a cylindrical inner wall comprising the UV transmissive wall.

10. The apparatus of any of the previous claims wherein the liquid steriliser comprises a flow control means arranged to control the velocity of liquid flow along the liquid duct based on the length of the liquid duct so that at least 300 Joules of UV energy per square metre of the surface area for irradiation is provided to the liquid during the dwell time of the liquid in the duct.

1 1 . The apparatus of claim 10 as dependent on claim 6 wherein the flow control means is configured to control the flow of liquid along the liquid duct such that the average velocity of the liquid flow between mixing stages of the liquid steriliser is between 0.5 and 4 metres per second, preferably between 0.6 and 1 .6 meters per second.

12. The apparatus of any of the previous claims wherein the liquid steriliser comprises two liquid ducts arranged in parallel, each liquid duct having a UV transmissive wall providing a surface area for irradiation and having a respective source of UV radiation arranged to irradiate liquid flowing in each duct through each UV transmissive wall.

13. The apparatus of any of claims 1 to 1 1 wherein the liquid steriliser comprises two liquid ducts arranged in parallel, each liquid duct having a UV transmissive wall providing a surface area for irradiation and sharing a source of UV radiation arranged to irradiate liquid flowing in both ducts through each UV transmissive wall.

14. The apparatus of any of the previous claims wherein the apparatus is arranged in a plurality of stages along the length of the channel, wherein each stage comprises a respective liquid steriliser and wherein the apparatus is arranged to recirculate the liquid through a respective liquid steriliser for a corresponding stage of the channel.

15. The apparatus of any of the previous claims wherein the tank comprises a barrier separating the liquid in the channel from the liquid in a second region; and

wherein the second region holds liquid adjacent to the ultrasonic transducer for providing ultrasonic energy to the products via the liquid in the second region, through the barrier and via the liquid in the channel for forcing microorganisms off the products and into the liquid in the channel.

16. The apparatus of claim 15 wherein the barrier comprises a material having an acoustic impedance greater than that of water.

17. The apparatus of any of the previous claims comprising a conveyor for carrying the products through the liquid in the channel; and

wherein the flow provider is arranged to provide a flow of liquid through the channel at a velocity selected based on that of the conveyor carrying the products through the channel.

18. The apparatus of claim 17 wherein the flow provider is configured to adjust the flow rate of liquid through the channel to match the velocity of the products being carried by the conveyor.

19. The apparatus of claim 17 or 18 wherein the flow provider has an output with a cross-sectional area configured to provide a laminar flow through the channel at the velocity selected based on that of the conveyor.

20. The apparatus of any of the previous claims comprising a plurality of ultrasonic transducers arranged along the length of the channel.

5

21 . The apparatus of claim 20 wherein the plurality of ultrasonic transducers are phase linked and/or synchronised.

22. A method for disinfecting products, the method comprising:

10 flowing a liquid for receiving microorganisms from the products along a channel in a tank;

carrying products into, along, and out of the channel;

delivering ultrasonic energy via the liquid to the products, for forcing microorganisms off the products and into the liquid;

15 sterilising and recirculating the liquid in the channel with a liquid steriliser, the liquid steriliser comprising a liquid duct having a UV transmissive wall providing a surface area for irradiation and a source of UV radiation arranged to irradiate liquid flowing in the duct through the UV transmissive wall.

20 23. The method of claim 22 comprising flowing the liquid through the liquid duct of the liquid steriliser at a velocity greater than that through the channel in the tank

24. The method of claim 22 or 23 comprising flowing the liquid through the liquid duct of the liquid steriliser in a direction opposite to that through the channel in the tank.

25

25. The method of any of claims 22 to 24 wherein the channel has an upper surface and a lower surface, the upper surface having at least an exposed portion for receiving the products; and wherein recirculating the liquid in the channel comprises drawing the liquid from a region near the lower surface of the channel and recirculating it to a region

30 near upper surface of the channel upstream of the direction of liquid flow through the channel.

26. The method of any of claims 22 to 25 wherein sterilising the liquid in the channel further comprises passing the liquid through a series of mixing stages configured to provide turbulent flow in the liquid.

27. The method of claim 26 comprising flowing the liquid through segments of the duct between the mixing stages adjacent to the UV transmissive wall.

28. The method of claim 26 or 27 in which the mixing stages comprise UV transmissive material and the mixing stages are arranged so that UV light from the UV source can reach the interior surfaces of the mixing stages when the mixing stage is filled with a UV transmissive liquid.

29. The method of any of claims 22 to 28 comprising flowing the liquid through the liquid duct between a cylindrical outer wall and a cylindrical inner wall comprising the UV transmissive wall.

30. The method of any of claims 22 to 29 comprising controlling the velocity of liquid flow along the liquid duct based on the length of the liquid duct so that at least 300 Joules of UV energy per square metre of the surface area for irradiation is provided to the liquid during the dwell time of the liquid in the duct.

31 . The method of claim 30 as dependent on claim 26 comprising controlling the flow of liquid along the liquid duct such that the average velocity of the liquid flow between mixing stages is between 0.5 and 4 metres per second, preferably between 0.6 and 1 .6 meters per second.

32. The method of any of claims 22 to 31 wherein the liquid steriliser comprises two liquid ducts arranged in parallel, each liquid duct having a UV transmissive wall providing a surface area for irradiation and having a respective source of UV radiation arranged to irradiate liquid flowing in each duct through each UV transmissive wall, the method comprising flowing the liquid through the two liquid ducts in parallel.

33. The method of any of claims 22 to 31 wherein the liquid steriliser comprises two liquid ducts arranged in parallel, each liquid duct having a UV transmissive wall providing a surface area for irradiation and sharing a source of UV radiation arranged to irradiate liquid flowing in both ducts through each UV transmissive wall, the method comprising flowing the liquid through the two liquid ducts in parallel.

5 34. The method of any of claims 22 to 33 comprising recirculating the liquid through a plurality of liquid sterilisers over the length of the channel.

35. The method of any of claims 22 to 34 comprising:

holding a liquid in a second region separated from the channel by a barrier;

10 delivering ultrasonic energy via the liquid in the second region separated from the channel, and through the barrier to the products in the channel, to force microorganisms off the products and into the liquid in the channel.

36. The method of claim 35 wherein the barrier comprises a material having an 15 acoustic impedance greater than that of water.

37. The method of any of claims 22 to 36 comprising carrying the products through the liquid in the channel with a conveyor; and

providing a flow of liquid through the channel at a velocity selected based on that 20 of the conveyor carrying the products through the channel.

38. The method of claim 37 comprising adjusting the flow rate of liquid through the channel to match the velocity of the product being carried by the conveyor.

25 39. The method of claim 37 or 38 comprising adjusting the flow rate of liquid through the channel to provide a laminar flow through the channel.

40. The method of any of claims 37 to 39 comprising flowing the liquid through the channel at a velocity based on that of the product being carried through the channel; and

30 holding the liquid in the second region at a relatively stationary velocity.

41 . The method of any of claims 37 to 40 wherein the barrier comprises a material having an acoustic impedance greater than that of water.

42. The method of any of claims 22 to 41 comprising a plurality of ultrasonic transducers arranged along the flowpath.

5 43. The method of claim 42 wherein the plurality of ultrasonic transducers are phase linked and/or synchronised.

44. A method substantially as described herein and as illustrated in the drawings. 10 45. An apparatus substantially as described herein and as illustrated in the drawings.