GB2453820A

GB2453820A - Washing food product

Info

Publication number: GB2453820A
Application number: GB0814240A
Authority: GB
Inventors: David Barney; Susan Feuerhelm
Original assignee: BAKKAVOR Ltd
Current assignee: BAKKAVOR Ltd
Priority date: 2007-08-03
Filing date: 2008-08-04
Publication date: 2009-04-22
Anticipated expiration: 2028-08-04
Also published as: GB0814240D0; GB2453820B; GB0715174D0

Abstract

An apparatus for washing food products such as salad leaves, herbs, chopped and whole vegetables e.g. carrots, new potatoes, cucumber, sliced onion, trimmed lettuce heads and fruits e.g. berries comprises a vessel 110 for receiving a volume of water in which product to be washed is immersed, an inclined member such as conveyor 120 having a belt having a porous structure extending into the water and an arrangement 130 for directing a stream of bubbles towards the underside of the inclined member in order to impact upon the product as it passes beneath the inclined surface. A deflector 136 may be present to prevent the passage of bubbles through the immersed portion of the conveyor.

Description

1 2453820 Methods and apparatus for washing food product The present invention relates to methods and apparatus for washing product, in particular, but not exclusively, to methods and apparatus for washing delicate food product such as salad leaf.

Pre-packaged salads, sliced vegetables and fruits are commonplace in supermarkets.

Typically, the food product is washed prior to packaging. In the case of lettuce leaf and other delicate food products, it is known to immerse the unwashed product in a bath of water in order to displace unwanted soiling and microbial material from the surface of the product.

There are numerous problems associated with this type of washing process. For example, heavily soiled product may need to be washed several times, in order to achieve a safe and consistent level of cleanliness. The product and or water may be agitated, as this is known to speed up the removal of microbial material. However, conventional agitation methods may damage the visual quality of the washed product. Moreover, turbulent washing conditions may cause one or more items of the food product to be immersed for a longer period of time than desired, leading to deterioration in the integrity of the product.

The quality of the water used to wash the product decreases after a period of use. it is known to use biocides to clean the water. However, such techniques are not favoured by today's consumer. As such, the conventional solution is to wash the product in a continuous flow of clean water or a regularly replenished volume of clean water. However, an alternative solution is required to meet growing environmental pressures to reduce water consumption.

It is an object of the invention to provide a method and/or apparatus which addresses one or more of the problems referred to above.

According to a first aspect of the invention, there is provided an apparatus for washing product, the apparatus comprising: a vessel for receiving a volume of liquid (preferably water) in which product to be washed is to be immersed; an inclined surface extending in the vessel and beneath which product to be washed is intended to pass; and an arrangement for directing a stream of bubbles up towards an underside portion of the inclined surface, in order to impact upon the product as it passes beneath the inclined surface.

In use, a volume of liquid is present in the vessel, such that at least lower portion of the inclined surface is immersed in the liquid, and a stream of bubbles is directed up through the liquid to the underside of the immersed portion of the inclined surface. Product to be washed is introduced to the liquid and the inclined surface acts as a guide to submerge the product and direct the product through the stream of bubbles.

Using bubbles to wash product as it passes beneath an inclined surface is believed to improve the efficiency of the washing process. In particular, it is believed that the inclined surface enables the rising bubbles to impact and shear across the surface of the immersed product in a more effective manner than if directed against product moving beneath an horizontal surface, such as the horizontal surface used in US5,640,925. This effect is t believed to be particularly effective if the volume of liquid in the vessel is effectively static, i.e. with little or no through flow of liquid beneath the inclined surface.

An additional benefit has been observed, namely that the upward action of the bubbles causes a slight downward current which is effective in assisting the movement of surface material such as soil and other unwanted microbial matter down and away from the washed product. This is particularly the case if the volume of liquid in the vessel is effectively static.

In a preferred embodiments, the angle of inclination of the inclined surface is in the range of 15 to 45 degrees from horizontal. However, more preferably the angle of inclination is in the region of 15 to 30 degrees (more preferably in the region of 20 to 25 degrees) from horizontal, as this is believed to provide a suitable shearing effect whilst avoiding an unduly steep angle of immersion for the product as it is guided down by the inclined surface.

In use, the apparatus defines a treatment zone for product to be washed, namely the region directly beneath the inclined surface towards which the bubbles are directed, It is particularly preferred if the apparatus is configured for preventing or reducing the passage of bubbles from the treatment zone to a region directly above said treatment zone. For example, the inclined surface may be impermeable to the bubbles or a suitably impermeable deflector may be arranged immediately behind the inclined surface, for preventing or reducing the upward passage of bubbles beyond the inclined surface.

In practice, this ensures that a high percentage of the bubbles is instead guided upstream along the immersed section of the inclined surface and over any product in contact with or adjacent said surface, thereby maximising the effect of the bubbles on the product to be washed.

The inclined surface may take the form of a plate or sheet arranged at an angle of inclination within the vessel. However, in more preferred embodiments, the apparatus includes a conveyor having a moving surface (e.g. a product carrying belt) which is arranged at an angle of inclination within the vessel, wherein the moving surface on the underside of the conveyor provides said inclined surface. The moving surface may be advantageously operated for assisting the immersion of product within the vessel, e.g. with the moving surface operable to move downwards with respect to the underside of the conveyor.

In addition, the conveyor may be advantageously arranged for carrying washed product up and out of the liquid within the vessel, e.g. after passage through the stream of bubbles.

Hence, in preferred embodiments, a lower portion of the conveyor is intended to be immersed in liquid within the vessel, in particular a portion of the conveyor which overlies the stream of bubbles in use, and an upper portion of the conveyor is intended to extend from the liquid.

In a preferred embodiment, the moving surface of the conveyor has a porous or permeable structure, such that excess liquid from washed product carried on the upper side of the conveyor is free to drain through the moving surface.

However, the conveyor is preferably arranged and/or configured to prevent or reduce the direct upward passage of the bubbles. This may also prevent or reduce the upward passage *I of any dislodged soil or microbial particles through the conveyor towards washed product above the conveyor. For example, one or more deflectors may be arranged directly behind an immersed portion of the moving surface at the underside of the conveyor, preferably at least behind the portion of moving surface which overlies the stream of bubbles in use. As discussed above, this also has the benefit of ensuring that a high percentage of the bubbles is instead guided upwards along the immersed section of the inclined surface and over any product in contact with or adjacent said surface.

The vessel is preferably in the form of a bath or tank configured for receiving a generally static body of liquid, i.e. without any significant through flow of liquid. However, the apparatus preferably includes a mechanical paddle, a wave generator or an hydraulic or pneumatic nozzle configured for inducing a directional flow of product towards the underside of the inclined surface. If the inclined surface forms part of a conveyor within the vessel, the apparatus may include the same or similar flow inducing means for directing product towards the upper side of the conveyor after the product has passed beneath the conveyor.

The vessel is preferably configured for reducing the volume of water required for the washing process. In particular, the vessel may have a shallow feed region and be deepest in the region of the immersed portion of the conveyor.

The apparatus may include a source of gas for generating the bubbles to be directed towards the underside of the inclined surface.

I I

According to another aspect of the invention, there is provided a method of washing product using the apparatus of the first aspect of the invention.

According to another aspect of the invention, there is provided a method of washing product including the steps of using a conveyor to draw product to be washed down into a body of liquid, preferably water, and applying a controlled upward stream of bubbles to product passing beneath the conveyor or moving under the influence of the conveyor.

As described above, the use of rising bubbles to wash product as it passes beneath an inclined surface is believed to improve the efficiency of the washing process, particularly if the body of liquid is effectively static. Hence, the method is preferably carried out in an essentially static body, i.e. in a bath or tank having little or no through flow of liquid.

The conveyor has a moving surface which is preferably arranged at an of inclination, i.e. at an angle to the horizontal, and which extends into a bath for washing the product, such that at least a lower portion of the conveyor is immersed in liquid, in particular the portion of the conveyor which overlies the stream of bubbles in use.

According to the method, the product is preferably guided down into the liquid by the underside of the conveyor. Having passed beneath the conveyor, the washed product may then be transferred out of the body of liquid on the upper side of the conveyor.

Deflector means are preferably employed to prevent or reduce the passage of bubbles up through the conveyor, at least in the region which is arranged directly above the stream of bubbles in use. This maximises the contact of the bubbles with product to be washed, ensuring that a high percentage of the bubbles passes up along the underside of the inclined surface and over any product in contact with or adjacent said surface.

It may be preferred to replace the conveyor with a static inclined member, e.g. a sheet or plate.

The method may include the use of a flow of liquid (as opposed to the generally static body of water described above) to carry the product through the bubble region beneath the inclined surface.

There is also provided an apparatus for carrying out the method of the above aspect of the invention.

The apparatus and methods set forth above have particularly preferred application in the field of washing food product, such as salad leaf. However, the methods and apparatus set forth above may have use in other washing applications, in particular for dislodging unwanted surface material.

Other aspects and preferred features of the invention will be readily apparent from the following description, made by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic part-cross-sectional side view of a washing apparatus according to a preferred embodiment of the invention; Figure 2 is a schematic part cross sectional side view of part of a further bath and conveyor combination; Figure 3 is similar to Figure 2, illustrating the use of bubbles for washing product beneath the conveyor; Figure 4 shows another part of the washing apparatus from Figures 3 and 4; Figure 5 is a schematic perspective view of part of a modified bath and conveyor combination; Figure 6 is a schematic perspective view of a feed portion of a further modified bath; and Figure 7 is a schematic perspective view of an exit portion of another modified bath.

Referring firstly to Figure 1 there is shown an example of a washing apparatus 100, in the form of a bath 110 for containing a volume of water into which product to be washed is to be immersed. A conveyor 120 extends into the bath 110 at an angle to the horizontal, and an arrangement for directing bubbles towards an underside region of the conveyor 120 is indicated at 130.

As will be described in more detail below, the conveyor 120 has a movable product carrying surface which is specifically intended for drawing product down into the bath 110 so that the product is caused to pass through a generally vertical stream of bubbles beneath the inclined moving surface of the conveyor 120, before being transporting up and out of

I I

the bath 110 on the upper side of the conveyor 120. The angle of inclination of the moving surface of the conveyor is in the region of 15 to 30 degrees.

The bath 110 is configured to reduce the volume of liquid required for the washing process.

In particular, the bath 110 includes a shallow feed region 112 having a generally horizontal base wall 114. In use, product to be washed is first introduced into the feed region 112, before being moved towards the underside of the conveyor 120. The bath 110 also includes a treatment region 116 into which the conveyor 120 extends. The treatment region 116 has an inclined base wall 118, which is substantially parallel with the moving underside surface of the conveyor 120. The base walls 114 and 118 cooperate to reduce the overall volume of water required to fill the bath to a desired level.

The arrangement 130 includes a manifold 132 which is mounted on the base wall 118 of the treatment region 116. The manifold 132 has an array of arms 134 spaced parallel to one another and extending in the transverse axis of the bath 110. Each arm 134 includes an array of apertures (not shown) through which a stream of bubbles can be introduced to the bath 110. A gas source (not shown) is coupled to the manifold, for generating the bubbles, and a controller may be provided for controlling the rate, size and or pressure of the bubbles, dependent upon the nature of the product to be washed.

As can be seen, the manifold 132 is arranged beneath the conveyor 120, so that the stream of bubbles from each aperture is directed upwards towards an immersed underside portion of the inclined conveyor 120, in use. The manifold 132 is arranged to be parallel with the conveyor 120 and base wall 118.

I I

The conveyor 120 preferably includes drainage regions, so that water can drain from the upper side of the conveyor 120 and back into the bath 110. For example, the product carrying surface of the conveyor 120 may be discontinuous or include drainage apertures.

In preferred embodiments, the moving surface of the conveyor 120 has a grid or lattice type mesh structure, which is generally permeable to water but which is configured to prevent the passage or capture of the product to be washed.

It may be preferred if the conveyor is arranged or configured so that the passage of bubbles through or around the conveyor is substantially reduced or prevented. This ensures that a high percentage of the bubbles passes over the upstream immersed section of the moving surface and over any product in contact with or adjacent said surface, thereby maximising the effect of the bubbles on the product to be washed.

In one example, the side walls of the bath 110 are arranged close to or against the sides of the conveyor, to restrict or exclude space available for the passage of bubbles up and around the sides of the conveyor. Additionally or alternatively, one or more impermeable deflectors may be used to guide the bubbles upstream against or parallel to the underside of the moving surface of the conveyor. Of course, if the moving surface of the conveyor is impermeable to the bubbles, the deflectors may be unnecessary.

The moving surface of the conveyor 120 defines a beach' region where it emerges from the body of liquid in the bath 110, as indicated at 138 in Figure 1. In use, washed product which has already passed beneath the conveyor 120 is intended to be deposited or beached' on the moving surface at 138, and then carried up and out of the bath 110.

-. -II Bubbles passing through or around the conveyor to 120 the beach region 138 have the potential to cause turbulent conditions, which could prevent the controlled or steady passage of washed product on to the conveyor 120. This could cause some product to stay immersed in the bath 110 for a longer period of time than is desired. Moreover, there is the risk that dislodged material from the washed product could be carried up to the beach region, so as to re-contaminate the washed product.

In Figure 1, a deflector 136 (e.g. in the form of an impermeable sheet or plate) is arranged directly behind an immersed portion of the moving surface at the underside of the conveyor. The deflector 136 extends over a portion of the moving surface which overlies the stream of bubbles in use, referred to as the treatment zone, and more particularly the portion which is directly beneath the beach region 138. The deflector 136 prevents the passage of bubbles directly up through the immersed portion of the conveyor 120 to the beach region 138.

In the illustrated embodiment, the bath 110 is mounted on adjustable legs 140, so that a substantially horizontal water level 102 can be achieved. An over flow aperture 142 is provided in a wall of the bath 110, for maintaining a substantially constant water level 102 in the bath 110.

Although Figure 1 shows a bath having an inclined base wall 118 (which assists in reducing the volume of water required by the apparatus 100), in other embodiments the bath 110 may be of uniform depth and/or not configured to be parallel or generally aligned with an inclined conveyor 120. Furthermore, the bubble arrangement 130 may be horizontal and/or not generally aligned with the inclined conveyor 120.

I I

It is preferred if the body of water in the bath 110 is generally static, wherein the movement of product through the system is principally the result of the conveyor 120. However, mechanical, hydraulic or pneumatic urging means may be provided adjacent either end of the conveyor 120, for assisting the movement of product towards the underside and upper side of the conveyor 120, respectively.

A method of washing food product in such apparatus will now be described with reference to Figures 2 to 4.

With a body of water present in the bath 110 up to the overflow level 102, food product to be washed (indicated generally at 150), for example salad leaf, is introduced to the bath 110 adjacent the projecting end of the conveyor at X. In the case of salad leaf, the product will float in the water. This level of immersion will enable a degree of surface material to soften or fall away from the product.

It may be necessary to provide directional assistance to move the floating product towards the underside of the conveyor 120. This can be done by hand or using mechanical means.

However, it may be preferred to introduce a gentle flow of air or water at the in-feed end of the bath 110 to urge the product along. The introduction of water would have the added effect of causing overflow from the bath 110 (e.g. via outlet 142), which may assist in removing any surface detritus resulting from the washing process, as well as providing a refreshing effect.

The conveyor 120 is operates to draw the floating product down into the water (e.g. moving clockwise as viewed in Figure 2), and to move the product through the stream of bubbles from the manifold 132 (see Figure 3, in which the upward stream of bubbles is indicated by arrows 152).

It is believed that the effect of the inclined member 120 is to cause the rising bubbles to impact and shear across the surface of the immersed product. The product is maintained in the zone of influence of the bubbles against the underside of the conveyor, to effect cleaning of the product.

The size and/or rate of the bubbles is preferably controlled so as to provide a suitable cleaning effect whilst minimising damage to the product. The appropriate nature of the bubbles for a given product and level of surface content or desired surface cleaning can be determined by trial and error.

The upward action of the bubbles causes a slight downward current which is effective in assisting the movement of surface material such as soil and other unwanted microbial matter away from the washed product.

After the product has been moved beyond the lower end of the conveyor 120, it is free to float upwards to the surface of the water (see Figure 4). It may be preferred to extend the manifold beyond the lower end of the conveyor to assist in this process, in particular for products heavier or less buoyant than salad leaf. However, in the embodiment of Figure 1 the manifold does not extend beyond the lower end of the conveyor 120.

It may be preferred to assist the movement of washed product on to the upper side of the conveyor, so that the washed product can carried up and out of the bath 110. As at the inflow end, this can be done manually or with mechanical or pneumatic means, although a gentle water flow may be preferred.

The conveyor 120 can then be used for transporting the washed product to a further processing stage, e.g. by feeding the washed product into the in-feed end of an adjacent washing apparatus 100 or the same apparatus for a further washing operation.

A modified bath 110 is shown in Figure 5, wherein the conveyor 120 projects beyond the longitudinal extent of the bath 110, so that product falling from the upper end of the conveyor 120 will not falf back into the bath 110.' In this embodiment, the inlet region 154 of the bath 110 is curved in plan view, so as to extend in a generally transverse direction, relative to the conveyor 120. When used with a flow of water for assisting movement of product towards the underside of the conveyor 120, this offset arrangement has been found to reduce the risk of downstream turbulence.

Figure 6 shows an example of a mechanical arrangement 200 for creating a directional flow of product within an essentially static body of water 202, either at the feed end 204 or the exit end (not shown) of a washing bath 206. The arrangement 200 includes a plate 208 which is hinged at a pivot point 210 on a frame 212, so as to extend down into the water 202. The plate 208 is intended to be gently rocked about the pivot point 210, in order to induce a minor degree of flow in the static body of water to assist movement of the product towards the conveyor (not shown).

Figure 7 shows an example of a mechanical arrangement 214 for use at the exit end of a washing bath 216. The arrangement 214 includes a pusher or plate 218 which is movably mounted on a frame 220 above the water level 222. The plate 218 extends below the water level 222 and is movable along the frame 220, from left to right and vice versa, as viewed.

The purpose of the plate 222 is to push or urge washed product onto the beach region 224 of an inclined conveyor 226 in the bath 216. The plate is preferably hingedly mounted on the frame, so as to be movable between a first downward position when travelling in the direction of the conveyor 226 and a raised position (indicated by the dotted lines at 228 in Figure 7, wherein the lower end of the plate 222 is free from the water and any product floating therein) when travelling in a return direction.

In any of the embodiments described above, a removable filter (not shown) may be provided in the bottom of the bath 110 for collecting matter falling as a result of the washing process. Additionally or alternatively, water can be drawn off from the base of the tank, for removing fallen matter.

Scale tests suggest that the apparatus should provide improved surface cleaning, reducing the need for turbulence in the water and/or multiple washing operations, when compared with conventional techniques. Preferred embodiments should also provide a net reduction in water consumption.

The apparatus has been described with particular reference to washing salad leaf, but is equally applicable for use in washing herbs, chopped and whole vegetables (e.g. carrots, new potatoes, cucumber, sliced onion, trimmed lettuce heads) and fruits (e.g. berries). The apparatus may also be of use for washing non-food product, such as plastics items.

It may be preferred to replace the conveyor with a static inclined member, and even to use a flow of water (as opposed to the generally static body of water described above) to carry the product beneath the inclined member through the bubble region.

Claims

Claims 1. Apparatus for washing product, the apparatus comprising: a vessel for receiving a volume of liquid in which product to be washed is to be immersed; an inclined surface extending in the vessel beneath which product to be washed is intended to pass; and an arrangement for directing a stream of bubbles up towards an underside portion of the inclined surface, in order to impact upon the product as it passes beneath the inclined surface.
2. Apparatus according to claim 1, including a conveyor having a moving surface which is arranged at an angle of inclination within the vessel, wherein said inclined surface is provided by the moving surface on the underside of the conveyor.
3. Apparatus according to claim 2 wherein the moving surface operable for assisting the immersion of product to be washed.
4. Apparatus according to claim 2 or 3 wherein, in use, a lower portion of the conveyor is immersed in liquid within the vessel, and an upper portion of the conveyor extends from the liquid in the vessel, and wherein the moving surface on the upper side of the conveyor is arranged for carrying washed product up and out of the vessel.
5. Apparatus according to claim 4 including mechanical means for directing washed product onto the moving surface on the upper side of the conveyor.
6. Apparatus according to any of claims 2 to 5 wherein the moving surface of the conveyor has a porous structure, and one or more deflectors is arranged directly behind an immersed portion of the moving surface at the underside of the conveyor, for preventing or reducing the upward passage of the bubbles.
7. Apparatus according to any preceding claim, wherein the region directly beneath the inclined surface towards which the bubbles are directed defines a treatment zone for product to be washed, and the apparatus is configured for preventing or reducing the passage of bubbles from the treatment zone to a region directly above said treatment zone.
8. Apparatus according to any of claim I to 7 including mechanical means for directing product to be washed towards the underside of the inclined surface.
9. Apparatus according to any of claims 1 to 8 wherein the vessel has a shallow feed region and is deepest in the region of the immersed portion of the conveyor.
10. A method of washing product including the steps of using the underside of a conveyor to draw product to be washed down into a body of liquid, and applying a controlled stream of bubbles to product passing beneath the conveyor.
11. A method according to claim 10 wherein the conveyor has a moving surface which is arranged at an of inclination extending into a bath for washing the product, and wherein the immersed portion of the conveyor overlies the stream of bubbles.
12. A method according to claim 10 or claim 12 wherein the washing operation takes place in a vessel containing an essentially static body of liquid.
13. A method according to any of claims 10 to 12 wherein having passed beneath the conveyor, the washed product is then be transferred out of the body of liquid on the upper side of the conveyor.
14. A method according to any of claims 10 to 13 wherein deflector means are employed to prevent or reduce the passage of bubbles up through the conveyor, at least in the region which is arranged directly above the stream of bubbles in use.
15. An apparatus for washing product substantially as herein described and/or illustrated in one or more of the accompanying drawings.