GB2539179B

GB2539179B - Manufacture of snack foods

Info

Publication number: GB2539179B
Application number: GB1509286.9A
Authority: GB
Inventors: Abbas Bob; Herring Peter; Maynard Dan
Original assignee: Frito Lay Trading Co GmbH
Current assignee: Frito Lay Trading Co GmbH
Priority date: 2015-05-29
Filing date: 2015-05-29
Publication date: 2019-09-18
Anticipated expiration: 2035-05-29
Also published as: GB201509286D0; WO2016193081A1; GB2539179A

Description

MANUFACTURE OF SNACK FOODS

This invention relates to an apparatus and method for controlling product flow in themanufacture of snack foods and in particular the control of the manufacture of potatoslices in the manufacture of potato chips, more particularly low oil potato chips whichhave been cooked by microwave energy.

It has been known for many years to produce potato chips from slices of potato which arefried in oil, usually vegetable oil. Typical conventional potato chips have an oil content ofabout 30 to 35 wt% oil, based on the total weight, of the potato chip. Potato chips exhibitspecific organoleptic properties, in combination with visual appearance, to the consumer.The consumer desirous of purchasing a potato chip has a clear expectation of theseproduct attributes in the product.

There is a general desire among snack food manufacturers, consumers and regulatoryauthorities for healthier food products. In the snack food industry, this has led to a desirefor lower fat products. However, even though there may be a general consumer awarenessof the benefits of eating lower fat versions of, or alternatives to, existing snack foodproducts, the consumer generally requires the product to have desirable attributes such astexture and flavour. Even if a snack food product is produced which has high nutritionalattributes, unless it also has the texture and flavour required by the consumer, the productwould not successfully provide the consumer with an acceptable product to replaceprevious, less healthy snack food products. The challenge among snack foodmanufacturers is to produce nutritional or more healthy foods which provide the consumerwith an improved taste and sensation experience, or at the very least do not compromiseon taste and sensation as compared to the consumer’s expectation for the particularproduct or class of products purchased.

There arc in the market so-called lower oil snack food products, including potato chips andother products. Some of these processes are produced by modified frying processes usingdifferent frying temperatures than those conventionally employed, or cooking processesother than frying, such as baking. Some of these products produce snack foods with lowoil, even as low as 5wt%, but the snack food product, is not regarded by the consumer to be an acceptable alternative to a potato chip, because the product cannot exhibit theorganoleptic properties, in combination with the visual appearance, of a potato chip. WO-A-2008/011489 and WO-A-2009/091674 in the name of Frito-lay Trading CompanyGmbH disclose processes for making a healthy snack food. In those processes, a snackfood is made so as to have an appearance and taste similar to conventional fried snackproducts, such as a potato chip. The potato slices are subjected to a sequence of stepswhich avoids frying of the slices in oil, and the result is a low fat potato chip.

In particular, these specifications disclose the use of microwave cooking of potato sliceswhich have been preconditioned, for example by being treated in oik Prior to the.microwave cooking process, the potato slices are flexible, and have a typical thickness of1 to 2.5 mm. The microwave cooking rapidly, or explosively, dehydrates the -potato slicesto achieve low moisture content in a drying step which simulates the conventional fryingdehydration rate. It is disclosed that the microwave drying may comprise linear belt orrotary microwave drying. The rapid microwave dehydration rigidities the cooked potatoslices, so that they have a crispness resembling that of typical fried potato chips.Additional final drying steps may be employed, for example using microwave drying.

The potato slices are fed into the microwave cavity on a conveyor, and the input productflow tends to have an uneven or non-uniform slice distribution. Such a distribution resultsfrom the original potato feed or from the preceding treatment steps, which may cause theinput product flow to come in surges or to be unevenly or non-uniformly distributed acrossthe width of the conveyor. In particular, there may be overlapping or clumping together ofpotato slices prior to the microwave treatment which explosively dehydrates the potatoslices. Such an uneven or non-uniform product distribution for the microwave inputchanges the amount of product in the conveyor and therefore correspondingly changes theload in the microwave cavity, for example the load changing significantly over a period ofless than one minute. The load represents the total amount of water at any given timewithin the microwave cavity which is energised by the microwave during the microwavetreatment of the products within the cavity. Such a variation of the load within themicrowave cavity can cause a number of problems, for example uneven drying of the potato slices ίο form the potato chips, insufficient drying, and/or excess microwave energywithin the cavity tor the current load, causing arcing.

One particular problem with the manufacture of potato chips from potato slices is that it isdifficult to provide, a completely uniform flow. Also, the slices vary in shape anddimension, so that the cooked slices exhibit the random three-dimensional shapes of potatochips. WO-A-2012/104218 discloses an apparatus for detecting products on a conveyor. Animaging system images products on the conveyor. A contouring step estimates a centre ofan imaged product and a reverse contouring step estimates an outline of the imagedproduct, which can provide an indication of product overlap which cannot easily beimaged using a direct imaging process. The estimated degree of overlap is indirectlydetermined from the input image data. The resultant estimated degree of overlap, or aparameter calculated from the estimated degree of overlap such as mass flow rate, can beused as an input parameter for controlling the manufacturing line. For example, the massflow rate can be used as an input parameter for controlling a variable such as microwaveenergy output from a microwave apparatus.

This can enhance the product quality and/or product uniformity of snack foods,particularly potato chips produced by a microwave cooking step, such as an explosivedehydration step discussed above, which not only have low oil but also have thecombination of flavour, organoleptic properties and shelf life in a non-fried potato chipwhich is equal or superior in consumer acceptance to conventional fried potato chips.

However, there is still a need to control the product flow in the manufacture of snackfoods, for example to control the product flow prior to a downstream operation.

For example, there is still a need to control the flow of potato slices in the manufacture ofpotato chips, more particularly low oil potato chips, prior to a microwave cooking whichcan explosively dehydrate the potato slices or a drying treatment, for example usingmicro wave energy.

There is furthermore still a need for an apparatus and method for efficiently and reliablymanufacturing, in a cost effective manner, a low fat potato chip which has not been friedbut has organoleptic properties, in combination with the visual appearance, of aconventional fried potato chip.

The present invention accordingly provides an apparatus for controlling product flow inthe manufacture of snack foods, the apparatus including a conveyor for conveying foodproducts from an upstream location to a downstream location, a first imaging systemadapted to image a first distribution of the food products on the conveyor at the upstreamlocation and to produce first data related to the first distribution, a processor coupled to theimaging system, the processor including a mapping unit for processing the first data toprovide second data related to coordinates of the imaged products on the conveyor, acontrol unit coupled to the processor and adapted to output a control signal based on thesecond data, and a pick-and-place unit connected to the control unit and being controllableby the control signal, the pick-and-place unit being adapted to move one or more selectedproducts on the conveyor so as to modify the first distribution of products on the conveyorto form a second distribution of the food products on the conveyor at the downstreamlocation, wherein the processor includes an overlap analysis module to determine productoverlap from the first data and to produce the second data, the second data including as aparameter a first function relating to an overlap of plural imaged products, and the controlunit includes an overlap control module to produce the control signal, the control signalincluding a second function, derived from the first function, to cause the pick-and-placeunit to pick up at least one overlapping first product and subsequently place the firstproduct in a non-overlapping configuration on the conveyor.

The present invention further provides a method of controlling product flow in themanufacture of snack foods, the method comprising the steps of: a. conveying food products from an upstream location to a downstream location; b. imaging a first distribution of the food products on the conveyor at the upstreamlocation to produce first data related to the first distribution; c. processing the first, data to provide second data related to coordinates of theimaged products on the conveyor; and d. outputting a control signal based on the second data to control a pick-and-placeunit to move one or more selected products on the conveyor so as to modify the firstdistribution of products on the conveyor to form a second distribution of the food productson the conveyor at the downstream location, wherein the method further comprises thestep of: determining product overlap from the first data; and wherein the second dataincludes as a parameter a first function relating to an overlap of plural imaged products,and the control signal includes a second function, derived from the first function, to causethe pick-and-place unit to pick up at least one overlapping first product and subsequentlyplace the first product in a non-overlapping configuration on the conveyor.

Preferred features are defined in the dependent claims.

An embodiment of the present invention will now be described, by way of example only,with reference to the accompanying drawings in which:

Figure 1 is a schematic side view of an apparatus for controlling product flow in themanufacture of snack foods according to an embodiment of the present invention; and

Figure 2 is an enlarged schematic side view of a head of a pick-and-place unit in theapparatus of Figure 1.

An embodiment of an apparatus for, and method of, controlling product flow, in particularpotato slices, prior to microwave cooking of the potato slices to form potato chips,according to one aspect of the present invention is illustrated in Figures 1 and 2.

In this embodiment the potato slices are the food products being conveyed, but the presentinvention may be utilised to control the product flow' of any conveyed food product,employed in the manufacture of snack foods, either before or after cooking or any otherprocess during manufacture of the snack food. Also, although the embodiment relates topotato slices, and morphology (other than a slice) of any composition (other than a potato)may be employed in accordance with alternative embodiments of the invention.

Referring to the drawings, an endless belt conveyor 2 having a substantially horizontalorientation, or being slightly inclined to the horizontal, is provided for conveying foodproducts, in this embodiment potato slices 6, from an upstream location to a downstreamlocation. An inlet end 4 of the conveyor 2 communicates with an upstream processingstation for the potato slices 6. The conveyor 2 carries a succession of the potato slices 6on its upper surface 8. The conveyor 2 is employed to feed the potato slices 6 to amicrowave apparatus 10 for cooking and explosively dehydrating the potato slices 6 inorder to produce potato chips, which have not been fried, as for a conventional potatochip.

The upper surface 8 of the conveyor 2, for example an endless belt of the conveyor 2, isselected to have a high visual contrast with the products to be conveyed by the conveyor 2.For example, when the conveyor 2 is to be used for conveying potato slices 6. the uppersurface 8 may be dark blue in colour.

The potato slices 6 have been randomly delivered onto the conveyor 2 but with a productflow along and across the conveyor 2 so as to provide a substantially constant productflow, but with less than 100 % uniformity and some slice overlap. The potato slices 6 aretypically delivered onto the conveyor 2 in a slice distribution so as to have no more thanabout 50% of the slices overlapping with an adjacent slice, with any such overlap to be nomore than about 50% of the slice dimension, and with no more than two slices 6 beingstacked one upon the other on the conveyor 2. This substantially provides a monolayer ofpotato slices 6 across the length and width of the conveyor 2, but with some overlappingand consequential variation of microwave load along and across the conveyor 2.

The potato slices 6 typically have a thickness of 1 to 2.5 mm, more typically about 1.3 mm(51 thousandths of an inch). Since the potato slices 6 are thin and flexible, they are readilyable to overlap each other. This means that the flow rate of the potato slices 6 along themanufacturing line, and in particular through specific apparatus in the manufacturing line,such as the microwave apparatus 10, can vary over a short period of time, for example lessthan one minute, with potential deterioration in product quality and/or uniformity. A first imaging system 11, comprising a camera 12, Is provided to image a firstdistribution 13 of the potato slices 6 on the conveyor 2, The camera 12 produces first datarelated to the first distribution 13.

As the potato slices 6 are carried on the upper surface of the primary conveyor 2, they areimaged by the camera 12. The camera 12 continuously or continually images the potatoslices 6 conveyed thereunder. The field of view of the camera 12 may be applied to all oronly a portion of the width of the conveyor 2. The high visual contrast upper surface 8 ofthe conveyor 2, optionally in combination with overhead illumination of the field of viewof the camera 12 by one or more lamps 14, enables the camera 12 readily to be able toimage the potato slices 6. The camera 12 is a digital camera which takes individual imagessuccessively, or is a video camera which takes a continuous film, of the product flowthereunder. Typically, the imaging system, including the camera 12 and the lamps 14when present, and including the upper surface 8 of the conveyor 2, are configured tooperate using visible radiation, such as white light. A processor 16 is coupled to the camera 12. In particular, the camera 12 is connected, by awired or wireless connection 15, to the processor 16 coupled to a display unit 18. Theprocessor 16 includes a mapping unit 17 for processing the first data to provide seconddata related to coordinates of the imaged potato slices 6 on the conveyor 2. A control unit 22 is coupled to the processor 16 and outputs a control signal based on thesecond data. The processor 16 has a signal output 20, which may be wired or wireless, andis transmitted to the control unit 22.

The processor 16 is programmed to process the data from the camera 12 representing theimaged potato slices 6 and to determine a parameter indicative of the overlap of pluralpotato slices 6 imaged by the camera 12. In particular, the processor 16 includes anoverlap analysis module 19 to determine potato slice overlap from the first data.Specifically, the overlap analysis module 19 analyses a plurality of clusters 25 ofoverlapping potato slices 6. The second data is produced from the overlap analysis module19 and includes as a parameter a first function relating to an overlap of plural imagedpotato slices 6. A pick-and-place unit 30 is connected to the control unit 22 and is controllable by thecontrol signal. The pick-and-place unit 30 is upstream, along the conveyor 2, of themicrowave apparatus 10. The pick-and-place unit 30 is adapted to move one or moreselected potato slices 6 on the conveyor 2 so as to modify the first distribution 13 of potatoslices 6 on the conveyor 2 to form a second distribution 33 of the potato slices 6 on theconveyor 2 at the downstream location.

The control unit 22 includes an overlap control module 24. A control signal is producedfrom the overlap control module 24 and includes a second function, derived from the firstfunction, to cause the pick-and-place unit 30 to pick up at least one overlapping potatoslice 6 and subsequently place the potato siice(s) 6 in a non-overlapping configuration onthe conveyor 2.

The overlap control module 24 causes the pick-and-place unit 30 to operate on a selectednumber of clusters 25 within a given time period. The overlap control module cancalculate a maximum number of clusters 25 that can be operated on by the pick-and-placeunit. 30 within a preset time period. The number of clusters 25 is reduced by the operationof the pick-and-place unit 30. A second imaging system 40 is downstream along the conveyor 2 of the first imagingsystem and the pick-and-place unit 30. As for the first imaging system IT, the. secondimaging system 40 may comprise a camera 42 and one or more lamps 44. The secondimaging system 40 is adapted to image the second, modified, distribution 33 of the potatoslices 6 on the conveyor 2 formed by operation of the pick-and-place unit 30. The secondimaging system 40 produces third data related to the second, modified, distribution 33.The processor 16 is coupled to the second imaging system 40 and the mapping unit 17 isadapted to process the third data to provide fourth data related to coordinates of thesecond, modified, distribution 33 of the imaged potato slices 6 on the conveyor 2. A comparator 48 is provided, typically in the processor 16, for comparing the coordinatesof the second, modified, distribution 33 in the fourth data against a preset, distribution ofthe potato slices 6 on the conveyor 2. A feedback unit 50, typically in the processor 16, provides to the control unit 22 afeedback signal related to the fourth data. The feedback signal modifies the control signaland controls the pick-and-place unit 30 so as to adapt the modified distribution 46 towardsthe preset distribution.

In the pick-and-place unit 30 a movement mechanism 50 is connected to a head member52. The movement mechanism 50 is controllably movable, in response io the controlsignal, over at least a portion of a surface area of the conveyor 2.

The head member 52 of the pick-and-place unit 30 defines a lower engaging surface 54and has an opening 56 in the lower engaging surface 54. A fluid conduit 58 is connected tothe opening 56. The fluid conduit 58 is connected to a source of gas, typically compressedair. The opening 56 is shaped, for example substantially conically shaped, to provide aventuri effect, thereby to provide a Bernoulli grip effect on an underlying product such asa potato slice 6, when gas is emitted from the opening 56. The opening comprises a centraloutlet 60 surrounded by an annular recess 62.

The pick-and-place unit 30 comprises a sensor 64 located at the lower engaging surface54. The sensor 64 is located at the opening 56 and a lower surface 66 of the sensor 64 isaligned with the lower engaging surface 54. The sensor 64 is adapted to detect thepresence of a food product, such as a potato slice 6, adjacent to the lower engaging surface66, and preferably comprises a capacitance sensor 64. Typically, the capacitance sensor64 is calibrated to detect, the presence of a food product, such as a potato slice 6, within asensing range of up to 4 mm.

The sensor 64 is connected to the control unit 22 and is adapted to emit a sensor signal tothe control unit. 22 to control the operation of the pick-and-place-unit 30.

The sensor 64 emits a positive sensor signal to the control unit 22 when the sensor 64detects the presence of a food product adjacent to the lower engaging surface 66. Thecontrol unit 22 is adapted to proceed with a pick-and-place operation upon receipt of thepositive sensor signal.

In contrast, the sensor 64 emits a negative sensor signal, or no sensor signal, to the controlunit 22 when the sensor detects the absence of a food product adjacent to the lowerengaging surface 66. The control unit 22 is adapted not to proceed with a pick-and-placeoperation upon receipt of the negative sensor signal or in the absence of a sensor signal.

The pick-and-place unit 30 is adapted to carry out sequential pick-and-place cycles. Eachcycle comprises the sub-steps of (i) receipt of a control signal from the control unit 22, (ii)movement of the pick-and-place unit 30 to a first location above the conveyor 2 inresponse to the second data, (hi) picking up of a potato slice 6 at the first location, (iv)movement of the pick-and-place unit 30 carrying the picked-up potato slice 6 to a secondlocation, different from the first location, above the conveyor 2 in response to the seconddata, the second location including a portion of the conveyor surface which is free ofpotato slices 6, and (v) depositing the potato slice 6 at the second location on the portionof the conveyor surface.

The pick-and-place unit 30 is adapted to sense the presence or absence of a food producttricked up by the pick-and-place unit 30 and to abort the respective pick-and-place cycle inthe event of a change of state of the presence or absence of the picked-up food productbetween the pick-up and deposition steps. For example, if the potato slice 6 falls off thehead 52, the pick-and-place cycle is aborted, and the head 52 is moved to pick up a potatoslice 6 at another cluster 25. Typically, the apparatus is adapted to carry out at least threepick-and-place cycles per minute by the pick-and-place unit 30.

The overlap analysis module. 19 preferably functions in the manner described in WO-A-2012/104218. In particular, each imaged potato slice 6 is analysed in the processor 16 andthe processor 16 determines an outline of the. imaged potato slice 6. The outline may beapproximate, for example a pixellated image. The processor 16 converts an image signalfrom the camera 12 into data representing a first outline of at least one imaged product.The product may be represented on the display unit 18 as a pixellated image. Thepixellated image may have an outline which suggests that the imaged product is likely tobe two products in an overlapping configuration. The processor 16 then applies analgorithm to the outline which reduces the dimensions of the outline substantially equally around the entire periphery of the outline to produce a first, contoured outline. For exampiethe contoured outline is produced by reducing the outline by one or more pixels around theperiphery of the outline. This contoured outline is a reduced dimension outline which issimilar to providing a contour line on a map. Such a contouring step is carried outiteratively a number of times to produce a series of progressively smaller outlines. Thedifferent outlines may be displayed as having different respective colours. Thiscontouring is carried out in the processor 16 which operates on the data to reduce the firstoutline to produce data representing a second outline of at least one central region of the atleast one imaged product. The number of iterative steps, which may be predetermined, isselected so that, for the particular product dimensions and the contouring dimensionsbetween adjacent outlines, the last and smallest outline is statistically likely to indicate theexistence of any product overlap. The smallest outline comprises two such separate anddistinct outlines, each of which is substantially centred on a respective one of twooverlapping products. The imaging and processing system has indirectly determined theexistence of a product, overlap, which could not be directly imaged by the imaging systemincluding the camera 12. Subsequently, a series of iterative reverse contouring steps iscarried out on each of the outlines. In such a reverse contouring step, an algorithm to theoutlines which increases the dimensions of each respective outline substantially equallyaround the entire periphery of the outline is used to produce a first enlarged contouredoutline. Then the subsequent reverse contouring steps are carried out on each outline withthe same number of reverse contouring steps to produce an enlarged outline as the numberof initial contouring steps to produce a reduced outline. By applying the reversecontouring to each of two initial outlines, the final reverse contouring step provides twooverlapped outlines each of which represents an image of a respective estimatedoverlapped product. Such reverse contouring is carried out by the processor 16 which isoperable on the data for increasing the second outline of the or each central region toproduce data representing an estimated third outline of the at least one imaged product.The area of each third outline, can be readily determined, to enable the mass of thecorresponding two products to be calculated. Individual products, not in an overlappingconfiguration, may also readily have their area determined, to enable the respectiveproduct mass to be calculated.

The use of such an imaging and data processing system enables on-line real-timedetermination of the flow rate, typically expressed as total mass, of products, such aspotato slices 6, passing along the manufacturing line, for example through the microwaveapparatus 10. The determined parameter is employed, in a feed-forward or feedback mode,as an input parameter to control the operation of the manufacturing line, for example tocontrol a variable such as the microwave energy output of a microwave apparatus. Forexample, the signal output 20 of the processor 16 sends a control signal to the controlapparatus 22 which in turn sends a control command, by a wired or wireiesss connectionto the microwave apparatus 10 which modulates the microwave energy emitted in themicrowave cavity dependent upon the immediately upstream product flow imaged by thecamera 12. This correlates the microwave energy to the mass flow rate of the products. Ifdesired, a delay may be introduced for a feed-forward control.

Alternatively, the control signal may control an upstream operation. For example, if theproportion of overlapping slices is determined to be above a desired threshold, or thedegree of overlap or number of slices in any stacked overlap is determined to be above adesired threshold, or the overlap proportion is so low that the product flow rate can beincreased without significantly increasing product overlap, the control signal may beemployed to modify the product distribution in upstream processing, for exampledeposition of the products onto the conveyor.

Various modifications to the illustrated embodiment will be readily apparent to thoseskilled in the art. For example, the imaging system could operate using other than whitelight, and may use non-visible radiation.

Claims

CLAIMS;

1. An apparatus for controlling product flow in the manufacture of snack foods, theapparatus including a conveyor for conveying food products from an upstream location toa downstream location, a first imaging system adapted to image a first distribution of thefood products on the conveyor at the upstream location and to produce first data related tothe first distribution, a processor coupled to the imaging system, the processor including amapping unit for processing the first data to provide second data related to coordinates ofthe imaged products on the conveyor, a control unit coupled to the processor and adaptedto output a control signal based on the second data, and a pick-and-place unit connected tothe control unit and being controllable by the control signal, the pick-and-place unit beingadapted to move one or more selected products on the conveyor so as to modify the firstdistribution of products on the conveyor to form a second distribution of the food productson the conveyor at the downstream location, wherein the processor includes an overlapanalysis module to determine product overlap from the first data and to produce thesecond data, the second data including as a parameter a first function relating to an overlapof plural imaged products, and the control unit includes an overlap control module toproduce the control signal, the control signal including a second function, derived from thefirst function, to cause the pick-and-placc unit to pick up at least one overlapping firstproduct and subsequently place the first product in a non-overlapping configuration on theconveyor.

2. An apparatus according to claim 1, wherein the overlap analysis module is adaptedto analyse a plurality of clusters of overlapping first products and the overlap controlmodule is adapted to cause the pick-and-place unit to operate on a selected number ofclusters within a given time period.

3. An apparatus according to claim 2, wherein the overlap control module is adaptedto calculate a maximum number of clusters that can be operated on by the pick-and-placeunit within a preset time period.

4. An apparatus according to any foregoing claim, further including a secondimaging system downstream along the conveyor of the first imaging system and the pick- and-place unit, the second imaging system being adapted to image the second distributionof the food products on the conveyor formed by operation of the pick-and-place unit, andto produce third data related to the second distribution, the processor being coupled to thesecond imaging system and the mapping unit being adapted to process the third data toprovide fourth data related io coordinates of the second distribution of the imaged productson the conveyor.

5. zkn apparatus according to claim 4, further including a comparator for comparingthe coordinates of the second distribution in the fourth data against a preset distribution ofthe products on the conveyor.

6. An apparatus according to claim 5, further including a feedback unit adapted toprovide to the control unit a feedback signal related to the fourth data thereby to modifythe control signal and control the pick-and-place unit so as to modify the seconddistribution towards the preset distribution.

7. An apparatus according to any foregoing claim, wherein the pick-and-place unitcomprises a head member defining a lower engaging surface and having an opening in thelower engaging surface, a fluid conduit connected to the opening, the fluid conduit beingconnectable to a source of gas, the opening being shaped to provide a venturi effect whengas is emitted from the opening so that the head member provides a Bernoulli grip on afood product thereunder, and a movement mechanism connected to the head member andadapted to be controllably movable, in response to the control signal, over at least aportion of a surface area of the conveyor.

8. An apparatus according to claim 7, wherein the opening comprises a central outletsurrounded by an annular recess.

9. An apparatus according to claim 7 or claim 8, wherein the pick-and-place unitcomprises a sensor located at the lower engaging surface and adapted to detect thepresence of a food product adjacent to the lower engaging surface.

10. An apparatus according to claim 9 wherein the sensor is located at the opening.

11. An apparatus according to claim 9 or claim 10 wherein a lower surface of thesensor is aligned with the lower engaging surface.

12. An apparatus according to any one of claims 9 to 11 wherein the sensor comprisesa capacitance sensor.

13. An apparatus according to claim 12 wherein the capacitance sensor is calibrated todetect the presence of a food product within a sensing range of up ίο 4 mm.

14. An apparatus according to any one of claims 9 to 13 wherein the sensor isconnected to the control unit and is adapted to emit a sensor signal to the control unit tocontrol the operation of the pick-and-place-unit.

15. An apparatus according to claim 14 wherein the sensor is adapted to emit apositive sensor signal to the control unit when the sensor detects the presence of a foodproduct adjacent to the lower engaging surface and the control unit is adapted to proceedwith a pick-and-place operation upon receipt of the positive sensor signal.

16. .An apparatus according to claim 14 or claim 15 wherein the. sensor is adapted toemit a negative sensor signal, or no sensor signal, to the control unit when the sensordetects the absence of a food product adjacent to the lower engaging surface and thecontrol unit is adapted not to proceed with a pick-and-place operation upon receipt of thenegative sensor signal or in the absence of a sensor signal.

17. An apparatus according to any foregoing claim, wherein the pick-and-place unit isadapted to carry out sequential pick-and-place cycles, each cycle comprising receipt of acontrol signal from the control unit, movement of the pick-and-place unit to a first locationabove the conveyor in response to the second data, picking up of a food product at the firstlocation, movement of the pick-and-place unit, carrying the picked-up food product to asecond location, different from the first location, above the conveyor in response to thesecond data, the second location including a portion of the conveyor surface which is free of food products, and depositing the food product at the second location on the portion ofthe conveyor surface.

18. An apparatus according to claim 17, wherein the pick-and-place unit is adapted tosense the presence or absence of a food product picked up by the conveyor and to abort therespective pick-and-place cycle in the event of a change of state of the presence or absenceof the picked-up food product between the pick-up and deposition steps.

19. An apparatus according to claim 17 or claim 18, which is adapted to carry out atleast three pick-and-place cycles per minute by the pick-and-place unit.

20. An apparatus according to any foregoing claim, wherein the pick-and-place unit isadapted to move food slices, optionally potato slices, on the conveyor.

21. An apparatus according to any foregoing claim, further comprising a microwaveapparatus located for cooking products on the conveyor, wherein the pick-and-place unit, isupstream, along the conveyor, of the microwave apparatus.

22. A potato chip manufacturing line including the apparatus of any foregoing claim.

23. A method of controlling product flow in the manufacture of snack foods, themethod comprising the steps of: a. conveying food products from an upstream location to a downstream location; b. imaging a first distribution of the food products on the conveyor at the upstreamlocation to produce first data related to the first distribution; c. processing the first data to provide second data related to coordinates of theimaged products on the conveyor; and d. outputting a control signal based on the second data to control a pick-and-placeunit to move one or more selected products on the conveyor so as to modify the firstdistribution of products on the conveyor to form a second distribution of the food productson the conveyor at the downstream location, wherein the method further comprises thestep of: determining product overlap from the first data; and wherein the second dataincludes as a parameter a first function relating to an overlap of plural imaged products. and the control signal includes a second function, derived from the first function, to causethe pick-and-place unit to pick up at least one overlapping first product and subsequentlyplace the first product in a non-overlapping configuration on the conveyor.

24. A method according to claim 23, further comprising the step of: analysing aplurality of clusters of overlapping first products and causing the pick-and-place unit tooperate on a selected number of clusters within a given time period.

25. A method according to claim 24, further comprising the step of: calculating amaximum number of clusters that can be operated on by the pick-and -place unit within apreset time period.

26. A method according to any one of claims 23 to 25, further comprising the steps of:imaging, downstream along the conveyor of the imaging step a, the second distribution ofthe food products on the conveyor formed by operation of the pick-and-place unit toproduce third data related to the second distribution, and processing the third data toprovide fourth data related to coordinates of the second distribution of the imaged productson the conveyor.

27. A method according to claim 26, further comprising the step of: comparing thecoordinates of the second distribution in the fourth data against a preset distribution of theproducts on the conveyor.

28. A method according to claim 27, further comprising the step of: providing afeedback signal related to the fourth data to modify the control signal and control the pick-and-place unit so as to modify the second distribution towards the preset distribution.

29. A method according to any one of claims 23 to 28, wherein the pick-and-place unitcomprises a head member defining a lower engaging surface and having an opening in thelower engaging surface, a fluid conduit connected to the opening, the fluid conduit beingconnectable to a source of gas, the opening being shaped to provide a venturi effect whengas is emitted from the opening so that the head member provides a Bernoulli grip on afood product thereunder, and a movement mechanism connected to the head member and which is controllably moved, in response to the control signal, over at least a portion of asurface area of the conveyor.

30. A method according to claim 29, wherein the opening comprises a central outletsurrounded by an annular recess.

31. A method according to claim 28 or claim 29, wherein the pick-and-place unitcomprises a sensor located at. the lower engaging surface which detects the presence of afood product adjacent to the. lower engaging surface.

32. A method according to claim 31 wherein the sensor is located at the opening.

33. A method according to claim 31 or claim 32 wherein a lower surface of the sensoris aligned with the lower engaging surface.

34. A method according to any one of claims 31 to 33 wherein the sensor comprises acapacitance sensor.

35. A method according to claim 34 wherein the capacitance sensor is calibrated todetect the presence of a food product within a sensing range of up to 4 mm.

36. A method according to any one of claims 31 to 35 wherein the sensor emits asensor signal to control the operation of the pick-and-place-unit.

37. A method according to claim 36 wherein the sensor emits a positive sensor signalwhen the sensor detects the presence of a food product adjacent to the lower engagingsurface to cause a pick-and-place operation by the pick-and-place-unit to proceed.

38. A method according to claim 36 or claim 37 wherein the sensor is adapted to emita negative sensor signal, or no sensor signal, when the sensor detects the absence of a foodproduct adjacent to the lower engaging surface to cause a pick-and-place operation not tobe proceeded with.

39. A method according to any one of claims 23 to 37, wherein the pick-and-place unitcarries out sequential pick-and-place cycles, each cycle comprising receipt of a controlsignal, movement of the pick-and-place unit to a first location above the conveyor inresponse to the second data, picking up of a food product at the first location, movementof the pick-and-place unit carrying the picked-up food product to a second location,different from the first location, above the conveyor in response to the second data, thesecond location including a portion of the conveyor surface which is free of food products,and depositing the food product at the second location on the portion of the conveyorsurface.

40. A method according to claim 39, wherein the pick-and-place unit senses thepresence or absence of a food product picked up by the conveyor aborts the respectivepick-and-place cycle in the event of a change of state of the presence or absence of thepicked-up food product between the pick-up and deposition steps.

41. A method according to claim 39 or claim 40, which carries out at least three pick-and-place cycles per minute by the pick-and-place unit.

42. A method according to any one of claims 23 to 41, wherein the products are foodslices, optionally potato slices.

43. A method according to any one of claims 23 to 42, further comprising microwavecooking the products on the conveyor downstream, along the conveyor, of the pick-and-place unit.

44. A method of manufacturing potato chips including the method of any one ofclaims 23 to 43.