WO2016193081A1

WO2016193081A1 - Manufacture of snack foods

Info

Publication number: WO2016193081A1
Application number: PCT/EP2016/061748
Authority: WO
Inventors: Bob ABBAS; Peter Herring; Dan MAYNARD
Original assignee: Frito-Lay Trading Company Gmbh
Priority date: 2015-05-29
Filing date: 2016-05-25
Publication date: 2016-12-08
Also published as: GB201509286D0; GB2539179B; GB2539179A

Abstract

An apparatus for controlling product flow in the manufacture of snack foods, the apparatus including a conveyor for conveying food products from an upstream location to a downstream location, a first imaging system adapted to image a first distribution of the food products on the conveyor at the upstream location and to produce first data related to the first distribution, a processor coupled to the imaging system, the processor including a mapping unit for processing the first data to provide second data related to coordinates of the imaged products on the conveyor, a control unit coupled to the processor and adapted to output a control signal based on the second data, and a pick-and-place unit connected to the control unit and being controllable by the control signal, the pick-and-place unit being adapted to move one or more selected products on the conveyor so as to modify the first distribution of products on the conveyor to form a second distribution of the food products on the conveyor at the downstream location. Also disclosed is a method of controlling product flow in the manufacture of snack foods.

Description

MANUFACTURE OF SNACK FOODS

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

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

There is a general desire among snack food manufacturers, consumers and regulatory authorities for healthier food products. In the snack food industry, this has led to a desire for lower fat products. However, even though there may be a general consumer awareness of the benefits of eating lower fat versions of, or alternatives to, existing snack food products, the consumer generally requires the product to have desirable attributes such as texture and flavour. Even if a snack food product is produced which has high nutritional attributes, unless it also has the texture and flavour required by the consumer, the product would not successfully provide the consumer with an acceptable product to replace previous, less healthy snack food products. The challenge among snack food manufacturers is to produce nutritional or more healthy foods which provide the consumer with an improved taste and sensation experience, or at the very least do not compromise on taste and sensation as compared to the consumer's expectation for the particular product or class of products purchased.

There are in the market so-called lower oil snack food products, including potato chips and other products. Some of these processes are produced by modified frying processes using different frying temperatures than those conventionally employed, or cooking processes other than frying, such as baking. Some of these products produce snack foods with low oil, 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 the organoleptic properties, in combination with the visual appearance, of a potato chip.

WO-A-2008/01 1489 and WG-A-2009/091674 in the name of Frito-lay Trading Company GmbH disclose processes for making a healthy snack food. In those processes, a snack food is made so as to have an appearance arid taste similar to conventional fried snack products, such as a potato chip. The potato slices are subjected to a sequence of steps which 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 slices which have been preconditioned, for example by being treated in oil. Prior to the microwave cooking process, the potato slices are flexible, and have a typical thickness of 1 to 2.5 mm. The microwave cooking rapidly, or explosively, dehydrates the potato slices to achieve low moisture content in a drying step which simulates the conventional frying dehydration rate. It is disclosed that the microwave drying may comprise linear belt or rotary microwave drying. The rapid microwave dehydration rigidifies the cooked potato slices, 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 product flow tends to have an uneven or non-uniform slice distribution. Such a distribution results from the original potato feed or from the preceding treatment steps, which may cause the input product flow to come in surges or to be unevenly or non-uniformly distributed across the width of the conveyor. In particular, there may be overlapping or clumping together of potato slices prior to the microwave treatment which explosively dehydrates the potato slices. Such an uneven or non-uniform product distribution for the microwave input changes the amount of product in the conveyor and therefore correspondingly changes the load in the microwave cavity, for example the load changing significantly over a period of less than one minute. The load represents the total amount of water at any given time within the microwave cavity which is energised by the microwave during the microwave treatment of the products within the cavity. Such a variation of the load within the microwave cavity can cause a number of problems, for example uneven drying of the potato slices to form the potato chips, insufficient drying, and/or excess microwave energy within the cavity for the current load, causing arcing.

One particular problem with the manufacture of potato chips from potato slices is that it is difficult to provide a completely uniform flow. Also, the slices vary in shape and dimension, so that the cooked slices exhibit the random three-dimensional shapes of potato chips.

WO-A-2012/104218 discloses an apparatus for detecting products on a conveyor. An imaging system images products on the conveyor. A contouring step estimates a centre of an imaged product and a reverse contouring step estimates an outline of the imaged product, which can provide an indication of product overlap which cannot easily be imaged using a direct imaging process. The estimated degree o overlap is indirectly determined from the input image data. The resultant estimated degree of overlap, or a parameter calculated from the estimated degree of overlap such as mass flow rate, can be used as an input parameter for controlling the manufacturing line. For example, the mass flow rate can be used as an input parameter for controlling a variable such as microwave energy 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 explosive dehydration step discussed above, which not only have low oil but also have the combination of flavour, organoleptic properties and shelf life in a non-fried potato chip which 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 snack foods, 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 of potato chips, more particularly low oil potato chips, prior to a microwave cooking which can explosively dehydrate the potato slices or a drying treatment, for example using microwave energy. There is furthermore still a need for an apparatus and method for efficiently and reliably manufacturing, in a cost effective manner, a low fat potato chip which has not been fried but has organoleptic properties, in combination with the visual appearance, of a conventional fried potato chip.

The present invention accordingly provides an apparatus for controlling product flow in the manufacture of snack foods, the apparatus including a conveyor for conveying food products from an upstream location to a downstream location, a first imaging system adapted to image a first distribution of the food products on the conveyor at the upstream location and to produce first data related to the first distribution, a processor coupled to the imaging system, the processor including a mapping unit for processing the first data to provide second data related to coordinates of the imaged products on the conveyor, a control unit coupled to the processor and adapted to output a control signal based on the second data, and a pick-and-place unit connected to the control unit and being controllable by the control signal, the pick-and-place unit being adapted to move one or more selected products on the conveyor so as to modify the first distribution of products on the conveyor to form a second distribution of the food products on the conveyor at the downstream location.

The present invention further provides a method of controlling product flow in the manufacture 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 upstream location to produce first data related to the first distribution;

c. processing the first data to provide second data related to coordinates of the imaged products on the conveyor; and

d. outputting a control signal based on the second data to control a pick-and-place unit to move one or more selected products on the conveyor so as to modify the first distribution of products on the conveyor to form a second distribution of the food products on the conveyor at the downstream location.

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 the manufacture 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 the apparatus of Figure 1.

An embodiment of an apparatus for, and method of, controlling product flow, in particular potato 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 present invention 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 other process during manufacture of the snack food. Also, although the embodiment relates to potato 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 horizontal orientation, or being slightly inclined to the horizontal, is provided for conveying food products, in this embodiment potato slices 6, from an upstream location to a downstream location. An inlet end 4 of the conveyor 2 communicates with an upstream processing station for the potato slices 6. The conveyor 2 carries a succession of the potato slices 6 on its upper surface 8. The conveyor 2 is employed to feed the potato slices 6 to a microwave apparatus 10 for cooking and explosively dehydrating the potato slices 6 in order to produce potato chips, which have not been fried, as for a conventional potato chip.

The upper surface 8 of the conveyor 2, for example an endless belt of the conveyor 2, is selected 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 upper surface 8 may be dark blue in colour.

The potato slices 6 have been randomly delivered onto the conveyor 2 but with a product flow along and across the conveyor 2 so as to provide a substantially constant product flow, but with less than 100 % uniformity and some slice overlap. The potato slices 6 are typically delivered onto the conveyor 2 in a slice distribution so as to have no more than about 50% of the slices overlapping with an adjacent slice, with any such overlap to be no more than about 50% of the slice dimension, and with no more than two slices 6 being stacked one upon the other on the conveyor 2. This substantially provides a monolayer of potato slices 6 across the length and width of the conveyor 2, but with some overlapping and 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 readily able to overlap each other. This means that the flow rate of the potato slices 6 along the manufacturing 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 less than one minute, with potential deterioration in product quality and/or uniformity.

A first imaging system 1 1 , comprising a camera 12, is provided to image a first distribution 13 of the potato slices 6 on the conveyor 2. The camera 12 produces first data related to the first distribution 13.

As the potato slices 6 are carried on the upper surface of the primary conveyor 2, they are imaged by the camera 12. The camera 12 continuously or continually images the potato slices 6 conveyed thereunder. The field of view of the camera 12 may be applied to all or only a portion of the width of the conveyor 2. The high visual contrast upper surface 8 of the conveyor 2, optionally in combination with overhead illumination of the field of view of the camera 12 by one or more lamps 14, enables the camera 12 readily to be able to image the potato slices 6. The camera 12 is a digital camera which takes individual images successively, or is a video camera which takes a continuous film, of the product flow thereunder. Typically, the imaging system, including the camera 12 and the lamps 14 when present, and including the upper surface 8 of the conveyor 2, are configured to operate using visible radiation, such as white light.

A processor 16 is coupled to the camera 12, In particular, the camera 12 is connected, by a wired or wireless connection 15, to the processor 16 coupled to a display unit 18. The processor 16 includes a mapping unit 17 for processing the first data to provide second data 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 the second data. The processor 16 has a signal output 20, which may be wired or wireless, and is transmitted to the control unit 22.

The processor 16 is programmed to process the data from the camera 12 representing the imaged potato slices 6 and to determine a parameter indicative of the overlap of plural potato slices 6 imaged by the camera 12. In particular, the processor 16 includes an overlap analysis module 19 to determine potato slice overlap from the first data. Specifically, the overlap analysis module 19 analyses a plurality of clusters 25 of overlapping potato slices 6. The second data is produced from the overlap analysis module 19 and includes as a parameter a first function relating to an overlap of plural imaged potato slices 6.

A pick-and-place unit 30 is connected to the control unit 22 and is controllable by the control signal. The pick-and-place unit 30 is upstream, along the conveyor 2, of the microwave apparatus 10. The pick-and-place unit 30 is adapted to move one or more selected potato slices 6 on the conveyor 2 so as to modify the first distribution 13 of potato slices 6 on the conveyor 2 to form a second distribution 33 of the potato slices 6 on the conveyor 2 at the downstream location.

The control unit 22 includes an overlap control module 24. A control signal is produced from the overlap control module 24 and includes a second function, derived from the first function, to cause the pick-and-place unit 30 to pick up at least one overlapping potato slice 6 and subsequently place the potato slice(s) 6 in a non-overlapping configuration on the conveyor 2. The overlap control module 24 causes the pick-and-place unit 30 to operate on a selected number of clusters 25 within a given time period. The overlap control module can calculate a maximum number of clusters 25 that can be operated on by the pick-and-place unit 30 within a preset time period. The number of clusters 25 is reduced by the operation of the pick-and-place unit 30.

A second imaging system 40 is downstream along the conveyor 2 of the first imaging system and the pick-and-place unit 30. As for the first imaging system 1 1, the second imaging system 40 may comprise a camera 42 and one or more lamps 44. The second imaging system 40 is adapted to image the second, modified, distribution 33 of the potato slices 6 on the conveyor 2 formed by operation of the pick-and-place unit 30. The second imaging 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 is adapted to process the third data to provide fourth data related to coordinates of the second, 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 coordinates of the second, modified, distribution 33 in the fourth data against a preset distribution of the potato slices 6 on the conveyor 2.

A feedback unit 50, typically in the processor 16, provides to the control unit 22 a feedback signal related to the fourth data. The feedback signal modifies the control signal and controls the pick-and-place unit 30 so as to adapt the modified distribution 46 towards the preset distribution.

In the pick-and-place unit 30 a movement mechanism 50 is connected to a head member 52. The movement mechanism 0 is controllably movable, in response to the control signal, 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 54 and has an opening 56 in the lower engaging surface 54. A fluid conduit 58 is connected to the opening 56. The fluid conduit 58 is connected to a source of gas, typically compressed air. The opening 56 is shaped, for example substantially conically shaped, to provide a venturi effect, thereby to provide a Bernoulli grip effect on an underlying product such as a potato slice 6, when gas is emitted from the opening 56. The opening comprises a central outlet 60 surrounded by an annular recess 62.

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

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

In contrast, the sensor 64 emits a negative sensor signal, or no sensor signal, to the control unit 22 when the sensor detects the absence of a food product adjacent to the lower engaging surface 66. The control unit 22 is adapted not to proceed with a pick-and-place operation 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. Each cycle 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 in response to the second data, (iii) 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 second location, different from the first location, above the conveyor 2 in response to the second data, the second location including a portion of the conveyor surface which is free of potato slices 6, and (v) depositing the potato slice 6 at the second location on the portion of the conveyor surface.

The pick-and-place unit 30 is adapted to sense the presence or absence of a food product picked up by the pick-and-place unit 30 and to abort the respective pick-and-place cycle in the event of a change of state of the presence or absence of the picked-up food product between the pick-up and deposition steps. For example, if the potato slice 6 falls off the head 52, the pick-and-place cycle is aborted, and the head 52 is moved to pick up a potato slice 6 at another cluster 25. Typically, the apparatus is adapted to carry out at least three pick-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 and the processor 16 determines an outline of the imaged potato slice 6. The outline may be approximate, for example a pixellated image. The processor 16 converts an image signal from 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. The pixellated image may have an outline which suggests that the imaged product is likely to be two products in an overlapping configuration. The processor 16 then applies an algorithm 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 example the contoured outline is produced by reducing the outline by one or more pixels around the periphery of the outline. This contoured outline is a reduced dimension outline which is similar to providing a contour line on a map. Such a contouring step is carried out iteratively a number of times to produce a series of progressively smaller outlines. The different outlines may be displayed as having different respective colours. This contouring is carried out in the processor 16 which operates on the data to reduce the first outline to produce data representing a second outline of at least one central region of the at least one imaged product. The number of iterative steps, which may be predetermined, is selected so that, for the particular product dimensions and the contouring dimensions between adjacent outlines, the last and smallest outline is statistically likely to indicate the existence of any product overlap. The smallest outline comprises two such separate and distinct outlines, each of which is substantially centred on a respective one of two overlapping products. The imaging and processing system has indirectly determined the existence of a product overlap, which could not be directly imaged by the imaging system including the camera 12. Subsequently, a series of iterative reverse contouring steps is carried out on each of the outlines. In such a reverse contouring step, an algorithm to the outlines which increases the dimensions of each respective outline substantially equally around the entire periphery of the outline is used to produce a first enlarged contoured outline. Then the subsequent reverse contouring steps are carried out on each outline with the same number of reverse contouring steps to produce an enlarged outline as the number of initial contouring steps to produce a reduced outline. By applying the reverse contouring to each of two initial outlines, the final reverse contouring step provides two overlapped outlines each of which represents an image of a respective estimated overlapped product. Such reverse contouring is carried out by the processor 16 which is operable on the data for increasing the second outline of the or each central region to produce 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 the corresponding two products to be calculated. Individual products, not in an overlapping configuration, may also readily have their area determined, to enable the respective product mass to be calculated.

The use of such an imaging and data processing system enables on-line real-time determination of the flow rate, typically expressed as total mass, of products, such as potato slices 6, passing along the manufacturing line, for example through the microwave apparatus 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 to control a variable such as the microwave energy output of a microwave apparatus. For example, the signal output 20 of the processor 16 sends a control signal to the control apparatus 22 which in turn sends a control command, by a wired or wirelesss connection to the microwave apparatus 10 which modulates the microwave energy emitted in the microwave cavity dependent upon the immediately upstream product flow imaged by the camera 12. This correlates the microwave energy to the mass flow rate of the products. If desired, a delay may be introduced for a feed- forward control. Alternatively, the control signal may control an upstream operation. For example, if the proportion of overlapping slices is determined to be above a desired threshold, or the degree of overlap or number of slices in any stacked overlap is determined to be above a desired threshold, or the overlap proportion is so low that the product flow rate can be increased without significantly increasing product overlap, the control signal may be employed to modify the product distribution in upstream processing, for example deposition of the products onto the conveyor.

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

Claims

CLAIMS:

1. An apparatus for controlling product flow in the manufacture of snack foods, the apparatus including a conveyor for conveying food products from an upstream location to a downstream location, a first imaging system adapted to image a first distribution of the food products on the conveyor at the upstream location and to produce first data related to the first distribution, a processor coupled to the imaging system, the processor including a mapping unit for processing the first data to provide second data related to coordinates of the imaged products on the conveyor, a control unit coupled to the processor and adapted to output a control signal based on the second data, and a pick-and-place unit connected to the control unit and being controllable by the control signal, the pick-and-place unit being adapted to move one or more selected products on the conveyor so as to modify the first distribution of products on the conveyor to form a second distribution of the food products on the conveyor at the downstream location.

2. An apparatus according to claim 1, wherein the processor includes an overlap analysis module to determine product overlap from the first data and to produce the second data, the second data including as a parameter a first function relating to an overlap of plural imaged products, and the control unit includes an overlap control module to produce the control signal, the control signal including a second function, derived from the first function, to cause the pick-and-place unit to pick up at least one overlapping first product and subsequently place the first product in a non-overlapping configuration on the conveyor.

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

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

5. An apparatus according to any foregoing claim, further including a second imaging 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 distribution of the food products on the conveyor formed by operation of the pick-and-place unit, and to produce third data related to the second distribution, the processor being coupled to the second imaging system and the mapping unit being adapted to process the third data to provide fourth data related to coordinates of the second distribution of the imaged products on the conveyor.

6. An apparatus according to claim 5, further including a comparator for comparing the coordinates of the second distribution in the fourth data against a preset distribution of the products on the conveyor.

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

8. An apparatus according to any foregoing claim, wherein the pick-and-place unit comprises a head member defining a lower engaging surface and having an opening in the lower engaging surface, a fluid conduit connected to the opening, the fluid conduit being connectable to a source of gas, the opening being shaped to provide a venturi effect when gas is emitted from the opening so that the head member provides a Bernoulli grip on a food product thereunder, and a movement mechanism connected to the head member and adapted to be control lably movable, in response to the control signal, over at least a portion of a surface area of the conveyor.

9. An apparatus according to claim 8, wherein the opening comprises a central outlet surrounded by an annular recess.

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

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

12. An apparatus according to claim 10 or claim 1 1 wherein a lower surface of the sensor is aligned with the lower engaging surface.

13. An apparatus according to any one of claims 10 to 32 wherein the sensor comprises a capacitance sensor.

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

15. An apparatus according to any one of claims 10 to 14 wherein the sensor is connected to the control unit and is adapted to emit a sensor signal to the control unit to control the operation of the pick-and-place-unit.

16. An apparatus according to claim 15 wherein the sensor is adapted to emit a positive sensor signal to the control unit when the sensor detects the presence of a food product adjacent to the lower engaging surface and the control unit is adapted to proceed with a pick-and-place operation upon receipt of the positive sensor signal.

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

18. An apparatus according to any foregoing claim, wherein the pick-and-place unit is adapted to carry out sequential pick-and-place cycles, each cycle comprising receipt of a control signal from the control unit, movement of the pick-and-place unit to a first location above the conveyor in response to the second data, picking up of a food product at the first location, movement of 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, 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 of the conveyor surface.

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

20. An apparatus according to claim 1 8 or claim 19, which is adapted to carry out at least three pick-and-place cycles per minute by the pick-and-place unit.

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

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

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

24. A method of controlling product flow in the manufacture of snack foods, the method comprising the steps of:

25. A method according to claim 24, further comprising the step of: determining product overlap from the first data; and wherein the second data includes 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 cause the pick-and-place unit to pick up at least one overlapping first product and subsequently place the first product in a non-overlapping configuration on the conveyor.

26. A method according to claim 25, further comprising the step of: analysing a plurality of clusters of overlapping first products and causing the pick-and-place unit to operate on a selected number of clusters within a given time period.

27. A method according to claim 26, further comprising the step of: calculating a maximum number of clusters that can be operated on by the pick-and-place unit within a preset time period.

28. A method according to any one of claims 24 to 27, further comprising the steps of: imaging, downstream along the conveyor of the imaging step a, the second distribution of the food products on the conveyor formed by operation o the pick-and-place unit to produce third data related to the second distribution, and processing the third data to provide fourth data related to coordinates of the second distribution of the imaged products on the conveyor.

29. A method according to claim 28, further comprising the step of: comparing the coordinates of the second distribution in the fourth data against a preset distribution of the products on the conveyor.

30. A method according to claim 29, further comprising the step of: providing a feedback 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.

31. A method according to any one of claims 24 to 30, wherein the pick-and-place unit comprises a head member defining a lower engaging surface and having an opening in the lower engaging surface, a fluid conduit connected to the opening, the fluid conduit being connectable to a source of gas, the opening being shaped to provide a venturi effect when gas is emitted from the opening so that the head member provides a Bernoulli grip on a food 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 a surface area of the conveyor.

32. A method according to claim 31 , wherein the opening comprises a central outlet surrounded by an annular recess.

33. A method according to claim 30 or claim 31 , wherein the pick-and-place unit comprises a sensor located at the lower engaging surface which detects the presence of a food product adjacent to the lower engaging surface.

34. A method according to claim 33 wherein the sensor is located at the opening.

35. A method according to claim 33 or claim 34 wherein a lower surface of the sensor is aligned with the lower engaging surface.

36. A method according to any one of claims 33 to 35 wherein the sensor comprises a capacitance sensor.

37. A method according to claim 36 wherein the capacitance sensor is calibrated to detect the presence of a food product within a sensing range of up to 4 mm.

38. A method according to any one of claims 33 to 37 wherein the sensor emits a sensor signal to control the operation of the pick-and-place-unit.

39. A method according to claim 38 wherein the sensor emits a positive sensor signal when the sensor detects the presence of a food product adjacent to the lower engaging surface to cause a pick-and-place operation by the pick-and-place-unit to proceed.

40. A method according to claim 38 or claim 39 wherein the sensor is adapted to emit a negative sensor signal, or no sensor signal, when the sensor detects the absence of a food product adjacent to the lower engaging surface to cause a pick-and-place operation not to be proceeded with.

41. A method according to any one of claims 24 to 39, wherein the pick-and-place unit carries out sequential pick-and-place cycles, each cycle comprising receipt of a control signal, movement of the pick-and-place unit to a first location above the conveyor in response to the second data, picking up of a food product at the first location, movement of 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, 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 of the conveyor surface.

42. A method according to claim 41 , wherein the pick-and-place unit senses the presence or absence of a food product picked up by the conveyor aborts the respective pick-and-place cycle in the event of a change of state of the presence or absence of the picked-up food product between the pick-up and deposition steps.

43. A method according to claim 41 or claim 42, which carries out at least three pick- and-place cycles per minute by the pick-and-place unit.

44. A method according to any one of claims 24 to 43, wherein the products are food slices, optionally potato slices.

45. A method according to any one of claims 24 to 44, further comprising microwave cooking the products on the conveyor downstream, along the conveyor, of the pick-and- place unit.

46. A method of manufacturing potato chips including the method of any one of claims 24 to 45.