GB2482251A

GB2482251A - Manufacture of curved low-oil potato chips

Info

Publication number: GB2482251A
Application number: GB1114982.0A
Authority: GB
Inventors: Oliver Herbert; Richard Andrew Bailey; Barbara Louise Warburg; Greg Paul Hilliard; Paul David Worth
Original assignee: Frito Lay Trading Co GmbH
Current assignee: Frito Lay Trading Co GmbH
Priority date: 2011-01-31
Filing date: 2011-01-31
Publication date: 2012-01-25
Anticipated expiration: 2031-01-31
Also published as: GB201114982D0; GB2482251B

Abstract

An apparatus for manufacturing curved, low-oil potato chips comprises a microwave oven (4) having a longitudinal cavity (6) forming a microwave chamber and a belt conveyor (24) extending through the microwave chamber. The conveyor has a continuously undulating surface with a maximum height of the undulations of from 5 to 15 mm and a pitch between adjacent undulations of from 35 to 75 mm. The conveyor preferably comprises a plurality of links 50 arranged in a plurality of rows, each row having a leading edge 62 and a trailing edge 64, each of which edges is pivotally connected to a respective adjacent row. Each row has a continuously convex arcuate upper surface for supporting slices of potato. The leading edge and trailing edge of adjacent rows intersect to form an intersection 66 at the intersecting upper surfaces. In a further embodiment, a conveyor surface is formed from a plurality of links wherein some of the intersections between links include a stop surface (90) to prevent potato slices from sliding past the intersection.

Description

MANUFACTURE OF LOW OIL POTATO CHIP

This invention relates to an apparatus and method for the manufacture of a low oil potato chip.

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 Swt%, 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-2OO8/O 489 and WO-A-2009/091674 in the name of Frito-Lay Trading Company GmbH disclose processes for making a healthy snack food. Tn those processes, a snack food is made so as to have an appearance and 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 flaccid, and have a typical thickness of 1 to 2.5 mm. The microwave cooking rapidly dehydrates the potato slices to achieve low moisture content in a drying step which simulates the conventional frying dehydration rate. The rapid microwave dehydration rigidifies the cooked potato slices, so that they have a crispness resembling that of typical fried potato chips, It is disclosed that the microwave drying may comprise linear belt or rotary microwave drying. One particular problem with linear belt microwave drying is that the resultant cooked potato slices are planar and resemble biscuits. These slices do not exhibit the random three-dimensional shapes of potato chips. In order to solve this problem, rotary microwave drying is proposed. These specifications also disclose the use of a catenary belt which is oriented around a longitudinally extending curved path, so that the potato slices are tumbled in the curved region of the path by longitudinal movement of the belt.

However, such a rotary microwave apparatus or catenary belt drive is complicated and expensive, and it is difficult to control the tumbling potato slices so that they do not overlap and inadvertently fuse together, cause arcing or ignite during the rapid dehydration process.

US-A-5,292,540 discloses the production of low fat potato chips by heating potato slices on a stationary plate in a microwave oven. This process would not produce commercially acceptable individual random three-dimensionally shaped potato chips. If the slices overlap before the microwave cooking, the slices would fuse together, cause arcing or ignite. If the slices do not overlap they would assume a planar regular shape and orientation resembling a biscuit.

US-A-5,298,707 discloses the production of fat free potato chips by cooking the potato slices in a high intensity microwave field, The slices are supported on a belt which passes through a plurality of successive apertures in a meander waveguide for the microwave energy. The belt comprises a plurality of links having an open lattice structure coupled by pivotally mounted pins, the open lattice structure being formed of a plurality of vanes intersected by a plurality of cross-pieces. The vanes each comprise a first surface having a hump for imparting a curved shape to the raw food slices. The hump is centrally disposed along the link and has an arcuate shape with a radius of curvature of approximately 12.7 mm (one half of an inch), with the link having a height of about approximately 35 mm (one and three-eighths of an inch). The shape and dimensions of the hump impart a corresponding shape and dimensions to the potato chips. In the disclosed process, prior to the microwave cooking step the potato slices are subjected to heated jets of air from air knives to reduce surface moisture.

However, this belt structure is not suitable for conveying raw potato slices which have a slippery outer surface, such as when coated with oil, because the raw potato slices tend to slide and fold over onto each other, thereby increasing the risk of arcing, potential ignition, and slice fusion during the microwave cooking step. Moreover, the use of heated jets of air to reduce surface moisture prior to the microwave cooking step causes the surface of the potato slices to case harden by crystallisation of starch, which forms a moisture barrier to subsequent bulk dehydration using microwave radiation.

There is accordingly 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 manufacturing potato chips from potato slices, the apparatus comprising an elongate microwave oven having a longitudinal cavity forming a microwave chamber, and an elongate longitudinal belt conveyor having a portion extending through the microwave chamber for supporting potato slices conveyed through the microwave chamber, the conveyor comprising a plurality of links arranged in a plurality of rows, each row transversely extending across the width of the endless belt conveyor, each row having a leading edge and a trailing edge, each of which edges is pivotally connected to a respective adjacent row, each row having a continuously convex arcuate upper surface, the leading edge and trailing edge of adjacent rows intersecting to form a transversely extending intersection at the intersecting upper surfaces, and between adjacent intersections the upper surface of each respective row defines a slice supporting surface which is entirely convex, The present invention further provides an apparatus for manufacturing potato chips from potato slices, the apparatus comprising an elongate microwave oven having a longitudinal cavity forming a microwave chamber, and an elongate longitudinal belt conveyor having a portion extending through the microwave chamber for supporting potato slices conveyed through the microwave chamber, the conveyor having a continuously undulating surface with a maximum height of the undulations of from 5 to 15 mm and a pitch between adjacent undulations of from 35 to 75 mm.

The present invention further provides an apparatus for manufacturing potato chips from potato slices, the apparatus comprising an elongate microwave oven having a longitudinal cavity forming a microwave chamber, and an elongate longitudinal belt conveyor having a portion extending through the microwave chamber for supporting potato slices conveyed on a conveyor surface through the microwave chamber, the conveyor comprising a plurality of links, the conveyor surface having a plurality of intersections of adjacent links, at least some of the intersections including a stop surface for preventing a potato slice from sliding in a first longitudinal direction past the intersection.

The present invention further provides a method of manufacturing a low oil potato chip, the method comprising the steps of: (a) providing a plurality of potato slices, each slice having been pretreated in oil; (b) randomly feeding the potato slices onto the upper surface of an elongate longitudinal belt conveyor, the conveyor comprising a plurality of links arranged in a plurality of rows, each row transversely extending across the width of the endless belt conveyor, each row having a leading edge and a trailing edge, each of which edges is pivotally connected to a respective adjacent row, each row having a continuously convex arcuate upper surface, the leading edge and trailing edge of adjacent rows intersecting to form a transversely extending intersection at the intersecting upper surfaces, and between adjacent intersections the upper surface of each respective row defines a slice supporting surface which is entirely convex; (c) conveying the potato slices on the belt through a microwave chamber; and (d) microwave dehydrating the potato slices to form potato chips.

The present invention further provides a method of manufacturing a low oil potato chip, the method comprising the steps of: (a) providing a plurality of potato slices, each slice having been pretreated in oil; (b) randomly feeding the potato slices onto the upper surface of an elongate longitudinal belt conveyor, the conveyor having a continuously undulating surface with a maximum height of the undulations of from 5 to 15 mm and a pitch between adjacent undulations of from 35 to 75 mm; (c) conveying the potato slices on the belt through a microwave chamber; and (d) microwave dehydrating the potato slices to form potato chips.

The present invention further provides a method of manufacturing a low oil potato chip, the method comprising the steps of: (a) providing a plurality of potato slices, each slice having been pretreated in oil; (b) randomly feeding the potato slices onto the upper surface of an elongate longitudinal belt conveyor, the conveyor comprising a plurality of links, the conveyor surface having a plurality of intersections of adjacent links, at least some of the intersections including a stop surface for preventing a potato slice from sliding in a first longitudinal direction past the intersection; (c) conveying the potato slices on the belt through a microwave chamber; and (d) microwave dehydrating the potato slices to form potato chips.

Preferred features are defined in the dependent claims, Embodiments 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 cross-section through an apparatus for microwave cooking of potato slices, the apparatus incorporating a conveyor belt, according to a first embodiment of the present invention; Figure 2 is a schematic perspective view of a portion of the conveyor belt of Figure 1; Figure 3 is an enlarged schematic side view of a series of links of the conveyor belt of Figure 1;and Figure 4 is an enlarged schematic plan view of a link of the conveyor belt of Figure 1 mounted on pivotable support rods; Figure 5 is an enlarged schematic side view of a series of links of a conveyor belt according to a second embodiment of the present invention; Figure 6 is a schematic cross-section through an apparatus for microwave cooking of potato slices, the apparatus incorporating a conveyor belt, according to a third embodiment of the present invention; and Figure 7 is an enlarged schematic side view of a series of links of a conveyor belt according to a fourth embodiment of the present invention; and A first embodiment of an apparatus for microwave cooking of potato slices to form potato chips according to one aspect of the present invention is illustrated in Figures 1 to 4.

The apparatus 2 comprises an elongate microwave oven 4 having a central longitudinal cavity 6 defined between upper and lower parts 8, 10 of the microwave oven 4. The upper part 8 includes the microwave generator and associated waveguide(s) 12. Choke pins 16 are provided at an inlet 1 8 and an outlet 20 of the cavity 6, the choke pins 16 depending downwardly from the upper part 8. The choke pins 16 are formed as an array and are mutually spaced, as known to those skilled in the art, so as, together with the lower part 10, to prevent leakage of microwave radiation from the central microwave chamber 22 of the microwave oven 4.

An elongate longitudinally-extending endless belt conveyor 24 has upper and lower portions 26, 28 separated by a pair of rotatable cylinders 30, 32 located at respective horizontally separated inlet and outlet ends 34, 36 of the endless belt conveyor 24. Other belt supports and rollers (not illustrated) are provided. The rotatable cylinders 30, 32 are provided with toothed sprockets (not shown) which couple to the endless belt conveyor 24. At least one of the rotatable cylinders 30, 32 is rotationally driven to cause rotation of the endless belt conveyor 24 and thereby translation of the upper portion 26 through the central microwave chamber 22. At the inlet end 34 a feed conveyor 38 is provided which feeds potato slices 40 onto the endless belt conveyor 24, and at the outlet end 36 a product conveyor 42 is provided which removes cooked potato chips 44, formed from the potato slices 40, from the endless belt conveyor 24.

The conveyor 24 has a continuously undulating outer surface, which constitutes the upper surface supporting and three-dimensionally shaping the potato slices 40 which are conveyed through the microwave oven 4.

As shown in detail in Figures 2 to 4, the endless belt conveyor 24 comprises a plurality of links 50 arranged in a plurality of adjacent rows 52 transversely extending across the width of the endless belt conveyor 24. Each link 50 comprises a moulded body of a polymer such as polypropylene. Each link 50 is formed of a plurality of transversely spaced longitudinally extending vanes 54. The upper surfaces 56 of the vanes 54 are aligned and together define a continuously curved convex slice supporting upper surface 58 of the link 50. The vanes 54 of each link 50 are connected together, for example as an integral injection moulding, by connector pieces 55 extending across the width of the link and typically located beneath the upper surfaces 56 of the vanes 54. In each row 52 the links 50 are transversely aligned so that the row 52 presents an upper continuously convex arcuate slice supporting surface 60 having a leading edge 62 and a trailing edge 64, each edge 62, 64 extending transversely across the endless belt conveyor 24. The leading edge 62 and trailing edge 64 of the upper surfaces of adjacent rows 52 intersect to form a transversely extending intersection 66 at the intersecting upper surfaces 60.

In the region between adjacent intersections 66, the upper convex surface 60 of a respective row 52 is entirely convex, with a substantially constant radius of curvature. At the intersection 66 the tangents of the adjacent convex surfaces 54 form an obtuse angle ci (i.e. an angle of greater than 900 but less than 1 80°), the angle ci. typically ranging from 95 to 135°.

The links 50 are assembled together with a plurality of transversely extending pivotable support rods 68 to form the belt conveyor 24. Each pivotable support rod 68 passes through a trailing end 70 of a leading row 52 and a leading end 72 of a trailing row 52.

The belt conveyor 24 can therefore be bent arcuately around the rotatable cylinders 30, 32.

In accordance with the invention, the upper surface of the belt conveyor 24 is shaped and dimensioned to provide the technical effect of imparting a random shape to the resultant cooked potato chips 44 formed from the initially flexible potato slices 40, and also to minimise the incidence of oil-coated potato slices 40, which have a rather slippery surface, inadvertently slipping on the belt 24 during transport through the microwave oven 4 which could result in inadvertent slice overlap.

Each potato slice 40 has been at least partly pre-treated in oil, typically vegetable oil such as sunflower oil, conventionally used for manufacturing potato chips. The oil content is from 5 to 20 wt% oil based on the weight of the cooked potato chip 2. Typically, the potato chip 2 comprises from 10 to 17.5 wt% oil, more typically about 15 wt% oil, based on the weight of the cooked potato chip 2, The oil is employed to provide the required organoleptic properties to the resultant potato chip, which has been cooked by the combination of the preliminary oil treating step and the subsequent microwave cooking step.

The feed conveyor 38 randomly feeds potato slices 40 onto the endless belt conveyor 24 so that there is substantially no or minimum overlap between the potato slices 40, as shown in Figure 2 which shows the resultant cooked potato chips 44 on the endless belt conveyor 24 exiting from the central microwave chamber 22. During the microwave cooking step in the central microwave chamber 22, such minimum overlap minirnises the possibility of slice fusion, arcing or ignition.

The upper convex surface 60 of a respective row 52 has a diameter of curvature of, for example, from 70 to 100 mm, typically from 75 to 95 mm, more typically from 80 to 90 mm. The longitudinal pitch between adjacent rows 52, namely the distance between the leading and trailing pivot axes of the pivotable support rods 68, is, for example, from 35 to mm, typically from 45 to 55 mm, more typically about 50 mm, The maximum height of the arcuate upper convex surface 60 above the pivot axes of each row 52 is, for example, from 15 to 50 mm, optionally from 15 to 25 mm, typically from 17 to 21 mm, more typically about 19 mm. The maximum height of the arcuate upper convex surface 60 above the intersections 66 is, for example, from 5 to 50 mm, optionally from 5 to 15 mm, typically from 7 to 10 mm. Typically, the rotatable cylinders 30, 32 have a diameter of from 75 to 125 mm, typically about 100 mm.

Accordingly, the continuously undulating surface of the belt conveyor 24 typically has a maximum height of the undulations of from 5 to 15 mm and a pitch between adjacent undulations of from 35 to 75 mm.

The continuously convex curvature of the adjacent rows 52, with a large radius curvature, coupled with the selected pitch length and the height of the upper convex surface 60 to provide an obtuse angle at the upper surface intersections provides that when a potato slice is deposited on the endless belt conveyor 24 the potato slice 40 assumes the shape of a typical conventionally fried potato chip.

The curvature of the upper surface is sufficiently high to introduce a smooth curvature into the potato slice and sufficiently low to prevent inadvertent slice slippage or folding over.

The relatively gentle undulation, with smoothly curved low convex "hills" separated by shallow and narrow "valleys" provides a corresponding curvature to the potato chips 44, and avoids inadvertent slice deformation or movement which could cause inadvertent slice overlap, with consequential problems of slice fusion, arcing or ignition.

The pitch length between the adjacent rows 52 is selected so that a potato slice 40 with typical length and/or width dimensions for potato chips, namely a lengthlwidth typically ranging from 40 to 60 mm, tends to bridge adjacent rows 52. This provides that the relatively shallow curvature of each row provides a positive curvature, i.e. a curvature in one rotational sense, and if the slice bridges an intersection the relatively shallow intersection provides a negative curvature, i.e. a curvature in the opposite rotational sense, and if the slice extends onto the adjacent row than the adjacent row imparts an additional positive curvature onto that part of the slice.

A second embodiment of a belt structure for use in an apparatus for microwave cooking of potato slices to form potato chips according to the present invention is illustrated in Figure 5. The endless belt conveyor 70 has the same general structure as the endless belt conveyor 24 of Figures ito 4 except for the shape of the slice supporting upper surface 72 of the links 74.

As shown in Figure 5, the endless belt conveyor 70 comprises a plurality of links 74 arranged in a plurality of adjacent rows 76 transversely extending across the width of the endless belt conveyor 70. Again, each link 74 comprises a moulded body of a polymer such as polypropylene and is formed of a plurality of transversely spaced longitudinally extending vanes, with the upper surfaces of the vanes being aligned and together defining a continuously curved convex slice supporting upper surface 72 of the link 74. Again, the vanes of each link 74 are connected together in a similar manner as for the link 50, Again, the links 76 are assembled together with a plurality of transversely extending pivotable support rods 88 to form the belt conveyor 70 in a manner similar to that of the first embodiment so that the belt conveyor 70 can be bent arcuately around rotatable cylinders.

In each row 76 the links 74 are transversely aligned so that the row 76 presents an upper continuously convex arcuate slice supporting surface 78 having a leading edge 80 and a trailing edge 82, each edge 80, 82 extending transversely across the endless belt conveyor 70. The leading edge 80 and trailing edge 82 of the upper surfaces of adjacent rows 76 intersect to form a transversely extending intersection 84 at the intersecting upper surfaces 72.

In the region between adjacent intersections 84, the upper convex slice supporting surface 72 of a respective row 76 is entirely convex.

The upper convex slice supporting surface 72 is shaped asymmetrically so that at the intersections 84 an upwardly directed wall portion 86 is presented on one side of the intersection 84. This is achieved by providing each surface 72 with a wall portion 86 and an adjacent curved portion 88, optionally the curved portion 88 having a substantially constant radius of curvature. The wall portion 86 may be perpendicular to the longitudinal direction of the endless belt conveyor 70 or inclined to the perpendicular, for example at an angle of up to 30 ° At the intersection 84 the tangent of the adjacent convex surface 90 of the curved portion 88 forms an acute angle f3 (i.e. an angle of less than 900) with the wall portion 86, the angle typically ranging from 30 to 85°.

Again, for the embodiment of Figure 5, the upper surface of the belt conveyor 70 is shaped and dimensioned to provide the teclmical effect of imparting a random shape to the resultant cooked potato chips 44 formed from the initially flexible potato slices 40. The asymmetric shape at the intersections 84 is specifically configured so as further to minimise the incidence of oil-coated potato slices 40, which have a rather slippery surface, inadvertently slipping on the belt 70 during transport through the microwave oven 4 which could result in inadvertent slice overlap. In particular, if a potato slice 40 slides down the curved portion 88 towards the intersection 84, the wall portion 86 acts as a stop surface 90 to prevent further sliding of the slice 40. The asymmetric configuration of the upper convex slice supporting surface 72 tends to cause slices, if subjected to sliding, to slide in a common longitudinal direction along the surface of a respective row 76 until the sliding stops, with sufficient sliding potentially by contact with the stop surface 90. This controlled slice sliding motion significantly reduces inadvertent slice contact.

In addition, the asymmetric structure of the upper surface of the belt 70 reduces the possibility of potato slices being dried and rigidified to the same shape. This reduces undesired shingling or nesting together of plural potato chips in a packet, which is not desirable to the consumer.

A particularly beneficial technical effect is that the mass of the potato slices which can be loaded onto a unit area of the belt conveyor, without increasing the incidence of inadvertent slice contact, can be increased by up to about 50%. By producing a belt upper surface with successive upwardly oriented stop surfaces, the three dimensional nature of the belt surface using the upward Z direction to increase the potential slice supporting area for any given x-y direction area footprint of the belt, the belt loading can be increased.

In accordance with another aspect of the present invention, it has been found that the use of the endless belt conveyors 24, 70 which impart a shape to potato slices during the explosive dehydration of the potato slices 40 in the microwave oven 4 can be employed additionally to reduce the cost of downstream potato chip drying and to increase product uniformity.

This aspect of the invention is predicated on the finding that when the explosively dehydrated potato slice has particular water and oil contents, the slice is sufficiently rigid that it no longer requires individual support on the three-dimensionally shaped endless belt. Instead, after these particular water and oil contents have been achieved by initial explosive dehydration, a bulk layer of the potato slices can be subsequently subjected to further drying.

During the explosive dehydration of the potato slices 40 in the microwave oven 4, the slices 40 lose significant amounts of moisture, and consequently shrink in area. Initially the slices 40 have a high water content and are flexible. As the explosive dehydration of the potato slices 40 in the microwave oven 4 continues, when the moisture content has been reduced to a value within the range of from 10 to 15 wt%, and the potato slice has an oil content of from 11 to 15 wt%, each weight being based on the total weight of the potato slice, water and oil, the potato slice 40 becomes substantially rigid.

Accordingly, in accordance with this other aspect of the invention, as shown in Figure 6 the potato slice 40 is removed from the endless belt conveyor 70 and deposited onto a secondary deep bed conveyor 92. In such a secondary deep bed conveyor 92, the slices are no longer a monolayer of mutually separated slices 40, as on the endless belt conveyor 70, but form a layered stack 94 of overlapping slices supported as a deep bed, for example having a height of up to 300 mm. Such a deep bed is subjected to a downstream drying process to reduce the moisture to below 10 wt%, even as low as I wt%, based on the total weight of the potato slice, water and oil.

Such a subsequent drying step using a deep bed can provide a more efficient process than continuing the drying on the endless belt conveyors 24, 70 because the deep bed includes a greater mass of products per unit area. Furthermore, in a deep bed conveyor the drying is more uniform. This enhances product uniformity. At a moisture content of at most 10 wt%, based on the total weight of the potato slice, water and oil, even if the subsequent drying step is carried out by microwave energy, the low moisture content reduces the risk of arcing or burning of the potato slices during drying to form the potato chips, The capital cost and production cost of using a deep bed conveyor and a shorter endless belt conveyor is lower than employing a longer endless belt conveyor.

A further embodiment of an elongate longitudinal belt conveyor according to the invention is illustrated in Figure 7. The elongate longitudinal belt conveyor 100 is adapted for supporting potato slices 102 conveyed on the conveyor upper surface 104 through a microwave chamber, such as a microwave oven. The conveyor 100 comprises a plurality of links 106, with the conveyor upper surface 104 having a plurality of intersections 108 of adjacent links 106. At least some of the intersections 108 include a stop surface 110 for preventing a potato slice 102 from sliding in one longitudinal direction Li past the intersection 108. In this embodiment, the stop surface 110 comprises a surface 112 of a first link 106 which is at least partly oriented towards the opposite longitudinal direction L2. The stop surface 112 is adjacent to an upper surface 114 of a second link 106 adjacent to the first link 106.

The stop surface 110 is formed in a pocket 116 defined between the upper surface 114 of one link 106 and an undersurface 112 of an adjacent link 106. The stop surface 110 is typically the undersurface 112 of an adjacent link 106. Additionally or alternatively, as also shown in Figure 7, the stop surface 110 may be part of a dedicated outwardly extending stop member 107, 109 formed on either of the adjacent links 106.

The links 106 comprise a convex outer support surface 118 and a concave inner surface 120, the outer support surface 118 and inner surface 120 being mutually connected at an upper free edge 122. The pocket 116 is formed between these surfaces 118, 120. The pocket 116 is inclined at an acute angle to the longitudinal directions LI, L2 and points upwardly and along one of the longitudinal directions L2. The height of an upper slice supporting surface 11 8 of the links 106 is greater than a pitch between adjacent links 106.

For example the height may be up to 75 mm and the pitch may be up to 50 mm. The lower closed end 124 of the pocket 116 is located beneath the upper slice supporting surface 11 8 of that link 106 which also includes the inner surface 120 forming the pocket 116. Thus the lower closed end 124 of a first pocket 116 overlaps in plan with the upper open end 126 of a second pocket 116 adjacent thereto This embodiment provides the advantage that the upper surface of the belt includes slice supporting surfaces which extend significantly in the Z (height) direction, for example the link height being greater than the link pitch, which increases the area of the support surface of any given X-Y area. The stop surfaces prevent slices from inadvertently touching, which increases the loading on the belt without increasing the incidence of slices mutually touching. Furthermore, by providing the inclined pockets, with the bottom of the pocket being beneath a slice supporting surface of the adjacent link, the longitudinally adjacent slices can in fact overlap or stack in plan view without touching because they are held in respective individual longitudinally separated pockets. This further increases the belt loading which minimising mutual touching of slices.

In any of the embodiments, one or more additional longitudinally extending barriers may be provided on the belt upper surface to prevent slice touching in the lateral direction across the transverse width of the belt, The barriers may be aligned with or inclined at an acute angle to the longitudinal direction of the belt and may extend along all or part of the belt length. An example of two such barriers 130 is illustrated in Figure 6, although plural barriers would be provided over the surface area of the belt.

Furthermore, in any of the embodiments, in addition to providing transversely oriented rows, the links may be alTanged to provide longitudinal columns of support surfaces, or other regular (e.g. diagonal) or irregular arrays of surface contouring to support the potato slices as they are conveyed through a process such as explosive dehydration in a microwave chamber, optionally the surface contouring providing restrictions against inadvertent slice contact by transversely adjacent slices.

Various other modifications to the illustrated embodiments will be apparent to those skilled in the art.

Claims

CLAIMS: 1. An apparatus for manufacturing potato chips from potato slices, the apparatus comprising an elongate microwave oven having a longitudinal cavity forming a microwave chamber, and an elongate longitudinal belt conveyor having a portion extending through the microwave chamber for supporting potato slices conveyed through the microwave chamber, the conveyor having a continuously undulating surface with a maximum height of the undulations of from 5 to 15 mm and a pitch between adj acent undulations of from 35 to 75 mm.
2. An apparatus according to claim 1, wherein the conveyor comprises a plurality of links arranged in a plurality of rows, each row transversely extending across the width of the endless belt conveyor, each row having a leading edge and a trailing edge, each of which edges is pivotally connected to a respective adjacent row, each row having a convex arcuate upper surface, the leading edge and trailing edge of the upper surfaces of adjacent rows intersecting to form a transversely extending intersection at the intersecting upper sur faces.
3. An apparatus according to claim 2, wherein the upper surface of each respective row has a substantially constant radius of curvature.
4. An apparatus according to claim 3, wherein the diameter of the upper surface of each respective row is from 70 to 100 mm.
5. An apparatus according to claim 4, wherein the diameter of the upper surface of each respective row is from 75 to 95 mm.
6, An apparatus according to claim 5, wherein the diameter of the upper surface of each respective row is from 80 to 90 mm.
7. An apparatus according to any one of claims 2 to 6, wherein at each intersection tangents of the adjacent upper surfaces forn-i an obtuse angle.
8. An apparatus according to claim 7, wherein the obtuse angle is from 95 to 135°.
9. An apparatus according to claim 2, wherein at each intersection tangents of the adjacent upper surfaces form an acute angle,
10. An apparatus according to claim 9, wherein the acute angle is from 30 to 85°.
11. An apparatus according to claim 9 or claim 10, wherein at each intersection one of the adjacent upper surfaces forms an outwardly directed stop surface for preventing a potato slice from sliding in one longitudinal direction past the intersection.
12. An apparatus according to claim 11, wherein the upper surface of each respective row is asymmetric in a longitudinal direction.
13. An apparatus according to claim 11 or claim 12, wherein the upper surface of each respective row includes the stop surface and a curved surface.
14. An apparatus according to claim 13, wherein the curved surface has a substantially constant radius of curvature,
15. An apparatus according to claim 14, wherein the diameter of the curved surface is from 70 to 100 mm.
16. An apparatus according to claim 15, wherein the diameter of the curved surface is from 75 to 95 mm.
17. An apparatus according to claim 16, wherein the diameter of the curved surface is from 80 to 90 mm.
18. An apparatus according to any one of claims 2 to 17, wherein the pitch between adjacent rows is from 45 to 55 mm, optionally about 50 mm.
19. An apparatus according to claim 18, wherein the pitch between adjacent rows is about 50 mm.
20. An apparatus according to any one of claims 2 to 19, wherein the maximum height of the upper surface above the pivot axes of each row is from 15 to 25 mm.
21. An apparatus according to claim 20, wherein the maximum height of the upper surface above the pivot axes of each row is from 17 to 21 mm.
22, An apparatus according to claim 21, wherein the maximum height of the upper surface above the pivot axes of each row is about 19 mm.
23. An apparatus according to any one of claims ito 22, wherein the maximum height of the undulations is from 7 to 10 mm.
24. An apparatus according to any one of claims 1 to 23, wherein an upper part of the microwave oven includes a microwave generator.
25. A method of manufacturing a low oil potato chip, the method comprising the steps of: (a) providing a plurality of potato slices, each slice having been pretreated in oil; (b) randomly feeding the potato slices onto the upper surface of an elongate longitudinal belt conveyor, the conveyor having a continuously undulating surface with a maximum height of the undulations of from 5 to 15 mm and a pitch between adjacent undulations of from 35 to 75 mm; (c) conveying the potato slices on the belt through a microwave chamber; and (d) microwave dehydrating the potato slices to form potato chips.
26. A method according to claim 25, wherein in step (b) the potato slices are fed onto the upper surface in a non-overlapping configuration.
27. A method according to claim 25 or claim 26, further comprising step (e) of transferring the potato chips from the elongate longitudinal belt conveyor when the potato chips have a moisture content within the range of from 10 to 15 wt%, the weight being based on the total weight of the potato slice, water and, when present, oil.
28. A method according to claim 27, wherein in step (e) the potato slice has an oil content of from 11 to 15 wt%, the weight being based on the total weight of the potato slice, water and oil, 29, A method according to claim 27 or claim 28, wherein in step (e) the potato chips are transfen'ed to a second conveyor and are conveyed to at least one drying station as a layer of overlapped potato chips.