GB2430345A

GB2430345A - A process for the manufacture of a snack product from a sheet of dough

Info

Publication number: GB2430345A
Application number: GB0618226A
Authority: GB
Inventors: Kevin Craig Smithson
Original assignee: United Biscuits Ltd
Current assignee: United Biscuits Ltd
Priority date: 2005-09-21
Filing date: 2006-09-15
Publication date: 2007-03-28
Anticipated expiration: 2026-09-15
Also published as: GB2430345B; GB0618226D0; GB0519292D0

Abstract

A process for the manufacture of a snack product comprises preparing a sheet of food dough, forming individual pieces from the dough, imparting a three-dimensional configuration to the pieces by passing the pieces between a pair of embossed rollers to and cooking to obtain a three-dimensionally shaped snack product. Preferably the embossed rollers are corrugated rollers that comprise parallel circumferentially extending grooves and ridges. The dough may be cut into individual pieces using a cutting roller. An apparatus for use in the process of manufacturing the snack product is also disclosed. The dough may be masa dough used to prepare tortilla chips.

Description

lmt,rovements in or relating to snack r,roducts The present invention

relates to snack products, and to methods and apparatus for their manufacture. In particular, the invention relates to fabricated snack food products, especially those made from doughs including one or more starchy ingredients, for example, savoury snacks known as "chips". The invention relates especially but not exclusively to a kind of snack product made from corn dough and known generally as "tortilla chips".

Snack products enjoy wide popularity, and in recent years snack products have been made in a variety of shapes. Tortilla chips have frequently been of substantially triangular shape. Some snack food products, especially snack products made from potato, have a 3-dimensional configuration imparted to them during manufacture. Thus, certain commercial potato snack food products have a generally rounded circumference, whilst also being corrugated by virtue of having a multiplicity of parallel ridges and grooves extending across the product.

Corrugated potato snack food products include potato chips (referred to as "crisps" in the UK) made from fried slices of potatoes, the corrugations having been imparted by using corrugated blades to cut the potato slices. Also included amongst corrugated potato snacks are fabricated potato snack products in which a snack dough is made from dry constituents, usually including one or more of potato starch, potato granules, dried potato powder and potato flakes mixed with water. A corrugated sheet is formed from the dough, which sheet is cut to produce individual corrugated pieces that are fried to obtain the corrugated snack product. The processes for making fabricated potato snack products involve the handling of a sheet of the dough material, to which the corrugated configuration is imparted. Doughs made from corn (known as "masa") are, however, crumbly, having little cohesive strength, and are therefore more difficult to handle compared with potato-based doughs. In particular, formation of a masa dough sheet and imparting thereto of a wavy configuration using corrugated rollers is difficult to achieve with the tackiness of the dough causing it to stick to the rollers, giving limited success and causing relatively high levels of wastage.

The invention provides a process for the manufacture of a snack product, comprising preparing a food dough, forming individual pieces from the snack dough, imparting a three-dimensional configuration to the individual pieces to obtain shaped individual pieces and cooking the shaped individual pieces to obtain a three-dimensionally shaped snack product.

The process of the invention enables snack doughs to be formed efficiently and reliably into individual three-dimensional, preferably corrugated, pieces, even in the case of sticky doughs, for example corn masa. Thus, the process of the invention provides, in particular, an effective way of manufacturing three-dimensionally shaped tortilla chips, although the process may also may also be used to manufacture other snack food products, for example potato snack products. Such shaped products are often referred to as "fabricated snack food products".

The imparting of a three-dimensional configuration to the individual dough pieces enables shaped pieces with a well-defined shape, especially at the edges of the pieces, to be provided. In contrast, if the configuration is imparted to a sheet of dough material which is then cut into individual pieces, the cutting of the pieces may distort the three- dimensional configuration, for example, by distorting the ridges of a corrugated piece and squashing the edges.

The three-dimensional configuration is preferably imparted to the individual pieces by means of passing the pieces between a pair of opposed embossed rollers. The three- dimensional configuration is advantageously a corrugated configuration.

Advantageously, the preferred corrugated configuration is imparted to the individual pieces by passing the individual pieces between a pair of opposed corrugated rollers.

Preferably, the pair of opposed corrugated rollers each comprise a multiplicity of parallel circumferentially extending grooves and ridges. It is especially preferred for the pitch of the ridges on a first of said opposed rollers to be equal to the pitch of the ridges on a second of said opposed rollers, the grooves on the first roller being arranged to cooperate with the apices of the ridges on the second corrugated roller. In that way, a substantially sinusoidally wavy product with a substantially uniform wavelength can be produced. Other corrugated configurations are not excluded, however, and other possibilities may include, for example, corrugated configurations in which the wavelength and/or the amplitude varies across the product. Non-corrugated configurations that may be imparted to the pieces include, for example, other patterns such as waffle patterns, or images such as company logos or novelty cartoon or other characters.

Advantageously, the individual pieces are formed by sheeting the dough to obtain a dough sheet and cutting the individual pieces from the dough sheet. The terms "sheeting" and "sheet" as used in this specification are to be understood as including the formation, from a dough in the form of lumps, granules or pieces, of any continuous layer of dough.

In particular, for the avoidance of doubt, "sheet" is not limited to a layer of dough which has sufficient cohesive strength to be selfsupporting. For example, "sheeting" is to be understood as including forming a layer of dough that is formed on or around an object and that can be carried by that object without the dough crumbling or otherwise breaking into discrete pieces, and "sheet" is to be correspondingly understood. In particular, as is apparent below, in a preferred embodiment of the invention a dough is sheeted by forming a layer of dough which extends around a part of the circumference of a roller, the sheet so formed then being cut before the dough becomes detached from the roller. It is preferred for the sheeting to be carried out using a pair of co-operating rollers. Any suitable method may be used to cut pieces from the dough sheet. It is preferred, however, for the cutting to be carried out by a cutting roller which advantageously effects said cutting using one of the sheeting rollers as a counter-surface.

Advantageously, at least one of said rollers, for example, at least one of the sheeting rollers and/or the cutting roller and/or embossed, especially corrugated, rollers for shaping the individual pieces, is maintained at a temperature lower than ambient temperature. As well, or instead, at least one of said rollers may be maintained at a temperature exceeding ambient temperature. Advantageously, the temperature of each of the rollers is different. The heating and/or chilling of rollers has been found to alter their release characteristics with respect to dough and so may aid the release of dough pieces from a roller. For example, it has been found that the release from a roller of a dough piece made from potato dough is aided by chilling the roller. Advantageously, an air stream is used to assist dough release from at least one of said rollers. Use of an air stream to assist dough release may in particular be advantageous where the dough is of high tackiness. In one embodiment, a stream of warm air may be directed onto the dough pieces before they are fed into the embossing apparatus. That may remove some of the surface moisture, thereby reducing the tackiness of the dough pieces.

Preferably, the speed of at least one of the rollers is varied. Preferably, the rollers are operated at different speeds. It has been found that varying the relative speed of a roller affects the release characteristics with respect to dough pieces.

The individual pieces may be cooked by any suitable method. Advantageously, said cooking comprises frying. The cooking may include a baking step. In one preferred method, the cooking comprises a baking step and a subsequent frying step. Where present, a baking step prior to a frying step serves to remove surface moisture, allowing formation of a hardened surface skin. The surface skin so obtained helps to retain the corrugated configuration on frying. Where a Crying step is present, the pieces are preferably fried in oil at a temperature in the range of from 165 to I 95CC, preferably 1 75 to I 85CC, for from 40 to 60 seconds, especially 45 to 55 seconds. Where the pieces are IS subjected to a frying step, it is preferred for the pieces to be unconstrained during the frying step. That allows the pieces to curve or otherwise deform during frying, giving rise to a variety of different conformations in the final product.

Advantageously, the food dough is based on one or more starchy constituents, and is especially a cereal (especially corn) or potatobased dough. Preferably, the food dough is a masa dough and the snack product is a tortilla chip. Advantageously, the tortilla chip is of overall triangular shape and is corrugated. The masa dough may optionally contain additional ingredients, for example, one or more ingredients selected from cereal grains, cereal flours, cereal starches and seeds.

The invention also provides an apparatus for use in the manufacture ofa snack product, comprising: an apparatus for preparing a snack dough; apparatus for forming individual pieces from the snack dough; an apparatus for imparting an embossed configuration to the individual pieces; and cooking apparatus for cooking the individual pieces.

Advantageously, the apparatus for forming individual pieces from the snack dough comprises a pair of opposed sheeting rollers for sheeting the dough and a device for cutting the individual pieces from the sheet. Advantageously, the device for cutting the individual pieces from the sheet comprises a cutting roller. Advantageously, the cutting roller cooperates with a said sheeting roller for cutting the individual pieces.

The apparatus for imparting an embossed configuration to the individual pieces comprises a pair of embossed rollers, for example, a pair of opposed embossed rollers.

The embossed rollers carry surface embossing which is so arranged that the co-operating opposed rollers impart a desired configuration to the individual pieces. Preferably, the embossed rollers are arranged to impart a corrugated configuration to the pieces and are a pair of corrugated rollers. Advantageously, the corrugated rollers each comprise a multiplicity of parallel circumferentially extending grooves and ridges. It is preferred for JO the first and second rollers of said pair of embossed rollers to be offset from one another in the direction of travel of the individual pieces. Preferably, the rollers are so arranged that their axes extend parallel to one another across the direction of travel of the pieces, with the axis of a first said roller being lower than the axis of the second roller.

Preferably, the axis of the second, that is the upper, corrugated roller is located IS downstream of the axis of the first, lower, corrugated roller, in the direction of travel of the pieces. The corrugated surfaces of the corrugated rollers are advantageously so arranged that the spacing between the ridges on one said roller and the grooves on the other said roller is not more than 6mm, preferably not more than 4mm, especially not more than 3mm. It is preferred for the corrugation to have grooves which form an included angle of from 80 to 120 , for example, 90 to 1100, especially 95 to 105 . The pitch of the corrugation, that is, the spacing between apices of adjacent ridges, is advantageously but not necessarily uniform and may be, for example, from I to 10mm, advantageously from 2 to 8mm, preferably from 4 to 6mm and especially preferably from 4.5 to 5.5mm. The height of the ridges (measured from the level of the base of the grooves) may be, for example, I to 8mm, advantageously from I. 5 to 3mm, and preferably from 2 to 2.5mm.

Whilst, in the embodiment described herein, the corrugation of the corrugated rollers are angular, it will be appreciated that the corrugations may be curved, for example, the corrugations may be sinusoidally wavy in section, with the dimensions being selected analogously.

Advantageously, the apparatus is arranged so that dough pieces are selectively adhered to one of a pair of embossing rollers and released from the other of the pair of embossing rollers. It has been found that the dough pieces generally remain adhered to the lower roller and/or to the upstream roller of a pair of rollers.

Advantageously, the release characteristics of the rollers with respect to dough pieces are different and, preferably, the release characteristics of a pair of embossing rollers are different from one another. Providing rollers with different release characteristics enables dough pieces to be selectively released from one of a pair of rollers whilst being retained on the other. Factors that have been found to affect the release characteristics of a roller include: the release characteristics of the material of the surface of a roller and in particular whether the roller is provided with a non-stick coating; the speed at which the roller is rotated; the temperature of the roller; and the characteristics of the surface of the dough pieces.

Preferably, one or more of the rollers is provided with a non-stick coating.

Preferably, the nature of the surfaces of each of a pair of embossing rollers are different, for example, only one may be provided with a nonstick coating.

Preferably, the rollers are variable speed rollers. Preferably, the apparatus is arranged so that each of a pair of embossing rollers may be operated at different speeds from one another. It has been found that the ability to vary the speed of the rollers to independently set their speed of rotation in operation can assist in controlling selective release of the dough pieces from one of the rollers.

Preferably, the apparatus is arranged so that the rollers may be heated and/or chilled.

Preferably, the apparatus is arranged so that each of a pair of embossing rollers may be heated and/or chilled to a different degree. Preferably, the apparatus is arranged so that the temperature of each of a pair of embossing rollers may be different from one another.

It has been found that operating the rollers at different temperatures may assist in controlling selective release of dough pieces from one of the rollers.

Preferably, the apparatus is arranged so that an air stream can be applied to the dough pieces. The air stream may be directed Onto the dough pieces in the embossing apparatus, for example, on to the pieces that are entrained on a roller. The apparatus may be arranged so that the air stream affects the release characteristics of one side of the dough pieces with respect to a roller. Thus, an air stream may be used to impart different release characteristics to each side of a dough piece and so control release of the dough pieces from a pair of rollers. The apparatus may be arranged to apply moisture to the dough pieces thereby increasing the tackiness of the dough pieces. For example, the apparatus may be arranged to apply moisture to one side of a dough piece thereby affecting its release characteristics with respect to one of a pair of rollers.

Advantageously, the apparatus includes one or more scrapers for removing dough pieces from a roller. Preferably, the apparatus is arranged so that the dough pieces are selectively adhered to one of the pair of embossed rollers and released from the other and a scraper is provided to remove the dough pieces from the roller to which they are selectively adhered.

Advantageously, the apparatus for forming individual pieces is arranged to form substantially triangular pieces.

One illustrative embodiment of the apparatus and method of the invention will now be described in detail with reference to the accompanying drawings in which: Fig. I is a flow diagram of the apparatus and process; Fig. 2 is a diagrammatic side view of the sheeting and cutting apparatus included in Fig. I; Fig. 3 is a view from the front and from below of the corrugated rollers of Fig. I; Fig. 4 is a side view of the rollers of Fig. 3 Figs. 5A to 5D are views of a corrugated tortilla chip prepared in a process according to the invention.

With reference to Fig. I of the accompanying drawings, solid constituents and water are mixed together in a plough shear mixer indicated by reference numeral I. The dough is transferred into a feeder 2a upstream of a sheeting apparatus 2. The feeder (which is of a kind well-known and widely used in the art) has two screw horizontal screw augers and one upright auger which serve to deliver the dough from above into the nip of the sheeter rollers 3,4 as shown in Fig. 2 by arrow D. In the embodiment shown, the sheeting apparatus 2 has two 25cm variable speed differential sheeter rollers 3,4, which are counter- rotating as indicated by arrows 3a,4a respectively. The rollers 3,4 are arranged with their axes parallel and in a common horizontal plane. Front roller 3 communicates with a conveyor belt 5, the upper run of which is arranged to travel in the direction of arrow E away from the sheeter apparatus roller 3. Rear roller 4 co-operates with front roller 3 to compress the sheet. Sheeted material emerging from the nip continues to travel around the circumference of front roller 3. At a part of the circumference of roller 3 between the nip of rollers 3,4 and the belt 5 there is provided a cutter roller 6 which rotates in the direction of arrow 6a and co- operates with the surface of front roller 3 (see Fig. 2, which is not to scale, the cutter roller in practice being smaller than shown). The cutter cuts the sheet into pieces, the roller 3 acting as a counter- surface, and a stainless steel wire (not shown) forces the pieces off the front roller 3 and onto the belt 5. The scrap remaining on the front roller 3 is carried around the front roller by brass bands (not shown) and delivered back into the sheeter roll nip area to be resheeted, as shown by the broken line in Fig. I. The belt 5 transfers the dough pieces to the embossing apparatus, which in the embodiment shown is a corrugating apparatus 7.

l5 The embossing apparatus 7 has a pair of variable speed embossed rollers 8,9, the curved surfaces 8a,9a, one or both of which are provided with a non-stick coating. The term "embossed" is used throughout the specification, including the claims, to refer to the configuration of the curved surfaces of the rollers, and not to the way in which the rollers are made. Thus, the term "embossed" is used herein to mean that the curved surface of an embossed roller bears a pattern, which is in relief. Because the pattern is in relief it imparts a corresponding threedimensional pattern to the dough pieces.

Depending upon the release characteristics required, it is possible for only one of the rollers 8, 9 to be provided with a non-stick coating, or for each of the rollers 8, 9 to be provided with a respective coating have different release characteristics with respect to the dough. It is also possible for the speed the rollers 8, 9 to be varied and/or for the temperature of the rollers 8, 9 to be controlled in order to alter the release characteristics of each of the rollers 8, 9 with respect to dough pieces.

The embossed rollers comprise an upper roller which is indicated generally by the reference numeral 8 and a lower roller which is indicated generally by the reference number 9. Referring to Fig. 3 the rollers 8 and 9, which are identical, are corrugated in 1) an axial direction, that is to say, they are corrugated with the individual corrugations extending circumferentially.

The form of the corrugation on the rollers 8 and 9 is such that, as seen in axial section and shown in Fig. 3, the curved surfaces 8a,9a of each of the rollers has a toothed profile. Again, with the rollers 8 and 9 seen in axial Section, the teeth 10 are bounded by straight lines which meet at an angle of 1000 at the apices of the teeth. Similarly, the lines that bound the teeth meet at an angle of 1000 at the bases of the gaps between adjacent teeth.

The rollers 8 and 9 are displaced axially relative to one another by half the pitch of the corrugations, that is to say, by half the separation between the apices of adjacent teeth 10. Thus, save for an end tooth of the teeth lOat one end of each roller, the apices of each of the roller teeth lie midway between the apices of a pair of adjacent teeth on the respective other roller of the pair. As an example of suitable dimensions for the corrugations on the embossed rollers, the spacing between the apices of adjacent teeth of IS the rollers shown in Fig. 2 may be 5.4mm, and the vertical spacing between the level of the apices and the level of the bottom of the grooves may be 2.2mm. The position of the front roller 8 is adjustable to increase or decrease the spacing between the rollers at the nip.

With reference to Fig. 4, the upper corrugated roller 8 is offset from the lower corrugated roller 9 in the direction of travel of the pieces, so that the axis of the lower (back) corrugated roller 9 is arranged slightly upstream of the axis of the upper (front) corrugated roller. The belt 5 transfers the dough pieces onto the upper circumferential surface of back roller 9 of the corrugating apparatus. The rotating back roller 9 carries the pieces into the nip between the rollers 8 and 9, where they are acted upon by those two rollers to impart a corrugated configuration to the pieces. On exit from the nip, the pieces, which now are corrugated, remain adhered to the descending surface of back roller 9. There are three scrapers mounted on the equipment namely two cleaning scrapers S2 and S3 for cleaning scraps of dough from the two rollers and one scraper SI to remove the corrugated pieces from the back roller 9. The pieces are removed from the back roller 9 with the assistance of the latter scraper and the pieces are transferred onto a conveyor belt II beneath the roller nip, which transfers the pieces to an oven 12.

The oven 12 is a travelling oven which is provided with three belts, namely top, middle and bottom belts. 24 ribbon burners per tier directly heat each belt. The pieces are transferred from the conveyor I I Onto the oven top belt. The oven temperature is approximately 400 C and the residence time is about 20 seconds. The oven removes moisture from the product and provides partial baking of the product.

An oven take-out conveyor 13 transfers the baked product onto the top belt of an equilibrium conveyor 14. The equilibrium conveyor 14 cOnsists of five belts along each of which in series the pieces travel, whilst cooling. The equilibrium belt provides a time delay, before further processing, of approximately three minutes to allow the product to cool and to remove moisture from the product.

An equilibrium take off conveyor 15 transfers the pieces to the inlet of the fryer 16 where it is fried in oil.

After the fryer the product is, after optional application of flavouring at a flavouring station 17, transferred to a packing station 18 where it is packed and forwarded 1 5 to a storage area 19.

In the manner described, it has been found that even a crumbly masa dough can be processed easily and effectively to form individual corrugated pieces. It is also an advantage of the process of the invention that imparting corrugations after cutting of the pieces allows there to be produced corrugated tortilla chips in which there is no distortion of the corrugations at the edges of the product as may be produced in cutting of an already corrugated sheet.

The following Example illustrates the invention:

Example

Tortilla chips are made using the apparatus described above. 91kg masa flour and 63kg water are mixed together in a plough shear mixer I. The dough is hand shovelled into the feeder 2a. The dough is fed from above into the nip between the sheeter rollers 3,4. On emerging from the sheeter rollers, the sheet has been considerably reduced in thickness, and continues to adhere to the front roller 3 as it passes around that roller towards the

- II -

cutter. The Cutter 6 cuts the sheet into triangular pieces and a stainless steel wire forces the pieces off the front roller 3. The piece weight of the pieces corresponds to a weight (after being subjected to the cooking steps described below) of 3.5g per piece. The scrap is carried around the front roller by brass bands and reworked. The sheeter belt transfers the triangular pieces to the corrugating apparatus 7.

The conveyor 5 transfers the dough pieces onto the back roller 9 of the corrugating apparatus 7. The pieces pass between the two corrugated rollers 8,9 of the unit and the corrugated pieces are removed from the back roller 9 with the assistance of the scraper. The corrugated pieces are transferred onto the conveyor belt I 1, which transfers the product to the oven.

The corrugated pieces are transferred from the conveyor I I onto the oven top belt.

The oven temperature is approximately 400 C and the residence time is 20 seconds. The oven removes moisture from the product and provides partial baking of the product.

The oven take-out conveyor 13 transfers the baked product onto the top belt of the equilibrium conveyor 14. The equilibrium conveyor provides a time delay of approx. 3 mins to allow the product to cool and to remove moisture from the product before frying.

The equilibrium take off conveyor transfers the product to the mouth of the fryer where it is fried at a temperature of I 75 to I 85 C. The product remains in the fryer for approx. 5Osecs.

After the fryer the product is then transferred, flavoured and packed. The fried products have a ridged configuration as shown in Figs 5A to 5D and are of generally even surface colour and texture, with appearance of some colouration due to the partial baking step and some surface bubbling. 4'

Claims

Claims: A process for the manufacture of a snack product, comprising

preparing a sheet of food dough, forming individual pieces from the snack dough, imparting a three-dimensional configuration to the individual pieces by passing the pieces between a pair of embossed rollers to obtain shaped individual pieces and cooking the shaped individual pieces to obtain a three-dimensionally shaped snack product.
2. A process according to claim I, in which the pair of embossed rollers are corrugated rollers that comprise a multiplicity of parallel circumferentially extending grooves and ridges.
3. A process according to claim I or claim 2, in which the individual pieces are IS formed by sheeting the dough to obtain a dough sheet and cutting the individual pieces from the dough sheet.
4. A process according to claim 3, in which the sheeting is carried out using a pair of co-operating rollers.
5. A process according to claim 4, in which the cutting is carried out by a cutting roller which optionally effects said cutting using one of the sheeting rollers as a counter-surface.
6. A process according to any one of claims I to 5, in which the release characteristics of the rollers with respect to the dough pieces are different.
7. A process according to any one of claims I to 6, in which at least one of said rollers is maintained at a temperature lower than ambient temperature. - 13-
8. A process according to any one of claims I to 6, in which at least one of said rollers is maintained at a temperature exceeding ambient temperature.
9. A process according to any one of claims I to 8, in which an air stream is used to assist dough release from at least one of said rollers.
10. A process according to any one of claims I to 9, in which the speed of at least one of said rollers is varied.
II. A process according to any one of claims 1 to 10, in which the rollers are operated at different speeds.
12. A process according to any one of the preceding claims, in which said cooking comprises frying.
13. A process according to claim 12, comprising a baking step and a subsequent frying step.
14. A process according to claim 12 or claim 13, in which the pieces are fried in oil at a temperature of I 75 to 1 85 C for from 40 to 60 seconds.
IS. A process according to any one of the preceding claims, in which said cooking comprises baking.
16. A process according to any one of the preceding claims, in which the food dough is a masa dough.
I 7. A process for making tortilla chips substantially as described herein with reference to the accompanying drawings.

I - 14-
18. An apparatus for use in the manufacture of a snack product, comprising: an apparatus for preparing a snack dough; apparatus for forming individual pieces from the snack dough; an apparatus for imparting an embossed configuration to the individual pieces comprising a pair of embossed rollers; and cooking apparatus for cooking the individual pieces.
19. An apparatus according to claim 18, in which the apparatus for forming individual pieces from the snack dough comprises a pair of opposed sheeting rollers for sheeting the dough and a device for cutting the individual pieces from the sheet.
20. An apparatus according to claim 1 9, in which the device for cutting the individual pieces from the sheet comprises a cutting roller.
21. An apparatus according to claim 20, in which the cutting roller cooperates with a said sheeting roller for cutting the individual pieces.
22. An apparatus according to any one of claims 18 to 21, in which the embossed rollers are corrugated rollers.
23. An apparatus according to claim 22 in which the corrugated rollers each comprise a multiplicity of parallel circumferentially extending grooves and ridges.
24. An apparatus according to claim 23, in which the pitch of the corrugation on a first of said opposed rollers is equal to the pitch of the corrugation on a second of said opposed rollers and the grooves on the first roller are arranged to co-operate with the apices of the ridges on the second corrugated roller.
25. An apparatus according to claim 24, in which the pitch of the corrugations is uniform along the length of each of the rollers. I,
26. An apparatus according to claim 22, in which the pitch varies along the length of each of the rollers, the variation in pitch in each roller being in correspondence with the variation in pitch of the other respective roller.
27. An apparatus according to any one of claims 18 to 26, in which the apparatus for forming individual pieces is arranged to form substantially triangular pieces.
28. An apparatus according to any one of claims 18 to 27, in which the release characteristics of the rollers with respect to dough pieces are different.
29. An apparatus according to claims 1 8 to 28, in which the release characteristics of the surface of the rollers are different.
30. An apparatus according to claim 18 to 29, in which at least one of the rollers is a variable speed roller.
31. An apparatus according to claim 18 to 30, in which at least one of the rollers is a heated roller.
32. An apparatus according to claim 18 to 31, in which at least one of the rollers is a chilled roller.
33. A corrugated tortilla chip obtainable by a process according to any one of claims ltol7.