WO2002069739A1

WO2002069739A1 - Cereals and extrusion die

Info

Publication number: WO2002069739A1
Application number: PCT/EP2002/002354
Authority: WO
Inventors: Roman Deutsch; Ernst Heck
Original assignee: Societe Des Produits Nestle S.A.
Priority date: 2001-03-02
Filing date: 2002-02-28
Publication date: 2002-09-12
Also published as: RU2292739C2; EP1236407B1; ES2228678T3; DK1236407T3; BR0207791B1; BR0207791A; DE60106380T2; ATE279124T1; PL363565A1; RU2003129274A; DE60106380D1; PT1236407E; EP1236407A1; MXPA03007880A

Abstract

The present invention relates to an extrusion die comprising an array of tubes placed parallel to each other, each tube being formed by the superimposition of two plates comprising, on the opposing faces, at least one groove. Cooked-extruded-expanded cereal product comprising an assembly of parallel expanded strands of a diameter between 0.75 and 10 mm, adjoining over all or part of their outer surface. Process of manufacturing a cereal product in the form of an array of adjoining parallel expanded strands.

Description

CEREALS AND EXTRUSION DIE

The present invention relates to an extrusion die for the manufacture of expanded cereals, the process using an extrusion die of this sort and the cereals obtained by the process.

Ready-to-use cereals, for breakfast for example, exist mainly in the form of flakes, of expanded grains, of extruded mass or of drawn grain in strand form.

The processes for manufacturing cereals of the drawn grain type in the form of strands or threads are lengthy and complex. They generally involve starting by cooking the cereal grains in an aqueous medium. These cooked grains are then drained, cooled and left to stand in order to allow the uniform distribution of the moisture within these grains. This equalizing or tempering step generally lasts between 15 and 20 hrs . The grains are then predried and shaped in the shape of strands or threads. This step is carried out by passing grains between two rollers, one smooth and the other fluted. Each grain is thus compressed and drawn into the form of a strand which then falls onto a collecting mat. In this way, a relatively thick layer of relatively aligned and relatively tangled strands is obtained. The sheets or layers of threads are then cut transversely and longitudinally in order to form squares or rectangles resembling biscuits. The latter are toasted in the oven, which provides them with colour and crispness.

Technology of this sort is well known and old. Although it makes it possible to obtain products having qualities appreciated by consumers, it is however very long (about 24hrs) , complex and expensive. The aim of the present invention is to provide a device for the simple and fast manufacture of cereals for breakfast in the form of an array of strands. To this end, the invention relates to an extrusion die comprising an array of tubes, the tubes being placed parallel to each other, characterized in that each tube is formed by the superimposition of two plates comprising, on the opposing faces, at least one groove of a length substantially equal to 5 to 15 times the diameter of the tubes and in that the distance between two contiguous tubes is between 0.8 and 1.2 times their diameter .

The tubes of the present die are generally rectilinear.

Similarly, the invention also relates to an extruder comprising an elongated barrel containing one or two processing screws, and at least one extrusion die of this sort.

Finally, the present invention also relates to a cooked-extruded-expanded cereal product comprising an assembly of parallel expanded strands of a diameter between 0.75 and 10 mm, preferably between 1 and 2 mm, adjoining over all or part of their outer surface.

The grooves present on the surface of the plates may preferably have a semi-cylindrical cross section so as to define, once joined, tubes of circular cross section, for example. However, the present invention is in no way limited to tubes of circular cross section and these grooves may also have a cross section of square, oval, elliptical or rectangular cross section, for example .

The tubes of the array may be arranged in at least one row of parallel tubes. They may also be arranged in several non-parallel rows. The term "row" of tubes refers to a series of tubes, the ends of which are placed along the same line.

On the other hand, it is not compulsory for the tubes to be arranged in a row. They may also be arranged so as to define one or more square, round or triangular contours or contours of any other geometry provided that these tubes are parallel and that the distance separating two contiguous tubes is between 0.8 and 1.2 times the diameter of these tubes, this so as to join the strands of extruded material by virtue of the expansion of the latter on its exit.

This die may comprise tubes of relatively small diameter. Specifically, the main drawback in implementing and using extrusion dies is their cleaning. Below a certain diameter, of around a few millimetres, it becomes very difficult to ensure complete and easy cleaning of the tubes of the dies, not to mention risks of blockage by particles present in the mixture to be extruded. The die according to the invention in fact consists of a stack of plates comprising, on the opposing faces, at least one groove extending longitudinally in the direction of flow of the mixture to be extruded. Once these plates are joined and clamped in a cartridge by means of clamps, the grooves then define tubes of a diameter between 0.5 and 4 mm. This assembly makes it possible to obtain a die comprising an array of tubes of relatively small diameter and which may be cleaned easily by dismantling and separating the plates. In a particular embodiment, the contacting surfaces of the plates and clamps comprise grooves placed face to face so as to form tubes at their interface. An array of small-diameter parallel tubes of this sort thus makes it possible to extrude a mixture based on cereal flour and water in the form of as many relatively thin expanded strands as there are tubes of the die. Furthermore, because of the spacing between two contiguous tubes, of the order of 0.8 to 1.2 times the diameter of these tubes, and because of the coefficient of expansion of the extruded mixture on exiting from the tubes, which can be between 1.5 and 2.5, the strands can touch each other and bond together so as to form a cohesive product.

The extruder according to the present invention therefore comprises an elongated barrel which can be thermostatted, containing one or two processing screws, and at least one extrusion die according to the present invention. In a preferred form, a downstream part of the barrel containing a downstream end of the processing screw or screws is terminated by a front plate secured to the barrel in which a chamber for distributing the material is provided. This chamber distributes the cooked material towards dies placed radially to the axis of rotation of the screw or screws, these dies being clamped in cartridges to which the channels of the distribution chamber lead.

The term "processing screw" refers to the screw or screws of the extruder rotated inside a bore or two intersecting bores provided in the barrel and on which are fixed processing members such as flights wound helically around the axis. The configuration of the screws, the pitch and the handedness of the flights may vary along the axis so as to define zones for processing the material, such as transporting, humidifying, mixing, kneading, shearing, cooking and compression.

The product according to the present invention is a cooked-extruded-expanded cereal product comprising an assembly of parallel expanded strands of a diameter between 0.75 and 10 mm, preferably between 1 and 2 mm, adjoining over all or part of their outer surface.

The expanded cereal according to the present invention capable of being obtained by extrusion through the present die therefore has the general shape of an array of adjoining parallel expanded strands.

The adjoining parallel strands of the array may be of similar or different shapes, for example. The array may have an overall thickness of about 4-20 mm, for example.

The array may be generally flat or relatively curved. It may have a perimeter of a generally varied shape, especially square, rectangular, circular, or oval, modified by the distribution of the tubes of the nozzle thus forming the expanded strands of the edge, for example.

It is possible to envisage various embodiments of the cereal product according to the present invention such as cereals for breakfast, dry pet food, salted or sugared snacks, infant cereals, confectionary products and dietary foods, for example.

In a particular form of the invention, the present cereal product is coextruded at the same time as a foodstuff based on cream, cheese, fruit puree, jam, meat, sauce or honey, for example. Thus in this case, the die according to the invention is connected to the end of an extruder comprising a central nozzle intended to take the material of the foodstuff and a peripheral nozzle intended to take the cereal material of the envelope. In a case of this sort, the die according to the invention is also constituted by the superposition of plates comprising grooves, but with the difference that this die is pierced centrally by an opening intended to accommodate the end of the central coextrusion nozzle taking the foodstuff.

A notable advantage of the cereal product according to the present invention is its aerated and crisp texture. Thus, by virtue of the thinness of the strands of the array and the laminated configuration obtained, it is possible to produce a product similar to a wafer. The product according to the invention thus has a particularly crisp and light texture which could be filled with cream or jam for example.

By varying the diameters of the holes, the coefficient of expansion of the material and its composition, it is possible to obtain products whose texture varies between glazed, hard, brittle, crusty, crumbly, crisp or crunchy, for example.

In a particular embodiment, the expanded cereal according to the present invention capable of being obtained by extrusion through the present die has the general shape of an array of adjoining parallel expanded strands of varied colours. Thus, upstream of the die and of the chamber for distributing the material to be extruded, the barrel of the extruder may comprise a means of separating the material into at least two streams of material which enabled it to be coloured by the addition of colouring. The material thus coloured is then extruded through the die according to the present invention and it is thus possible to obtain a cereal which is at least two- coloured in the form of coloured expanded adjoining strands .

In one embodiment as a cereal for breakfast, for example, the present cereal may be consumed as it is or coated, especially with a chocolate coating, a sugar syrup, a fruit syrup, a honey syrup, or with a coating containing vitamins and flavourings, for example.

The present process of manufacturing an expanded cereal having the general shape of an array of adjoining expanded strands consists in cooking-extruding- expanding, under a pressure of 40-180 bar at 105-180°C, a mixture comprising, in parts by weight, 60-90 parts of starch-containing substance, up to 15 parts of sugar, up to 10 parts of oil, and water added until the water content is 7 to 20% by weight of the mixture, extruding through at least one die according to the invention comprising an array of parallel extrusion tubes so as to obtain a bundle of strands of expanded thermoplastic material adhering to each other. The strands thus obtained may have a porous texture.

Furthermore, the mixture may comprise up to 1.5 parts of calcium, in the form of calcium carbonate or calcium triphosphate, for example.

Vitamins, trace elements and sodium chloride, for example, may be added to the mixture.

Colouring agents, flavouring agents, even flavouring ingredients such as cocoa, for example, may also be added. It is possible to add up to six parts of cocoa, for example.

The starch-containing substance may be a flour of a cereal, especially wheat, barley, rice and/or maize, and/or a starch, especially of wheat, barley, rice, tapioca, potato and/or maize, for example.

The sugar may be sucrose, glucose or fructose, for example.

The oil, preferably forming from 0 to 10 parts of the whole, may be butter oil or a vegetable oil such as palm nut oil, for example.

The cooking-extrusion may be carried out in a cooker- extruder having a length to diameter ratio of the screws of about 9-24, with a screw rotation rate of 240-370 rpm, at a pressure in the region of 40-180 bar and a temperature in the region of 105-180°C so as to obtain a coefficient of expansion of about 1.5-2.5, for example, for the extruded strands.

Water escapes from the thermoplastic mass in the form of steam during the expansion such that the extruded strands have a porous texture and may have a residual water content of 5-12%, for example.

The expanded cereal thus formed by bringing together strands may be cut as soon as it is expelled from the die or be formed in the shape of a long strip or bar, then subsequently cut, for example.

The expanded cereal this obtained may again be dried, especially by continuous passage through a hot air oven, until the residual water content is 1-3%, for example .

Given the relatively small diameter of the tubes of the die according to the invention, the size of the particles of the mixture must be less than or equal to the half-diameter of the tubes, in order to prevent or limit plugging of these tubes by particles of the mixture. Similarly, some pulverulant water-soluble ingredients such as sugar or salt, for example, may be dissolved in water before being introduced into the cooker-extruder .

The die is described below with reference to the appended drawing presented by way of example:

Figure 1 is a cross section through the axis of the tubes, of one embodiment of the extrusion die according to the present invention.

Figure 2 shows an axial section along the axis AA' shown in Figure 1. In the embodiment shown in Figures 1 and 2, the extrusion die has 5 rows of tubes 1, placed in staggered rows, consisting of an assembly of four plates 2 bearing grooves on each face, these plates being held between two clamps 3 held by two lateral pins 4 plugged into recesses 5. In this embodiment, the faces of the clamps in contact with the plates comprise grooves so as to form tubes once placed face to face against the grooves present on the outer faces of the plates.

Example

Using a twin screw cooker-extruder comprising several dies as illustrated in Figures 1 and 2, expanded cereals are produced having the shape of an array of adjoining strands.

In order to do this, a mixture having the following composition (in parts, except for the added water) is prepared:

Rice flour 40

Maize flour 12

Wheat flour 22

Sucrose 10

Palm nut oil 5

Salt/Spices 3

Water added up to a water content of 18%

In order to prepare the mixture, firstly the powders are mixed while dry. Next, the dry mixture, the oil and the added water are mixed in the extruder, in this case a CLEXTRAL twin-screw extruder of the BC-72 type having a screw diameter of 88 mm and a screw length of 900 mm.

The mixture is cooked and extruded at 170°C under 100- 120 bar, the screws of the extruder rotating at 310 rpm. The thermoplastic mass thus obtained is extruded through an array of 119 tubes, the tubes having a diameter of 0.6 mm and the distance between two tubes being 0.6 mm.

The thermoplastic mass is extruded into the ambient space in the shape of an elongated band of adjoining expanded strands 1mm in diameter. This band is cut using a vertical knife making it possible to obtain small rectangles of 2.5 cm x 2 cm formed by the adjoining of the expanded strands.

The cereal obtained has the general shape of an array of 119 adjoining expanded parallel strands of the same shape and the same dimensions. Because of pinching when cutting, the rectangles of expanded cereals have a rounded shape like a cushion.

Claims

1. Extrusion die comprising an array of tubes (1), the tubes being placed parallel to each other, characterized in that each tube is formed by the superimposition of two plates (2) comprising, on the opposing faces, at least one groove of a length substantially equal to 5 to 15 times the diameter of the tubes and in that the distance between two contiguous tubes is between 0.8 and 1.2 times their diameter.

2. Extrusion die according to Claim 1, characterized in that the groove has a semi-cylindrical cross section.

3. Extrusion die according to Claims 1 and 2, characterized in that the plates are held by clamps (3) .

4. Extrusion die according to Claim 3, characterized in that the surfaces of the plates and of the contacting clamps comprise grooves placed face to face so as to form tubes at their interface.

5. Die according to Claims 1 to 4 , characterized in that it is pierced with an opening intended to accommodate a central coextrusion nozzle.

6. Process of manufacturing an expanded cereal having the general shape of an array of adjoining expanded strands, consisting in cooking-extruding-expanding, under a pressure of 40-180 bar at 105-180°C, a mixture comprising, in parts by weight, 60-90 parts of starch- containing substance, up to 15 parts of sugar, up to 10 parts of oil, and water added until the water content is 7 to 20% by weight of the mixture, extruding through at least one die according to one of Claims 1 to 4.

7. Process according to Claim 6, in which the size of the particles of the mixture is less than or equal to the half-diameter of the tubes of the die.

8. Process according to Claim 6, in which a coefficient of expansion of 1.5 to 2.5 is obtained for the extruded strands.

9. Process according to Claim 6, in which the extruded strands have a porous texture.

10. Process according to Claim 6, in which the extruded strands have a residual water content of 5- 12%.

11. Expanded cereal capable of being obtained by extrusion through a die according to Claim 1, having the general shape of an array of adjoining parallel expanded strands.

12. Cooked-extruded-expanded cereal product comprising an assembly of parallel expanded strands of a diameter between 0.75 and 10 mm, adjoining over all or part of their outer surface.

13. Cereal product according to Claim 12, characterized in that it is at least two-coloured.

14. Cereal product according to Claim 12, characterized in that it comprises a foodstuff.