AP234A

AP234A - Process and apparatus for drying paste-form foods.

Info

Publication number: AP234A
Application number: APAP/P/1991/000247A
Authority: AP
Inventors: Ernest Badertscher; Gerald Bernard; Heribert Duc
Original assignee: Nestle Sa
Priority date: 1990-04-10
Filing date: 1991-04-08
Publication date: 1993-03-13
Also published as: AP9100247A0; ZA912434B; EP0451659A1; CH680611A5; TNSN91022A1; MA22111A1

Abstract

A paste-form food is distributed over an upper part of a rotatable

Description

This invention relates to a process and an apparatus for drying paste-form foods.

More particularly, the present invention relates to a process for the production of thick cereal flakes and to an apparatus for carrying out this process.

GB-PS 1,230,105, for example, relates to a process and apparatus in which a wet mixture is dried in the form of a film by application to the outer heated surface of a rotating roller.

According to that invention, the dried material has a natural tendency to curl so that it is possible, by detaching the film from the surface of the roller, to obtain a product having any desired thickness providing it is below

1.3 mm,

In the first place, however, the known process and apparatus cannot be used for the manufacture of products several millimetres in thickness and, in the second place, the material has to have a pronounced tendency to curl.

Accordingly, the object of the present invention is to solve these problems by making it possible to produce cereal flakes in any thickness, irrespective of the composition of the product in question.

Accordingly, the present invention relates to a process for drying paste-form foods in which a paste-form material is distributed over the upper part of a drying roller rotatable about its axis, the mixture adhering to an outer surface of the roller where it forms a film, characterized in that the film is separated from the drying roller after N revolutions thereof, N being greater than or equal to 2, so that a multilayer product consisting of at least two film thicknesses is formed.

The present invention also relates to an apparatus for carrying out the process according to the invention in which a drying roller rotatable about its axis is fed by a hopper, the film formed being removed by a scraper, characBAD ORIGINAL

AP 0 0 0 2 3 4 terized in that the movements cf the scraper are controlled by a sensor which measures the rotation of the drying roller.

The other features and advantages of the invention will become apparent from the following description in conjunction with the accompanying drawings, wherein:

Figure 1 diagrammatically illustrates the drying apparatus according to the invention.

Figures 2.a to 2.e are diagrammatic views illustrating the various phases of the process according to the invention .

Figure 3 is a variant of the drying apparatus shown in Fig. 1.

In one known process, the various starting materials which make up the paste-form food are mixed with addition of water. The quantity cf water is reduced to the minimum which still enables the mixture to be pumped and pasteurized. Thus, the dry matter content is greater than 50% by weight and preferably of the order of 55% by weight.

Various compositions may be used, depending on the purpose for which the product is ultimately intended. For example, the dry matter may have the following composition before the addition of water:
Wheat flour	55.9%
Sucrose	30.0%
Skimmed milk	10.0%
β-Carotene	0.1%
Moisture	4.0%

Other compositions, for example based on starchy products, such as potato purees, may also be used, as may other cereal compositions.

The paste-form material obtained is then pasteurized in known manner.

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It is after pasteurization that the process according to the invention is applied.

The paste-form material is distributed over the upper part of a drying roller of known type rotatable about its horizontal axis, adhering to the outer surface of the roller to form a film.

According to the principal feature of the process according to the invention, the film is deposited in several thicknesses on the outer surface of the roller to form a multilayer product consisting of at least two film thicknesses .

It is thus possible, through the thickness of the film and the numb.r of layers, obtain a product of considerable thickness.

Once the product has reached the desired thickness, it is separated from the drying roller.

During the separation of the product, the drying roller continues rotating so that the monolayer film continues to be deposited on the surface of the roller thus freed from the product.

After the multilayer product has been completely separated, the separation phase stops and another cycle can begin in the course of which a multilayer product will be formed and will be separated from the roller on reaching the desired thickness.

The apparatus for carrying out the process according to the invention will now be described.

In the preferred embodiment of the invention shown in Fig. 1, two parallel drying rollers 1 and 2 situated in the same horizontal plane are designed to rotate in opposite directions and are in contact with one another under a predetermined force along a generatrix common to the two rollers. The directions of rotation of the two rollers converge from the upper part of the rollers towards their generatrix of contact.

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In one known apparatus, each drying roller is heated by a device (not shown) to a temperature at which the paste-form food to be treated is dehydrated.

A hopper 3 fed with paste-form material pasteurized by a device (not shown) is situated above the two drying rollers 1 and 2 opposite their generatrix of contact.

The hopper 3 is formed by two lateral walls 4, which extend over the entire length of the drying rollers 1 and 2, and two sides 5 which delimit the hopper 3 at the ends of the lateral walls 4.

A scraper 6 is provided on the upper part of each drying roller 1,2 outside the hopper 3, each scraper 6 extending over the entire length of the opposite drying roller 1,2, Each scraper 6 is rotatable about an axis x-x parallel to the axis y-y of the roller 1,2 with which it is associated under the control of a mechanism connected to an end-of-stroke detector (not shown) which limits the travel of each scraper 6.

Each scraper 6 is controlled by two jacks 7, each jack being actuated by an electromagnetic valve 8.

Each drying roller 1,2 is provided with means for determining its rotation.

In one preferred embodiment of the invention, these means consist of a toothed wheel 9 which is connected to an inductive sensor 10 and to a pulse counter 11 and delivers a predetermined number of pulses per roller revolution, for example one hundred, to the pulse counter 11.

As shown in Fig, 1, the toothed wheel 9 is integral with the drying roller 1,2 while the inductive sensor 10 is independent of the drying roller 1,2.

The operation of the apparatus according to the invention will now be described.

The paste-form material accommodated in the hopper 3 is deposited in the form of a film F onto each of the drying rollers 1,2, each film F being compressed by the two

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drying rollers at the generatrix of contact between the rollers. The scrapers are in their raised position.

The monolayer film F begins to be deposited onto the drying roller 1,2 (Fig. 2.a.). When the drying roller 1,2 has completed one revolution, the monolayer film F closes up on itself and a second layer can be deposited (Fig.

2.b) .

When the multilayer product has the sufficient thickness required at the generatrix of the drying roller 1,2 corresponding to the line of impact of the scraper 6, the electromagnetic valves 3 of the jacks 7 are actuated so that the scraper 6 is lowered to the surface of the drying roller 1,2 (Fig. 2.c).

With the drying roller 1,2 continuing to rotate, the multilayer product is separated from the outer surface of the roller while the monolayer film continues to be deposited onto the preceding layer (Fig. 2.d), a zone where the monolayer film has not yet been deposited after the scraper 6 appearing on the outer surface of the drying roller 1,2.

The drying roller 1,2 continues its rotation and, when the multilayer product has been completely removed (Fig. 2.e), the electromagnetic valves 9 are re-actuated, this time raising the scraper 6.

Accordingly, it can be seen (Fig. 2.e) that, after the first production cycle, a zone Z where no film is deposited is present on the surface of the drying rollers 1,2, i.e. the zone Z situated - in the direction of rotation of the drying roller - between the generatrix of contact between the scraper 6 and the drying roller 1,2 and the generatrix of contact between the two drying rollers 1,2.

A monolayer film has been deposited on a zone Z1 of the drying roller 1,2 complementary to the zone Z. In general, the zone Z1 still has a single layer at the end of the first production cycle and irrespective of the number of layers of the multilayer product.

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From this stage, the apparatus can effectively operate automatically.

At the start of a cycle, the pulse counter 11 is at the value zero.

Pl is the number of pulses - delivered by the inductive sensor 10 via the toothed wheel 9 of the drying roller

1,2 - required for the zone Zl to pass from one layer to N layers at the height of the scraper 6. This set value thus corresponds to the number of revolutions which the drying roller has to complete before the multilayer product begins to be separated.

P2 - Pl is the number of pulses delivered by the toothed wheel 9 which corresponds to the time required for separation of the multilayer product of N layers.

S is the signal determining the rotation of the drying roller 1,2 and corresponding to the number of pulses recorded by the pulse counter 11. With the drying roller

1,2 rotating, the film F is thus deposited first onto the zone Z and, after the film F has closed up on itself in the zone Zl, another layer can be deposited.

When the signal S reaches the value Pl, the scraper 6 is lowered by the jacks 7 and the electromagnetic valves 8, the product of N layers being separated.

As the drying roller 1,2 continues to rotate, the signal S reaches the value P2 and the scraper 6 is raised, its upper position being determined by the end-of-stroke detector.

Another cycle can then begin, the pulse counter 11 having been reset to zero.

In one variant of the apparatus according to the invention, the drying system can be formed by a single heated drying roller 1, as shown in Fig. 3, the film F being formed by an unheated satellite roller 12 of smaller diameter.

Irrespective of the drying system selected (a single

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AP Ο Ο Ο 2 3 4 drying roller or two drying rollers), the flakes obtained during separation of the multilayer product are then sieved .

After sieving, the flakes may be coated, for example with a sucrose-based syrup, and are then subjected to final drying according to the particular coating selected before being packed.

Claims

1. A process for drying paste-form foods in which a paste-form material is distributed over the upper part of a drying roller rotatable about its axis, the mixture adhering to an outer surface cf the roller where it forms a film, characterized in that the film is separated from the drying roller after N revolutions thereof, N being greater than or equal to 2, so that a multilayer product consisting of at least two film thicknesses is formed.

2. A precess as claimed in claim 1, characterized in that the roller continues to rotate during separation of the multilayer product from the surface of the roller, a monolayer film being deposited on the surface of the roller thus continuously freed from the multilayer product.

3. A process as claimed in any of the preceding claims, characterized in that a signal (S) corresponding to the rotation of the roller is compared with a first set value (Pl) corresponding to the number of revolutions of the roller from which the multilayer product has to be separated and, when the signal (S) reaches the first set value (Pl) , means for separating the multilayer product are actuated until the signal (S) reaches a second set value (P2) corresponding to the end of separation of the multilayer product.

4. An apparatus for carrying out the process claimed in any of the preceding claims, in which a drying roller (1,2) rotatable about its axis is fed by a hopper, the film formed being removed by a scraper (6) , characterized in that the movements of the scraper (6) are controlled by a sensor (10) which measures the rotation of the drying roller (1,2).

5. An apparatus as claimed in claim 4, characterized in that the sensor (10) is an inductive sensor connected to a toothed wheel (9) of the drying roller (1,2).

6. An apparatus as claimed in claim 4 or 5, characterized

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AP Ο Ο Ο 2 3 4 in that the scraper (6) is controlled by at least one jack (7) actuated by an electromagnetic valve (8).