WO2000067908A1

WO2000067908A1 - Flouring process

Info

Publication number: WO2000067908A1
Application number: PCT/EP2000/002864
Authority: WO
Inventors: Rudolf Wespi; Ernest Badertscher
Original assignee: Societe Des Produits Nestle S.A.
Priority date: 1999-05-07
Filing date: 2000-04-03
Publication date: 2000-11-16
Also published as: MA25410A1; AP2001002316A0; OA12196A; AU4396900A

Abstract

Flouring process and equipment comprising surface moistening (1) cereal grains or legume seeds by treating them with vaporized superheated water, impact milling (2) the surface moistened grains or seeds and sieving (3) the milled grains or seeds.

Description

Flouring process

The present invention relates to a flouring process and equipment .

Traditional wheat flouring equipments are known to be heavy, complicated and costly as they comprise numerous, interconnected milling machines and screening machines.

EP0218012 discloses a wheat flouring pretreatment system consisting of a plurality of friction type wheat polishing machines disposed in series, moisture being supplied to the polishing chamber of at least one of the polishing machines to moisten and soften the entire pericarp of each grain in order to increase a frictional contact force between the grains. EP0218012 however discloses a flouring equipment which, in addition to this wheat flouring pretreatment system, still comprises numerous, interconnected milling machines and screening machines .

DE830604 discloses an impact mill which may be used for milling wheat and other cereal grains which have been prewetted in such a way that the bran gets slightly leathery. DE830604 however discloses a flouring equipment which comprises several such impact mills in series.

A first object of the present invention is to provide a flouring process and equipment which not only are light, simple and economical but also are actually efficient .

A second object of the present invention is to provide a versatile flouring process and equipment which may be used for milling any kind of cereal grains or legume seeds.

To this end the present process comprises the steps of surface moistening cereal grains or legume seeds by treating them with vaporized superheated water, impact milling the surface moistened grains or seeds and sieving the milled grains or seeds.

Similarly, the present equipment comprises means for surface moistening cereal grains or legume seeds by treating them with vaporized superheated water, these means being connected to an impact mill itself connected to a sieving machine .

It has surprisingly been found that it is possible with such a simple, light and economical process and equipment to prepare, with a relatively high extraction degree, from any kind of cereal grains or legume seeds, a flour which has a relatively high purity or quality and a relatively well defined granulometry.

It has also surprisingly been found that, in the case of wheat flouring, it is possible in this way not only to work very efficiently but also to take care of wheat gluten, because the grains are only heated to temperatures up to 45°C, for example.

Throughout the present description the expression "vaporized superheated water" means "water heated to a temperature well above 100 °C, especially at from 135 °C to 175°C, preferably at from 140 to 160°C, vaporized or sprayed under a pressure well above atmospheric pressure, especially under a pressure of from 3 to 8 bar, preferably under from 3.3 to 6 bar, through a spraying nozzle which opens into a space under atmospheric pressure and which is capable of holding the pressure difference between spraying pressure and atmospheric pressure" .

The expressions "particle size d¹ " and "regularity n" correspond to the "particle size index (d¹)" and the "uniformity index (n) " according to the International Norm ISO 2395 which are defined by interpreting sieving trials while applying the logarithmic form of the Rosin, Rammler and Sperling (RRS) equation and using the diagram of Puffe.

For carrying out the present process it is thus possible to start with dry grains of every kind of cereals such as wheat, rice, oat, barley or millet, or with dry seeds of every kind of legumes such as pea, bean or lentil, for example .

A starting superheated water may be tap water superheated by steam injection, for example.

The step of surface moistening the grains or seeds by treating them with vaporized superheated water may be carried out by means of an adequate screw conveyor and/or mixer of the food industry equipped with adequate spraying means, for example.

The adequate screw conveyor and/or mixer may be an Archimedean screw, a screw or twin screw of a traditional food extruder or mixer, or a hollow helical screw, in other word a helix, for example.

The adequate spraying means may comprise one or more spraying nozzles capable of holding the pressure difference between spraying pressure and atmospheric pressure. Such nozzles may comprise a cylindrical conduct having a circular opening of relatively small diameter positioned beneath or within a flow of grains or seeds to be treated within a screw conveyor and/or mixer, for example.

In a preferred case where the screw conveyor and/or mixer is a hollow helical screw or helix, one or more such spraying nozzles may be provided for at a down stream end or along the wall of a feeding tube positioned coaxially within the helix at an upstream end of the helix, for example .

The step of impact milling the surface moistened grains or seeds may be carried out by any adequate impact mill, especially good results being obtainable by using a pin mill, for example.

The step of sieving the milled grains or seeds may be carried out by an adequate sieving machine of the food industry such as an air stream classifier, an air jet sieve or a rotating and/or swingable group of superposed sieves or screens.

Preferably, the sieving step is carried out with a sieving machine at least one sieve of which has a mesh size of from 0.2 to 0.3 mm.

It has surprisingly been found that it is possible in this way to obtain, with a relatively high extraction rate, namely an extraction rate of from 65 to 90%, a flour which has a relatively high purity, namely an ash content of from 0.73 to 1.75% and which has a relatively well defined granulometry, namely a regularity n of from 1.0 to 3.0 for a particle size d¹ of from 0.04 to 0.10 mm, for example.

The present equipment thus comprises means for surface moistening cereal grains or legume seeds by treating them with vaporized superheated water, these means being connected to an impact mill itself connected to a sieving machine .

The means for surface moistening cereal grains or legume seeds by treating them with vaporized superheated water may comprise an adequate screw conveyor and/or mixer of the food industry equipped with adequate spraying means, for example .

The adequate screw conveyor and/or mixer may be an Archimedean screw, a screw or twin screw of a traditional food extruder or mixer, or a helix, for example.

The adequate spraying means may comprise one or more spraying nozzles capable of holding the pressure difference between spraying pressure and atmospheric pressure.

Such nozzles may comprise a cylindrical conduct having a circular opening of relatively small diameter positioned at one or more locations along the screw conveyor, for example.

In a preferred case where the screw conveyor and/or mixer is a hollow helical screw or helix, one or more such spraying nozzles may be provided for at a down stream end or along the wall of a feeding tube positioned coaxially within the helix, at an upstream end of the helix, for example .

The impact mill may be any adequate impact mill of the food industry, namely any impact mill capable of milling surface moistened cereal grains or legume seeds, with a relatively high extraction rate, especially an extraction rate of from 65 to 90%, to a flour having a relatively high purity, especially an ash content of from 0.73 to 1.75% and a relatively well defined granulometry, especially a regularity n of from 1.0 to 3.0 for a particle size d¹ of from 0.04 to 0.10 mm, for example.

An adequate impact mill may especially be a pin mill, for example . Such a mill may especially be capable of milling surface moistened soft wheat grains to a flour having an ash content of from 0.60 to 0.85, with an extraction rate of from 65 to 90%, for example.

Adequate impact mills, especially pin mills are currently manufactured and/or sold by companies such as Hosokawa Alpine in Augsburg (DE) , Atritor in Gentry (GB) , Bauermeister in Norderstedt (DE) , Denver in Salq (SE) , Jehmlich in Nossen (DE) , Kinematica in ittau (CH) ,

Netzsch-Condux in Hanau (DE) or Pallmann in Zweibrύcken (DE) , for example.

The sieving machine may be any adequate sieving machine of the food industry, namely a sieving machine capable of easily separating the bran from the flour obtained by milling the surface moistened cereal grains or legume seeds .

An adequate sieving machine may especially be an air stream classifier, an air jet sieve or a rotating and/or swingable group of superposed sieves or screens, for example.

Preferably, at least one sieve of the sieving machine has a mesh size of from 0.2 to 0.3 mm.

The equipment according to the present invention is described in greater detail below with reference to the accompanying drawing given by way of example and in which:

Figure 1 is an overall schematic representation of a preferred embodiment of the equipment.

In the preferred embodiment represented in Figure 1, the present equipment comprises means 1 for surface moistening cereal grains or legume seeds by treating them with vaporized superheated water, these means 1 being connected to an impact mill 2 itself connected to a sieving machine 3.

The means for surface moistening cereal grains or legume seeds by treating them with vaporized superheated water comprise a helix screw conveyor and/or mixer 4 equipped with spraying means 17.

The spraying means 17 are a spraying nozzle provided for at a down stream end of a feeding tube 5 positioned coaxially within the helix at an upstream end 6 of the helix conveyor .

The feeding tube 5 passes through a hollow shaft of a motor 18 driving the helix 4. The feeding tube 5 is itself fed through a valve 19 with superheated water 20 the temperature (T) and pressure (p) of which are checked by measuring means 21.

The impact mill 2 is a pin mill .

The sieving machine 3 is a group of rotatable and or swingable, superposed sieves 7.

During operation, grains or seeds are fed from a hopper 9 into the helix conveyor 1 through an inlet opening 8 provided for at the top of the upstream end 6 of the conveyor .

Superheated water is vaporized into the helix conveyor through the spraying nozzle 17 from which it escapes and expands at atmospheric pressure in form of a vapor or steam jet which immediatly condenses on the surface of the grains or seeds . The surface moistened grains or seeds are pushed out from the conveyor through an outlet opening 10 provided for in the bottom of a down stream end 11 of the conveyor, this outlet opening 10 being connected to the pin mill 2 through an inlet pipe 12.

The milled grains or seeds coming from an outlet pipe 13 of the pin mill are fed to a first sieve of the sieving machine 3 through an inlet pipe 14. Flour comming from the different sieves 7 is collected in a main container 15 while bran coming from a last sieve 22 is collected in a secondary container 16.

The process according to the present invention is described in greater detail in the examples presented below by way of illustration and in which the percentages are given by weight .

Example 1

An equipment corresponding to the preferred embodiment represented in Figure 1 is used, in which:

- the helix conveyor has a diameter of 80 mm and a length of 1600 mm, the helix itself has an inner diameter of 56 mm and an outer diameter of 76 mm,

- the single spraying nozzle is a TG type-TJniJet spraying opening or nozzle having a flow rate index of 0.3, a nominal opening of 0.51 mm, a free passage of max 0.41 mm in diameter, a flow rate of from 0.25 to 0.28 1/min for a spraying pressure of from 4 to 5 bar, and a dispersion angle of about 50°,

- the impact mill is an UPZ 315 type-ALPINE pin mill, and

- the sieving machine is a MPAR ROTOSTAR type-BUEHLER "Kleinplansichter" equipped with eight superposed sieves. 300 kg/h of soft wheat grains having a water content of 10.55% and an ash content of 1.62% were continuously heat treated along the helix conveyor by 17.5 kg/h of tap water previously steam heated to 156°C, this water being sprayed or vaporized under 4.4 bar into the helix rotating at 513 rpm.

The surface moistened grains coming out from the helix conveyor had a moisture content of 17.4% and a temperature of 31°C before entering into the pin mill which rotated at 8040 rpm.

The flour coming out from the mill was conducted onto the sieving machine each sieve of which had a mesh size of 0.20 mm.

The flour separated from the bran by the sieving machine had a moisture content of 13.27%, an ash content of 0.73%, a mean particle size d' of 0.06 mm, a regularity n of 1.18 and it was extracted at a rate or efficiency of 84.9%.

This means that the flour thus obtained was extracted at a relatively high rate and had a normal moisture content, a relatively high purity and a relatively well defined granulometry.

Examples 2 to 5

In a way similar to the way disclosed in Example 1, different flours were manufactured from different grains under different conditions.

The corresponding characteristics of the raw materials, intermediate products, process parameters and flours obtained are shown in table 1 herafter: Table 1

Table 1 shows that, as it was the case in Example 1, the flours obtained in Examples 2 to 5 were extracted at a relatively high rate and had a normal moisture content, a relatively high purity and a relatively well defined granulometry.

Claims

1. A flouring process, comprising the steps of surface moistening cereal grains or legume seeds by treating them with vaporized superheated water, impact milling the surface moistened grains or seeds and sieving the milled grains or seeds .

2. A process as claimed in claim 1, wherein the cereal grains or legume seeds are choosen from a group comprising wheat, rice, oat, barley and millet or pea, bean and lentil .

3. A process as claimed in claim 1, wherein the superheated water has a temperature of from 135 to 175 °C and it is vaporized under a pressure of from 3 to 8 bar.

4. A process as claimed in claim 1, wherein the superheated water has a temperature of from 140 to 160°C and it is vaporized under a pressure of from 3.3 to 6 bar.

5. A process as claimed in claim 1, wherein a flour is obtained, with an extraction rate of from 65 to 90%, which has an ash content of from 0.73 to 1.75% and a regularity n of from 1.0 to 3.0 for a particle size d' of 0.04 to 0.10 mm.

6. A process as claimed in claim 1, wherein the cereal grains are soft wheat grains and a soft wheat flour is obtained, with an extraction rate of from 65 to 90%, which has an ash content of from 0.60 to 0.85.

7. A flouring equipment, comprising means for surface moistening cereal grains or legume seeds by treating them with vaporized superheated water, these means being connected to an impact mill itself connected to a sieving machine .

8. An equipment as claimed in claim 7, in which the means for surface moistening cereal grains or legume seeds by treating them with vaporized superheated water comprise a screw conveyor and/or mixer equipped with spraying means .

9. An equipment as claimed in claim 8, in which the screw conveyor and/or mixer is choosen from a group comprising an

Archimedean screw, a screw or twin screw of an extruder or mixer and a hollow helical screw or helix.

10. An equipment as claimed in claim 8, in which the screw conveyor and/or mixer is a hollow helical screw or helix, a spraying nozzle being provided for at an upstream end of the conveyor, coaxially with the helix.

11. An equipment as claimed in claim 7, in which the impact mill is a pin mill.

12. An equipment as claimed in claim 7, in which the sieving machine is choosen from a group comprising an air stream classifier, an air jet sieve and a rotating and/or swingable group of superposed sieves.

13. An equipment as claimed in claim 7, in which at last one sieve of the sieving machine has a mesh size of from 0.2 to 0.3 mm .