FR2758332A1 - PROCESS FOR OBTAINING EXTRACT FROM ITS DESAMYLACE, REFINERY AND MATERIAL OBTAINED THEREBY - Google Patents

Abstract

The invention concerns a method for obtaining a starch-free bran extract and a cellulosed refined product, consisting in the following steps: a) mixing the bran with ten times its water volume at a temperature less than 50 DEG C and filtering it so as to recuperate starch milk and starch-free bran, the starch milk being then decanted, filtered or centrifuged, then dried; this step is repeated twice to obtain a starch-free bran with a starch content less than 1 % of dry matter by weight; b) contacting the starch-free bran with an aqueous sodium solution with a concentration ranging between 2 and 12 % by volume, in a liquid/solid ratio ranging between 5 and 100, at a temperature ranging between 20 and 100 DEG C, for a duration ranging between 5 and 120 minutes; then in diluting the mixture with water, if required, until a liquid/solid ratio higher than 25 is obtained and the solid residue is separated by filtering and by drying; in concentrating the filtrate, acidifying it to a pH ranging between 4.5 and 7, and precipitating with ethanol in a ratio of 2 to 4 volumes of alcohol for one volume of solution to obtain a coagulum, which is dried for obtaining an extract rich in hemicellulose. The invention is applicable to wheat bran.

Description

 The present invention relates to a process for obtaining a desamylated wheat bran extract, a raffinate and a material obtained from this process.

 Wheat bran is particularly rich in insoluble fiber, especially of hemicellulose type and is particularly known for its actions on digestibility, intestinal transit, inhibition of colon tumors.

Hemicelluloses constitute a vast family of cell wall polysaccharides, associated with cellulose, of very variable structure, depending on the nature of the plant and the organ from which they are extracted. They are used in fields as varied as pharmacy, cosmetics or food processing, as an excipient, flavoring agent and emulsifier as described for example in JP-A-07101881, JP-A-07079712, JP-A- 07101882,
JP-A-07099930, JP-A-071 02284, JP-A-060571176 and EP-A-301 440. They also have interesting effects especially for the regulation of cholesterol and blood pressure.

 Methods for splitting wheat bran such as described in US Patent No. 3879373 or in the publication Preparation and characterization of water soluble hemicellulose (arabinoxylan) from wheat bran in Nippon Shokukin Kogyo Gakkaish, 39, No. 12, are already known. p. 1147-1155 of 1992. These generally include an aqueous extraction step to remove the residual starch, followed by a step of solubilization of hemicelluloses in alkaline medium.

Very often, wheat bran will have previously undergone one or more pretreatments such as delipidation, deproteinization, delignification, using various solvents as described in the publications Constitution of a hemicellulose from wheat bran in Canadian Journal of Chemistry, 33, p. 56-67 of 1955 and Fractionation of wheat bran carbohydrates in J. Sci. Food. Agric. 32, p. These pretreatments associated with multiple purification operations for the purpose of isolating a hicellulosic fraction as pure as possible, result in yields of hemicellulosic extracts limited and weakly active rheologically. Moreover, none of these purified extracts have film-forming properties or coating agents.

 It is also an object of the present invention to provide a process for obtaining a desamylated wheat bran extract which limits the number of steps and reduces the use of solvents.

 Another object of the present invention is to provide such a method which makes it possible to obtain an extract of hemi-cellulose-derived dry wheat bran in a yield higher than those of known processes.

 A further object of the invention is to provide a method of this type which makes it possible to obtain such an extract having a rheological and film-forming interest, with an acceptable cost of production.

 Another additional object of the invention is to provide a process of this type which makes it possible, after recovery of the extract, to recover the cellulosic residue in the field of thermopressed materials, in order to obtain molded, recyclable and compostable parts, as a substitute for plastic parts for packaging and packaging.

These and other objects which will become apparent are attained by a process for obtaining a desamylated wheat bran extract, and a cellulosic raffinate which is characterized, according to the present invention, by the fact that it comprises the following steps a) the wheat bran is mixed with ten times its volume of water at a temperature
less than 50 ° C. and filtered so as to recover a starch milk and a deamylated bran, the starch milk then being decanted, filtered or centrifuged and then dried, this step is repeated once or twice to obtain a deamylated starch content less than 1% of the dry matter, by weight, b) the deaminated bran is brought into contact with an aqueous sodium hydroxide solution whose concentration is between 2 and 12%, by mass, in a liquid / solid ratio included between 5 and 100, at a temperature between 20 and 100 ° C, for a period of time between 5 and 120 minutes, then the mixture is diluted with water, if necessary, to obtain a higher liquid / solid ratio at 25 and the solid residue is separated by filtration or dewatering, the filtrate is concentrated, acidified to a pH of between 4.5 and 7, and precipitated with methanol in a ratio of 2 to 4 volumes. of alcohol for a volume of solution, for r obtain a coagulate, which is dried to obtain an extract rich in hemicellulose.

Advantageously, step a) is repeated one to two times to obtain a deamylated bran having a starch content of less than 1% of the dry matter, by weight.
As for the material according to the present invention, it is obtained by mixing the extract obtained above in a proportion of between 10 and 50% by mass of highly accessible activated cellulosic fiber, obtained by fractionation of wheat or barley straw, and by thermomolding this mixture without addition of additive or glue
Thus, according to the present invention, the wheat bran is desamylated, and then the desamylated fraction is treated to obtain a hemicellulosic extract and a cellulosic raffinate. The invention is based on the demonstration of the remarkable and unknown properties of the desamylated wheat bran extract as a rheological and film-forming agent, usable in formulation as additives or thickening and gelling ingredients, and as a coating agent for the finishing and the protection of surfaces achieved by the implementation of the method. The hemicellulosic fractions obtained under different conditions of this process, especially when they are purer, lose their properties. The cellulosic raffinate resulting from this process provides the thermomolded parts without additive or glue, based on fractionated straw fibers, a better flexibility for a satisfactory mechanical strength, and this unexpectedly because the incorporation of wheat bran in the panels of particle or fiber is currently known to lower their mechanical characteristics, even in the presence of glue.

 According to the claimed method of the present invention, the wheat bran is mixed with ten times its volume of water at a temperature below 50 ° C. In fact, beyond 50 ° C., the appearance of gelation phenomena starch may interfere with washing. The water-soluble fraction comprising the water-soluble compounds and the suspended starch granules is separated from the residue by filtration. The starch milk thus obtained is decanted and filtered, or centrifuged and then dried. Depending on the origin of the bran and its initial starch content, the operation will be repeated once or twice until a deamylated bran containing less than 1% of starch is obtained. In the case of so-called fat bran milling issue, nearly 40% of the initial dry matter is thus extracted.

 Wheat bran, thus deamylated, but not dried, is brought into contact with an aqueous solution of sodium hydroxide whose concentration is between 2 and 12% by weight, a liquid / solid ratio of between 5 and 100, at a temperature between 20 and 100 ° C., for a period of between 5 and 120 minutes, advantageously, the following procedure will be carried out: the deamylated bran is brought into intimate contact with the sodium hydroxide solution at a concentration by weight of between 5 and 10% in a liquid / solid ratio of between 6 and 10, and at a temperature of between 20 and 50 ° C., for a period of less than 15 minutes, by means of a suitable mixing mixer such as a pulper or twin-screw mixer, so The paste is then stored in a maturation tank for a period of between 5 and 60 minutes, without stirring, so as to allow the continuation of the solubilization reaction of the hemicellulos. The paste is then washed thoroughly with water in a liquid / solid ratio of between 25 and 50 in a stirred system. The liquid / solid separation after solubilization in the alkaline phase is preferably carried out by dewatering on a fabric support, by filtration or by centrifugation, this latter solution imposing additional washes because of the possible formation of a gelled phase. The residue obtained is isolated, then washed or not according to the chosen valuation axis. This one, largely enriched in fibers, finds in fact various axes of valorization such as the fields food, animal or dietary or the materials.

 The washing may advantageously be carried out at a temperature of less than 50 ° C. in an apparatus with cylindrical walls, and with an elongate axis, comprising two corotating screws and axes parallel to each other and to the axis of the apparatus, divided into three downstream zones according to the direction of mixing.

In the first zone, or upstream zone, wheat straw and the pulp of its alkaline coming from the maturation tank are introduced. The set of screws situated in this zone has a profile adapted to impose on the mixture the following effects: a shearing effect which reduces the particle size, a kneading effect which makes it possible to intimately contact the straws, the sound and the alkaline solution impregnating the latter, - a compression effect which promotes the diffusion of the liquid phase within the lignocellulosic matrices, - a retention effect of the mixture intended to increase the residence time in the apparatus, and - an effect conveying the mixture to the second zone.

 A screw profile for obtaining such a combination of effects is, for example, a sequence of direct screw elements for conveying the mixture, of kneading elements of suitable shapes for bilobed, trilobed or wheeled shearing and mixing. notched, - screw elements, with single or double-threads with decreasing direct pitch to allow the transport of the material, with shear stress (copenetrating screws) and axial compression (reduction of the screw pitch), - d ' screw elements, single or double-threaded, with a reverse pitch, the role of which is to form a plug of material which ensures the compression of the mixture in this screw element the action of shearing and mixing is also very intense The mixture crosses the counter-net thanks to the space between the screws and the wall and / or has slots in the screw.

 In the second zone, or intermediate zone, the intimate mixture of straw-its-solution of soda which has crossed the mesh, is taken up by screws with direct pitch to be conveyed towards a point of water injection. The mixture is thus relaxed to promote exchanges with water to ensure the extraction of hemicellulose solubilized by the action of sodium hydroxide, by dilution or washing effect. The liquid / solid mixture is then subjected to a mechanical effect of mixing and compression thanks to the combination of a sequence of screws with decreasing direct pitch and reverse pitch. The effect of the mixture favors the contacting of the phases, and the dilution of the solubilized hemicelluloses the presence of straw fibers promotes the formation of a plug in the screw element with reverse pitch allowing the pressurization of the material. upstream. The compression effect ensures the pressing and spinning of the mixture to evacuate the liquid through filter grids disposed in the cylindrical wall of the apparatus. The filtrate collected contains solubilized hemicelluloses.

 In the downstream zone, or third zone, the wrung product that has crossed the seam, is taken by screws with direct pitch to be sent to the outlet of the device. The mixture of fiber of bran and straw may in this downstream zone, undergo a drying treatment and shaping, for example by extrusion through a die. For drying, the cylindrical wall will comprise heating means and means for evacuating the water vapor formed.

 The cellulosic fiber matrix, collected at the outlet of the apparatus as described above, can be thermoformed to form molded shapes strong enough to be substituted for parts made from plastics or composites in their applications. .

The presence of sound fiber incorporated in a ratio by weight of its deaminyl / straw between 0.1 and 0.5 provides greater flexibility to the materials required for certain applications. Such forms can not be obtained by direct thermoforming straw-bran mixtures, even after grinding.

 The alkaline viscous solution obtained by separating the liquid and the solid is directly concentrated, for example, by ultrafiltration on a polysulfone membrane compatible with the pH of the solution, having a cut-off of 10,000 Da. an internal lumen greater than or equal to 1.1 mm, because of the high viscosity of the solution. The increase of this internal diameter makes it possible to reduce the duration of the step and to increase the rate of concentration of the solution. The temperature should not exceed 50 C in order not to alter the free polysaccharide structures in the medium.

 This step can also be carried out by evaporation on a thin-film evaporator at temperatures between 35 and 50 ° C. Above 50 ° C., the solution can be altered; moreover, a solid film may be formed on the walls of the apparatus.

 This concentration step by ultrafiltration directly performed on the basic solution, has several advantages. it reduces the amount of acid necessary for the subsequent acidification, thus reducing, on the one hand, the salt content in the solution, and on the other hand, the production costs, and allows a recycling of the basic permeate as well as got. This concentration step also makes it possible to considerably reduce the volumes of alcohol involved subsequently during the purification by precipitation of the hemicellulosic extract.

 After concentration, the solution is acidified to a pH between 4.5 and 7, with a preferred pH of 5.5. Indeed, a slightly acidic pH promotes the precipitation of proteins and hemicelluloses A in the medium, and also promotes the precipitation of the extract in the alcohol forming a firmer precipitate.

Below 5.5 a significant amount of acid is required to achieve lower pH values, which increases costs and salt content.

 The thus acidified solution, characterized by its blank appearance, is precipitated in methanol in a ratio of one volume of solution to 2 to 4 volumes of ethanol, 2.5 volumes of methanol being the volume preferably retained.

It is left for the time necessary for precipitation at room temperature, or placed at 4 ° C to promote the formation of coagulum.

 To dry the hemicellulosic fraction thus obtained, a filter press is used to transform the coagulate formed into a powder having, in addition to a very light color, a high thickening and film-forming power and excellent surface coating capacity. This step is, moreover, fully extrapolated on a large scale at very competitive costs. The powder obtained after grinding has a solids content between 25 and 30% at the outlet, it can be left in the air for subsequent drying or dried in a column under air or other gas to avoid the formation of micro-aggregates. The residual ethanolic phase is distilled and reused.

 According to the process of the present invention, yields of isolated hemicellulosic extract of between 21 and 30% of the dry matter of bran, and between 35 and 50% of the dry matter of its desamylace, characterized by: a majority composition are obtained in non-cellulosic parietal polysaccharides, greater than 75% of the dry matter by weight of arabinoxylan and glucan type with Arabosetxylose weight ratios of between 0.3 and 0.7, a glucose content of between 8 and 25% of the material dry weight, - a minor composition of protein materials between 1 and 25% of the dry matter by weight, - a mineral ash content of less than 15% of the dry matter by weight.

 As a consequence of these characteristics, modulated according to the operating conditions of their production, the hemicellulosic extracts have the following properties: a rheological behavior of Newtonian and thixotropic type in dilute aqueous solution of less than 1%, and rheofluidifier beyond. From a concentration of 2% in water, the hemicellulosic extract develops a strong increase in the viscosity of the medium which can reach values higher than 1,500 centipoise at 3% in water, at low speed gradients. which makes it comparable to commercial synthetic thickeners like cellulosic derivatives. This viscosity is remarkably stable in a large gram of pH (4 to 10) and insensitive to salt content. A very strong synergy develops with carob extracts leading to viscosities greater than 4,000 centipoise at low speed gradient and 300 centipoise at high speed gradient for concentrations of 1% of each of the polysaccharides in water. At higher concentrations (4 to 6%), the hemicellulose extract leads to obtaining gels comparable to those obtained from carrageenans.

a film-forming power allowing a surface coating of good quality, with breaking strengths of the films obtained without the addition of plasticizers greater than 40 M Pa, which places them in the range of films obtained from cellulosic solvents, starch or polyethylenes.

 Exemplary embodiments of the method according to the present invention are given below in order to better enable the person skilled in the art to implement it and to illustrate its advantages.

 The following examples are intended to illustrate the flexibility of the process which makes it possible to obtain extracts of its desamylate with yields and a rheological quality that can be modulated according to the operating conditions. All percentages are by weight unless otherwise indicated.

Example 1
In this example, we use a wheat bran without preliminary grinding that contains about 90% dry matter. Its composition is the following in% of the dry matter:
Hemicelluloses 38%
Lignines 7%
Celluloses 9%
Starch 13%
Protein 15%
Mineral ash 5% lo Desamylation
The device used is a stirred reactor equipped with an integrated filter. The operating conditions in this example are as follows:
The wheat bran is mixed with ten times its volume of water at a temperature of 40 ° C for 15 minutes, then the liquid phase, containing the suspended material, is drained through the filter. 4.3% dry matter, the suspension is allowed to decant, the residual sound is again mixed at ten times its volume at 40 ° C. for 15 minutes, the starch milk obtained in this second phase contains 1.3 % of dry matter. This second suspension is allowed to settle. Finally, the residual sound is once again mixed with ten times the volume of water at 40 ° C. for 15 minutes (the duration of the last steps can be reduced to 5 minutes) .The starch milk obtained contains 0.6% of dry matter, this third suspension is allowed to settle.

After complete decantation, the three supernatant phases are collected and can be reused as a wash phase on a new sound. The three fractions of starch pits are also collected, concentrated and then dried. They will find different valorization axes (textile, paper, glue ...).

A total of 40.6% of the initial dry matter was thus extracted and the composition of the desamylated wheat bran is as follows, as a percentage of the dry matter
Hemicelluloses 60%
Lignines 8%
Celluloses 15.5%
0.5% starch
Protein 15%
Mineral ash 1% 2 "Obtaining the hemicellulosic extract
The alkaline treatment of wheat bran thus desamylated is carried out in a stirred reactor under the following conditions:
Concentration of sodium hydroxide 4%
Reaction temperature 50 ° C
Liquid / solid ratio 50
Reaction time 1 hour
Its désamylacé 20 g sec
The mixture is then filtered on a propylene fabric with a porosity of between 1 and 5, wrn. The filtrate is concentrated 2 times under reduced pressure, adjusted to pH = 5.5 by addition of acetic acid, then mixed with 3 volumes of ethanol and placed for 12 hours at 4 ° C. to promote the formation of a coagulate. This is then taken up in methanol and then filtered on paper and dried at room temperature.

 The yield of hemicellulosic extract is 35.5% relative to the dry son désamylacé, or 21.3% compared to the initial dry son.

The hemicellulose powder thus isolated has the following characteristics
Arabinoselxylose ratio 0.41
Glucose content 12.1% of the dry matter
Protein content. 7.75% of the dry matter
Mineral ash content 10.4% of dry matter
The viscosity of a 2% organic solution of the hemicellulosic extract in water, measured using a Carrimed 50 imposed stress rheometer, at a temperature of 20 ° C and a pH of 7, is 210 cp at 0.5
N / m2 and 158 cp to 2N / m2
Example 2
The wheat bran used in this example belongs to the batch of its désamylacé obtained in Example 1, and therefore has the same characteristics.

The alkaline treatment conditions are as follows:
Concentration of sodium hydroxide 6%
Reaction temperature 25 ° C
Liquid / Solid Ratio 75
Reaction time 1 hour 30
Its désamylacé 20 g sec
The protocol for the following steps is in all respects similar to that described in Example 1. The hemicellulose powder thus isolated has the following characteristics:
Arabinose / xylose ratio 0.36
Glucose content 13.5% of the dry matter
Protein content: 9% of the dry matter
Mineral ash content 11.5% of dry matter
The extraction yield obtained under these conditions is 34.5% relative to the desamylated bran, ie 20.7% relative to the initial dry bran. The viscosity measured under the same conditions as in Example 1 is 411.degree. cp at 0.5 N / m2 and 241 cp at 2 N / m2
Example 3
The wheat bran used in this example belongs to the same batch of its désamylacé obtained in Example 1, and therefore has the same characteristics.

The alkaline solubilization conditions are as follows
Sodium concentration 6%
Reaction temperature 75 ° C
Liquid / Solid Ratio 75
Reaction time 1 hour 30
Its désamylacé 20 g sec
The protocol relating to the following steps is in all respects similar to that described in Example 1. The extraction yield obtained under these solubilization conditions is 45.5% relative to the desamylated bran, ie 27% relative to the broth. initial dry. The hemicellulose powder thus isolated has the following characteristics
Arabinose / xylose ratio 0.48
Glucose content 11.3% of dry matter
Protein content '3% of dry matter
Mineral ash content 11.5% of dry matter
The viscosity measured under the same conditions as in Example 1 is 61 cp at 0.5 N / m 2 and 54 cp at 2 N / m 2
These three examples illustrate that the best rheological qualities of the desamylated wheat bran extract are obtained for a rather weak arabinose / xylose ratio (0.36) corresponding to a less substituted hemicellulosic arabinoxylan fraction, for a rather high protein content. (9%), and a rather high glucose content (13.5%) corresponding to the presence of glucans.

 The following examples are intended to compare different conditions of implementation of the process and their impact on. the qualities of the extract of its désamylacé.

Example 4
The wheat bran is deylylated under the same conditions as those described in Example 1. The liquid / solid mixture is separated in a 50 liter capacity spinner on porous propylene fabric of between 1 and 5 μm. The cellulosic residue obtained is washed to pH 7.

 The basic filtrate obtained is concentrated 1.7 times and partially demineralized by ultrafiltration, at a temperature of less than 40 ° C., on a polysulfone hollow fiber membrane having a cut-off point of 10,000 Daltons, a light of i, 1 mm and a filtration area of 0.45 m2- The permeate which contains a part of the sodium hydroxide is stored for later recycling.The pH of the retentate is adjusted to 5.5 by adding acetic acid, mixed with 2.5 volumes of ethanol and stored at 4 ° C for 12 hours. The coagulate formed is removed and introduced into a filter press tank, for example of the type LAROX PF 0.1 H2 equipped with a calendered multifilament polyester filter cloth, with a quantity of ethanol such that the suspension has a content of 3 % of the dry matter. The capacity is 1.22 kg / m2 and a dryness of the hemicellulosic powder cake of 25 to 30% allows an automatic debate. The powder thus obtained is dried under a stream of air.

The yield of hemicellulosic extract is 27% compared to the dry son désamylacé, or 16% compared to the initial dry son. The hemicellulose powder thus isolated has the following characteristics:
Arabinose / xylose ratio 0.36
Glucose content 10% of the dry matter
Protein content: 7.4% of the dry matter
Mineral ash content 4% of dry matter
The viscosity measured under the same conditions as in Example 1 is 270 cp at 0.5 N / m 2 and 103 cp at 2 N / m 2.

The applicability as a rheological additive is illustrated by the qualities of a matte white acrylic emulsion paint, formulated with the hemicellulosic extract in substitution of a commercial rheological agent of the cellulose derivative type, all else being identical elsewhere.
Painting Formula
Aqueous gel of the rheological additive 308 g
Coatex Wetting Agent P 90 1.78 g
Nopco NXZ Antifoam 1.04 g
Titanium Dioxide Pigment Titration RL 68 62.34 g
Mineral filler Talc 20 MO 51.97 g
Calcium carbonate omyacarb extra CL 129.56 g
Durcal 5 331.94 g
Styrene-acrylic emulsion Rhodopas DS 910 108.92 g
Coalescence agent Texanol 3,12 9
Preservative agent Parmétol K 40 1.4 g
Quality compared to painting Manufacturing no difficulty
Storage stability 30 days at room temperature. identical to the control. Rheological behavior close to the control but with a more pronounced shear-thinning and thixotropic character Applicability of the paint compared with the control
- easier brushing
- less marked brushing marks
- better appearance of tension after drying
- better homogeneity and satin effect
- better drying.

 Matte. specular reflection almost identical to the control Water resistance or leachability: identical to the control.

The film-forming power of the hemicellulosic extract is measured by the stresses at break by stretching the films obtained by drying a controlled quantity of aqueous solution spread in a thin flat layer:

<tb><SEP> Concentration <SEP> of <SEP> Thickness <SEP> Constraint <SEP> Elongation
<tb><SEP> the <SEP><SEP> extract <SEP> solution of the <SEP><SEP> film obtained <SEP> to <SEP><SEP><SEP><SEP> break <SEP>SEP> rupture
<tb> hemicellulose <SEP> in <SEP> water <SEP> (mm) <SEP> (Mpa) <SEP> that of ultrafiltration. The demineralised aqueous solution obtained is separated into four equivalent fractions which will be dried according to four different drying modes. Lyophilization, Lyophilization with additive, Atomization, Atomization with additive.

The viscosity measurements of the aqueous solutions with 2% organic matter of the powders isolated at the end of these four drying treatments are grouped in the following table.

<tb><SEP><SEP> Mode <SEP> Dry <SEP> Viscosity <SEP> at <SEP> 0.6 <SEP> N / m2
<tb><SEP> Iophilization <SEP> 24
<tb> lyophilization <SEP> with <SEP> additive <SEP> 24
<tb><SEP> atomization <SEP> 25
<tb> atomization <SEP> with <SEP> additive <SEP> | <SEP> 10
<Tb>
This example illustrates the sensitivity of the qualities of the hemicellulosic powder to the conditions of its isolation.

Example 6
3 kg of dry matter of its désamylacé under the conditions described in Example 1 are intimate contact with an 8% sodium hydroxide solution, in a liquid / solid ratio of 7.2 to 50 C, in a pulper equipped with its base of a helicordal stirring turbine allowing an efficient mixing of the dough by a simultaneously circular and ascending movement. After dilution with water until a liquid / solid ratio of 50 is obtained, the hemicellulosic powder extracted is isolated according to the same protocol as described in Example 4. The results obtained are collated in the following table.

<tb> Time <SEP> of <SEP> contact <SEP> with <SEP> the <SEP> pulper <SEP> (min) <SEP> 5 <SEP> 60
<tb> Yield <SEP>(<SEP>%<SEP> / <SEP> initial <SEP>) <SEP> 14 <SEP> 20
<tb><SEP>(<SEP>%<SEP><SEP> / <SEP> its <SEP> desam <SEP> laced <SEP> 23 <SEP> 33
<tb> Report <SEP> arabinose / xVlose <SEP>. <SEP> 4 <SEP> 0 <SEP> 46 <SEP>
<tb> Content <SEP> in <SEP> material <SEP> protein <SEP>% <SEP>% <SEP> / MS) <SEP> 15 <SEP> 7
<tb> Content <SEP> in <SEP> ash <SEP> mineral <SEP>(<SEP>%<SEP> / <SEP> MS) <SEP> 3.5 <SEP> i <SEP> 6
<tb> Viscosity <SEP> of a <SEP> solution <SEP> to <SEP> 2 <SEP>% <SEP> to <SEP> 0.5 <SEP> N / m2 <SEP> (cp) <SEP> c <SEP> 244 <SEP> 103 <SEP>
<Tb>
Example 7
Wheat bran, difamylated under the conditions identical to those mentioned in Example 1, is brought into intimate contact with an 8% sodium hydroxide solution, at 50 ° C., in a twin-screw mixing reactor of the CLEXTRAL BC type. 45 with a screw profile equipped with bilobed kneaders and counter-kneaders to obtain an efficient mix The flow rate of its deylylated broth is 5.3 kg of dry matter per hour, for a flow rate of 8% sodium hydroxide solution. kg / h, defining a liquid / solid ratio of 8.1 For a screw rotation speed of 50 rpm, the residence time is 2 minutes on average.The pasty mixture obtained at the outlet of the twin-screw mixer is stored in a buffer tank for a variable duration, diluted with water to obtain a liquid / solid ratio of 50 before being treated according to the same protocol as in Example 4.

The isolated powder has the following characteristics

<tb> Time <SEP> of <SEP> contact <SEP> in <SEP><SEP> Tray <SEP> Buffer <SEP> (min) <SEP> 5 <SEP> 60
<tb> Yield <SEP>(<SEP>%<SEP> / <SEP> initial <SEP>): <SEP> 12.5 <SEP> 17
<tb><SEP>(<SEP>%<SEP> / <SEP> its <SEP> deoxylated) <SEP> 21 <SEP> 28
<tb> Report <SEP> arabinose <SEP> dare <SEP> O <SEP> 4 <SEP> 7 <SEP>
<tb> Content <SEP> in <SEP> material <SEP> protein <SEP>(<SEP>%<SEP> / MS) <SEP> 13 <SEP> 7
<tb> Content <SEP> in <SEP> ash <SEP> mineral <SEP>(<SEP>%<SEP> J <SEP> MS <SEP> 5 <SEP> 4 <SEP>
<tb> Viscosity <SEP> of a <SEP> solution <SEP> to <SEP> 2 <SEP>% <SEP> for <SEP> a <SEP> constraint <SEP> of <SEP> 0.5 <SEP > N / rnZ <SEP> 235 <SEP> 137
<tb> (cp)
<Tb>
These examples illustrate the best rheological qualities of the hemicellulosic extract obtained by a very effective contact of the sound and the alkaline solution with limited contact time and a low liquid / solid ratio (7 to 8).

EXAMPLE 8
In this example, the wheat bran desamylated under the conditions identical to those mentioned in Example 1, is placed in intimate contact with a 6.8% sodium hydroxide solution, with a liquid / solid ratio of 7 at 50 ° C. in a mixing reactor identical to that described in Example 7. The pasty mixture is stored for 15 minutes in a buffer tank, diluted with water to reach a liquid / solid ratio of 12 and introduced into the first zone of the Cylinder wall apparatus described above, with a flow rate of 35.9 kg / h, simultaneously with wheat straw with a flow rate of 5.47 kg of dry matter per hour. This apparatus or extractor-reactor is for example of the bi-screw type such as that marketed by CLEXTRAL. The speed of rotation of the screws is 170 rpm and the sleeve temperature is maintained at 50 ° C. In the second zone, water is injected at a flow rate of 85 kg / h, the liquid / solid ratio being then the filtrate is collected through the gates of the dewatering module and treated according to a protocol identical to that described in Example 1. The yield of isolated hemicellulosic powder is 22.5% with respect to the dry de-ionidized sound introduced.The yield of mixing straw fiber and its output from the reactor-extractor is 89% relative to the dry matter of bran and The qualities of this mixture of straw fiber and bran are illustrated by the fact that they lead to thermopressed materials of quality very similar to those obtained for straw-based materials treated under the same conditions. The quality s of the hemicellulosic powder are illustrated by the protective film and finishing obtained by coating the surface of a thermo-formed material based on straw or sound, by a 4% aqueous solution. This film gives the piece an excellent finish and a good surface finish.

Claims (3)

 1. Process for obtaining an extract of its désamylacé and cellulosic raffinate, characterized in that it comprises the following steps a) the sound is mixed with ten times its volume of water at a temperature below 50 ° C. and filter so as to recover a starch milk and a deamylated bran, the starch milk then being decanted, filtered or centrifuged and then dried, this step is repeated once or twice to obtain a deamylated bran having a starch content of less than 1% of the dry matter by weight, b) the deaminated bran is brought into contact with an aqueous solution of sodium hydroxide whose concentration is between 2 and 12%, by weight, in a liquid / solid ratio of between 5 and 100, at a temperature between 20 and 100 C, for a period between 5 and 120 minutes, then the mixture is diluted with water, if necessary, until a liquid / solid ratio greater than 25 and the solid residue is Sep After filtering or squeezing, the filtrate is concentrated, acidified to a pH between 4.5 and 7, and precipitated with methanol in a ratio of 2 to 4 volumes of alcohol for a volume of solution, to obtain a coagulate, which is dried to obtain an extract rich in hemicellulose.  2. Process according to claim 1, characterized in that step a) is repeated once or twice to obtain a deaminated bran having a starch content of less than 1% of the dry matter by weight.  3. Material characterized in that it is obtained by mixing the solid residue obtained according to claims 1 or 2, or in a proportion of between 10 and 50% by mass of highly accessible activated cellulose fiber, obtained by fractionation of straw of wheat or barley, and said mixture thermomolding without adding additive or glue.