DE3405208A1 - Process for the preparation of a water-binding agent based on hemicellulose, and the use of the agent - Google Patents

Abstract

In the process, hemicellulose is precipitated, using aliphatic alcohols, from the wood pulp alkalinisation liquor produced in the preparation of viscose. In order to obtain the technical-grade hemicelluloses, which are precipitated first, in readily separable form and to obtain these environmentally polluting hemicelluloses present in the hitherto virtually unusable alkalinisation liquors from a viscose fibre factory, in very pure form without expending a considerable amount of time and money, the following combination of measures is carried out: a) the alkalinisation liquor is concentrated to a hemicellulose content of from 90 to 140 g/l by ultrafiltration, b) the hemicellulose is precipitated from the concentrated alkalinisation liquor by means of a mixture of aliphatic alcohols and is centrifuged off, c) the centrifuged-off precipitate is washed at least once with a mixture of aliphatic alcohols in order to remove excess sodium hydroxide solution, d) the precipitate which has been pre-purified in this way is then treated successively with hydrochloric acid, hydrogen peroxide and magnesium hydroxide or magnesium salts, and e) finally the hemicellulose is separated off, dried and ground. The pure process product is suitably and usefully used as a water-binding or viscosity-increasing agent, preferably in foodstuff technology, for the production of high-fibre, reduced-calorie bakery products.

Description

Process for the preparation of a water-binding agent

based on hemicellulose and use of the agent The invention relates to a method for producing a water-binding agent based on Hemicellulose from the alkalizing liquor in cellulose in the preparation of viscose Felling of technical hemicellulose using aliphatic alcohols, as well as the use of products manufactured according to the process, in particular for Food technology.

When viscose is prepared in viscose fiber factories, the so-called "technical hemicelluloses", which are still discharged into the wastewater as waste and thereby undesirably reducing the biological oxygen demand of the waters raise. The term "technical hemicelluloses" is understood according to Götze (chemical fibers after the viscose process, 1967, page 120) generally those polysaccharides of the pulp, which are soluble in 18% sodium hydroxide solution. Chemically speaking these are both degraded cellulose and degradation products of the native hemicelluloses produced during the pulping process in the pulp production have arisen.

The analysis of a technical hemicellulose from the alkalizing liquor a viscose fiber mill derived from beech sulphite pulp gives, for example, the following Composition: 79% xylan, 2.5% araban, 7.5% glucan, 5% lignocellulose, 4% Moisture, 2% ash.

Since the technical hemicellulose pollutes the wastewater, became already tried to isolate these products. One method of this type is, for example described in DE-PS 873 650, the hemicellulose from the alkalizing liquor by means of a mixture of organic solvents, one of which in lye soluble and one is insoluble in alkali, is precipitated. In CH-PS 601.552 is a similar process described - where as. Aliphatic precipitants Alcohols are listed. A beneficial use of technical hemicellulose has not yet been proposed.

The problem with the known processes for the deposition is technical Hemicellulose from alkalizing liquors is that the precipitate is so voluminous and it is slimy that it cannot be filtered. The deposition of the precipitate can only be achieved by centrifugation using a solid bowl centrifuge, i.e. one Dekanters, which is very tedious.

The invention aims to avoid the disadvantages outlined and difficulties and the task arises, on the one hand, in a viscose fiber factory to treat the alkaline liquor in an environmentally friendly way by removing the wastewater burdensome technical hemicellulose after an improved and less time-consuming and costly process is obtained. Another to be solved according to the invention Task is to use the extracted hemicellulose in a more meaningful and beneficial way Way to use as a water-binding or viscosity-increasing agent, preferably in food technology.

The method with which the first-mentioned problem is solved exists from a combination of measures, u.zw.

a) that the alkalizing liquor by ultrafiltration to a hemicellulose content from 90 to 140 g / l is concentrated, b) that from the concentrated Alkalizing the hemicellulose by means of a mixture of aliphatic alcohols precipitated and centrifuged, c) that the centrifuged precipitate with a Mixture of aliphatic alcohols is washed at least once to remove excess To remove sodium hydroxide solution, d) that then the pre-purified precipitate one after the other treated with hydrochloric acid, hydrogen peroxide and magnesium hydroxide or magnesium salts and e) finally the hemicellulose is separated, dried and ground.

The treatment of the hemicellulose precipitate is preferably carried out with Hydrogen peroxide and magnesium hydroxide in an approximately 10% suspension in at least 60%, e.g. carried out in 80% aqueous methanol.

As far as the first two steps of the method according to the invention are concerned, so these are based on the knowledge that an ultrafiltration before the actual Precipitation facilitates the separation of the hemicellulose considerably.

With the help of this filtration the higher molecular weight hemicelluloses are removed with a molecular weight of over 4 - 5,000 from the low molecular weight hemicelluloses with a molecular weight of <4 - 5,000 separated and concentrated au.

The hemicellulose-containing one is advantageous in ultrafiltration Alkalizing liquor under a pressure of 0.15 bar and at a temperature of 60.degree pressed through a porous polysulfone membrane. Be in the continuous process the liquor flows are adjusted so that 80% of the liquid passes through the membrane and a hemicellulose concentration of 20 g / l point. 20% of the liquid are retained and as a concentrate with 120 g / l hemicellulose, this corresponds to 60% of the supplied hemicellulose, with a mixture of different stirred aliphatic alcohols. For example, if you have a portion of the concentrate with one part of a mixture of 3 parts of methanol, 2 parts of ethanol and 1 part Mixed isopropanol, 70% of the hemicellulose precipitates out as a solid precipitate and can now easily be separated with a solid bowl centrifuge. If carries out the same process, however, with a non-ultrafiltered lye a slimy precipitate, the precipitation yield is only 40% and the centrifugation time is three times as long. The cause of the poor sedimentation ability of this Precipitation is due to the fact that the low molecular weight hemicelluloses are more soluble in alcohol than the high molecular weight hemicelluloses and therefore give the precipitate a slimy consistency. Through ultrafiltration these harmful low molecular weight hemicelluloses are separated.

The precipitate obtained in this way consists, for example, of 40% hemicellulose. The rest is caustic soda, methanol, ethanol and isopropanol.

In order to obtain pure hemicellulose, according to the third step of the process according to the invention, the precipitate is subjected to a pre-cleaning, those in at least one, better two, washing with a pure alcohol mixture consists. The excess caustic soda is removed. The pre-cleaned one Precipitation can then consist, for example, in an alcohol / water mixture from 60% ethanol and 40% water, are suspended, whereupon the suspension saric acid is added until a pH value of about 2 is enough. Afterward the solid can be centrifuged off and again in an alcohol / water mixture for further cleaning, E.g. consisting of 80% methanol and 20% water, suspended with stirring and thereby an approximately 10% suspension can be obtained. Then this suspension with a hydrogen peroxide solution - for example with 5% of a 30% hydrogen peroxide solution - added and stirred for a while, about 15 min. Finally there is another Treatment with a suspension of magnesium hydroxide or magnesium salts for the purpose of Neutralization. The last step is centrifugation of the solid, which can be dried at 700C and ground to powder in a ball mill will.

This produced by the combination of the measures listed Hemicellulose powder is tasteless and odorless. The color of the powder, measured due to diffuse reflection at a wavelength of 457 nm, is pure white and thermal stable, i.e. unchanged after 10 minutes after heating to 220 C. Freedom of undesirable taste or odor is used in a taste test in the manner found that a 10% suspension of the hemicellulose powder produced with water at 700C Tasted by 10 different people and no negative taste judgment was determined will.

It should be noted that freedom from undesirable tastes and odor can only be achieved by combining the specified cleaning measures will. One would be treating with hydrochloric acid, hydrogen peroxide, and magnesium hydroxide or magnesium salts, or even omit just one of them, the result would be Hemicellulose powder is not sensory in terms of color, taste and smell to satisfy.

The invention further comprises the use of the in described Well-made hemicellulose powder for making with dietary fiber enriched, joule-reduced baked goods, which baked goods by preparing and Baking a dough containing cereal flour. The suggested use according to the invention is characterized in that during the preparation of the dough 5 to 50% of the solids, i.e. of the cereal flour including those used Additives and flavorings can be replaced by the hemicellulose powder.

According to a preferred embodiment of the invention, the hemicellulose powder used for the production of pastry products, with the base of the solid ingredients Wheat flour is. According to the invention, a hemicellulose powder is used in the preparation of the dough with a grain size of more than 90% below 60 ji and with a reflection of 70 to 75% used, the content of the hemicellulose powder based on 5 to 50% can amount to the solids content of the dough.

The proposed use according to the invention satisfies a long-standing one Need in food technology, particularly in the field of manufacture of baked goods. It is known that rye and wheat flour contains arabinoxylan, which, due to its great swelling capacity, the water-binding capacity of the flour and improves the toughness of the bread dough (D'Appolonia, B.L., McArthur, L.A., Amer. Assoc. Cereal, Chem. 52, 1975, p. 230).

In the literature it is also mentioned that certain, in grain seed husks occurring xylohemicelluloses have similar gelling and thickening properties such as gum arabic and karaya gum (Whistler, R.L., Shah, R.N., in Modified Cellulosics, Editors: Rowell, R.M., Young, R.A., Academic Press, New York, London, 1978). One tried, the bread quality like the enlargement to improve the bread volume by adding to the naturally in the flour Occurring hemicelluloses are added to bread and other hemicelluloses obtained from other sources incorporated.

In DE-OS 2 047 504 it is proposed that in grasses or gramineae species To extract contained pentosans with dilute sodium hydroxide solution and after appropriate Add cleaning to the bread flour in a concentration of 1 - 3%. There is also rye and wheat belong to the Gramineae, the extracts are hemicelluloses, which are peculiar to flour.

The task is to make bread, especially white and fine bread, which stay fresh longer than normal due to a higher pentosan content. Another advantage of a high pentosan content in bread is that the hemicelluloses are indigestible. This fact is related to the fact that the Saccharide residues are linked by p-glycosidic bonds, which the cannot split the human organism. All hemicelluloses are accordingly Dietary fiber, which stimulates the activity of the intestinal flora, also a feeling of satiety without leading to the formation of superfluous fat deposits. Since the Nutritional science has recognized that a low-fiber diet is the disease of civilization the modern diet prefers fiber-rich, joule-diminished Food. In this endeavor it was also suggested to use part of the bread flour to replace it with powdered cellulose. Cellulose has the advantage of being large in size Quantities are available cheaply, making 20 to 30% of the flour at no extra cost replaced by this fiber could become. The physiological Aspects of adding cellulose powder to foods have been discussed in several reports of the World Health Organization, e.g. in WH0 Food Additives, Series No. 8, Toxicological Evaluation of some Foodcolours Geneva, 1975 b. It is believed that the cellulose crystallites penetrate the intestinal wall and enter the bloodstream and can trigger microembolisms in the blood vessels. This process is also called Persorption. Another disadvantage of cellulose is that it is in contrast to hemicellulose does not swell in water. Bread containing cellulose powder therefore does not have that either Ability to stay fresh longer due to a higher water content.

In contrast, the proposal according to the invention, cereal flour, in particular wheat flour, in the preparation of a baked goods dough according to the invention to replace manufactured hemicellulose powder, all demands made. These Additives bind water without forming rubbery gels; they provide fiber and cause a longer freshness time. They are in large quantities too available at a price that does not increase the cost of making bread, and they are completely indifferent to taste.

In order to have favorable conditions for the ripening of the bread To ensure some of the dough can, according to a preferred embodiment, a Starch degrading enzyme and / or an emulsifier based on diacetyltartaric acid and Lecithin can be added.

Those produced using hemicellulose according to the invention Baked goods showed significantly improved properties in storage tests baked goods produced in a conventional manner. Have so Storage tests in room air show that breads made without hemicellulose do after a day and a half have dried out to a moisture content of 20z. With an addition of 20% hemicellulose based on the total solid substance the so defined storage time four and a quarter days.

The value of the proposal according to the invention is particularly clear, if you compare the hemicellulose powder with wheat bran, the substance that is normally used to make high-fiber breads. Wheat bran is a brown colored and fibrous material that you can only add special types of bread such as graham bread. Whole grain breads too are high in fiber, but they have a grainy texture, which is rejected by many consumers. In contrast, according to the invention is produced Outwardly, hemicellulose powder is indistinguishable from the finest wheat flour. the Grain size is over 95% below 60 p, the reflection at 75%. Has for comparison Wheat flour of the type W 700 has a grain diameter of approx. 50 P and a reflection of 73%. It follows that hemicellulose powder can also be used for the preparation of Finest white bread and toasted bread can be used without texture or appearance affect the baked goods in any way.

In this context it should also be emphasized that until today no meaningful utilization for the hemicellulose contained in the alkalizing liquor could be found. There are only two proposals, these are technical ones To use hemicelluloses in the paper industry as an additive to paper stock (Das Österreichische Papier, January 1978, 31 (short message from the Finnish pulp and paper research institutes), Poppel E., Petrovici, V. Cellul. Chem. Technol. 1976, 101). However, these proposals have not yet become industrial Realized because of the color and strength of the paper thanks to the addition of hemicellulose be worsened.

The invention is illustrated in more detail by the following examples: Example 1: Beech sulphite pulp with a & -cellulose content of 91% in a continuously working mash chest in a ratio of 1: 37 for one At a temperature of 500C, alkalized with sodium hydroxide solution with a concentration of 225 g NaOH / l. After squeezing off the alkali cellulose, a filtrate liquor containing 40 g / l hemicellulose was obtained contained. It was heated to 60 ° C. and under a pressure of 15 bar in the circuit pumped around, constantly flowing past a porous polysulfone membrane. As a result at an overpressure of 15 bar, 80% of the liquid flowed through the membrane. This The filtrate contained 20 g / l hemicellulose with a molecular weight of 44-5,000. In the cycle, the hemicellulose fractions with a molecular weight accumulated from over 4 - 5,000 up to a concentration of 120 g / l. With this hemicellulose content the concentrate was drawn off continuously and in a ratio of 1: 1 with a Mixture of 3 parts of methanol, 2 parts of ethanol and 1 part of isopropanol stirred. 70% of the hemicellulose contained in the concentrate fell as a solid precipitate and were centrifuged in a full-wall centrifuge. The centrifuge sediment was stirred up twice with 10 times the amount of the alcohol mixture each time and centrifuged off again. The crude precipitation product, which has been pre-cleaned to this extent, was in 80% aqueous methanol in a ratio of 1:10 suspended and acidified to pH 2 with concentrated hydrochloric acid. After an hour Stirring, the solid was centrifuged off again and now in 60% aqueous Suspended methanol. The suspension was based on 5% with vigorous stirring the solids content of 30% hydrogen peroxide solution was added and then so much magnesium hydroxide that the pH rose to 7. After stirring for one hour the 0 precipitate was centrifuged off again and at 70 C in a circulating air drying cabinet dried. The dried cake was ground with a ball mill for so long until only 5% of the powder is retained by a sieve with a mesh size of 60M became. The taste of this powder was neutral. The reflectance was 72 and after 0 10 minutes heating to 220 C at 40%.

Example 2: This example is for comparison purposes. It became the same Procedure carried out as in Example 1, only with the difference that the last suspension has not been neutralized with magnesium hydroxide. This product was used by the test subjects attested an unpleasantly sour taste. The reflectance was 69 and after Heat at 29% for 10 minutes.

Example 3: This example was also used for comparison purposes. The powder was prepared in the same way as described in Example 1, only with the The difference is that the last suspension contains neither hydrogen peroxide nor magnesium hydroxide was moved. The taste of this powder was bitter. The reflection was 59 and after 10 minutes heating at 2200C at 34%.

Example 4: This and the following examples deal with the riding of toasted bread.

First, a bread dough was made from the following ingredients: 730 g wheat flour, type W 700 300 g hemicellulose powder, manufactured accordingly Example 1 20 g of diastase (starch-degrading enzyme) 10 g of emulsifier from diacetyltartaric acid and lecithin 35 g table salt 80 g baker's yeast 1 1 water The ratio of flour to The water was 100: 97, corresponding to a water content of 49.2% in the dough. To If the dough was left to rest for 30 minutes, breads were formed from the dough, which had a dough fermentation were also exposed for 30 minutes. After a baking time of 40 minutes at 2400C a baking loss of 9% was found. After the bread has cooled completely the water content of the bread was determined by drying it at 110 ° C. for 24 hours.

It was 46.4%. After a storage period of five and a half days the water content was 20% and the bread was hard to the touch.

Example 5: A bread dough was made from the following ingredients: 481 g wheat flour, type W 700 474 g wheat flour, type W 1600 244 g hemicellulose, according to Example 1, 40 g of diastase 20 g of emulsifier. Diacetyl tartaric acid and Lecithin 35 g salt 80 g yeast 1 1- water The dough yield was 100: 83.3, corresponding to a water content of 45% in the dough. According to the normal Dough rest and dough fermentation, the breads were baked at 240 ° C. for 29 minutes. The loss of baking was 6%, the water content of the bread was 43.1%. After a storage time of three and a half Days a moisture content of 20% was determined. Example 6: It was a Bread dough made from the following ingredients: 1,042 g wheat flour, type W 700 267 g hemicellulose, corresponding to Example 1 40 g diastase 30 g emulsifier from diacetyltartaric acid and lecithin 35 g table salt 80 g yeast 1 1 water The dough yield was 100: 76.5 determined, corresponding to a water content of the dough of 43.5%.

The baking loss was 10% and the water content of the finished bread at 41.5%. The moisture content of 20% is achieved after a storage time of four and a quarter days in an indoor space.

Example 7: This example was for comparison purposes. The dough became made without the use of hemicellulose powder and is composed as follows: 1,750 g flour, type W 700 40 g niastase 35 g table salt 80 g yeast 1 1 water the Dough yield was 100: 57, corresponding to a water content of the dough of 36.4 %. The times for dough resting and dough proofing were again 30 minutes each. The baking time at 2400C was also 30 minutes.

The baking loss was determined to be 10%. The water content of the so produced Breads was 34.9%. After only 1 1/3 days of storage there was a water content set of 20%. All storage experiments were carried out with halved bread, so that the water both directly from the breadcrumb and through the layer of bark could escape.

In the finished, fiber-enriched and joule-reduced Baked goods can be sorted according to the baking loss and the remaining water content 2 to 50 z of the hemicelluloses produced according to the invention may be included, with these hemicellulosai mainly consist of xylan in addition to araban, glucan and lignocellulose exist.

Another possible use of the manufactured according to the invention Hemicellulose powder is used as a starch substitute. Strength becomes more extensive Way as a thickener and gelling agent of aqueous preparations, in particular in the food industry, but also in the textile industry for finishing, as a plain, etc. is also used as a filler or carrier in pharmacology. The hemicellulose powder produced according to the invention can in most cases and especially in the manufacture of reduced Joule food preparations Substitute starch, with about 4 to 5 parts by weight hemicellulose about 1 part by weight Strength match.

Claims (7)

Claims: 1. A method for producing a water-binding Means based on hemicellulose from the alkalizing liquor of cellulose in the Viscose preparation by precipitating the technical hemicellulose using aliphatic alcohols, characterized by the combination of the measures: a) that the alkalizing liquor by ultrafiltration to a hemicellulose content of 90 to 140 g / l is concentrated, b) that from the concentrated alkalizing liquor the hemicellulose is precipitated by means of a mixture of aliphatic alcohols and is centrifuged, c) that the centrifuged precipitate with a mixture from aliphatic alcohols is washed at least once to remove excess caustic soda to remove, d) that then the pre-cleaned precipitate successively with hydrochloric acid, Treated hydrogen peroxide and magnesium hydroxide or magnesium salts and e) finally the hemicellulose is separated, dried and ground. 2. The method according to claim 1, characterized in that the treatment of the hemicellulose precipitate with hydrogen peroxide and magnesium hydroxide an approx. 10% suspension in at least C-acidic methanol will. 3. Use of the according to the method according to claims 1 or 2 obtained hemicellulose for the production of fiber enriched, Reduced joule baked goods by preparing and baking a cereal flour containing it Dough with the proviso that in the preparation of the dough 5 to 50% of the solids by Hemiceilulose powder can be replaced. 4. Use of the according to the method according to claims 1 or 2 obtained hemicellulose for the production of pastry products by preparation and baking a dough containing wheat flour with the proviso that in the preparation of the Doughs the hemicellulose powder with a grain size of more than 90 + below 60 P. and is incorporated into the dough with a reflex on of 70 to 75%, the Content of the hemicellulose powder 5 to 50% based on the solids content of the Can be dough. 5. Use of the hemicellulose according to claim 4 with the proviso that a starch-degrading enzyme and / or a rmuiciator based on diacetyl tartaric acid in the dough and lecithin can be incorporated 6. Fiber-fortified, joule-reduced Baked goods, characterized in that they are pure, tasteless and as roughage Contain odorless hemicelluloses in an amount of 2 to 50%, the hemicelluloses consist mainly of xylan in addition to araban, glucan and lignocellulose. 7. Use of the according to the method according to claims 1 or 2 obtained hemicellulose as a starch substitute in water-containing food preparations with the proviso that about 4 to 5 parts by weight of Kemicellulose about 1 part by weight Replace starch.