NL1002494C2 - Method for oxidizing starch. - Google Patents

Description

Work WQZC for oxidizing starch

The invention relates to a method for reducing the viscosity of carbohydrates by oxidative degradation without metal catalysts.

Before it can be used industrially, starch has to undergo a treatment which reduces the viscosity. To this end, the starch is generally treated oxidatively at an elevated temperature (40-60 ° C) in an acid medium. For example, when using hypochlorite as an oxidizing agent in combination with sulfuric or phosphoric acid at about 60 ° C, the treatment takes 4-15 hours. The disadvantage of this method is the amount of salt formed and the extensive breakdown of starch.

Another method uses hydrogen peroxide with a heavy metal as the catalyst. However, the usually toxic catalyst is difficult to remove afterwards, even using compounds such as EDTA. A further drawback is the discoloration of the product.

US-A-5,362,868 discloses a method according to which the viscosity of (hydroxyethyl) starch is reduced by oxidation with a peracid. Peroxosulphuric acid (H2S05) or peracetic acid is used as peracid. The peroxysulfuric acid must be prepared on site from hydrogen peroxide and sulfuric acid, or a salt of the acid must be used, which has the drawback of producing salts as a by-product. The reactivity of peracetic acid is lower and leads to longer reaction times. US-A-5362,868 also describes that reaction with hydrogen peroxide leads to unacceptable reaction times.

According to DE-A-40.35053, one can bleach cellulosic materials such as cotton by treating the materials with peracetic acid without activators and simultaneously subjecting it to ultrasound (35 kHz).

The object of the invention is to provide a method for reducing the viscosity of starch and other carbohydrates with simple means, without the use of heavy metals and salt-forming agents, and without organic by-products.

This object is achieved by a process in which the carbohydrate is oxidized with hydrogen peroxide in the presence of an acylated carbohydrate as a catalyst.

1002494 2

As the carbohydrate that can be treated according to the method according to the invention, any wholly or partly water-soluble polysaccharide is suitable. This primarily includes starch and fractions and derivatives thereof, such as amylose, ethoxylated starch and carboxymethyl starch. Furthermore, the solubility of cellulose derivatives and inulin and derivatives thereof can be improved or the viscosity thereof reduced by the method according to the invention.

The acylated carbohydrate used as a catalyst can be any mono-, di- or polysaccharide that has been fully or partially acylated. It has been found that only a small amount of acylated carbohydrate is required to effect an efficient reaction. Sufficient if there is one tetraacylated monosaccharide unit or the equivalent amount, i.e., four monoacylated monosaccharide units, per 100 anhydroglucose (or anhydrofructose) units. Generally, the equivalent of 1-50 wt% acylated carbohydrate, based on the total of carbohydrate and acylated carbohydrate, in particular 2-20 wt%, is used. The term acylated here includes alkanoylated (acetylated, propionylated, etc.), benzoylated, sulphated, phosphorylated, etc.

The acylated carbohydrate can be easily obtained by treating a carbohydrate with an acylating agent such as acetic anhydride according to standard techniques. Some acylated carbohydrates are commercially available, such as peracetyl glucose, galactose and sucrose, and acetyl starch with a DS of about 2.5%.

The advantage of using an acylated carbohydrate is that the oxidation reaction proceeds smoothly and no unwanted by-products are formed; after all, the acylated carbohydrate or the oxidation product thereof can form part of the treated carbohydrate product.

The amount of hydrogen peroxide to be used depends entirely on the desired degree of oxidation. In general, an amount of 1% by weight is sufficient to achieve an effective viscosity reduction. Advantageously, 1-40 wt.%, In particular 2-20 wt.%, Of hydrogen peroxide are used, based on the total of carbohydrate and acylated carbohydrate.

The reaction can be carried out at room temperature, but preferably at an elevated temperature, generally from 20 to 90 ° C, especially from 40 to 100249460 ° C. The reaction time at that temperature is from a few minutes to several hours, depending on the carbohydrate and the desired degree of viscosity reduction.

Example

To a slurry of starch (70 g dry weight in 130 g water: 35 wt%) 5 is added 2 g glucose pentacetate at 50 ° C. Then a solution of 10 ml of hydrogen peroxide (30% by weight) is added at once. The pH is lowered to 1.4 with 1N hydrochloric acid. After a reaction time between 15 minutes and 6 hours, the reaction mixture is neutralized, and the oxidized starch is filtered off, washed with water and dried with acetone. The viscosity of a suspension of 10 g of product in 380 ml of water is determined with a Brabender viscometer.

Table 1 shows the results of the product after 3 hours and after 6 hours. The result of the treatment with hydrogen peroxide after 3 hours is also shown for comparison.

Table 1 15 Starch viscosity after oxidation oxidation reaction time start temp. top temp. peak viscosity final viscosity (h) ("C) 1 (° C) 2 sity η3 sity η4 no n / a 61 80 3200 1180 (blank) 20 H202 3 64 86 1560 500 H202 + 3 64 72 520 120

GluAcj H202 + 6 66> 90 500 440

GluACj 25 1 Start temperature Brabender curve 2 Temperature from the top of the Brabender curve 3 Brabender units at the top of the Brabender curve: 75 rpm, temp. gradient: 1 ^ ° Omin, t8tart 40 ° C, thold 90 ° C, hold: 30 min .; AVEBE standard 019142 4 Brabender units in the valley of the Brabender curve (as 3) 1002494

Claims (4)

Process for reducing the viscosity of carbohydrates by treatment with hydrogen peroxide in the presence of a catalyst, characterized in that an acylated carbohydrate is used as the catalyst. The process according to claim 1, wherein the equivalent of 1-50 wt% acylated carbohydrate, based on the total of carbohydrate and acylated carbohydrate, is used. The process according to claim 1 or 2, wherein 2-20 wt.% Hydrogen peroxide, based on the total of carbohydrate and acylated carbohydrate, is used. A method according to any one of claims 1-3, wherein the carbohydrate is starch. 1002494 OMiVICil tl * unun ^ va y * w «; REPORT ON NEWNESS RESEARCH OF INTERNATIONAL TYPE _________. ___ ...... .—— »IDENTIFICATION OF THE NATIONAL APPLICATION Characteristic of the applicant ot of the registered N.O. 40489 TM Naoananeaa application w. ' · Motaongsoaum 1002494 · February 29, 1996____ In ga roe pan priority seed Applicant (Name) INSTITUTE FOR AGRICULTURAL RESEARCH (ATO-DLO) Dew of wet request feed to undoZDex of mtamatonaai type By aa bisante for Internat on aai OnoarzoeK (SA) to network an underglobal type of eegekend nr - SN 27261 EN I. CLASSIFICATION OF THE SUBJECT (pipe of verscnillenoe etassilicates. state all etassificaoe symbols) According to ee in manorial # eassificaae (IPC) Int. Cl. 6: C 08 B 31/18, C 08 B 30/12: II. FIELDS OF TECHNIQUE RESERVED Untested minimum documentation I Classification system Classification reports Int. Cl.6 C 08 B Unaerzoe anoere ooeumenate o oe the oe minimum documentation insofar as primal documentation is included in the research »completed sentence III. I! NO RESEARCH POSSIBLE FOR CERTAIN CONCLUSIONS {noteChina on supplementoad) (! IV.! _; DISCUSSION UNIT OF INVENTION (remarks including supplemental adad) j = crrn PCT / ïSA / 23liai CS> 99 »