CA1052718A - Process for recovering dextrose and dextrins from protein-containing starch products - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Dextrose and dextrins are obtained from protein-containing starch products by subjecting the starch product to an incomplete or complete acid or enzymatic hydrolysis or a com-bination of both types of hydrolysis and then circulating the hydrolysate containing a low viscosity sugar solution and water-soluble high molecular proteins through an ultrafilter to separate the proteins from the sugar solution whereupon the dextrose or, in case of incomplete hydrolysis, the dextrins are recovered from the filtrate obtained in the ultrafilter.

Description

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The invention relates to a process for obtaining dextrose and dextrins from portein-containing starches.
The starting product constituting the starch is pre-ferably a vegetable product such as potatoes, arrow-root or manioc (cassava) as well as grain feeds such as maize, sorghum, wheat, rice, rye or barley.
The complete hydrolysis of starch leads to dextrose.
At present, principally two processes are in use for making dextrose from starch. One of the processes employs a pure acid hydrolysis.
The other moves through a two-stage acid-enzyme process or a two-stage enzyme-enzyme process.
~ From the German published application 15 67 365 a process for making starch hydrolysates is known. In this case a syrup is obtained of a low dextrose value. The hydrolysis is effect-ed in a two-step process with alpha-amylase.
A process for extracting starch from maize grit and the subsequent enzymatic saccharification is described by K.
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Kroyer in the publication Die Starke, 10, 312 (1966).
In the German published application 24 17 639 a process is disclosed for liquefying corn starch. The starch there -is mixed with water, a bacterial alpha-amylase and glucoamylase and is then processed at elevated temperatures. The German published application 17 17 126 likewise deals with a process for liquefying starch.
The shortcoming of all these prior art processes is ,il that it is necessary to wash out to the extent possible all water-soluble components of the starch by swelling or elutriation with water in order to obtain a pure starch for the enzymatic hydrolysis and the recovery of a pure dextrose. This purification step causes substantial difficulties, particularly in case of wheat, rye and .: ' ' '7~

1 barley because of the grain size which is small compared with potatoe starch or corn starch and because of byproducts from the precipitation. A filtration in the classic sense of the word is not possible slnce what is involved is -the separation of a solid from solids and a liquid.
In addition to the difficulties in obtaining a pure starch, further problems arise during the hydrolysis of the starch because of the unavoidable formation of byproducts during the de-gradation.
It is therefore an object of the present invention to provide for a process of obtaining dextrose and dextrins from pro-tein-containing starches, for instance by enzymatic hydrolysis without requirlng to use a pure starch as the s-tarting product for ~he enzyme treatment.
Another object of the invention is to provide for a process whereby the main hydrolysis products, that is dextrose and ,- dextrins can easily be separated from the protein and other accom--~ panying substances.
:, These objects are accomplished by subjecting the , 20 initial starch product to an acid or enzymatic hydrolysis or a combination of ~oth types of hydrolysis, then circulating the hydro-lyzate containing a low viscosity sugar solution and water-soluble high molecular proteins through an ultrafilter to separate the pro-teins from the sugar solution and recovering the dextrose or, in case of an incomplete hydrolysis, the dextrins from the filtrate obtained in the ultrafilter.
FIG. 1 is a flow sheet showing in diagrammatic form a process for obtaining dextrose and further obtaining isomerose from the dextrose;
FIG. 2 is a flow sheet illustrating a modification of .

~5~8 1 the process shown in FIG. l;
FIG. 3 iS a flow sheet disclosing another modification of the process of FIG. l;
FIG. 4 is a flow sheet of a process for making dextrose only; and FIG. 5 is a flow sheet which illustrates another modi-fication of the final processing steps.
As has already been brought out, the advantage of the present process is that it is not necessary to start with pure starch. Rather, the hydrolysis can be carried out in conventional form immediately after the wet grinding and dilution of the ground initial material Following the hydrolysis the dextrose formed therein or, if the hydrolysis is only partly carried through, the dextrins are separated as such by means of ultrafiltration.
The dextrose may be obtained as such in the form of pure dextrose. However, it can also be used without any preceding refining step to make isomerose therefrom.
An additional advantaye of the ultrafiltration is the recovery of pure protein from the concentrate of the ultra-20 filtration. This pure protein constitutes a first class food product for human consumption.
Apart from the recovery of dextrose and dextrins, the obtaining of protein from protein-containing starches is of substantial interest for instance as a substitute for chic]cen al-bumin, for instance in the bakery industry.
During the hydrolysis of the protein-containing starches, such as, cereals and legumes, insoluble protein is ob-tained in addition to the water-soluble protein. The soluble portions are subject to strong foaming in an aqueous solution and can parti-cularly be used as substitutes for chicken albumin. The water in-',,'' "
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- 1 soluble pro-teins which contain fibrous contaminations are filteredoff by means of a coarse filter prior to the ultrafiltration or are separated by means of a centrifuge.They can then be used as animal feed.
With reference to the flow sheets and in particular ;,:
those of FIG. 1, it will be seen that the swollen grains of maize received from the bunker 1 are subjected to a coarse and fine grind-:
ing mill 2 (this symbol standing for both types of mills) and pre-ferably to a wet grinding, and are then passed into the stirrer tanks 3 and 3'. The mass is there sub~ected -to an acid or enzymatic hydrolysis. Preferably there is carried out a hydrolysis successive-ly with two different enzymes obtained from the containers 4 and 4' such as alpha amylase and amyloglucosidase. The hydrolysis may be carried out with the first enzyme at a temperature of 70 to 80 and ' with the second enzyme at a temperature of 5Q to 60. The pH during the hydrolysis may be adjusted by addition of acid to a range be-tween 3.5 and 4. The time of the hydrolysis may be between 40 and 72 hours depending on the type of raw material and the presence of calcium chloride.
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After completion of the hydrolysis the entire solution is passed by means of a pump 5 onto a strainer 6 where the cereal husks and similar hard materials are removed. The mass then passes to a separator 7 where the fatty components including the corn oil are eliminated. Likewise, the precipitate, that is water insoluble ; proteins such as zein, are removed from the remaining sugar-contain-'!~' ing low viscosity phase. This separator may for instance be in the ;~ form of a centrifuge.
; The separation of the water soluble high molecular pro-, teins from the dextrose and the lower molecular dextrins is then ef-fected in the ultrafilter 8. The low viscosity phase may for instance ~..
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1 be circulated through the ultrafilter for a time from 15 to 20 ; hours at a temperature of 20 to 50C and a pxessure of 2 to 6 bar.
The circulation in the ul-tra~ilter is effected by a rotary pump 9. The ultrafiltration may be carried out at a pH in the range between 3 and 9. Preferably, the material is washed during the ultrafiltration with relativelv smc~ll amounts of water for a time sufficient to cause the concentrate which is obtained from the retenate to have a concentration of at least 70 to 80% protein as ..~
dry solids. This is accomplished by passing the retenate to a spray dryer 10 whereupon the protein can be discharged into a packaging material 11.
The sugar solution on the other hand which constitutes ' the permeate resulting in the ultrafiltration, is passed through a ; bleaching column 12 which for instance may be an ion exchange column and it may also additionally be treated with activated coal. If ~` desired, it may also be subjected to a desalting step. The decolor-ized, that is bleached solution, is then subjected to concentration in an evaporator 13~ If a glucose syrup is to be obtained at this place the concentration is effected to an 85% dry contents.
If it is desired to obtain isomerose, the concentra-tion is carried out only to a dry contents of 40%. The concentrate is in the form of a syrup which may then be treated with, for in-stance magnesium sulfate and cobalt sulfate and glucose isomerase at a pH for instance between 6.6 and 7.5 and a temperature for in-stance of 60C.
The syrup may then be subjected to a purification at 15 which for instance can be effected by a cation-anion exchange com-pound and a subsequent treatment with activated coal. The product :
; is then discharged into the container 16 as an isomerose syrup or sugar.

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1 The drawing in FIG. 2 shows a modifica~ion of the process for obtaining isomerose from cereals via an interrnediate product in the form of dextrose.
If not otherwise indicated, the symbols have the same , meanin~ as in FIG. 1. The product whichis pretreated in the mill 2 in the same manner as in FIG. 1 is subjected to a treatment with an ~; amylase in the stirring container 3. The enzyme is obtained from the container 4. Prior to adding the enzyme the contents of the container 3 are subjected to a homogenization in the homogenizer 17 for such time until the desired small particle size has been obtained. After carrying ou-t the hydrolysis in the same manner as in FIG. 1, the now liquefied starch is passed to a separator 18 which may be in the form of a centrifuge or filter in order to eliminate the water insoluble proteins. The remaining low viscosi-ty phase then is passed into a second reactor 19 where it is reacted with amyloglycosidase received from the container 20. Thus, the so-lution is degraded to obtain dextrose. After the degradation the -; solution is separated in the ultrafilter 8 into a protein concen-trate and pure dextrose. The protein concentrate is then dried in the spray dryer 10. The dextrose containing ~ermeate is further processed to obtain isomerose in the same manner as shown in FIG. 1.
FIG. 3 illustrates another modification of the pro-i cesses shown in FIG. 1 and FIG. 2. If not otherwise indicated the reference letters again have the same meaning.
The separation of the first enzyme solution which isformed in the same manner as shown in FIG. 2 is effected in a centrifuge 18. By this centrifuge the residues and (water soluble) proteins are removed. The solution is then directly passed into the ~; ultrafiltration. In the ultrafilter the soluble protein is con-centrated and is then passed to a spray dryer 10 in order to obtain :`
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, 1 water soluble protein concentra-te. The permeate formed in the ultrafilter 8 is, however, passed into a second enzyme reactor 19 and is there treated with amyloglycosidase received from the container 20. There is thus obtained a glucose solution which then is subjected to a bleaching in the column 12 and is desalted in an ion-exchanger 210 The further processing by means of isomerase is effected in the same manner as shown in FIGS. 1 and 2.
FIG. 4 shows a process for making dextrose. In the enzyme reactor 3 there is again formed a solution in the same manner as in FIG. 2. This solution is passed to a separator 18 where the residues and the liquid phase are separated. The re-sidues are collected in a container 22 and are treated in a stirring vessel 23 with alkali 20 received from the tank 24 so as to obtain a pH of 8 to ~. In this manner the remaining proteins are dissolved out of the comminuted husks. The thus formed suspension is then passed into a separator 18' where it is separated into a protein-free residue and a protein containing solution. The protein-free :.
residue is collected in a receptacle 25 and may then be further '~ subjected to drying. The protein-containing solution is united with -~ 20 the solution received from the separator 18. The two solutions are ,;
subjected to a neutralizing step in the vessel 26. The neutralized total solution is then treated in the reactor 19 with amylglyco-' sidase received from the tank 20.
The further treatment of the reaction product is the "~ same as shown and described in connection with FIG. 3.
FIG. 5 shows a detail of a further processing modific-ation of the enzyme solution.
The suspension received from -the enzyme reactor 3 is - here subjected to a filtration in the filter vessel 18. The residue . ~
; 30 from the filtration is treated with sodium hydroxide and further !.:
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-~3-., l processed as indicated in FIG. 4 (tank 23, separator 18' and :~ neutralizing vessel 26). The filtrate from the filter 18 on the :, other hand is passed into a reactor l9 to receive a second enzyme treatment. During this treatment 76% of the total initial crude maize go into solution. The solution now contains the sugar and the soluble proteins. The neutralization then is effected together ~i~ with the previously NaOH treated residue solution so as to obtain a pH of 3.5. Subsequently, the solution is passed to the ultra-filter 8 to separate the protein from the sugar solution. The further proces~sing is effected as described in connection with the previous embodiments.
The following is a specific working example of a process carried out in accordance with the present invention.
EX~LE
100 kg of untreated maize of a 15% water contents are suspended in 900 l water and after addition of 0.1 to 0.2%
alpha amylase, stirred at 70 to 80C and subjected to homogeniza-- tion. The pH is maintained at about 7. After l -to 2 hours the mass is cooled down to 50 to 60 and is then reacted with a second en-zyme, amyloglucosidase in an amount of likewise 0.1 to 0.2%.
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. The alpha amulase used in this case was a product identified as "HTl000 Miles Laboratories" whiLe the amyloglucos-idase was a "Diazyme L100 Miles Laboratories".
The adjustment of the pH to 3.5 to ~ was effected with dilute hydrochloric acid. The hydrolysis was carried out during a total period of ~8 hours in the presence of calcium chlor-,~ ide (0.01 mol/l).
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The protein-containing suspension was then passed to a vibration strainer which in the drawing of FIG. 1 is indicated at 6. There the yellow husk portions were removed. The suspension ~, _g_ .~
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, 1 was also subjected to centrifuging to remove the fat components.
The amount of crude maize oil thus eliminated was about 2.950 to 3.000 kg per 100 kg maize of a 15% water contents.
The residue from the centrifuge indicated in FIG. 1 :,., - at 7 consisted of fibers and water insoluble (precipitated) pro-teins. The amount of this residue was 10 to 15 kg relative to 100 kg of maize of a 15% water contents.
The low viscosity phase containing the susar and the water soouble proteins as received from the centrifuge was then subjected to ultrafiltration during 20 hours. The ultrafilter employed was the type Westinghouse S-tyle No. Poly-184 Ser. No.
4-1197. It had tubings of 10 mm diameter and a length of 1200 mm.
The filter surface was 0.68 m with a total number of 18 tubings.
'~ The filtration was carried out at a differential pressure of about 5 bar and at a temperature of 35C. In the ultrafilter the solution :' was separated into a glucose solution and a protein concentrateO
~- During the ultrafiltration water was repeatedly added for washing.
- Prior to drying, the protein concentrate contained 12 to 15% c~ude protein. The total yield of protein after drying ~, 20 was 0.5 to 1.0 kg protein relative to 100 kg of the untreated maize . ~ .
of 15% water contents. While this protein is a high value protein ~, since it is water soluble, and when dried has a contents of 70 to 80% crude protein its amount is not large compared with the total amounts processed.
-- The permeate resulting from the ultrafiltration con-,~ sisted predominantly of a glucose-salt solution. It was bleached ,.,,:
(decolorized) with activated coal. This step was not even absolute-ly necessary since the treatment with an ion-exchange resin already i.
; accomplished a sufficient decolorization.
The concentration then was eEfected in a three-stage ;~
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vacuum evaporator in conventional form. The inlet temperature was about 100C and the outlet temperature 45 to 50~ If a glucose syrup was wanted the evaporation was carried out to ob-tain an 85% concentration dry substance.
For obtaining isomerose the concentration was carried out only to obtain a syrup of a 40% concentration dry substance. To the syrup obtained in the evaporator there were then added, per liter syrup, as conventional, 1 g magnesium sul-fate (MgSO4 7H20) and 0.1 g cobalt sulfate (CoSO4 7H20) as well as 8.5 GIN (Glucose isomerase Novo SP 103) per gram of - glucose as the enzyme. This enzyme is made by the Novo Industry -~ A/S Co. of Denmark. The conversion temperature was 60 C at a pH of 6.6 to 7.5. The pH was maintained constant by means of sodium hydroxide of a concentration of 0.1 to 0.5 mol per liter. The re-action was carried out under an atmosphere of nitrogen as protec-tion against oxidation ` The syrup was then purified by a cation-anion ex-change compound and subsequent treatment with activated coal. The conversion obtained was 45 to 50~ relative to the initial glucose employed.
As appears, the great advantage of the process of the invention is that it is not necessary -to use a purified starch as the starting material for the enzyme treatment. A further advantage is that in none of the described processes are there obtained any substantial amounts of drainage water.
A further advantage is also the recovery of byproducts .
which constitute not only animal feeds but also top value protein ~ food for human consumption.

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Claims (14)

The embodiments of the invention in which an ex-clusive property or privilege is claimed are defined as follows:

1. A process for obtaining dextrose and dextrins from a protein-containing starch product comprising subjecting the starch product to an incomplete or com-plete acid or enzymatic hydrolysis or a combination of both types of hydrolysis, then circulating the hydrolysate containing a low viscosity sugar solution and water soluble high molecular proteins through an ultrafilter to separate the proteins from the sugar so-lution, and recovering the dextrose or, in case of incomplete hydrolysis, the dextrins from the filtrate obtained in the ultra-filter.

2. The process of claim 1 wherein the starch product is a cereal or legume.

3. The process of claim 2 wherein the starch product is constituted by potatoes, arrowroot, manioc (cassave), maize, sorghum, wheat, rice, rye or barley.

4. The process of claim 1 wherein the high molecular protein is separately recovered from the retenate resulting from the ultrafiltration and is then subjected to spray-drying to ob-tain a high protein product useful as human food or animal feed.

5. The process of claim 4 wherein the mass while cir-culatiing in the ultrafilter is subjected to a waterwash for so long as to cause the protein concentrate formed in the spray dry-ing to have at least 70 to 80% solid contents of dry protein.

6. The process of claim 1 wherein the ultrafiltra-tion is effected at a pH of 3 to 9.

7. The process of claim 1 which includes the step of separating out the insoluble resins including the water-insoluble proteins resulting from the hydrolysis by centrifuging or filtering by the hydrolysate prior to said ultrafiltration.

8. The process of claim 1 which includes the step of removing the husks and fat from the hydrolysate by mechanical sep-aration prior to said ultrafiltration.

9. The process of claim 1 wherein the initial starch product is subjected to a wet grinding step prior to said hydrolysis.

10. The process of claim 1 wherein the sugar solution obtained as the filtrate in the ultrafiltration is successively subjected to bleaching, concentration and conversion by reaction with isomerase so as to obtain isomerose.

11. The process of claim 10 wherein the sugar solution obtained as the filtrate from the ultrafiltration is subjected to a second hydrolysis in the form of an enzymatic hydrolysis followed by said conversion to obtain said isomerose.

12. The process of claim 11 wherein the insoluble proteins are removed from said hydrolysate and the remaining low viscosity solution is then subjected to a second hydrolysis prior to being passed through the ultrafiltration step.

13. The process of claim 11 wherein the two hydrolysis steps are in the form of enzymatic hydrolyses.

14. The process of claim 1 wherein the residue obtained as the retenate in the ultrafiltration is subjected to an alkaline treatment to dissolve the residual water insoluble proteins present therein out of the husks which also are present in the residue, followed by separating the said proteins from the husks and then recirculating the said proteins into the remain-ing hydrolysate, neutralizing the total hydrolysate and subjecting it to another hydrolysis step in form of an enzymatic hydrolysis prior to passing the hydrolysate through the ultrafilter.