GB2029846A

GB2029846A - Producing concentrated dextrin solutions

Info

Publication number: GB2029846A
Application number: GB7915645A
Authority: GB
Original assignee: Ajinomoto Co Inc
Current assignee: Ajinomoto Co Inc
Priority date: 1978-05-08
Filing date: 1979-05-04
Publication date: 1980-03-26
Also published as: JPS5516A; MY8500372A; JPS6246159B2; GB2029846B

Abstract

A process for producing a concentrated dextrin solution containing from 50 to 65% by weight of dextrin comprises preparing a less concentrated dextrin solution containing 30 to 45% by weight of dextrin by enzymatic starch conversion of a starch suspension at an elevated temperature of 50-95 DEG C, cooling to a lower temperature and adding more starch, and then subjecting to further starch conversion at an elevated temperature of 80-95 DEG C. This process enables the desired product to be produced more economically than with conventional processes involving evaporation. The concentrated dextrins produced may be subsequently saccharified to give glucose or maltose solutions.

Description

SPECIFICATION Production of a concentrated dextrin solu tion This invention relates to a process for produc ing a concentrated dextrin solution which in volves liquefying a concentrated starch sus pension with an alpha amylase.

By employing a conventional double enzyme process which comprises an enzymatic conversion with an alpha amylase of an aque ous suspension of starch into a dextrin solution, followed by an enzymatic conversion of the resulting dextrin solution into a desired sugar solution such as glucose or maltose using a saccharifying amylase, a large amount of glucose, maltose, or saccharified sugar liquor has been manufactured industrially.

According to the conventional process mentioned above, 30-45% by weight aqueous dextrin solution may be prepared by an enzymatic conversion with an alpha amylase of an aqueous starch suspension into a dextrin solution having a relatively low viscosity. However, a dextrin solution containing more than 50% by weight of dextrin cannot be produced since the viscosity of the starch suspension increases suddenly when the starch content increases beyond 50% by weight, and the high viscosity makes stirring and transportation of the suspension difficult if not impossible. Accordingly, the content of the starch suspension, and hence the content of the saccharified sugar liquor prepared by an enzymatic conversion of a dextrin solution, is usually within the range of 30 to 45% by weight.

According to the conventional process, glucose, maltose, or concentrated saccharified sugar liquor has been produced by evaporating the saccharified sugar liquor, but a considerable amount of steam is necessary for this.

According to the present invention, there is provided a process for producing a concentrated dextrin solution containing from 50 to 65% by weight of dextrin, which process comprises the steps of: (1) preparing a less concentrated aqueous dextrin solution containing from 30 to 45% by weight of dextrin, by an enzymatic conversion of a starch suspension into the less concentrated dextrin solution with an alpha amylase at a temperature in the range from 80 to 95"C; (2) causing or allowing the temperature of the less concentrated aqueous dextrin solution to fall to less than 80"C and then admixing therewith solid starch; and (3) converting the solid starch admixed in step (2) with the less concentrated dextrin solution into a dextrin with an alpha amylase at a temperature in the range from 80 to 95"C to prepare the desired concentrated dextrin solution having a dextrin content of from 50 to 65% by weight.

The present invention provides an economical process for producing a concentrated dextrin solution without the expensive evaporat ing step.

The alpha amylase employed in the process of the present invention can be of any conventional type and need not be a special one: for example, an alpha amylase preparation de rived from a bacteria belonging to Bacillus subtilis, B. licheniformis, B. amyloliquefaciens and a commercially available alpha amylase such as Rhozyme (produced by Rohm 8 Haas), Maxamyl (produced by Gist-Brocades) and Klaistase (produced by Daiwa Kasei Co.

Ltd.) are preferably used.

The first step of the process of the present invention is to prepare a 30-45% by weight aqueous dextrin solution and this step may be carried out according to a conventional technique, which is as follows: Tap water is added to a starch such as sweet potato starch, potato starch, tapioca or corn starch, to prepare a 30-45% by weight aqueous starch suspension, of which the pH is adjusted to 6.5-7.5 with an alkali. To the starch suspension, a stabilizing agent such as NaCI, CaCI2 or MgSO4 is preferably added.

Then preferably from 20 to 50 units of an alpha amylase per gram of starch are added to the starch suspension and an enzymatic liquefaction is carried out at a temperature within the range from 80 to 95"C for 30 to 60 minutes. In this way the starch suspension is liquefied, and a 30-45% by weight aqueous dextrin solution having a reduced viscosity is obtained.

Afterwards, the liquefied solution is cooled, e.g. to a temperature of at least 50"C but less than 80"C; more starch, which can be the same as or different from that used in the first step, is added to the dextrin solution to prepare a 50-65% by weight starch-dextrin containing suspension, to which more alpha amylase is added if necessary. The additional starch added is solid starch, either as a dry solid or in the form of a concentrated suspension or paste.

The viscosity of the suspension is similar to that of the starch suspension containing 35-45% by weight of starch, and therefore stirring and transportation of the suspension can be easily conducted.

This suspension is then heated to a temperature in the range from 80 to 95"C and the second enzymatic liquefaction is carried out at 80-95"C, preferably for from 30 to 60 minutes, to prepare a 50-65% by weight concentrated dextrin solution. The second enzymatic liquefaction may, like the first one, be carried out according to a conventional technique and not by any special technique.

The process of the present invention may be carried out either in a batchwise manner or continuously.

A glucose, maltose or a concentrated solu tion thereof, i.e. saccharified sugar liquor, may be produced more economically using the concentrated dextrin solution prepared according to the present invention then with a conventional method containing an expensive evaporating step. For this purpose, it is desirable that the concentrated dextrin solution is heated at a temperature in the range from 11 0"C to 120"C for from 10 to 20 minutes prior to an enzymatic saccharification step with a saccharifying amylase.

In the field of fermentation, a saccharified sugar solution has been used as a carbon source for various kinds of fermentation, and the saccharified sugar liquor is usually fed to a fermentation tank continuously during the fermentation. In this case, the higher the sugar concentration of the feed solution, the more advantageously the fermentation may be carried out. The concentrated saccharified sugar liquor thus prepared is therefore preferably used as an economical carbon source for various kinds of fermentation.

The present invention will now be illustrated by the following Example.

EXAMPLE 2.1 kilograms of tapioca containing 1.8 kg of starch were suspended in 2.2 litres of tap water, and the pH of the resulting suspension was adjusted to 7.0 with 1.3% by weight NaOH solution. To this suspension were added 100 ml of an enzyme solution containing 0.366 g of Klaistase (commercial bacterial alpha amylase, manufactured by Daiwa Kasei Co. Ltd.), and the resulting suspension was then heated with stirring until the temperature of the suspension rose to 90"C; the enzymatic conversion of the starch suspension into a dextrin solution was carried out by maintaining the temperature of the suspension at 90"C for 30 minutes with stirring.

After the conversion, the dextrin solution, which had a dextrin content of 40% by weight, was cooled to a temperature below 80"C, in this case to a temperature of 60"C, then a further 1.81 kg of tapioca and 0.8 g of Klaistase were added to the cooled solution, of which the pH was then adjusted to 7.0.

Then, an enzymatic starch liquefaction was carried out in the same manner as described above, i.e. at 90"C for 30 minutes with stirring.

After the second starch liquefaction, the liquefied solution was heated at 120"C for 10 minutes in a small autoclave, whereby a concentrated aqueous dextrin solution containing 61 percent by weight of dextrin was prepared; the Dextrose Equivalent (D.E.) was 13.5.

The pH of the concentrated dextrin solution was then adjusted to 4.8 with 6 N H2SO4, after which 100 ml of an enzyme solution containing 2.26 g of Gluczyme (a commercial fungus saccharifying amylase, manufactured Amano Seiyaku Co. Ltd.) were added to the dextrin solution. An enzymatic conversion of the concentrated dextrin solution into saccharified sugar liquor was carried out at 55"C for 72 hours with stirring according to the conventional technique. The hydrolysis ratio of the saccharified sugar liquor was 98.5% and the content of direct sugar in the saccharified sugar liquor was 60.53% by weight.

Claims

1. A process for producing concentrated dextrin solution containing from 50 to 65% by weight of dextrin, which process comprises the steps of: (1) preparing a less concentrated aqueous dextrin solution containing from 30 to 45% by weight of dextrin, by an enzymatic conversion of a starch suspension into the less concentrated dextrin solution with an alpha amylase at a temperature in the range from 80 to 95"C; (2) causing or allowing the temperature of the less concentrated aqueous dextrin solution to fall to less than 80"C and then admixing therewith solid starch; and (3) converting the solid starch admixed in step (2) with the less concentrated dextrin solution into a dextrin solution into a dextrin with an alpha amylase at a temperature in the range from 80 to 95"C to prepare the desired concentrated dextrin solution having a dextrin content of from 50 to 65% by weight.

2. A process according to Claim 1, wherein the starch of the starch suspension or the solid starch is sweet potato starch, potato starch, tapioca or corn starch.

3. A process according to Claim 1 or 2, wherein the starch suspension has a pH of from 6.5 to 7.5 before the enzymatic conversion of step (1).

4. A process according to Claim 1, 2 or 3, wherein the starch suspension has present therein a stabilizing agent in step (1).

5. A process according to any preceding claim, wherein there are from 20 to 50 units of starch amylase per gram of starch in the starch suspension in step (1).

6. A process according to any preceding claim, wherein the enzymatic conversion of step (1) is continued for from 30 to 60 minutes.

7. A process according to any one of Claims 3 to 6, wherein the enzymatic conversion in step (3) is carried out under substantially the same conditions as that in step (1).

8. A process according to Claim 1, substantially as described in the foregoing Exam ple.

9. A concentrated dextrin solution contain ing from 50 to 65% by weight of dextrin, whenever produced by a process according to any preceding claim.

10. A glucose, maltose or a concentrated solution thereof, whenever produced by heat ing and subjecting to an enzymatic saccharifi cation step with a saccharifying amylase, a concentrated dextrin solution according to Claim 9.

Printed for Her Majesty's Stationery Office by Burgess s Son (Abingdon) Ltd.-1980.

Published at The Patent Office, 25 Southampton Buildings.

London, WC2A lAY, from which copies may be obtained.