U.S. patent application number 09/796027 was filed with the patent office on 2002-01-31 for high purity maltose process and products.
Invention is credited to Antrim, Richard L., Lee, Clark P..
Application Number | 20020012973 09/796027 |
Document ID | / |
Family ID | 22681121 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020012973 |
Kind Code |
A1 |
Antrim, Richard L. ; et
al. |
January 31, 2002 |
High purity maltose process and products
Abstract
Maltose products are prepared by hydrolyzing starch with an
enzyme that consists essentially of a beta-amylase enzyme. The
product thus prepared may be spray dried, or a high purity maltose
product may be obtained therefrom via ultrafiltration. The high
purity maltose product has a low content of glucose and saccharides
in the DP 3-10 range.
Inventors: |
Antrim, Richard L.; (Solon,
IA) ; Lee, Clark P.; (Blue Grass, IA) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
TWO PRUDENTIAL PLAZA, SUITE 4900
180 NORTH STETSON AVENUE
CHICAGO
IL
60601-6780
US
|
Family ID: |
22681121 |
Appl. No.: |
09/796027 |
Filed: |
February 28, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60185474 |
Feb 28, 2000 |
|
|
|
Current U.S.
Class: |
435/100 ;
536/123.13 |
Current CPC
Class: |
C13K 7/00 20130101; C12P
19/22 20130101; C12P 19/04 20130101; C08B 30/18 20130101 |
Class at
Publication: |
435/100 ;
536/123.13 |
International
Class: |
C12P 019/12; C07H
003/04 |
Claims
What is claimed is:
1. A method for preparing a high maltose product, comprising:
treating a starch with an enzyme that consists essentially of a
beta-amylase enzyme under conditions suitable to form a product
mixture that includes maltose and at least one higher molecular
weight carbohydrate; and recovering a maltose-rich fraction from
said product mixture via ultrafiltration of said product mixture,
thereby at least substantially separating maltose from said higher
molecular weight carbohydrate.
2. A method according to claim 1, said product mixture being a
liquid product mixture that contains retrograded amylose, the
method further comprising allowing at least a portion of said
retrograded amylose to crystallize from said mixture; and
separating the crystallized retrograded amylose from said
mixture.
3. A method according to claim 1, further comprising liquefying
said starch with an alpha-amylase enzyme; and quenching said alpha
amylase enzyme prior to treating said starch with said beta-amylase
enzyme.
4. A method according to claim 1, said maltose-rich fraction
comprising at least 85% maltose by weight by dry solids basis.
5. The maltose-rich fraction prepared by the method of claim 4.
6. A method according to claim 1, said maltose-rich fraction
comprising at least 90% maltose by weight by dry solids basis.
7. The maltose-rich fraction prepared by the method of claim 6.
8. A method according to claim 1, said maltose-rich fraction
comprising at least 95% maltose by weight by dry solids basis.
9. The maltose-rich fraction prepared by the method of claim 8.
10. A method for preparing a spray-dried maltose product,
comprising: treating a starch with an enzyme that consists
essentially of a beta-amylase enzyme under conditions suitable to
form a product mixture that includes maltose and at least one high
molecular weight carbohydrate; and spray-drying said product
mixture.
11. A method according to claim 10, said product mixture being a
liquid product mixture that contains retrograded amylose, the
method further comprising: allowing at least a portion of said
retrograded amylose to crystallize from said product mixture; and
separating the crystallized retrograded amylose from said product
mixture prior to spray drying said product mixture.
12. A method according to claim 10, further comprising liquefying
said starch with an alpha amylase enzyme; and quenching said alpha
amylase enzyme prior to treating said starch with said beta amylase
enzyme.
13. The spray dried product prepared in accordance with claim
10.
14. A maltose product comprising: at least 70% maltose by weight by
dry solids basis and at least 20% by weight by dry solids basis of
a carbohydrate having a DP greater than 10, said maltose product
being provided by a process comprising: treating a starch with an
enzyme that consists essentially of a beta-amylase enzyme under
conditions suitable to form a product mixture that includes at
least 70% maltose by dry solids basis.
15. A maltose product comprising: at least 30% maltose by weight by
dry solids basis and 0-10% by weight by dry solids basis combined
glucose and oligosaccharides having DP ranging from 3-10, said
maltose product being provided by a process comprising: treating a
starch with an enzyme that consists essentially of a beta-amylase
enzyme under conditions suitable to form a product mixture that
includes at least 30% maltose by dry solids basis.
16. A maltose product according to claim 15, said maltose product
including at least 50% by weight by dry solids basis maltose.
17. A maltose product according to claim 15, said maltose product
including at least 65% by weight by dry solids basis maltose
18. A maltose product according to claim 15, said maltose product
including at least 70% by weight by dry solids basis maltose.
19. A method for preparing a maltose product, comprising:
initiating treatment of a starch with an enzyme that consists
essentially of a beta-amylase enzyme under conditions suitable to
form a product mixture that includes maltose, and quenching said
enzyme when the maltose content of said product has reached a
desired level, said quenching occurring after a reaction time, said
reaction time being determined based on a predetermined correlation
between reaction times and maltose contents for said enzyme and
said starch.
20. A method according to claim 19, further comprising making an
empirical determination of said correlation between reaction times
and maltose contents.
21. A method for preparing a maltose product, comprising providing
an amylose-containing starch; liquefying said starch; and treating
such starch with an enzyme that consists essentially of a
beta-amylase enzyme under conditions suitable to form a product
mixture that includes at least 30% maltose by dry solids basis,
said liquefaction being performed under conditions suitable to
render said starch at least substantially liquid at the temperature
at which said starch is treated with said beta-amylase enzyme while
resulting in a product mixture in which the combined content of
glucose and oligosaccharides having a DP ranging from 3-10 is not
greater than 10%.
22. A method according to claim 21, said maltose product including
at least 65% maltose by weight by dry solids basis.
23. A method according to claim 21, in which the combined content
of glucose and oligosaccharides having a DP ranging from 3-10 is
not greater than 5%.
24. A method according to claim 23, wherein said starch is
liquefied to a dextrose equivalent of between 0 and 1.
25. A method according to claim 21, wherein said starch is
liquefied to an extent whereby the viscosity of said starch ranges
from 25-45 centipoise (Shell Cup) at the temperature at which said
starch is treated with said beta-amylase enzyme.
26. The product prepared by the method of claim 21.
Description
RELATED APPLICATION
[0001] This application claims priority to prior provisional
application Ser. No. 60/185,474, the entire contents of which are
hereby incorporated by reference.
TECHNICAL FIELD OF THE INVENTION
[0002] This invention is in the field of oligosaccharides, and in
particular, the invention pertains to the preparation of a
high-purity maltose product.
BACKGROUND OF THE INVENTION
[0003] Maltose, an alpha 1-4 linked disaccharide, is a commercially
important chemical with numerous industrial and consumer uses, for
instance, as a sweetener or in the preparation of maltitol, a
different sweetener in confectioneries intended for the low calorie
or diabetic market. Maltose is also commercially important in the
brewing industry, wherein it is provided as a fermentable component
of brewing worts. In these applications, it is desirable to provide
maltose in a substantially pure form, i.e., to the substantial
exclusion of other carbohydrates. For instance, it is desirable in
brewing applications to provide maltose to the substantial
exclusion of dextrose. Although dextrose is fermentable, dextrose
begins to inhibit yeast growth when present in the brewing wort,
for reasons believed to relate to metabolic disturbances of the
yeast used in the fermenting process. Similarly, in the preparation
of maltitol, it is commercially desirable to provide maltose in a
substantially pure form, so that sorbitol and higher molecular
weight hydrogenated sugars such as maltotritol are not formed upon
hydrogenation of the maltose. For these reasons, the production of
maltose in a highly pure form is highly commercially desirable. It
is particularly desirable to avoid substantial amounts of glucose,
maltotriose, or other lower molecular weight sugars, because of the
difficulty in separating maltose from such other carbohydrates.
[0004] Generally, maltose is prepared via the enzymatic hydrolysis
of starch, whereby certain enzymes, known as beta amylases, convert
starch into maltose. Natural starches are composed of two
molecules, amylose, a linear saccharide, and amylopectin, a
branched starch molecule which for a given starch ordinarily is of
higher molecular weight than amylose and in which approximately 4%
of the glucoside bonds are alpha 1-6 bonds. With the exception of
so-called waxy (corn) or glutinous (rice) specialty starches, most
starches found in nature are composed of between 20% and 30%
amylose. In the case of amylose, beta-amylase enzymes catalyze
hydrolysis from the non-reducing end of the molecule, thus
releasing maltose units sequentially until the reducing end is
reached. Presumably, if the amylose molecule contains an even
number of glucose units, the sole product will be maltose; however,
if the amylose molecule contains an odd number of glucose units,
then, in addition to maltose, one glucose molecule is released per
amylose molecule from the reducing end. In addition to glucose,
maltotriose is often seen as an end product due to the relatively
slow conversion of maltotriose to glucose and maltose. Moreover, if
the amylose were present as a large number of short molecules, such
as would be the case if the amylose had been partially hydrolyzed
with an acid or alpha-amylase enzyme, then relatively larger
amounts of glucose and maltotriose would result upon treatment of
the short-chain amylose with beta-amylase. With respect to
amylopectin, beta-amylase enzymes release maltose by sequential
hydrolysis, but when the sequential hydrolysis reaches an alpha 1-6
branch point, the hydrolysis stops because the enzyme is unable to
hydrolyze the branch point. As a result, the highest yield of
maltose obtainable from amylopectin is about 50%. The remaining 50%
of the original amylopectin exists as large, essentially
water-soluble molecules.
[0005] For the foregoing reasons, the purity of the maltose product
obtained via enzymatic hydrolysis of a starch is related to the
number of amylose molecules per given weight of starch, and is
limited by the extent of branching in the amylopectin component of
the starch. Because of the production of by-products such as
glucose and maltotriose, it is difficult to obtain a high-purity
maltose from starch without subsequent purification steps.
Conventionally, chromatographic processes have been employed to
separate maltose from the glucose and other by-products of the
beta-amylase hydrolysis product. Chromatographic separations are
expensive and difficult to perform, however, thus resulting in an
increased cost for a high-purity maltose product.
[0006] In recognition of this problem, the prior art has provided a
number of attempts to improve the yield of maltose from starch. For
instance, yields of maltose from amylopectin can be significantly
increased by cleaving (hydrolyzing) the amylopectin structure
between branch points with acid or with an alpha-amylase enzyme.
This can be done either before treating the starch with a
beta-amylase enzyme, or concurrently therewith. By cleaving between
branch points, additional non-reducing ends are produced, thus
providing more sites for attack by the beta-amylase enzyme. Using
this technique, yields of maltose can be increased, but in addition
to maltose, small branched molecular products undesirably are
produced. Another strategy for increasing yields of maltose for
amylopectin is the use of enzymes that hydrolyze the alpha 1-6
branch points. Enzymes such as pullulanse and isoamylase are known;
such enzymes are generally known as alpha 1-6 glucosidases.
[0007] Such techniques are somewhat effective in improving the
yield of maltose. For example, if normal starch (containing about
25% amylose and 75% amylopectin) is liquefied using conventional
alpha-amylase or acid liquefaction techniques, and then treated
with barley beta-amylase, a yield of about 55% maltose can be
expected, the yield depending somewhat on the extent of prior
hydrolysis with alpha-amylase. Barley malt-derived beta-amylase
enzymes, which contain an alpha-amylase component, will provide a
maltose yield of closer to 60%. The use of starch de-branching
enzymes will provide even higher yields, ranging up to 75% maltose.
Other attempts have focused on the development of new enzymes for
use in the production of maltose from starch. One such enzyme
(Maltogenase, from Novozymes A/S) is used in combination with an
alpha-amylase enzyme, a beta-amylase enzyme, and a pullulanse
enzyme to obtain maltose from starch. The maximum yield of maltose
using these four enzymes appears to be about 80%.
[0008] The use of multiple enzymes on a commercial scale is
expensive, both in connection with the purchase of such enzymes and
the removal of the enzymes from the maltose product thus prepared.
In addition, although the yield of maltose is high relative to
other known processes, still the product obtained via the use of
such enzymes contains substantial amounts of dextrose and of higher
order oligosaccharides (typically having a degree of polymerization
(DP) ranging from 3 to about 10). The presence of such other
saccharides is undesirable for many purposes, in particular in
brewing applications and in maltitol production, and thus expensive
chromatographic processes are still required before a high-purity
maltose product is obtained. In addition, although it may be
feasible to develop new enzymes in an effort to further increase
the yield of maltose, such development of new enzymes is
extraordinarily expensive, and it is by no means certain that such
new enzymes will be more effective than known techniques in
preparing maltose products.
[0009] For the foregoing reasons, the prior processes for
preparation of maltose discussed hereinabove suffer from a number
of drawbacks. The present invention seeks to address these
drawbacks by providing a process for the production of maltose from
starch.
THE INVENTION
[0010] It has now been found that the treatment of starch with an
enzyme that consists essentially of a beta-amylase enzyme, and
which is to the substantial exclusion or complete exclusion of
alpha-amylase enzymes and de-branching enzymes, will yield a
product mixture that includes maltose and that is substantially
free of glucose and of other malto-oligosaccharides having a DP
from 3-10. The maltose may be readily separated from the product
mixture thus formed via ultrafiltration to yield a high-purity
maltose product in which the maltose content is greater than 70%
based upon total carbohydrate and in which the combined content of
glucose and oligosaccharides having a DP ranging from 3-10 is below
10%. In some embodiments the maltose product prepared via enzymatic
hydrolysis content will have a maltose content greater than 70%.
Using the invention, a maltose content greater than 85%, more
preferably greater than 90%, and even more preferably greater than
95% may be obtained, and in each case, the combined content of
glucose and of oligosaccharides having a DP ranging from 3-10 can
be kept below about 10%, preferably below about 5%. The production
of high purity maltose in accordance with the invention can be very
inexpensive relative to known processes. It has further been
discovered that the product formed upon enzymatic hydrolysis of the
starch may be spray dried to yield a spray dried maltose
product.
[0011] In accordance with one embodiment of the invention, a starch
is treated with an enzyme that consists essentially of a
beta-amylase enzyme, and which is to the substantial exclusion or
complete exclusion of alpha-amylase enzymes and de-branching
enzymes. The starch is so treated under conditions that are
suitable for the hydrolysis of the amylose component of the starch
to form maltose, and for the hydrolysis of the amylopectin
component of the starch to form maltose and at least one higher
molecular weight carbohydrate. Generally, the resulting mixture of
starch hydrolysis products will comprise maltose and the higher
molecular weight carbohydrates to the substantial exclusion of
other malto-oligosaccharides. This mixture may itself have a high
maltose content, and may easily be resolved via ultrafiltration
into a maltose fraction that has a maltose content greater than
70%, in most cases substantially greater. Moreover, because of the
substantial absence of other malto-oligosaccharide by-products in
the maltose fraction, such as would be present via conventional
processes for maltose production, the mixture may be resolved via
ultrafiltration, and no column chromatographic process is required.
Upon ultrafiltration, most of the maltose passes through the
membrane, leaving some maltose in the retentate. If desired,
diafiltration may be used to separate substantially all of the
maltose from the high molecular weight carbohydrates in the
retentate.
[0012] In accordance with anther embodiment of the invention, a
starch is treated with an enzyme that consists essentially of a
beta-amylase enzyme under conditions that are suitable for the
hydrolysis of the amylose and amylopectin components of the starch
to form maltose and at least one higher molecular weight
carbohydrate. After further optional treatments, such as to remove
retrograded amylose, the product mixture that is formed is
spray-dried. The spray-dried product readily may be transported and
processed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] The invention contemplates the production of maltose from
starch. Any suitable starch may be employed in connection with the
invention, and thus, for instance, starches such as corn, rice,
wheat, tapioca, maize, potato, barley, oat, and, more generally,
any starch suitable for enzymatic hydrolysis may be used in
connection with the invention. It is not necessary to use a
so-called waxy or glutinous starch in connection with the
invention, but to the contrary the starch can have any suitable
amylose content, such as an amylose content of 10%, 15%, 20%, 25%,
or a greater amylose content. It is contemplated that the starch
may be a partially derivatized or otherwise modified starch, or may
be a starch that has been thinned or enzymatically treated. For
instance, a starch that has been lightly oxidized may be
employed.
[0014] The starch should be liquefied via heat, enzymatic, or acid
treatment prior to treatment with the beta-amylase enzyme.
Preferably, the starch is liquefied via acid treatment, although
low amylose starches may require liquefaction only with heat and
may be suitably liquefied at the operating temperature of the
enzymatic hydrolysis. Generally, the starch should be liquefied to
an extent such that it would remain liquid at the operating
temperature of the beta-amylase hydrolysis, but not liquefied to an
extent such that the starch is converted to saccharides having so
low a degree of polymerization that it is difficult to separate
such saccharides from maltose via ultrafiltration. In other words,
the degree of liquefaction should be such that, upon enzymatic
hydrolysis with the beta-amylase enzyme, the combined content of
glucose and oligosaccharides in the DP 3-10 range does not exceed
about 10%, and preferably does not exceed about 5%. It has been
found acceptable to liquefy the starch to a dextrose equivalent
(DE) value of about 2 as measured via conventional techniques.
Generally, the DE of the starch should be kept below about 1, and
should thus range between 0 and about 1, although it may be
difficult to measure the DE with precision in this range. For corn
starch, it is preferable that the starch is liquefied in an aqueous
solution at a liquefaction temperature ranging from about
220.degree. F. to about 320.degree. F., and for a time ranging from
about 5 minutes to about 30 minutes.
[0015] The starch solids level preferably ranges initially from
about 5% to about 30%, more preferably, from about 15% to about
30%. It is believed that a lower solids level in the starch slurry
will result in a higher purity maltose upon enzymatic hydrolysis.
While it is not intended to limit the invention to a particular
theory of operation, it is believed that a lower solids content
requires a lesser degree of liquefaction to attain the desired
viscosity range. In the case of dent corn starch, it has been found
that a viscosity window of between 25 and 45 centipoise (Norcross
Shell Cup) is optimal. In the case of waxy starches, viscosities
outside this range may be acceptable. The pH of the starch slurry
should be adjusted to a level sufficient to provide controlled acid
hydrolysis of the starch in the presence or absence of catalyzing
alpha amylase enzymes; most preferably, under a given set of
conditions, the variability of the slurry pH should be no more than
+/-0.1 pH, with the precise pH value depending upon the starch
source, the slurry solids, and the operational conditions of the
liquefaction equipment employed. As a practical matter, the pH can
vary more widely while still resulting in a satisfactory maltose
product. Preferably, the starch liquefaction is monitored via
viscosity and adjusted accordingly.
[0016] In accordance with one embodiment of the invention, the
starch is liquefied with an alpha-amylase enzyme to reduce the
molecular weight of the starch, thereby reducing the viscosity of
the starch and thereby permitting processing at a higher solids
level. Suitable commercial liquefying enzymes may be obtained from
Genencor International or from Novozymes A/S. Any suitable
liquefaction conditions may be employed. The dosing level of the
alpha-amylase enzyme depends upon the desired solids level and the
desired maltose purity, and desirably ranges from about 0.005% to
about 0.02% of a commercial strength enzyme by dry solids basis
starch. In this embodiment, the alpha-amylase enzyme preferably is
quenched prior to saccharification via any suitable quenching
procedure. For instance, when the starch is liquefied at a
temperature less then 250.degree. F. and 5 minutes residence, the
alpha-amylase enzyme is quenched by reducing the liqefact pH to
less than 4.0 and holding at a temperature of from 180 to
190.degree. F. for at least about 15 minutes.
[0017] Upon liquefaction, the liquefact is immediately cooled and
the pH is adjusted to the optimum conditions for beta-amylase
activity. The starch then is treated with the enzyme under any
conditions suitable to result in the hydrolysis of this liquefied
starch to form maltose. A preferred enzyme is OPTIMALT BBA,
available from Genencor International, Inc. The enzyme may be added
in any amount sufficient to achieve this result, but generally, the
dosing of the enzyme should be in excess of the minimum viscosity
limited conversion of approximately two Genencor International,
Inc. OPTIMALT BBA Diastatic Power units per kilogram of starch, the
Diastatic Power units being defined as being the amount of enzyme
contained in 0.1 ml of a 5% solution of the sample enzyme
preparation that will provide sufficient reducing power to reduce 5
ml of Fehling's solution when the sample is incubated with 100 ml
of substrate for one hour at 20.degree. C.
[0018] The enzymes should be allowed to act on the starch for any
amount of time suitable to form maltose. Under the preferred
reaction conditions discussed hereinabove, saccharification
generally is 90% complete within 4 hours. The optimum temperature
and pH of the starch hydrolysis will vary depending on the
particular beta-amylase enzyme employed, but typically the
temperature will range from about 55.degree. C. to about 65.degree.
C. and the pH will range from about 5.0 to about 6.0.
[0019] At the conclusion of the enzymatic hydrolysis, a product
that contains maltose and at least one higher molecular weight
carbohydrate will be provided. Optionally, but preferably, this
product mixture is clarified and decolored by any suitable
procedure, such as carbon treatment, filtration, centrifugation,
and/or precipitation, before it is further processed. Maltose
content in the product may be at least about 30% by weight, and in
some cases much higher. If the enzyme is allowed to act under
optimum conditions for an optimum reaction time, the maltose
content of such product may be equal to or greater than about 50%,
in some cases equal to or greater than 60%, in some cases equal to
or greater than 65%, in some cases greater than or equal to about
70%, and even in some cases equal to or greater than about 75%,
while the content of higher molecular weight carbohydrates having a
dextrose equivalent value (DE) less than 5 may be greater than
about 20%. The combined content of glucose and of oligosaccharides
in the DP 3-10 range is below about 10%, and preferably is below
5%.
[0020] It is contemplated that in some instances a lower maltose
content in the product may be desired. In such case, the enzyme may
be quenched prior to the optimum reaction time, such as by
adjusting the pH or applying heat. In a highly preferred
embodiment, a correlation between enzyme reaction time and
resulting maltose content is prepared or is provided in advance.
Such a correlation between reaction time and maltose content may be
determined empirically, for instance, by performing at least two
experiments in which the enzyme is quenched at different reaction
times each less than the optimum reaction time, and measuring the
maltose content in each case. Once the correlation has been
prepared or provided in advance, a desired maltose content may be
obtained by quenching the enzyme after a reaction time determined
with reference to the predetermined correlation. It is also
contemplated that the maltose content may be controlled by
conducting the liquefaction under less than optimal conditions,
although such is not preferred inasmuch as a higher content of
glucose and/or lower molecular weight sugars in the product mixture
may thereby result. In accordance with this embodiment of the
invention, various products having differing maltose contents can
be prepared. For instance, it is contemplated that a product in
which the maltose content is 10%, 20%, or 30% may be prepared. In
each case the combined content of glucose and of oligosaccharides
in the DP 3-10 range can be kept below about 10%, and preferably
below 5%.
[0021] Retrograded amylose may be found as a by-product of the
enzymatic hydrolysis. In accordance with one embodiment of the
invention, at least some of the retrograded amylose is separated
from the product mixture. For instance, the saccharified solution
may be maintained at a temperature below about 140.degree. F. to
allow at least a portion of the retrograded amylose to crystallize.
The crystallized amylose then may be separated from the
saccharified starch mixture by any suitable technique, such as via
microfiltration, by which is contemplated separation at a
resolution sufficient to separate the retrograded amylose but not
sufficient to separate maltose from higher molecular carbohydrates
in the product mixture. Alternatively, the retrograded amylose may
be separated via centrifugation, using any technique known in the
art or otherwise found to be suitable.
[0022] In accordance with one embodiment of the invention, a high
purity maltose product is separated from the product mixture. Most
preferably, a maltose product is separated from the product mixture
via ultrafiltration of the product mixture, by which is
contemplated separation of the maltose from higher molecular weight
carbohydrates using a membrane or other suitable separation medium
that is effective for this purpose. Generally, a membrane having a
molecular weight cut off (MWCO) of 10,000 or less, preferably a
MWCO of 5000 or less, is suitable. Suitable commercially available
membranes available from Sydnar Filtration and from Osmonics De
Sal. Upon ultrafiltration, the permeate includes a high purity
maltose liquid, which may be evaporated to a high solids content
(greater than 55%) that crystallizes upon cooling. The purity of
the maltose obtained upon crystallization can be as high as 98%,
with dextrose levels below the detection level of conventional HPLC
analysis. The retentate typically will include a higher molecular
weight carbohydrate having a DE less than 5 and some retained
maltose. If desired, the retentate may be diafiltered to recover
additional maltose by flushing the filter with excess water.
[0023] In accordance with another embodiment of the invention, the
product mixture obtained upon enzymatic hydrolysis of the starch is
spray-dried. Surprisingly, it has been found that it is possible to
spray dry a maltose product prepared as discussed hereinabove.
While it is not intended to limit the invention to a particular
theory of operation, it is believed that the composition of the
product is especially suitable for spray drying, perhaps because of
the relatively low amount of maltotriose, which is substantially
more hygroscopic than maltose. The high molecular weight
carbohydrate in the product may function as an effective spray
drying enhancer. Prior to spray drying, the product mixture may be
clarified and decolored, and retrograded amylose may be removed as
discussed above.
[0024] Carbohydrate percentages given herein are expressed on a dry
solids basis per total carbohydrate weight.
[0025] The following examples are provided to illustrate the
invention, but should not be construed as limiting in scope.
EXAMPLE 1
[0026] This example illustrates the preparation of maltose from
waxy corn starch.
[0027] Starch from waxy corn was made to an aqueous slurry
containing 12 to 15% solids and pH 6.0 to 7.0. The slurry was then
liquefied by jet cooking through a Hydro Thermal Jet (Model
#M103-030) at 300.degree. F., 60 to 65 psi with a 5 minute
residence time at 300.degree. F., 50 to 55 psi. The liquefact was
immediately cooled, the pH was adjusted to 5.5 with hydrochloric
acid, and dosed with beta-amylase. Using a commercial barley
beta-amylase enzyme (Genencor International, Inc. OPTIMALT BBA),
dosing was 6.15 DP units per kilogram of starch or 0.05 wt. % grams
of liquid enzyme per gram of dry starch. Saccharification was
performed at 140.degree. F. for 4 to 24 hours. The solution was
then separated by ultrafiltration through a polysulfone 3000 MWCO
membrane (Syndar Filtration). The permeate, containing
approximately 6% solids, was then evaporated to 70% solids which
contained not less than 95% maltose. The malto-oligosaccharide
content in the permeate solution was evaluated by HPLC using a
Phenomenex Rezex-RSO-oligosaccharide/Silver column with RI
detection and found to be as follows:
1 DP1 Maltose DP3 >DP3 0.2% 97.9% 0.4% 1.4%
[0028] As seen, the invention provided a maltose product of
extremely high purity, with only about 2% glucose and saccharides
having a DP greater than 3.
EXAMPLE 2
[0029] This Example illustrates the preparation of maltose from wet
mill processed yellow dent corn starch under various liquefaction
conditions.
[0030] Dent corn starch was liquefied under various reaction
conditions, as given in the following Table. The pH of the starch
was adjusted where necessary, and then was saccharified with a
beta-amylase enzyme as in Example 1. Samples then were filtered
through a 3000 MWCO membrane and analyzed as in Example 1, yielding
the results reported in the Table below.
2 % Residence Higher Example solids pH Temp (F.) Time (min)
Dextrose Maltose DP3 DP 2A 15 3.5 300 5 0.3 96.4 0.8 3.2 2B 20 3.0
300 5 Nd 96.0 1.2 2.8 2C 20 2.75 300 5 Nd 89.9 2.2 7.9 2D 25 2.75
300 5 Nd 93.8 2.2 4.0 2E 25 3.0 300 20 Nd 89.4 2.9 7.7 2F 25 2.75
300 20 1.2 84.8 4.6 9.4 2G 30 3.0 300 20 Nd 91.6 3.7 4.7 2H 30 2.75
300 20 1.3 84.9 4.8 9.0 2I 30 3.0 300 20 Nd 92.3 2.9 4.8 2J 30 3.0
280 20 Nd 92.5 2.5 5.0 Nd = not detected
[0031] All of the examples provided a very high purity maltose
product, with even Example 2F providing a higher purity product
than is obtainable conventionally without chromatographic
separation.
EXAMPLE 3
[0032] This Example illustrates the liquefaction of wet mill
processed yellow dent corn starch with an alpha-amylase enzyme.
[0033] In two separate runs, starch from wet mill processed yellow
dent corn was adjusted to a solids content of 12 or 25% dry solids
basis and the pH was adjusted to pH 5.50 with hydrochloric acid.
Each starch slurry was then dosed with a liquefying alpha-amylase
enzyme (Novo TERMAMYL SC) to 0.005-0.02% dry solids basis. The
slurries were then jet cooked at 230.degree. to 290.degree. F. with
a 5 to 20 minute residence. The alpha-amylase then was quenched by
reducing the liquefact pH to less than 4.0 and holding at 180 to
190.degree. F. for 15 minutes. The liquefacts then were
saccharified with a beta-amylase enzyme, then filtered and
evaporated as in Example 1.
[0034] This procedure was followed for the following reaction
conditions, yielding the following products.
3 12% solids, 0.01% dsb Termamyl SC, 270.degree. F./20 min, 4%
solids product DP1 Maltose DP3 >DP3 0% 96.6% 0.5% 2.9%
[0035]
4 25% solids, 0.2% dsb Termamyl SC, 230.degree. F./5 min, acid
kill, 18% solids product DP1 Maltose DP3 >DP3 0% 88.3 4.3
7.4
[0036] The later example provided a maltose content of 88.3%,
which, while lower than that for some of the previous examples, was
higher than that conventionally attainable.
EXAMPLE 4
[0037] This Example illustrates crystallization of retrograded
amylose from the saccharified starch mixture.
[0038] This saccharified solution from Example 2 was held at
130.degree. F. for 18 to 24 hours. This hold time was necessary for
the slow, complete formation of amylose crystals. This saccharified
mixture was then pre-filtered through a minimal microfilter of
porosity 0.1 to 0.8 micron (U.S. Filter ceramic membranes). The
filtration was performed at temperatures not greater than
140.degree. F. to maintain the insoluble retrograded amylose. The
filter pore size was selected to produce maximum flux with minimum
turbidity in the permeate. For a process using 15% dry solids
starch feed at pH 3.5, a 0.8 micron filter will adequately clarify
the feed material.
[0039] The retentate from the pre-filtration was enriched in the
amylose faction and the permeate contained maltose and high
molecular weight carbohydrates. Analysis of the amylose particle
size using a Malvern Instruments Ltd. Mastersizer showed that 90%
of the amylose crystals were of a size between 1 and 20 microns.
The crystal size distribution appears to broaden and decrease in
size as the process increases in solids and decreases in pH. At a
25% solids content and pH of 3.0, a 0.1 micron filter is necessary
for minimal clarification.
[0040] The permeate from the microfiltration step was then
ultrafiltered as previously described to generate a high purity
maltose product.
EXAMPLE 5
[0041] This Example illustrates recycling of a high molecular
weight carbohydrate fraction.
[0042] The retentate obtained from Example 2 was recycled and
blended with wet milled starch to a solids content of 12 to 14% at
a ratio of 3:2 retentate solids to starch solids and processed as
described in Example 2, with the saccharification step being kept
to 4-5 hours. The maltose permeate obtained upon ultrafiltration
was analyzed and found to have the following composition:
5 DP1 Maltose DP3 >DP3 0.4% 96.5% 0.7% 2.4%
[0043] As seen, a high purity maltose product was provided.
EXAMPLE 6
[0044] This Example illustrates that various membranes may be used
in the ultrafiltration of maltose from the product formed upon
enzymatic saccharification.
[0045] Material was processed through the microfiltration step as
described in Example 4. Laboratory scale samples were processed on
a hollow fiber unit from A/G Technology Corp. (AGT UFP-3-C-4A 3000
NMWC). This filter was run with a Masterflex peristaltic pump
(model 7553-70) with a Masterflex head (model 70 15-52) connected
with Norprene tubing (model 6402-15). Recirculation rates were
adjusted to maintain pressures between 10 psi and 20 psi.
[0046] Large scale samples were tested on commercially available
spiral wound elements installed and operated on a NIRO Inc. Model
R16 Single Stage UF/RO Pilot Plant. Elements evaluated were
purchased from Syndar Filtration (PES 3000 MWCO VT2B3838) or
Osmonics De Sal (GH/G-10, GK/G-20 and GM/G-50 3838). Operating
conditions were those specified by the membrane manufacturer.
[0047] Permeate was sampled and analyzed by HPLC. Results are
averages from multiple permeate samples.
6 Membrane MWCO Solids DP1 Maltose DP3 DP>3 AGT 3000 3000 25 Nd
93.8 2.2 4.0 Syndar 3000 14 0.1 97.2 0.6 2.187 3000 Desa1 Gl0 2500
25 Nd 96 0.65 3.3 DeSa1 G20 3500 25 Nd 97.4 1.5 1.2 DeSa1 G50 8000
25 Nd 96.5 1.5 2.0
EXAMPLE 7
[0048] This Example demonstrates the ability to spray dry maltose
syrups of various compositions.
[0049] Maltose syrup was prepared as described in Example 2 using a
15% dsb starch feed. Three compositions were evaluated, including
the ultrafilter feed material that contained 65% maltose and 35%
high molecular weight carbohydrate material having a DE less than 5
(the "65/35 material"), the ultrafilter permeate material that
contained 95% maltose and 5% high molecular weight carbohydrate
(the "95/5 material"), and a blend of these materials that
contained 90% maltose and 10% high molecular weight carbohydrate
(the "90/10 material"). These solutions were spray dried on a
Yamoto-Ohkawara Spray Dryer DL-41 with a 2850-SS nozzle and a 65-5
SS orifice. Operating conditions were: drying air 0.75 m.sup.3/min,
atomizing air 0.25 Mpa, feed rate 20 ml/min, inlet temperature
300.degree. C. outlet temperature 100.degree. C. The feed solids
were from 6% to 30% dsb for the 65/35 and 90/10 material. The dry
powder produced from these two products contained moisture content
of 2-3%. The 95/5 material melted in the receiver line at these
temperatures but was effectively dried at reduced temperature of
200.degree. C. inlet temperature, 80.degree. C. outlet temperature
with a resulting moisture content of 2.5%.
EXAMPLE 8
[0050] This Example describes a scale-up pilot production of high
purity maltose.
[0051] A commercial yellow dent starch available from Grain
Processing Corporation of Muscatine, Iowa (B 200) was slurried to a
solids level of 15% dsb and a pH of 3.5 with hydrochloric acid. The
slurry was fed at a rate of 2 gpm through a Hydroheater jet Series
M103 AS at a pressure of 60 psi and a temperature of 300.degree. F.
The post-jet residence time was 7.5 minutes resulting in a primary
liquefact of a Shell Cup viscosity (Norcross Corp.) of 25 cp. The
pH of the liquefact was continuously adjusted to 5.5 with soda ash
and cooled through a heat exchanger to 140.degree. F. The liquefact
was dosed with Spezyme BBA (Genencor International, Inc.) at a
level of 0.05% dsb and converted at temperature through an 8-stage
plug flow reactor with continuous agitation and a total residence
time of eight hours. The saccharified product was clarified by
passing the product through a NIRO Model-C ceramic filtration unit
with a 19-element Membrelox, 0.8 um ceramic bundle. The clarified
permeate was then ultrafiltered through a NIRO Model-U
ultrafiltration unit containing DeSal G-50 membranes. Ultrafiltered
permeate was collected, evaporated to 70% solids and stored in 50
pound lots. Twelve lots were sampled and assayed for maltose purity
by HPLC and ion content by Dionex ion chromatography. The following
table summarizes those results.
7 Analysis Average Std. Dev. % DP1 Nd % DP2 97.54 0.87 % DP3 0.96
0.15 % higher 1.51 0.79
[0052]
8 Analysis Average Analysis Average Li ppm 0 F ppm 27.17 Na ppm
187.8 Cl ppm 1691.00 NH.sub.4 ppm 0.8 NO.sub.2 ppm 18.50 K ppm 44
NO.sub.3 ppm 67.33 Mg ppm 250.4 SO.sub.4 ppm 671.00 Ca ppm 1023
PO.sub.4 ppm 69.67
[0053] As seen, a maltose product having a very high purity was
produced. No glucose was detected, and the total content of sugars
in the DP 3-10 range was very low.
EXAMPLE 9
[0054] This Example describes the production of a 75% maltose syrup
low in dextrose and maltotriose.
[0055] A commercially available yellow dent corn starch was
slurried to a solids content of 25% dsb and a pH of 3.0 with
hydrochloric acid. The slurry was liquefied at 300.degree. F. on a
lab scale reactor as described in Example 1 with a 7.5 minute
residence time resulting in a liquefact of Shell Cup viscosity of
21 cp. The liquefact was cooled to 140.degree. F., the pH was
adjusted to 5.5 with soda ash, and was dosed with Spezyme BBA at
0.5% dsb as previously described. After an 8-hour hold at
140.degree. F., the saccharified product was microfiltered on a
NIRO Model-R unit using a Membralox 0.1 urn ceramic filter. The
permeate was at 17% solids and spray dried on a 60 inch pilot scale
spray dryer with a SC 43 nozzle, at a feed pressure of 2000 psi,
inlet temperature of 510-550 F, outlet temperature 250F. The
product was analyzed by HPLC.
[0056] As a control, two commercially available maltose syrups were
analyzed via HPLC. The following table shows the results of the
analyses of each product.
9 Sample ID Example 9 Commercial syrup A Commercial syrup B DP1 0.7
1.6 2.0 DP2 74.6 72.3 63.1 DP3 2.5 18.7 17.9 DP4 0.2 0.3 0.5 DP5 0
1.1 0.2 DP6 0 2.1 1.6 DP7 0 0.8 1.3 DP8 0 0.6 2.8 DP9 0.3 0.3 1.4
DP10 0.2 0.1 0.7 Higher DP 21.5 2.1 8.6
[0057] The DP profile of the maltose product prepared in accordance
with Example 9 was markedly different from that of the commercially
available syrups. As seen, the product of Example 9 had a much
lower maltotriose (DP3) content than either of the commercial
syrups.
[0058] It is thus seen that the invention provides a process for
preparing a high purity maltose product. The product can be
prepared without chromatographic separation to yield a product that
has a very low content of glucose and malto-oligosaccharides having
a DP ranging from 3-10.
[0059] While particular embodiments of the invention have been
shown, it will be understood that the invention is not limited
thereto since modifications may be made by those skilled in the
art, particularly in light of the foregoing teachings. It is,
therefore, contemplated by the appended claims to cover any such
modifications as incorporate those features which constitute the
essential features of these improvements within the true spirit and
scope of the invention. All references and pending applications
cited herein are hereby incorporated by reference in their
entireties. U.S. patent application Ser. No. ______, filed Feb. 28,
2001 by Richard L. Antrim and Clark Lee and assigned attorney
docket number 209498, also is hereby incorporated by reference.
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