High solids maltodextrin syrups, some of which are useful as the base for remoistenable adhesives, are prepared by a high solids alpha amylase enzyme conversion process. They are characterized by their high solids content (at least 55 wt. %) and light color. A granular chemically derivatized, optionally converted, starch having a degree of substitution of greater than about 0.01 and less than about 0.5 is used as the starting material. The maltodextrins have a reducing sugar content of about 5-19 dextrose equivalent and a distinct polymodal molecular weight distribution. When a granular highly esterified starch (D.S. of 0.5-1.8) is used as the starting material in the high solids process, the resulting enzyme-converted, esterified maltodextrins are characterized by their improved water dispersibility.

BACKGROUND OF THE INVENTION 
In its broadest sense, the term "dextrin" covers any starch degradation 
products, with the exceptions of mono- and oligosaccharides, regardless of 
how the starches are degraded. All dextrins belong to a large and varied 
group of D-glucose polymers which can be linear, highly branched, or 
cyclic. Their complexity creates problems in any classification based on 
their chemical character. Hence, they are often classified based on how 
they are prepared. 
The hydrolytic procedures used for their preparation fall into four major 
groups: products obtained by hydrolysis of dispersed starch by the action 
of liquefying enzymes such as amylases; products obtained by the acid 
hydrolysis of dispersed starch; Schardinger dextrins formed from dispersed 
starch by the action of Bacillus macerans transglycosylase; and 
pyrodextrins produced by the action of heat or heat and acid on dry 
starch. 
Maltodextrins include enzyme- and/or acid-converted dextrins, defined by 
the Food and Drug Administration (FDA) as non-sweet, nutritive saccharide 
polymers which consist of D-glucose units linked primarily by 
alpha-1.fwdarw.4 glucosidic bonds and which have a dextrose equivalent 
(DE) of less than 20. Corn syrup solids are defined by the FDA as dried 
glucose syrups in which the reducing sugar content is 20 DE or higher. The 
degree of hydrolysis strongly affects the functional properties of 
maltodextrins and corn syrup solids. 
Manufacturing processes for preparing maltodextrins include single-stage 
and dual-stage starch slurry processes using acid and/or enzyme. A solids 
content of about 18-35% is considered high solids. 
A single-stage process combines either acid or enzyme conversion at 
relatively high temperatures with gelatinization of the starch. The 
hydrolysis may then be continued in hold tanks until the appropriate DE is 
reached, at which point the hydrolysis is terminated by either pH 
adjustment or heat deactivation. The product may then be refined or 
purified, concentrated and spray-dried. 
A dual-stage process involves first a high temperature (usually&gt;105.degree. 
C.) gelatinization/liquefaction with either acid or enzyme to a low DE 
(usually&lt;3) followed by a high temperature treatment (as in a jet cooker) 
to ensure gelatinization of the starch. After pH adjustment and lowering 
of the temperature to around 82.degree.-105.degree. C., a second 
conversion step, usually with a bacterial alpha-amylase, is conducted 
until the desired DE is achieved. The enzyme is then deactivated and the 
product may then be refined and spray-dried. 
Some of the patents covering acid- and/or enzyme-conversion of starches to 
maltodextrins are discussed below. 
U.S. Pat. No. 2,609.326 (issued Sep. 2, 1952 to W. W. Pigman et al.) 
discloses rapidly gelatinizing and dispersing starch granules in hot water 
while subjecting the starch to intense agitation and shearing, immediately 
converting the gelatinized and dispersed starch at an elevated temperature 
with a starch-liquefying amylase characterized by its ability to hydrolyze 
the starch molecules into large fragments, inactivating the enzyme, and 
immediately drying the enzyme converted starch. The dry cold water 
dispersible converted starches are characterized by a very low content of 
reducing sugars (3% or less). 
U.S. Pat. No. 3,560,343 (issued Feb. 2, 1971 to F. C. Armbruster et al.) 
discloses a process where a starch is acid hydrolyzed to a D.E. less than 
15 and then converted with a bacterial alpha-amylase to a DE between 10 
and 25. 
Japanese 46-14706 (published Apr. 20, 1971) discloses a continuous process 
for preparing a granular converted starch which swells, but does not 
dissolve in cold water, and which is reduced in viscosity. A starch alpha 
amylase mixture having a water content of 40-60%, containing buffer to 
adjust the pH to 5-7, is cured for several hours at room temperature, or a 
temperature at or below the gelatinization temperature, after which it is 
put into a starch dryer maintained at 70.degree..congruent.150.degree. C. 
During the drying, the temperature and water content change to those 
suitable for hydrolyzing the starch. The hydrolysis, drying of the 
hydrolyzed starch, and deactivation of the residual enzyme simultaneously 
occur during the heating at 70.degree.-150.degree. C. A liquefaction-type 
amylase shows the strongest hydrolytic activity at 70-90.degree. C., but 
at higher temperatures (i.e., above 90.degree. C.), if the moisture 
content is above 35%, the starch undergoes the hydrolytic activity but is 
gelatinized at the same time and if the water content of the mixture is 
less than 30%, it becomes more difficult to gelatinize the starch, but at 
the same time the hydrolysis by the enzyme shows a tendency to fall off 
rapidly. To satisfy these opposing tendencies, it is necessary to reduce 
the water content of the mixture from 40-60% to 30-35% in the dryer and to 
increase the temperature to 90.degree.-100.degree. C. during the enzyme 
hydrolysis. 
U.S. Pat. No. 3,849,194 (issued Nov. 19, 1974 to F. C. Armbruster) 
discloses treating a waxy starch with a bacterial alpha-amylase at a 
temperature above 85.degree. C. to liquify the waxy starch, cooling the 
liquified waxy starch to about 80.degree. C., and converting the liquified 
waxy starch with the bacterial alpha-amylase to a D.E. of from about 5 to 
about 25. 
U.S. Pat. No. 3,663,369 (issued May 16, 1972 to A. L. Morehouse et al.) 
discloses a two-stage hydrolysis. The first stage is carried out with 
acids or enzymes at elevated temperatures for short periods to liquify the 
starch with very little dextrinization or saccharification. The second 
stage is carried out at an alkaline pH with bacterial alpha-amylase to 
achieve the desired D.E. 
U.S. Pat. No. 3,853,706 (issued Dec. 10, 1974 to F. C. Armbruster) 
discloses hydrolyzing starch with a bacterial alpha-amylase to a DE of 
less than 15, terminating the hydrolysis by heat treatment, and further 
converting to a DE of between about 5 and 20. 
U.S. Pat. No. 3,974,034 (issued Aug. 10, 1976 to H. E. Horn) discloses 
maltodextrins which are prepared by the enzymatic hydrolysis of an 
oxidized starch. The starch is first simultaneously liquefied and oxidized 
at elevated temperatures and then converted with a bacterial alpha amylase 
to a D.E. not substantially above 20. 
U.S. Pat. No. 4,014,743 (issued Mar. 29, 1977 to W. C. Black) discloses a 
method for the continuous enzyme liquefication of starch. Preferably, the 
starch is a raw starch, but pregelatinized or modified starches may be 
used (see Column 6, lines 1-7). A suitable enzyme is bacterial alpha 
amylase. An enzyme-containing suspension of raw starch (10-45 wt. % on a 
dry solids basis) is continuously added to an agitated body of heated 
(77.degree.-99.degree. C.-170.degree.-210.degree. F.) converted starch. 
The incoming starch is gelatinized and mixed with the partially converted 
starch to maintain a blend having a viscosity low enough to be readily 
agitated and pumped. A stream of the blend is continuously removed from 
the conversion tank and treated to inactivate the enzyme. The process is 
controlled to limit the maximum viscosity of the blend to a Brookfield 
viscosity of not over 5000 cps (100 rpm and 88.degree. C.-190.degree. F.). 
The reducing sugar content is usually less than 3% on a dextrose 
equivalent basis. A blend of starches that have been subjected to 
different degrees of enzyme conversion is obtained since the heating and 
enzyme treatment is not uniform for the individual starch granules or 
molecules. 
U.K. 1,406,508 (published Sep. 17, 1975) discloses a continuous process for 
liquefying natural or chemically modified starch to give starch pastes 
having a solid content of up to 70% by weight. The starch in granular 
form, without the intermediate formation of a slurry, is continuously 
supplied to a reaction zone where it is subjected to the action of an 
enzyme (e.g., alpha amylase) in a stirred aqueous medium at an elevated 
temperature (50.degree.-98.degree. C.) and pH of 4.5-8. Once the 
liquefaction is completed the liquefied starch is stabilized by 
deactivating the enzyme. A greater proportion of large molecules and a 
broader molecular weight distribution results as compared to a 
discontinuous process where the molecules are smaller and substantially 
the same size. 
DE 37 31 293 A1 (laid open Apr. 8, 1980) discloses a process for 
continuously degrading and digesting starch. A dry starch powder together 
with liquid water or an aqueous starch suspension is charged to a stirred 
converter containing a starch degrading enzyme, preferably alpha amylase, 
while the temperature is increased to 70.degree.-90.degree. C. by the 
injection of steam at 120.degree.-125.degree. C. and 2-4 bar. The product 
leaving the converter is treated with an enzyme deactivating agent before 
final dilution to the desired concentration. 
U.S. Pat. No. 4,921,795 (issued May 1, 1990) to F. A. Bozich, Jr.) 
discloses an improved slurry method for producing dextrin adhesives using 
alpha amylase in combination with glucoamylase. The function of the 
glucoamylase is to eliminate the limit dextrin problem and the mechanical 
shearing step. The alpha amylase randomly cleaves the .alpha.(1.fwdarw.4) 
linkages of the linear amylose molecules and cleaves the branched 
amylopectin molecules up to the (1.fwdarw.6) glucosidic linkages of the 
limit dextrin. The slurry is stirred sufficiently to create a vortex in 
the aqueous reaction slurry, thereby maintaining adequate mixing without 
shearing. The hydrolysis is allowed to continue until an optimal mix of 
fragment sizes is achieved (as indicated by a Brookfield viscosity of 
1000-2000 cps at 20 rpm, 110.degree. F., 45-55% solids, and 0 to 16% 
sodium borate pentahydrate). The enzyme is then inactivated. The 
Theological properties of the resultant slurry can be adjusted as needed. 
There is a need for high solids, stabilized (i.e., chemically derivatized) 
maltodextrins which can be used where pyrodextrins or maltodextrins are 
conventionally used, for example in remoistenable adhesives. 
SUMMARY OF THE INVENTION 
The present invention is directed to a clear, off-white to beige 
maltodextrin syrup having a solids content of at least 55% by weight, 
which is prepared from a chemically derivatized converted or non-converted 
granular starch. The maltodextrin has (i) substituents in an amount 
sufficient to provide a degree of substitution greater than about 0.01 and 
less than about 0.5, preferably between 0.05 and about 0.17; (ii) a 
reducing sugar content of between about 5 and about 19 dextrose 
equivalents, preferably between about 10 and about 17; and (iii) a 
polymodal molecular weight distribution having one peak between about 630 
to about 1600 Daltons and at least one other peak between about 1600 and 
about 2,500,000 daltons, preferably peak(s) between about 1600 and about 
160,000 daltons. 
The chemically derivatized maltodextrin may be prepared from any cereal, 
tuber, root, legume, or fruit starch. 
Typical substituents include ester and/or ether groups and cationic groups 
such as diethylaminoethyl chloride hydrochloride or 
3-chloro-2-hydroxypropyl trimethyl ammonium chloride groups. Suitable 
ether groups include hydroxyethyl, hydroxypropyl, or like hydroxyalkyl 
groups. Suitable ester groups include acetate, propionate, butyrate, 
hexanoate, benzoate, and octenylsuccinate groups and mixed starch esters 
such as acetate/propionate, acetate/butyrate and the like. Slightly 
crosslinked starches which contain mono-functional ether and/or ester 
substituents are also useful herein and can be converted by the process 
described below. 
The high solids maltodextrin syrups are prepared by a high solids enzyme 
conversion process which comprises the steps of: 
a) adding, to chemically derivatized starch having a degree of substitution 
of about 0.01 to about 0.50, an alpha amylase enzyme and water in an 
amount sufficient to produce a single phase powdered mixture without a 
visible free water phase; 
b) activating the enzyme by heating the powdered mixture to about the 
optimum temperature for the enzyme while maintaining a substantially 
constant moisture content (i.e., .+-.5% of the starting moisture content) 
in the mixture; 
c) allowing the enzyme to hydrolyze the starch to a degree sufficient to 
give a chemically derivatized maltodextrin syrup having a reducing sugar 
content of between about 5 and about 19, preferably between about 10 and 
about 17; and 
d) preferably inactivating the enzyme after the desired dextrose equivalent 
is reached. 
In step (d) the solids content may be reduced by adding water. 
Optionally, the water can be removed from the aqueous maltodextrin syrup 
and the maltodextrin recovered as a powdered chemically derivatized 
maltodextrin. 
The present invention is also directed to enzyme-converted, highly 
esterified starch esters having a degree of substitution of about 0.5 to 
about 1.8 which are characterized by their self emulsifying properties in 
water. Preferably, the starch esters are highly acetylated waxy maize or 
corn starch esters having a degree of substitution (D.S.) of about 1 to 
about 1.25. The starch esters are prepared by adding, to a cold 
water-insoluble starch ester having a degree of substitution of about 0.5 
to about 1.8, an alpha amylase enzyme and water in an amount sufficient to 
produce a powdered mixture without a visible free water phase and allowing 
the alpha amylase to hydrolyze and liquefy the starch. The alpha amylase 
may be mixed with a beta amylase or a glucoamylase. 
A suitable method for preparing the starch esters is described in U.S. Pat. 
No. 5,321,132 (issued Jun. 14, 1994 to R. L. Billmers et al.), the 
disclosure of which is incorporated herein by reference. The starch esters 
have the formula 
##STR1## 
where St is the starch base and R and R' are different and are selected 
from the group consisting of alkyl, aryl, alkenyl, alkaryl, and aralkyl 
groups having 1 to 7 carbon atoms. Starch esters of this type include the 
acetate, propionate, butyrate, hexanoate, benzoate, and mixed esters such 
as the acetate/propionate. The granular base starch may be any of the 
native starches described hereafter or may be any of the chemically and/or 
physically modified starches disclosed in the '132 patent. 
The esters are prepared by reacting a granular starch with a sufficient 
amount of an organic anhydride to obtain the desired D.S. Typically, from 
about 35-300%, preferably 50-200%, by weight, of anhydride is used based 
on the dry weight of the starch. The reaction is carried out in an aqueous 
medium at a pH of about 7-11, preferably 7.5-10, and a temperature of 
about 0.degree.-40.degree. C., preferably 5.degree.-20C. Because of the 
large amount of anhydride required, it is desirable to use a concentrated 
amount of aqueous alkali, e.g., about 10-50%, preferable 20-30%, by 
weight. Any alkali is suitable. Preferred alkalies are the alkali metal 
hydroxides, most preferably sodium hydroxide. 
As will be shown in the examples, when a starch ester, e.g., the acetate, 
is converted by the high solids, single phase enzyme conversion process, 
the original non-water-dispersible starch ester becomes readily 
dispersible in water at room temperature after the enzyme conversion. The 
significant reduction in viscosity indicates that the highly substituted 
starch is hydrolyzed even though chemical substituents typically interfere 
with enzyme conversion. The hydrolyzed starch still retains a high degree 
of substitution. The GPC molecular weight profile shows multiple peaks. As 
used herein, "starch" is intended to include non-pregelatinized granular 
starches, pregelatinized granular starches, and starches which are 
pregelatinized but not cold-water-soluble. 
As used herein, "single phase" means a mixture which has no visible free 
water, whereas a "slurry" consists of two phases, i.e., a water phase and 
a starch phase. The preferred total water content herein is about 15 to 
40% by weight of the total mixture, except when a converted granular 
starch is being prepared with only alpha amylase where the total water 
content is about 15-35%. 
The powdered or preferably liquid enzyme and sufficient water to give the 
desired total moisture content are dispersed onto a granular starch 
powder. The typical moisture content of granular starches is about 10-14%. 
Thus, sufficient water is added in step (a) to bring the total amount of 
water to the desired amount. As used herein, the term "total amount of 
water" refers to the total of the equilibrium moisture typically present 
in a granular starch and the added water. 
If the moist single phase powdered mixture is subjected to a mixing process 
which kneads and compacts, such as that typical of dough mixing equipment 
or viscous polymer compounding equipment, it may, depending upon the water 
content and amount of solubles present, become a very high viscosity 
compact doughy mass before the onset of gelatinization and conversion. 
Continued mechanical shearing will raise the temperature and cause 
gelatinization and conversion. 
When the powdered starch mixture contains a granular starch, as the 
powdered mixture is heated, the heat and moisture initiate the swelling of 
the starch granules and the starch is completely or partially gelatinized 
and simultaneously converted. When the powdered mixture contains a 
pregelatinized, non-cold-water-dispersible starch, the heat and moisture 
disperse the starch and the starch is fully gelatinized and simultaneously 
converted. As the starch is converted, usually the powder liquefies. The 
peak viscosity of the native starch is never reached. 
The maltodextrin may be in the form of a syrup, a converted granular 
starch, or a mixture of the syrup and the converted granular starch. As 
used herein, "syrup" covers liquids and viscous pastes. The resulting 
starch syrup is obtained at a high solids content (e.g., at least 60%, 
typically 65-75% by weight). The syrup may be spray dried, belt-dried, or 
freeze dried. The enzyme-converted starch may be recovered from the starch 
syrup as a water-soluble powder. If desired, the sugar by-products may be 
removed from the granular converted starch by washing. 
Optionally, an enzyme activator such as certain inorganic salts and/or a pH 
adjuster such as an acid, a base, or a buffer may be used. 
The enzyme may be activated by direct or indirect heating and/or pH 
adjustment to the optimum temperature and pH for the particular enzyme 
used. The enzyme may be inactivated by reducing the pH, adding an 
inhibiting salt, or increasing the temperature. 
The water content during the conversion is affected by the product solids, 
the condensation of injected steam used for direct heating, and moisture 
evaporation during the conversion. The product solids are increased by the 
hydrolysis. During conversion to a D.E. of 100, the dry weight of the 
starch is increased by 11.11% due to water covalently bound to the 
hydrolysis reaction products. This dry weight increase is proportional to 
the degree of conversion. The solids are decreased due to the condensed 
steam and increased by evaporation. 
The powdered mixture of the starch, water, and enzyme does not require 
stirring during the enzyme conversion step. In contrast to prior art 
enzyme conversion processes, the process is carried out at such a high 
solids content that the mixture is a single phase. 
Suitable starches can be derived from any source. Typical sources for the 
starches are cereals, tubers, roots, legumes, fruit starches, and hybrid 
starches. Suitable native sources include corn, pea, potato, sweet potato, 
sorghum, wheat, rice, waxy maize, waxy tapioca, waxy rice, waxy barley, 
waxy wheat, waxy potato, waxy sorghum, and the like. 
Using the unique high solids, single phase enzyme conversion process, one 
obtains a high solids maltodextrin syrup directly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
There are other potential routes for preparing similar chemically 
derivatized maltodextrins. For example, a chemically derivatized starch 
could be slurried in water, cooked to gelatinize and disperse the starch, 
then enzyme converted with alpha amylase to yield a maltodextrin syrup. 
There are several drawbacks to this process. First, the solids during the 
conversion will be limited by the viscosity of either the slurry or the 
dispersed, unconverted starch, whichever is higher. Second, enzyme 
activity at lower solids, probably 25 to 40%, will be less than at higher 
solids and, hence, to obtain comparable enzyme conversion to a D.E. in the 
maltodextrin range will require high enzyme levels and repeated doses at 
long conversion times. The claimed products are at or near the limit of 
conversion for chemically derivatized starches having the desired degree 
of substitution. This difficult process will only yield similar products 
at lower solids. Another potential process would be to slurry a native 
starch in water and then cook and enzyme convert as for conventional, 
commercial maltodextrins. A commercial maltodextrin having the desired DE 
and molecular distribution could then be chemically modified. This 
process, while producing a high solids syrup, has other drawbacks. The 
by-products of the chemical reaction, i.e., salts such as buffers, pH 
adjustments by-products, residual reagents, and reagent by-products, will 
be present in the final syrup limiting the syrup's use in food or products 
having indirect food contact such as envelope or packaging adhesives. 
Also, the distribution of the chemical substituents over the range of 
molecular weight components in the maltodextrin will be different. 
Further, the chemical derivatization of the maltodextrin tends to produce 
dark colored products under alkaline conditions. Hydroxypropylated 
maltodextrins made by this process are black. 
Any starch is useful herein. Suitable starches include corn, pea, potato, 
sweet potato, sorghum, waxy maize, waxy tapioca, waxy rice, waxy barley, 
waxy potato, and waxy sorghum, and starches having amylose contents of 40% 
or above (also referred to as high amylose starches). Preferred starches 
are waxy maize and corn. 
It may be possible to convert chemically derivatized flours provided 
effective enzyme levels are used to obtain the required conversion. 
It may be possible to prepare enzyme-converted, chemically derivatized 
maltodextrins prepared from starches having an amylose content above 40% 
(commonly referred to as high amylose starches) by the high solids, single 
phase enzyme conversion process. In order to use these high amylose 
maltodextrins in adhesives, one would have to use them at lower solids and 
the adhesives will need to be formulated with additional polyvinyl acetate 
and humectants to reduce the adhesive's initial viscosity. Further, 
additional ingredients such as glyoxal, alkalies, or salts will be 
required to provide the adhesive with long term viscosity stability. The 
use of humectants causes hygroscopic blocking. The use of salts such as 
nitrites, ureas, or chlorides also causes hygroscopic blocking. 
Since high amylose starches are harder to gelatinize, it will also be 
necessary to use a higher level of chemical substitution to lower the 
starch's gelatinization temperature. The increased substitution, however, 
inhibits the enzyme conversion. 
Granular starches which have not been pregelatinized are preferred. 
Granular pregelatinized starches are also useful herein. The 
pregelatinized granular starches are prepared by processes known in the 
art. The pregelatinization is carried out in such a way that a majority of 
the starch granules are swollen, but remain intact. Exemplary processes 
for preparing pregelatinized granular starches are disclosed in U.S. Pat. 
Nos. 4,280,851, 4,465,702, 5,037,929, and 5,149,799, the disclosures of 
which are incorporated by reference. Predispersed (i.e., pregelatinized 
starches) can also be used in the high solids, single phase enzyme 
conversion process provided they are not cold-water-soluble. They can be 
prepared by jet-cooking and spray-drying. 
Chemically derivatizing the starch can lower the gelatinization temperature 
and make it easier to carry out the conversion. The chemical modifications 
useful herein include heat- and/or acid-conversion, oxidation, 
phosphorylation, etherification, esterification, and conventional enzyme 
modification. These modifications are preferably performed before the 
starch is enzyme converted. Procedures for chemically modifying starches 
are described in the chapter "Starch and Its Modification" by M. W. 
Rutenberg, pages 22-26 to 22-47, Handbook of Water Soluble Gums and 
Resins, R. L. Davidson, Editor (McGraw-Hill, Inc., New York, N.Y. 1980). 
Physically modified starches, such as the thermally-inhibited starches 
described in WO 95/04082 (published Feb. 9, 1995), are also suitable for 
use herein provided they have also been chemically modified. 
Suitable enzymes for use herein include bacterial, fungal, plant, and 
animal enzymes such as endo-alpha-amylases which cleave the 1.fwdarw.4 
glucosidic linkages of starch, beta-amylases which remove maltose units in 
a stepwise fashion from the non-reducing ends of the 
alpha-1.fwdarw.4-linkages, glucoamylases which remove glucose units in a 
stepwise manner from the non-reducing end of starch molecules and cleave 
both the 1.fwdarw.4 and 1.fwdarw.6 linkages, and mixtures of the enzymes 
with debranching enzymes such as isoamylase and pullulanese which cleave 
the 1.fwdarw.6 glucosidic linkages of amylopectin-containing starches. 
Alpha amylases or mixtures thereof with other enzymes are preferred and 
are used for preparing the enzyme-converted, chemically derivatized 
maltodextrins having unique bimodal or polymodal molecular weight 
profiles. 
Enzymes can be purified by selective absorption or precipitation, but many 
commercial products contain significant amounts of impurities in the form 
of other enzymes, as well as in the form of inert protein. For example, 
commercial bacterial "amylases" will sometimes also contain "proteinases" 
(enzymes which break down protein). After extraction and partial 
purification, commercial enzymes are sold either as powders or as liquid 
concentrates. 
Process conditions for the use of a particular enzyme will vary and will 
usually be suggested by the supplier. The variables include temperature, 
pH, substrate solids concentration, enzyme dose, reaction time, and the 
presence of activators. Very often there are no absolute optimum reaction 
conditions. The "optimum" pH may depend on temperature; the "optimum" 
temperature may depend on reaction time; the "optimum" reaction time may 
depend on cost, and so on. The reaction time can vary from 10 minutes to 
24 hours or more, typically 1 to 4 hours for alpha amylase. The 
recommended conditions therefore are usually compromises. 
The stability of an enzyme to adverse conditions is usually improved by the 
presence of its substrate. Some enzymes are also stabilized by certain 
salts (e.g., bacterial amylase is stabilized by calcium salts). It is 
necessary rigorously to exclude heavy metals and other enzyme poisons, 
such as oxidizing agents, from an enzyme reaction. These materials usually 
result in permanent inactivation (i.e., denaturization) of the enzyme. 
There are many instances however where enzyme activity is reduced 
reversibly, frequently by the products of a reaction (product inhibition) 
or by a substance which is structurally related to the usual substrate 
(competitive inhibition). Reversible inhibitors complex temporarily with 
the enzyme and therefore reduce the amount of enzyme available for the 
normal reaction. 
Typical enzyme reaction conditions are discussed in "Technology of Corn Wet 
Milling" by P. H. Blanchard, Industrial Chemistry Library, Vol. 4 
(Elsevier, New York, N.Y. 1992). 
Test Procedures Dextrose Equivalent 
The dextrose equivalent (D.E.) is an indication of the degree of conversion 
as shown by the reducing sugar content of the maltodextrin. A Fehling 
Volumetric Method, as adapted from the Eynon-Lane Volumetric Method #423 
of the Cane Sugar Handbook by Spencer and Mead (John Wiley and Son Inc.), 
is used to determine the D.E. 
A starch solution (w/v) of known concentration on an anhydrous starch basis 
is prepared. The usual concentration is 10 g/200 ml. The starch solution 
is transferred to a 50 ml/burette. To 50 ml of distilled water in a 500 ml 
Erlenmeyer flask are added by pipette 5 ml each of Fehling Solutions A and 
B. Fehling Solution A contains 34.6 g of copper sulfate 
(CuSO.sub.4.5H.sub.2 O) dissolved in and brought to volume in a 500 ml 
volumetric flask. Fehling Solution B contains 173 g of Rochelle salt 
(NaKC.sub.4 H.sub.4 O.sub.6.4H.sub.2 O) and 50 g of sodium hydroxide 
dissolved in and brought to volume in a 500 ml volumetric flask. The 
Fehling Solutions are standardized against Standardized Dextrose obtained 
from the Bureau of Standards. 
To determine the Fehling Factor, the test procedure is followed except that 
0.5000 anhydrous grams of dextrose per 200 ml of distilled water is used 
as the test solution. Using the following formula the factor is then 
computed: 
##EQU1## 
The factor applies to both Fehling solutions A and B and is computed to 4 
decimal places. The contents of the flask are brought to a boil over a hot 
plate. The starch solution, while at a boil, is titrated to the 
distinctive reddish-brown colored end point (precipitated cuprous oxide 
complex). The ml of starch solution used is recorded. 
The D.E. is calculated using the following formula: 
##EQU2## 
where the starch solution equals the ml of starch solution used in the 
titration to reach the end point and "starch concentration" equals the 
concentration of the starch solution on an anhydrous basis expressed in 
g/ml. 
Gel Permeation Chromatography (GPC) 
Molecular weight (MW) distribution is determined using a Water Associates 
GPC-150C Model with a refractive index (RI) detector. Two PL gel columns 
(10.sup.5 and 10.sup.3 obtained from Polymer Laboratories of Amherst, 
Mass.) made of highly crosslinked spherical polystyrene/divinylbenzene, 
are connected in sequence. Dextrans from American Polymer Standards Corp. 
(Mentor, Ohio) are used as the standards. The experimental conditions are 
a column temperature of 80.degree. C. and a flow rate of 1 ml/min. The 
mobile phase is dimethyl sulfoxide (DMS) with 5 mM of sodium nitrate 
(NaNO.sub.3). The sample concentration is 0.1%. The injection volume is 
150 
Brookfield Viscometer 
Test samples are measured using a Model RVT Brookfield Viscometer and the 
appropriate spindle which is selected based on the anticipated viscosity 
of the material. The test sample is placed in position and the spindle is 
lowered into the sample to the appropriate height. The viscometer is 
turned on and the spindle is rotated at a constant speed (e.g., 10 or 20 
rpm) for at least 3 revolutions before a reading is taken. Using the 
appropriate conversion factors, the viscosity (in centipoises) of the 
sample is recorded. 
EXAMPLES 
In the examples which follow, non-pregelatinized granular starches are used 
unless it is otherwise stated and the various enzymes described hereafter 
were used. 
The alpha amylases were Ban 120 L and Termamyl. They were obtained from 
Novo Nordisk. Ban 120 L is a conventional alpha amylase with an optimum 
temperature of approximately 70.degree. C., optimum pH of 6.0-6.5, an 
activity of 120 KNU/g, and recommended usage (based on the weight of the 
starch) of 0.005-1.0, preferably 0.01-0.5. Termamyl is a heat-stable alpha 
amylase with an optimum temperature greater than 90.degree. C., an 
activity of 120 KNU/g, and recommended usage (based on the weight of the 
starch) of 0.005-1.0, preferably 0.01-0.5. One Kilo Novo unit (1 KNU) is 
the amount of enzyme which breaks down 5.26 g of starch (Merck, Amylum 
Solubile, Erg. B6, Batch 994 7275) per hour in Novo Nordisk's standard. 
Method for determining alpha amylase using soluble starch as the 
substrate, 0.0043M calcium content in solvent, 7-20 minutes at 37.degree. 
C. and pH 5.6. 
Example 1 
This example shows the conversion of a chemically derivatized high amylose 
starch (70% amylose) using the high solids, single phase enzyme conversion 
process. 
A hydroxypropylated high amylose starch (PO Hylon VII - D.S. 0.47) (1000 g) 
was placed in a Ross Mixer with standard blades (Charles Ross & Son Co., 
Hauppauge, N.Y.). Sufficient water was added to give a total water content 
of 40%; 0.2% Termamyl was used. The starch was hydrolyzed at 98.degree. C. 
for 4 hours, the starch was liquefied, and upon cooling the final product 
was a viscous solution. 
FIG. 1 shows the molecular weight distribution of the hydroxypropylated 
Hylon VII and the alpha amylase converted hydroxypropylated Hylon VII. 
Example 2 
This example shows the conversion of a waxy maize starch ester using the 
single phase, high solids enzyme conversion process. 
A waxy maize octenylsuccinate, prepared by treatment with octenylsuccinic 
anhydride (OSA), was treated with a mixture of alpha-amylase and 
beta-amylase as described in Example 1, using 1,000 g of starch, 40% total 
water, and a mixture of 1.0 g of Ban 120 L and 0.5 g of Spezyme. The 
mixture was held at 60.degree. C. for 4 hours. A doughy material was 
formed. The product was broken up and air-dried. Part of the product (400 
g) was slurried in 1,000 ml of water, adjusted to pH 3.0 for 30 minutes 
with 0.1M hydrochloric acid, adjusted back to pH 6.0 with 3% sodium 
hydroxide, and spray-dried. 
The results show that when the OSA-treated waxy maize was converted with a 
mixture of alpha-amylase and beta-amylase, a low molecular weight peak 
(800) was observed (see FIG. 2). However, the low normalized area of the 
peaks detected indicates that most of the sample is excluded and not 
detected. The low molecular weight-material was estimated to be about 12% 
based on the weight of the final product. 
Example 3 
This example describes a series of enzyme conversions run in a ten gallon 
gate mixer reactor using Ban (B) and Termamyl (T), and mixtures thereof. 
The resulting maltodextrins were used in remoistenable adhesives. 
Part A Preparation of Enzyme-Converted Chemically Derivatized Maltodextrins 
The internal dimensions of the tank were 16 inches tall by 16 inches 
diameter. The gate agitator, made from 1/2 inch wide by 2 inch deep 
stainless steel bar stock, had four vertical rakes 101/2 inches tall. The 
outside rakes cleared the inside tank wall by 1/2 inch; the inside rakes 
were 31/4 inches from the outside set. Attached to the tank top were four 
breaker bars, of the same bar stock, located 13/4 and 51/4 inches in from 
the tank wall. A electric drive, variable from 0 to 60 rpm, powered the 
agitator. A vent in the tank top provided variable draft forced exhaust. 
The tank sides and bottom were jacketed for steam heating or water 
cooling. A M inch diameter steam injection port was provided in the side 
wall 1 inch above the tank bottom. A thermocouple probe was attached to 
the bottom of one outside breaker bar. In the tank bottom a 2 inch port 
with a ball valve was provided for product draw off. For these conversions 
a removable metal plug was inserted into the draw port, flush with the 
tank bottom, to eliminate the possibility of a portion of the initial dry 
charge receiving non-uniform moisture, enzyme, or heat. 
For each conversion 33 pounds of a commercially dry granular starch was 
added to the tank. The enzyme charge was diluted with sufficient water to 
bring the charge to 25 percent moisture on an anhydrous basis. This 
water/enzyme mix was added to the starch with mixing. The mixture, after 
addition of the enzyme/water mix, was a blend of dry starch and moist 
starch aggregates less the one half inch in diameter. 
At this point, the agitator is turned off for about 30 minutes to allow the 
water to diffuse through out the starch. The starch, after this rest, was 
a moist flowable powder. 
The mixture was heated, generally by injection of live steam (at 32 psi 
except where indicated otherwise) into the mixture and/or optionally by 
heating the tank jacket. Typically, the mass was mixed during heating, but 
this was not required. Mixing only improved heat transfer. 
As the granular starch gelatinized (or the cold-water-insoluble 
predispersed starch was solubilized), it was converted and the reaction 
mixture changed from a moist powder to a wet doughy mass and then to a 
dispersed syrup. These changes occurred as the temperature was increased 
from 50.degree. C. to 90.degree. C. The temperature at which the onset of 
liquefaction occurred varied depending on the water activity, enzyme 
activation temperature, and starch type. 
In this vented tank, there was some loss of moisture during the full 
heating cycle. When the injection steam was shut off, the temperature was 
maintained at the indicated temperature with jacket heating for 30 
minutes. The batch was then cooled to less than 50.degree. C. and drawn 
off. Optionally, the pH was reduced to 3.5 with phosphoric and the mixture 
was held for 30 minutes to deactivate any residual enzyme. The pH was 
readjusted if required. 
To 43.52 parts of the indicated starch were added a mixture of 6.95 parts 
water and the indicated amount of Ban 120 L and/or Termamyl. The gate 
mixer was at 30 rpm while the premix was slowly added in steady stream. 
Mixing was continued until the starch was uniformly damp. The agitator was 
shut down and the mixture was heated with live steam and jacketed steam to 
82.degree.-93.degree. C. (180.degree.-200.degree. F.) for 30 minutes. Then 
6.94 parts of water were added. 
The mixer was restarted and agitation was continued at 30 rpm while the 
mixture was being heated at 93.degree.-99.degree. C. 
(200.degree.-210.degree. F.). When the adhesive product clarified and was 
smooth, the viscosity and solids were tested. After the test results were 
recorded, the pH was adjusted to 3.5 with 85% phosphoric acid, and 
additional acid added, if needed, to end the enzyme activity. 
The starch base used, enzyme and amount used, and properties of the 
resulting suitable and comparative maltodextrins (solids, D.E., and D.S.) 
are summarized in Table 1. The three month viscosity stability of the same 
maltodextrins is reported in Table 2. The GPC molecular weight profiles of 
Sample Nos. 1 and 2 are shown in FIG. 3 and of Sample Nos. 4 and 5 are 
shown in FIG. 4. 
TABLE 1 
______________________________________ 
Maltodextrin 
No. Starch Enzyme Solids D.E. D.S. 
______________________________________ 
1* 35 WF, 0.045 B 62.2 13.7 0.16 
Hydroxypropylated 
0.045 T 
Waxy Maize 
2 35 WF, 0.09 T 70.9 11.0 0.16 
Hydroxypropylated 
Waxy Maize 
3 35 WF, 0.18 T 62.8 10.6 0.16 
Hydroxypropylated 
Waxy Maize 
4 Hydroxypropylated 
0.09 T 68.9 13.2 0.09 
Waxy Maize 
5 Octenyl-succinate 
0.09 T 60.2 15.2 0.02 
Waxy Maize 
6** 35 WF, 0.045 T 60.0 7.4 0.16 
Hydroxypropylated 
0.045 T 
Waxy Maize 
7 35 WF, 0.09 T 69.0 0.16 
Hydroxypropylated 
Waxy Maize 
______________________________________ 
*For Sample No. 1, the steam pressure was 8 psi. 
**For Sample No. 6, the enzyme addition was carried out in two steps. 
Example 4 
This example shows the preparation of an enzyme-converted, highly 
acetylated starch which is characterized by its water dispersibility. It 
was prepared using the single phase, high solids process. 
Part A 
Waxy maize was acetylated using the procedure of U.S. Pat. No. 5,321,132, 
discussed previously. The starch solids were 40% (as is), the pH 8.5, the 
temperature 25.degree. C, and reaction time 4 hours. The granular starches 
(1.05 D.S.) were recovered by filtering, washing to less than 500 
micromhos conductivity, and air drying to 10% moisture. 
Part B 
The water-insoluble acetylated waxy maize starch (1.05 D.S.) was converted 
by alpha amylase, as described above, using 1,000 g starch, 40% total 
water, and 1 ml each of Ban 120L and Termamyl. The starch began to liquify 
at about 80.degree. C. A watery liquid product was observed in the Ross 
Mixer as the temperature increased to 95.degree.-98.degree. C. After the 
mixture was held at 95.degree.-98.degree. C. for 2 hours, a hardened, 
rock-like material formed in the Ross mixer. 
The unconverted acetylated waxy maize (1.05 D.S.) cannot be detected by 
GPC, probably because of its high molecular weight or great hydrodynamic 
volume in the DMSO mobile phase. The GPC molecular weight profile of this 
converted acetylated waxy maize (1.05 D.S.) showed multiple peaks (see 
FIG. 5). Its Brookfield viscosity (5% solids in DMSO, Spindle #1, 100 rpm) 
was 56 cps, whereas the Brookfield viscosity of the non-converted 
acetylated waxy maize at the same concentration was 2,480 cps (5% solids, 
Spindle #4, 20 rpm). This significant viscosity reduction indicates that 
the acetylated waxy maize has been hydrolyzed and depolymerized even 
though it had a DS of 1.05. 
Part C 
A 3.4 gram sample of the above enzyme-converted intermediate D.S. 
acetylated waxy maize was dispersed in 96 grams of distilled water at room 
temperature with mixing provided by a magnetic stirrer. Within a few 
minutes, the sample had dispersed into a milky white dispersion. A small 
portion settled out over several hours. The remaining dispersion was 
stable for three days at room temperature. The dispersed cloudy product 
turned into a clear solution when propanol or ethanol was added. The high 
alcohol solubility indicates that the enzyme-converted product still 
contains a high degree of acetate substitution. 
This demonstrates the utility of the enzyme converted, intermediate D.S. 
acetylated waxy maize prepared by the high solids, single phase process in 
application areas where the converted starch will be added as an aqueous 
emulsion. 
Now that the preferred embodiments of the invention have been described in 
detail, various modifications and improvements thereon will become readily 
apparent to those skilled in the art. Accordingly, the spirit and scope of 
the present invention are to be limited only by the appended claims and 
not by the following specification.