Note: Descriptions are shown in the official language in which they were submitted.
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WOg''~C7~3 PCT/U~ 7~7l
THERMALLY-INHIBITED GRANUIAR STARCHES
AND F~OURS AND PROCESS FOR THEIR PRODYCTION
BACKGROUND OF THE lNV~NllON
This invention relates to dehydrating and heat
treating granular starches and flours to inhibit: the
starch or flour.
Starches have been heat treated for various
reasons, including drying, vaporizing off-flavors,
imparting a smokey taste, dextrinizing, and thermally
inhibiting.
U~S. 4 303 451, (issued Dec 1, 1981 to Seidel,
et al.) discloses heating waxy maize starch at a
te~perature of 120-200 C for less than 1 hour up to about
24 hours at its naturally occurring pH before
pregelatinization. The heat treatment prevents the
formation of woody off flavors during the
pregelatinization and modifies the texture and flavor.
Japanese No. 61-254602, (published December 11,
1986) discloses heating a waxy corn starch and/or waxy
corn starch derivatives at a temperature of 100-200 C and
a pH of 3.5-8, preferably 4.0-5.0, for 0.5-8 hours,
preferably 3-4.5 hours to improve the stability and
emulsifiability after gelatinization so that the starch
can be used as gum arabic replacement. The starch is
heated by a dry method (water content of less than 10%,
preferably less than 5% or a wet-method (water content of
5-50%, preferably 20-30%).
U.S. 4.303 4s2 (issued Dec. 1, 1981 to T. Ohira
et al.) discloses a smoke treatment of waxy maize starch
to improve the gel strength and impart a smokey taste.
In order to counteract the acidity of the smoke and to
CA 02221~20 1997-12-04
W O 9f~12~193 PCT~U5~/C7071
obtain a final starch pH of 4 to 7, the pH of the starch
is raised to 9-11 before smoking. The preferred water
content of the starch during the smoking is 10-20%.
When native starch granules are dispersed in
water and heated, they become hydrated and swell at about
60 C and reach a peak viscosity at about 65 -95 C. This
increase in viscosity is desired for many food and
industrial applications and results from the physical
force or friction between the highly swollen granules.
Swollen, hydrated starch granules, however, are quite
fragile, and when the starch slurry is held at 92 -95 C,
the starch granules fragment, the starch polymers
dissociate and are solubilized, and the viscosity of the
starch solution breaks down. Shear or extreme pH also
tend to disrupt the granules, leading to a rapid
breakdown from the initially high viscosity.
The swelling of the starch granules and the
breakdown in viscosity can be inhibited by reacting the
starch with chemical crosslinking reagents which
introduce intermolecular bridges or crosslinks between
the starch molecules. The crosslinks also reinforce the
associative hydrogen bonds holding the granules together,
restrict the swelling of the starch granules, and
consequently inhibit fragmentation and disruption of the
granules. Because of this inhibition, crosslinked
starches are commonly referred to as "inhibited"
starches.
Chemically inhibited starches are used in many
applications where a starch paste or starch solution with
a stable viscosity is needed. There would be an
advantage in cost, time, and in the reduced use of
chemicals if native starches or modified starches can be
inhibited without the use of chemicals so that they
perform in the same way as chemically inhibited starches.
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W O ~f'1~73 PcT/u~ 3f'~7~71
PCT International Patent Application No.
WQ 95/04082, published February 9, 1995, discloses a
process for making a heat treated, non-chemically
modified non-cohesive starches and flours which are
prepared by providing a granular starch or flour at a
ne~tral or basic pH, thermally dehydrating it to a
moisture content of preferably less than 5%, and then
heating the starch or flour at greater than 100~C and for
a period of time effective to obtain a product that is
non-cohesive when dicpersed in an aqueous mediu~ and
gelatinized. The dehydrating and heat treating are
carried out in any conventional heating apparatus.
It is desirable for a starches and flours to be
bland in flavor. Many starches such as corn, sorghum,
and wheat contain small quantities of lipids, e.g.,
unsaturated fatty acids. The fatty acids, especially
unsaturated may develop rancid flavors due to oxidation.
In addition, the proteins present give the starches and
flours an undesirable cereal taste. Certain starches,
such as corn and waxy maize, are not used in th:ickened
food compositions due to '3woody" or "popsicle s1_ick" off-
flavors resulting from pregelatinization. See IJ.S.
4.303,451 (issued Dec. 1, 1981 to W.C. Seidel) ~hich
discloses a method for preventing the development of
"woody" off-flavors in pregelatinized waxy maize
starches. The starch granules are heated, prior to
gelatinization, at about 120-200~C for 0.1-24 hours. The
heating time must be insufficient to effect
dextrinization but sufficient to prevent formation of
woody off-flavors during pregelatinization. The texture
and flavor of corn, wheat, rice and sago were modified by
this heat treatment but these starches gave inconsistent
and non-reproducible results in food compositions (see
Col. 2, lines 14 18).
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W O g61.C193 PCT/U','/~)~71
Thus, there is a need for granular starches
which have the textural properties of chemically
crosslinked granular starches and which are substantially
free of off tastes.
SUMMARY OF THE lNV~l'lON
The starches and flours of this invention are
thermally inhibited using a process which results in the
starch or flour having the characteristics of a
chemically crosslinked starch without the use of chemical
crosslinking reagents. When these thermally-inhibited
starches and flours are dispersed in water and cooked,
they exhibit the properties characteristic of an
inhibited starch, i.e., the starches and flours which are
substantially completely inhibited resist gelatinization;
the starches and flours which are highly inhibited
gelatinize to a limited extent and show a continuing
increase in viscosity but do not attain a peak viscosity;
the starches and flours which are moderately inhibited
exhibit a lower peak viscosity and a lower percentage
breakdown in viscosity compared to the same starch which
is not inhibited; and the starches and flours which are
lightly inhibited show a slight increase in peak
viscosity and a lower percentage breakdown in viscosity
compared to the same starch which is not non-thermally
inhibited.
The thermal inhibition process comprises the
steps of non-thermally dehydrating a granular starch or
flour until it is anhydrous or substantially anhydrous
and then heat treating the dehydrated (i.e., anhydrous or
substantially anhydrous) granular starch or flour at a
temperature and for a period of time sufficient to cause
inhibition. Both the non-thermal dehydrating step and
heat treating step are conducted under conditions which
avoid degradation or hydrolysis of the starch or flour.
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As used herein "non-thermally dehydrating"
r~fers to dehydration methods which remove the water from
the starch or flour but which do not involve raising the
starch temperature directly to cause the removal of the
water. Suitable methods include, but are not ~imited, to
~ e~traction with solvents, preferably hydrophilic
solvents, more preferably solvents which form ~zeotropes
with water (e.g., ethanol) and freeze-drying. Heat may
be used in the solvent extraction which may be carried
out in any continuous extractor, preferably one where the
starch is contacted with the cooled condensed solvent.
As will be shown hereafter, dehydration with
ethanol improves the flavor (i.e., taste and aroma) and
color of the thermally-inhibited starches compared to
thermally-inhibited s~arches which were dehydrated with
direct heat such as those of W0 9504082. It i5 expected
t~lat dehydration by freeze drying will also provide a
ta~te advantage.
As used herein, "substantially anhydrous" means
that the starch or flour contains less than 1% moisture
by weight.
The starch or flour can be non-thermally
dehydrated and heated either at its naturally occurring
pH, which typically is pH 5.0-6.5 or preferably the pH
can be raised to neutral or greater. As used herein,
"neutral" covers a pH of around 7 and is meant to include
a range of about pH 6.5-7.5.
The substantially anhydrous or anhydrous
starch, preferably pH-ad~usted~ is heat treate~ at a
temperature and for a time sufficient to inhibit the
starch, e.g., at 100~C or greater.
By varying the process conditions, including
the initial pH, the dehydration conditions and the heat
treating conditions, the level of inhibition can be
varied to provide granular starches or flours with
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WO9G!I:/Y3 PCT/U',~ ~,7~71
different viscosity characteristics when cooked.
Inasmuch as the heat treating parameters can be a
function of the particular apparatus used for the heat
treating, the choice of heat treating apparatus will also
be a factor in controlling the level of inhibition.
Removal of various proteins, lipids, and off
flavor components prior to or after the thermal
inhibition im~ov~s the flavor (i.e., taste and aroma) of
the thermally-inhibited starches. A sodium chlorite
extraction of the protein is exemplified hereafter.
Other procedures which can be used for protein, lipid,
and off flavor component removal include washing the
starch at an alkaline pH (e.g., pH 11-12) and/or treating
the starch with proteases. Polar and non-polar solvents
which have an affinity for proteins and/or lipids can
also be used. Examples are alcohols (e.g., ethanol),
ketones (e.g., acetone), ethers (e.g., dioxane), aromatic
solvents (e.g., benzene or toluene), and the like. For
food applications, suitable food grade solvents should be
used.
These starches are useful in food and
industrial applications where chemically crosslinked
ungelatinized granular starches are known to be useful.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The thermally inhibited starches and flours of
this invention are granular starches which can be derived
from any native source. The native source can be banana,
corn, pea, potato, sweet potato, barley, wheat, rice,
sago, amaranth, tapioca, sorghum, waxy maize, waxy rice,
waxy barley, waxy potato, waxy sorghum, starches and
flours cont~;n;ng high amylose, and the like. The
preferred starches are the waxy starches, including waxy
maize, waxy rice, waxy potato, waxy sorghum and waxy
barley. Unless specifically distinguished, references to
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W O 9G/4~7~3 PcT/u'~T~7
"fitarch" in this description are meant to include their
c~rresponding "flours~'.
As used herein, a "native starch" is one as it
ic found in nature, i.e, unmodified. Suitable starches
include native starches or starches which have been
modified by conversion (e.g., enzyme-, heat- or acid-
conversion), oxidation, phosphorylation, etherification,
esterification, and chemical crosslinking. Usually these
modifications are per~ormed before the starch is
dehydrated and heat treated.
When starches are subjected to heat in the
presence of water, hydrolysis and degradation of the
starch occurs. Hydrolysis or degradation will reduce
viscosity thus limiting the effect of inhibition.
Therefore, the conditions ~or dehydrating and heat-
treating the granular starch or flour are chosen so that
i~hibition is favored over hydrolysis or degradation.
The preferred pH is at least 7, typically the
ranges are pH 7.5-10.5, preferably greater than pH 8,
most preferably 8-9.5. At a pH above 12, gelatinization
mGre easily occurs; therefore, pH adjustments below 12
are used. The textural and viscosity benefits of the
thermal inhibition process tend to be enhanced as the pH
is increased, although higher pHs tend to increase
browning of the starch during the heat treating step.
To adjust the pII, the granular starch is
slurried or dissolved in water or another aqueous medium,
typically in a ratio of 1.5 to ~.0 parts water to 1.0
part starch, and the pH is raised by the addition of any
suitable base. If needed, buffers, such as sodium
phosphate, may be used to maintain pH. The starch slurry
is then either dewatered and dried, or dried directly
(without gelatinization) using conventional drying
methods, such as spray-drying or flash drying. The
starch is dried to a moisture content of about 2-15%,
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W O 9~"C753 PCT/U~ 7~71
preferably 2-6%. Alternatively, a solution of a base may
be sprayed onto the powdered starch until the starch
attains the desired pH, or an alkaline gas such ac
ammonia, can be infused into the starch.
For food applications, suitable food grade
bases for use in the pH adjustment step include, but are
not limited to, sodium hydroxide, sodium carbonate,
tetrasodium pyrophosphate, ammonium orthophosphate,
~Co~;um orthophosphate, trisodium phosphate, calcium
carbonate, calcium hydroxide, potassium carbonate, and
potassium hydroxide, and any other base approved for food
use under the Food and Drug Administration laws or other
food regulatory laws. The preferred food grade base is
sodium carbonate. If the starch or flour is not going to
be used in a food, any inorganic or organic base that can
raise the pH of the starch or flour may be used. The
bases chould be washed from the starch or flour so that
the final product conforms to the required manufacturing
practices for the intended end use.
For a laboratory scale dehydration with a
solvent, the starch or flour (about 4-5% moisture) is
placed in a Soxhlet thimble which is then placed in the
Soxhlet apparatus. A suitable solvent is placed in the
apparatus, heated to the reflux temperature, and refluxed
for a time sufficient to dehydrate the starch or flour.
Since during the refluxing the solvent is condensed onto
the starch or flour, the starch or flour is exposed to a
lower temperature than the solvent's boiling point. For
example, during ethanol (boiling point about 78~C)
extraction the temperature of the starch is only about
30-40~C. When ethanol is used as the solvent, the
refluxing is continued for about 17 hours. The
dehydrated starch or flour is removed from the thimble,
spread out on a tray, and the excess solvent is allowed
to flash off. With ethanol the time required for the
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WO ~1a~3 PcT/u~ 7~7
ethanol to flash off is about 20-30 minutes. The starch
or flour is immediately placed in a suitable heating
aplparatus for the heat treatment. For a commercial scale
dehydration any continuous extraction apparatus is
suitable.
For dehydration by freeze drying, the starch or
flour (4-5% moisture) is placed on a tray and put into a
freeze dryer. A suitable bulk tray freeze dryer is
available from FTS Systems of Stone Ridge, New York under
the trademark Dura-Tap. The freeze dryer is run through
a programmed cycle to remove the moisture from the starch
or flour. The starch or flour temperature is held
constant at about 20~C and a vacuum is drawn to about 50
milliTorrs (mT). The time required to dehydrate the
starch or flour is about 3 days. The starch or flour is
remove~ from the freeze dryer and immediately placed into
a suitable heating apparatus for the heat treat~ent.
After the starch is dehydrated, it is heat
treated for a time and at a temperature, or range of
temperatures, sufficient to inhibit the starch. The
preferred heating temperatures are greater than 100 C.
For practical purposes, the upper limit of the heat
treating temperature is usually 200 C, at which
temperature highly inhibited starches can be obt:ained.
T~?ically the heat treating is carried out at lZ0~-180~C,
preferably 140~-160~C, more preferably 160~C. ~he level
of inhibition is dependent on the pH and heating
temperature and time. For example, if the starch or
flour is adjusted to p~ of about 8.0-9.5 and the oven
temperature is 160~C, a lightly inhibited starch or flour
will require about 3 4 hours of heating, a moderately
inhibited starch or flour will require about 4-5 hours of
heating, and a highly inhibited starch or flour will
require 5-6 hours of heating. For lower t~- -ratures,
longer heating times are required. When the starch or
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W O ~ 793 PCT~U3~ 7~71
flour is at a lower pH, as with a native starch which has
a pH of about 5.0-6.5, the heating will provide less
inhibition.
For flours lower temperatures and/or shorter
heating times are required to reach the same level of
inhibition as compared to the corresponding starch.
For most industrial applications, the heat
treating step will be carried out by heating the
dehydrated granular ~tarch from ambient t~ ~~ature to
the desired heat treatment temperature which will depend
upon the level of inhibition desired. Some level of
inhibition may be att~; nF~A before the final heat treating
temperature is reached. Usually, at these initial levels
of inhibition, the peak viscosities are higher than at
inhibition levels reached with longer heat treating
times, although there will be greater breakdown in
viscosity from the peak viscosity. With continued heat
treating, the peak viscosities are lower, but the
breakdowns in viscosity are less.
The starches or flours may be inhibited
individually or more than one may be inhibited at the
same time. They may be inhibited in the presence of
other materials which will not interfere with the non-
thermal dehydration and heat treating, i.e., with the
thermal inhibition process, or alter the properties of
the thermally-inhibited starches.
-The heat treating apparatus can be any
industrial oven, for example, conventional ovens,
microwave ovens, dextrinizers, fluidized bed reactors and
driers, mixers and blenders equipped with heating devices
and other types of heaters, provided that the apparatus
is fitted with a vent to the atmosphere so that moisture
does not accumulate and precipitate onto the starch.
Preferably, the apparatus is equipped with a means for
removing water vapor from the apparatus, such as a vacuum
-
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W O 96~C/~3 PCT/U~'J~71
o~ a blower to sweep air from the head-space of the
apparatus, or a flui~izing gas.
Superior thermally inhibited granular starches
and flours having high viscosities with no or low
percentage break~own in viscosity are obtained in shorter
times in a fluidized bed reactor than other conventional
heating ovens. Suitable fluidizing gases are air and
nitrogen. For safety reasons, it is preferable to use a
gas contA;ning less than 12% oxygen. The fluidizing gas
is used at a velocity of 5-21 meter/min. A suitable
fluidized bed reactor is manufactured by Procedyne
Corporation of New Brunswick, New Jersey. The cross-
sectional area of the fluidized bed reactor is 0.05 sq
meter. The starting bed height is 0.3 to 0.8 meter, but
usually 0.77 meter. The sidewalls of the reactor are
heated with hot oil, and the fluidizing gas is heated
with an electric heater. The samples are loaded into the
fluidized bed and then the fluidizing gas is introduced,
or the samples are loaded while the fluidizing gas is
being introduced. The anhydrous or substantially
a~hydrous samples are brought from ambient temperature to
the specified heat treating temperatures. When the heat
treating temperature is 160 C, the time to reach that
temperature should be less than three hours.
The alcohol dehydration step is done at
atmosphoric pressure. The freeze drying step is done
under vacuum, typically 50 milliTorr (mT). The heat
treatment step may be performed at normal pressures,
under vacuum or under pressure, and may be accomplished
u~.ing any heating means known to practitioners, although
the preferred method is the application of dry heat in
air or in an inert gaseous environment.
Following the heat treating step, the thermally
inhibited granular starch or flour may be screened to
select a desirable particle size and slurried in water
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W O 9f'~793 PCTrUS9~.!07071
and washed, filtered, and dried, or otherwise refined.
The pH may be adjusted as desired. In particular, the pH
may be readjusted to the naturally occurring pH of the
starch.
~HARACT~IZATION OF INHIBITION BY BRABENDER DATA
Characterization of a thermally inhibited
starch is made more conclusively by reference to a
measurement of its viscosity after it is dispersed in
water and gelatinized. The instrument used to measure
the viscosity is a Brabender VISCO\Amylo\GRAPH,
(manufactured by C.W. Brabender Instruments, Inc.,
Harkenc~ck, NJ). The VISCO\Amylo\GRAPH records the
torque required to balance the viscosity that develops
when a starch slurry is subjected to a programmed heating
cycle. The accuracy is + 2%.
For non-inhibited granular starches, the cycle
p~c~c through the initiation of viscosity, usually at
about 60 -70 C, the development of a peak viscosity in the
range of 65 -95 C, and a breakdown in viscosity when the
starch is held at an elevated temperature, usually 92 -
95 C. The record consists of a curve tracing the
viscosity through the heating cycle. The viscosity is
reported in arbitrary units of measurement termed
Brabender Units (BU).
Inhibited starches will show a Brabender curve
different from the curve of the same base starch that has
not been inhibited. At low levels of inhibition, an
inhibited starch may attain a peak viscosity somewhat
higher than the peak viscosity of the base starch, and
there may be no decrease in percentage breakdown in
viscosity compared to the base starch. As the amount of
inhibition increases, the peak viscosity and the
breakdown in viscosity decrease. At high levels of
inhibition, the rate of gelatinization and swelling of
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W O 9~ 93 PCTIU~ 7~71
the granules decreases, the peak viscosity disappears and
with prolonged cooking the Brabender curve becomes a
rising curve indicating a slow continuing increase in
vi~cosity. At very high levels of inhibition, the starch
qranules no longer gelatinize and the Brabender curve
remains flat.
S~MPT~ PREPARATION
All the starches and flours used were provided
~y National Starch and Chemical Company of Bridgewater,
New Jersey. The controls were from the same native
source as the test sample, were unmodified or modified in
the same manner as the test sample, and were at the same
pH, unless otherwise indicated. All starches and flours,
both test and control samples, were prepared and tested
individually.
The pH of the granular starch samples was
rA;~~~ by slurrying the granular starch or flour in water
at 30-40% solids and A~i~g a sufficient amount of a 5%
sodium carbonate solution until the desired pH was
reached. After the pH adjustment, the starches were oven
dried (without gelatinization) to about 2-6% moisture.
Measurements of pH, either on the sa~mples
before or after the dehydration step and after the
thermal inhibition step, were made on samples consisting
of one part anhydrous starch or flour to four ]parts
waterO
The test samples were heat treated in a
conventional oven or dextrinizer.
Portions of the samples were removed and tested
for inhibition at the temperatures and times indicated in
the tables using the following textual characterizations
and Brabender Procedures.
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W O S'/~C~Y3 PCT/U',h!O~O71
BRABENDER PROCEDURE
All samples, except for corn, tapioca and waxy
rice flour, were slurried in a sufficient amount of
distilled water to give a 5% anhydrous solids starch
slurry. Corn, tapioca, and waxy rice flour were slurried
at 6.3% anhydrous solids. The pH was adjusted to pH 3.0
with a sodium citrate/citric acid buffer. The slurry was
introduced into the sample cup of a Brabender VISCO\Amylo
GRAPH fitted with a 350 cm/gram cartridge. The starch
slurry was heated rapidly to 92 C and held for 10
minutes.
The peak viscosity and the viscosity ten
minutes (10') after peak viscosity were recorded in
Brabender Units (BU). The percentage breakdown in
viscosity was calculated according to the formula:
% Breakdown = peak - (peak + 10 Min.) X 100,
peak
where "peak" is the peak viscosity in Brabender Units,
and "(peak + 10 Min.)" is the viscosity in Brabender
Units at ten minutes after the peak viscosity.
Using data from Brabender curves, inhibition
was determined to be present if, when dispersed at 5-6.3%
solids in water at 92 -95 C and pH 3 during the Brabender
heating cycle, the Brabender data showed (i) no or almost
no viscosity, indicating the starch was so inhibited it
did not gelatinize or strongly resisted gelatinization;
(ii) a continuous rising viscosity with no peak
viscosity, indicating the starch was highly inhibited and
gelatinized to a limited extent; (iii) a lower peak
viscosity and a lower percentage breakdown in viscosity
from peak viscosity compared to a control, indicating a
moderate level of i~hibition; or (iv) a slight increase
in peak viscosity and a lower percentage breakdown
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W O 9''~t~ PCT/U~f~7~71
c ~~ed to a control, indicating a low level of
~nhibition.
CHARACTERIZATION OF INHIBITION BY l~XLu~E
Starches or flours with a low to moclerate
degree of inhibition will exhibit certain texkural
characteristics when dispersed in an aqueous medium and
heated to gelatiniza~ion. In the following examples, the
~tarches or flours were determined to be inhibited if a
heated gelatinized slurry of the starch or flour
exhibited a non-cohesive, smooth texture
EXAMPLE 1
A granular waxy maize starch was slurried in
1.5 parts water based on the weight of the starch and
adjusted to pH 7 and 9.5 with 5% sodium carbonate, held
~or 30 minutes, filtered, and dried on a tray to a
moisture content of about 5-6% moisture. The starch
having the pH of 5.3 was a native starch which was not pH
adjusted.
For the dehydration, the dried pH 5.3, pH 7.0,
and pH 9.5 starches were each separated into two samples.
For comparison, one sample was dried on trays in a forced
draft oven at 80~C overnight to dehydrate the starch to
~1% (0~) moisture. The other sample was placed in a
~oxhlet extractor and allowed to reflux overnight (about
17 hours) with anhydrous ethanol (boiling point 78.32~C).
The ethanol-extracted sample was placed on paper so that
the excess alcohol could flash off which took off about
30 minutes. The ethanol extracted starch was a free
Elowing powder which was dry to the touch.
For the heat treatment, oven-dehydrated starch
and ethanol-extracted starch were placed on trays in a
forced draft oven and heated for 3, 5, and 7 hours at
160~C.
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WO !)~ 3 PCT/u' ,~S!Il,J'071
The thermally-inhibited (T-I) starches and the
controls were evaluated using the BrAh~n~er Procedure
previously described.
BRABENDER RESULTS
Vi co~iq ~t
D-,h.~d Hc t P~ 10 rnin
Bue 2~ Methodi Tre tment Yi cositv ~fler Pe-k P ' '
(BU) (BU)
W~y 5.3 -- -- 1245 330 74%
M ize'
0 Wuy 5.3 oven -- 1290 3S0 73%
M ize~
Wuy S.3 eth nol -- 1205 24S 80%
M ize~
T-l Wuq S.3 oven S hr-. ~t 95 45 53%
M ize 160~C
T-l Wuy S.3 e~nol 5 hr . ~t 255 185 28%
M~tize 160~C
T-l W ~y 5.3 oven 7 hn. ~t 60 35 42%
M ize 160-C
2 0 T-l Wuy S.3 oth wl 7 hn. ~t 165 IOS 36%
M ize 160~C
T-IW ~q 7.0 oven -- 1240 380 69X
M ize'
T-l Wuq 7.0 oven 7 hn. ~t 298 240 20%
M ize 160~C
T-l W xy 7.0 eth nol 7 hn. ~t 400 310 23%
M ize 160~C
W~xy 9.5 Oven -- 12S0 400 68 %
M-ize'
3 0 Wuy 9.S E~nol - 1070 350 67%
M ize'
T-l W xy 9.S Eth-nol 3 h~ ~t 66S 63S S g
M-ize 160~C
T-l W ~y 9.5 Oven 3 hr rt 680 655 4%
3 5 Mdze 160~C
T-I W xy 9.5 Oven S hn. rt 245 460 risin~ cun~e
M ize 160~C
T-l W xy 9.5 E~nol S hn. rt 160 375 ridnE curvc
M ize 160~C
T-l W xy 9.5 Oven 7 hn. rt 110 295 ri~inE curve
M ize 160~C
T-l W xy 9.5 Etlunol 7 hn. ~t 110 299 ri5in~ curve
M-ize 160~C
CA 02221520 1997-12-04
W O 96~1C79~ P ~/V~ 71
Br e d-rch
Controls.
Both of the thermally-inhibited pH 7 starches
were higher in visco~ity than the pH 5.3 (as i~)
thermally-inhibited starches. The starches which were
thermally-inhibited at pH 9.5 were moderately highly
i~hibited or highly inhibited (rising curve).
~AMPLE 2
Using the procedure described in Example 1,
tapioca, corn and waxy rice starches and waxy rice flour
were adjusted to pH 9.5, dehydrated in an oven
(comparative sample~) and dehydrated by extrac1:ion with
ethanol, and heat treated at 160~C.
The Brabender results are shown below:
Vi~cosity ~t
D~ ' lle t Po lc lO min
2 0 B~se ~ Metbod Tre~tment Vi cositv Afler P~ lc El~ ' ' ,.
(BU)
T~pioc; 9 S ovcn -- 74S 330 S8%
T pioc; 9 S etb nol -- no 330 S4%
T-lT pioc- 9 5 o~en S hr- ~t 270 260 3%
160~C
T-l T~pioc~ 9 S ctb-nol 5 hrs rt 260 2S8 1 %
160~C
T-lT piOC~I 9S oven 7hrs -t 110 155 rbingcurve
160~C
T-l T pioc~ 9 5 etb nol 7 hrs rt 100 145 rising curve
160~C
Corn~ 9 S oven -- 330 280 15%
Corn~ 9 S ethcnol -- 290 2S0 14%
T-l Corn 9 5 oven S hr ~t 10 80 rising curve
160-C
3 0 T-l Corn 9 5 etlunol 5 hrs nt 10 170 rising curve
160~C
T-l Com 9 5 oven 7 hrs ~t 10 65 risin~ curve
160~C
T-l Corn 9 S etb nol 7 hrs ~t 10 45 rising curvc
160~C
W~xy Rice' 9 5 oven -- 1200 590 50 8%
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Vi co-ity ~t
Dch~ ' He~t Pe~k 10 min
Buc ~ Method Tre~tment Vi co~itv Aficr Pe~k Bre~kdown (BU)
Wu~y Rice~ 9 5 etn nol -- IISS 450 610%
T-I W xy 9 S oven S hr ~t 518 640 ridng cu~e
Rice 160~C
T-I W ~y 9 5 oven 7 b~ ct 265 458 rirug cu~e
Rice 160-C
T-I W xy 9 5 eth nol 7 h~ ~t 395 520 ri-ing curve
Rice 160~C
W xy Rice 9 5 oven -- 895 700 22%
Flour"
W~xy Rice 9 S eth nol -- 870 410 53%
Flour''
T-l W xy 9 5 oven 5 hr~ ~t 38 73 rising curve
Rice Flour 160~C
T-I W xy 9 5 etbJnol S hrr ~t 140 260 ri~ curve
Ricc Plour 160~C
T-l W~xy 9 S o~en 7 hrr ~t 10 16 ri~ulg cume
Rice Flour 160~C
T-I W ~y 9 5 eth nol 7 hrr ~t 40 100 ri~ing curve
Rice Flour 160~C
B c ~rch
~ Control~
The results show that pH 9.5 adjusted ethanol-
extracted, heat-treated tapioca and corn starches had
viscosity profiles generally similar to those of the same
thermally-inhibited starches which were oven-dehydrated.
The 7 hours heat-treated samples were more inhibited than
the 5 hour heat-treated samples.
~AMPLE 3
This example compares ethanol (EtOH)-extracted
waxy maize starches and oven-dehydrated waxy maize
starches which were heat treated in an oven for 5 and 7
hours at 160~C at the same pH, i.e., pH 8.03.
The Brabender results are shown below.
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Viscosity
10 Minutes
Dehydration/ Peak After Peak
Heat Treatment Viscosity Viscosity Breakdown
(B-U-)
Oven/None 1160 360 69~
EtOH/None 1120 370 67%
Oven/5 hrs. 510 455 11%
EtOH/5 hrs. 490 445 9%
oven/7 hrs. 430 395 8%
EtOH/7 hrs. 360 330 8%
The thermally-inhibited starches were slurried
at 6.6% solids (anhydrous basis), pH adjusted to 6.0-6.5,
and then cooked out in a boiling water bath for 20
minutes. The resulting cooks were allowed to cool and
then evaluated for viscosi~y, texture, and color.
Method of Time at
DehYdration 140~C ViscositY Texture Color
Oven None heavy to cohesive slightly
very heavy off-white
Ethanol None heavy to cohesive slightly
very heavy off-white
Oven 5 hours moderately non- slightly
heavy to cohesive, tan,
heavy smooth darker*
Ethanol 5 hours moderately non- slightly
heavy to cohesive, tan
heavy smooth
Oven 7 hours moderately non- moderately
heavy to cohesive, tan,
heavy smooth darker*
Ethanol 7 hours moderately non- moderately
heavy to cohesive, tan
heavy smooth
* Slightly darker than ethanol-dehydrated ~ample~. ~
~ .
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These Brabender results show that highly
inhibited starches can be obtained by both thermal and
non-thermal dehydration. The cook evaluation results
show that there is a benefit for the ethanol-dehydrated,
thermally-inhibited starches in terms of reduced color.
As will be shown hereafter, there is also a flavor
improvement with ethanol dehydration.
~AMPLE 4
A waxy maize starch was pH adjusted to pH 9.5
using the procedure described in Example 1. The starch
was then placed in a freeze dryer and dried for 3 days
until it was anhydrous (0% moisture). The freeze-dried
(FD) starch was heat treated for 6 and 8 hours at 160~C
in a forced draft oven.
Brabender evaluation were run. The results are
shown below:
Vi co~ity ~t
Dch~ ' Nert Perk 10 min
2 0 ~ ~H Method Trelttment ViscodtY Afler Pcrk Bre kdo~Yn
(BU)
W~x,Y 9 5 -- -- 1200 320 ~5%
Mrize~
W~xy 9 5 FD -- 1240 320 74%
M-ize
25 T-l W~xy 9 5 FD 160~C/6 hrs 340 465 rising cun~e
M-ize
T-l W~xy 9 5 FD 160~C/8 hrs 285 325 ri~ing culve
Mrize
3 0 ~ Bn~e ~rch
~ Control
The results show that the starch can be
dehydrated by freeze drying and that the subsequent heat
treatment is necessary to inhibit the starch. The
starches are highly inhibited as shown by their rising
viscosity.
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~X~P~E 5
This example shows that alcohol dehydration
provides better tasting thermally-inhibited starches.
The test performed was a "Triangle Taste Test"
which employs three coded samples, two identical and one
dif~erent, presented simultaneously. None of 1:he samples
i~ identified as the stAn~rd. Control and experimental
treat~ents were systematically varied so that each was
presented in odd and identical sample positions an equal
number of timesO The judge determined which o$ the three
samples differed from the other two. A forced choice was
required. Statistical analysis was used to determine
whether a signi~icant difference between treatments
existed. The probability of choosing the different or
odd sample by chance alone was one-third. Once the odd
sample was chosen the judges were asked why the samples
were different and which they preferred.
The starches tested were waxy maize starches
adjusted to pH 9.5 and heat treated for 7 hours at 140~C
but one sample was dehydrated by ethanol extraction and
the other sample was thermally dehydrated prior to the
thermal inhibition step.
The thermally-inhibited starches were washed by
slurring the granular starch with 1.5 parts water, mixing
for l0 minutes on a stir plate, vacuum filtering the
slurry, and washing the starch cake twice with 50 mis of
distilled water. Then sufficient water was added to
bring the slurry solids to 3%, the pH was adjusted to
6.0-6.5 and the slurry was cooked 20 minutes in a boiling
water bath, cooled to slightly above room temperature,
and evaluated.
The judges were given 20 ml samples for
tasting. They observed a significant difference between
the oven-dehydrated and ethanol-dehydrated starches.
3S Nine out of the twelve judges chose the one different
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sample. All nine of the judges who could determine the
different sample preferred the sample that was ethanol-
extracted. Attributes that were used to describe the
ethanol-extracted sample included clean, not bitter, and
smooth compared to the oven-dehydrated sample.
EXAMPLE 6
This example shows that an alcohol extraction
after a granular starch is thermally-inhibited provides a
better tasting starch.
A thermally-inhibited, granular waxy maize
(adjusted to pH 9.5 and heat treated for 180 minutes in a
fluidized bed at 160~C) was placed in a Soxhlet
extraction apparatus and allowed to reflux overnight
(about 17 hrs) using ethanol as the solvent (bp-78~C).
The extracted starch was then laid on paper to allow
excess ethanol to flash off. The resulting dry starch
was washed by slurring the starch with 1.5 parts water,
mixing for 10 minutes on a stir plate, vacuum filtering
the slurry, and washing the starch cake twice with 50 ml
of distilled water. Then sufficient water was added to
bring the slurry solids to 3%, the pH was adjusted to
6.0-6.5, and the slurry was cooked in a boiling water
bath for 20 minutes. The cook was cooled to slightly
above room temperature and evaluated. The thermally-
inhibited, non-ethanol-extracted base was used as the
control.
The taste test performed was a "Paired-
Preference Test". Two samples are presented,
simultaneously or sequentially. The judge is requested
to express a preference based on a specific attribute,
here which sample is cleaner. Results are obtained in
terms of relative frequencies of choice of the two
samples as accumulated for all participants. Six of the
eight trained judges identified the ethanol-extracted
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sample as having a blander, cleaner flavor with less
aftertaste.
This çxample describes the effect of the
J removal of various proteins, lipids, and other off flavor
components on the flavor (i.e., taste and aroma) of a
thermally-inhibited waxy maize.
Prior to the thermal inhibition process (i.e.,
solvent extraction or freeze drying and heat treatment),
the protein is extracted from a waxy maize starch as
follows. The starch is slurried at W=1.5 (50 lbs starch
to 75 lbs of water) and the pH is adjusted to 3-3.5 with
sulfuric acid. Sodium chlorite is added to give 2% on
the weight of the starch. The starch is steeped
overnight at room temperature. The pH is raised to about
9.5 using a 3~ sodium hydroxide solution and washed well
prior to drying. The protein level of the starch is
reduced to about 0.1%. The protein level of an untreated
waxy maize control (pH 9.5) is about 0.3%.
This treatment should improve the flavor of the
thermally-inhibited granular starches prepared using the
non-thermal dehydration methods since the same treatment
of a thermally-inhibited granular starch prepared using
thermal dehydration improved the flavor as reported
below. Removal of various proteins, lipids, and other
off flavor components is expected to improve the flavor
of all starch bases and flours.
Using a one-sided, directional difference taste
testing procedure, as described in "Sensory Evaluation
Techniques" by M. Meilgaard et al., pp. 47-111 (CRC Press
Inc., Boca Raton, Florida 1987), the protein-reduced
thermally-inhibited waxy maize (adjusted to pH 9.5;
dehydrated and heat treated for so min at 160~C in a
fluidized bed) was compared to the thermally-inhibited
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waxy maize (pH 9.5; 160~C/90 min) which had not been
protein-reduced prior to heat treatment.
For the taste test, 3% starch cooks (samples
heated at 100~C for 15 min) were prepared and panelists
were asked to select which sample was "cleaner" in
flavor. All tests were done in a sensory evaluation room
under red lights in order to negate any color differences
that may have been present between samples. The results
are shown below:
Number of Significance
Number of Positive Level
Trial ~ Panelists Res~onses~ risk) 2
1 15 12 5%
2 14 11 5%
1 The number indicates those respondents who selected
the protein-reduced product as being cleaner in flavor.
2 The ~ values were determined from a statistical
table. An ~ risk of 5% indicates (with 95% confidence)
that the samples are statistically different, i.e., that
the protein-reduced product is cleaner than the control.
The results show that protein removal prior to
the heat treatment helps to improve the flavor of the
thermally-inhibited granular waxy maize starch.
Now that the preferred embodiments of the
invention have been described in detail, various
modifications and improvements thereon will become
readily apparent to the practitioner. Accordingly, the
spirit and scope of the present invention are to be
limited only by the appended claims, and not by foregoing
specification.
