WO1996040793A1

WO1996040793A1 - Thermally-inhibited granular starches and flours and process for their production

Info

Publication number: WO1996040793A1
Application number: PCT/US1996/007071
Authority: WO
Inventors: Chung-Wai Chiu; Manish B. Shah; David J. Thomas; Douglas J. Hanchett; Roger Jeffcoat
Original assignee: National Starch And Chemical Investment Holding Corporation
Priority date: 1995-06-07
Filing date: 1996-05-16
Publication date: 1996-12-19
Also published as: CA2221520A1; AU5861296A

Abstract

Thermally inhibited starches and flours are prepared by a process which comprises the steps of non-thermally dehydrating a granular starch or flour to anhydrous or substantially anhydrous and heat treating the dehydrated starch or flour for a time and at a temperature sufficient to inhibit the starch or fluor and provide textural and viscosity characteristics comparable to chemically cross-linked starches and flours. Preferably, prior to the dehydrating and heat treating steps, the granular starch or flour is adjusted from its natural pH to a pH of 7 or above, preferably about 8-9.5. Preferably protein and/or lipids are removed from the starch or fluor prior to or after the thermal inhibition. Non-thermal dehydration (e.g., ethanol extraction or freeze drying) as well as alcohol extraction improves the taste.

Description

THERMALLY-INHIBITED GRANULAR STARCHES AND FLOURS AND PROCESS FOR THEIR PRODUCTION

BACKGROUND OF THE INVENTION

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 smo ey 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 temperature 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. 4.303.452 (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 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. PCT International Patent Application No. WO 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 neutral 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 dispersed in an aqueous medium 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 thickened food compositions due to "woody" or "popsicle stick" off- flavors resulting from pregelatinization. See U.S. 4.303.451 (issued Dec. 1, 1981 to W.C. Seidel) which 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). 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 INVENTION

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. As used herein "non-thermally dehydrating" refers 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 limited, to extraction with solvents, preferably hydrophilic solvents, more preferably solvents which form azeotro^es 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 starches which were dehydrated with direct heat such as those of WO 9504082. It is expected that dehydration by freeze drying will also provide a taste 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-adjusted, is heat treated 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 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 improves 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 containing 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 "starch" in this description are meant to include their corresponding "flours".

As used herein, a "native starch" is one as it is 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 performed 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 for dehydrating and heat- treating the granular starch or flour are chosen so that inhibition 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 more 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 pH, the granular starch is slurried or dissolved in water or another aqueous medium, typically in a ratio of 1.5 to 2.0 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%, 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 as 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, disodium 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 should 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 ethanol to flash off is about 20-30 minutes. The starch or flour is immediately placed in a suitable heating apparatus 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 removed from the freeze dryer and immediately placed into a suitable heating apparatus for the heat treatment. 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 obtained. Typically the heat treating is carried out at 120°-180°C, preferably 140°-160°C, more preferably 160°C. The level of inhibition is dependent on the pH and heating temperature and time. For example, if the starch or flour is adjusted to pH 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 temperatures, longer heating times are required. When the starch or 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 starch from ambient temperature to the desired heat treatment temperature which will depend upon the level of inhibition desired. Some level of inhibition may be attained 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 or a blower to sweep air from the head-space of the apparatus, or a fluidizing gas.

Superior thermally inhibited granular starches and flours having high viscosities with no or low percentage breakdown 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 containing 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 anhydrous 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 using 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 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.

CHARACTERIZATION 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., Hackensack, 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 passes through the initiation of viscosity, usually at about 60°-70^βC, 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 the granules decreases, the peak viscosity disappears and with prolonged cooking the Brabender curve becomes a rising curve indicating a slow continuing increase in viscosity. At very high levels of inhibition, the starch granules no longer gelatinize and the Brabender curve remains flat.

SAMPLE PREPARATION All the starches and flours used were provided by 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 raised by slurrying the granular starch or flour in water at 30-40% solids and adding 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 samples 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 water.

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. 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 inhibition; or (iv) a slight increase in peak viscosity and a lower percentage breakdown compared to a control, indicating a low level of inhibition.

CHARACTERIZATION OF INHIBITION BY TEXTURE Starches or flours with a low to moderate degree of inhibition will exhibit certain textural characteristics when dispersed in an aqueous medium and heated to gelatinization. In the following examples, the starches 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 for 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^βC overnight to dehydrate the starch to <1% (0%) moisture. The other sample was placed in a

Soxhlet 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 flowing 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. The thermally-inhibited (T-I) starches and the controls were evaluated using the Brabender Procedure previously described.

BRABENDER RESULTS

Viscosity at

Dehydration Heat 10 min

Base EM Method Treatment After Peak Breakdown (BU)

Waxy 5.3 - - 1245 330 74% Maize*

Waxy 5.3 oven - 1290 350 73% Maize**

Waxy 5.3 ethanol - 1205 245 80% Maize**

T-I Waxy 5.3 oven 5 hrs. at 95 45 53% Maize 160°C

T-I Waxy 5.3 ethanol 5 hrs. at 255 185 28% Maize 160°C

T-I Waxy 5.3 oven 7 hrs. at 60 35 42% Maize 160-C

T-I Waxy 5.3 ethanol 7 hrs. at 165 105 36% Maize 160^βC

T-I Waxy 7.0 oven - 1240 380 69% Maize^*

T-I Waxy 7.0 oven 7 hrs. at 298 240 20% Maize 160°C

T-I Waxy 7.0 ethanol 7 hrs. at 400 310 23% Maize 160°C

Waxy 9.5 Oven - 1250 400 68% Maize*

Waxy .9.5 Ethanol - 1070 350 67% Maize*

T-I Waxy 9.5 Ethanol 3 hrs at 665 635 5% Maize 160^βC

T-I Waxy 9.5 Oven 3 hrs at 680 655 4% Maize 160^oC

T-I Waxy 9.5 Oven 5 hrs. at 245 460 rising curve Maize 160^βC

T-I Waxy 9.5 Ethanol 5 hrs. at 160 375 rising curve Maize 160°C

T-I Waxy 9.5 Oven 7 hrs. at 110 295 rising curve Maize 160°C

T-I Waxy 9.5 Ethanol 7 hrs. at 110 299 rising curve Maize 160°C * Base starch. Controls.

Both of the thermally-inhibited pH 7 starches were higher in viscosity than the pH 5.3 (as is) thermally-inhibited starches. The starches which were thermally-inhibited at pH 9.5 were moderately highly inhibited or highly inhibited (rising curve) .

EXAMPLE 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 samples) and dehydrated by extraction with ethanol, and heat treated at 160°C.

The Brabender results are shown below: > ₂e

Viscosity at

Dehydration Heat 10 min

Base EM Method Treatment After Peak Breakdown

Tapioca* 9.5 oven - 745 330 58%

Tapioca* 9.5 ethanol - 720 330 54%

T-I Tapioca 9.5 oven 5 hrs. at 270 260 3% 160'C

T-I Tapioca 9.5 ethanol 5 hrs. at 260 258 1 % 160°C

T-I Tapioca 9.5 oven 7 hrs. at 110 155 rising curve 160°C

T-I Tapioca 9.5 ethanol 7 hrs. at 100 145 rising curve 160°C

Corn* 9.5 oven - 330 280 15%

Corn* 9.5 ethanol - 290 250 14%

T-I Corn 9.5 oven 5 hrs. at 10 80 rising curve 160°C

T-I Corn 9.5 ethanol 5 hrs. at 10 170 rising curve 160^βC

T-I Com 9.5 oven 7 hrs. at 10 65 rising curve 160°C

T-I Corn 9.5 ethanol 7 hrs. at 10 45 rising curve 160°C

Waxy Rice* 9.5 1200 590 50.8% Viscosity at

Dehydration Heat Peak 10 min

Base EH Method Treatment Viscosity After Peak Breakdown (BU)

Waxy Rice 9.5 ethanol - 1155 450 61.0%

T-I Waxy 9.5 oven 5 hrs. at 518 640 rising curve

Rice 160°C

T-I Waxy 9.5 oven 7 hrs. at 265 458 rising curve

Rice 160^βC

T-I Waxy 9.5 ethanol 7 hrs. at 395 520 rising curve

Rice 160^βC

Waxy Rice 9.5 895 700 22%

Flour*

Waxy Rice 9.5 ethanol 870 410 53%

Flour*

T-I Waxy 9.5 5 hrs. at 38 73 nsing curve

Rice Flour 160°C

T-I Waxy 9.5 ethanol 5 hrs. at 140 260 rising curve

Rice Flour 160^βC

T-I Waxy 9.5 7 hrs. at 10 16 rising curve

Rice Flour 160°C

T-I Waxy 9.5 ethanol 7 hrs. at 40 100 nsing curve

Rice Flour* 160^βC

* Base starch.

** Controls.

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.

EXAMPLE 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. Viscosity 10 Minutes

Dehydration/ Peak After Peak Heat Treatment Viscosity Viscositv 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 viscosity, 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 samples. 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.

EXAMPLE 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:

Viscosity at

Dehydration Heat Peak 10 min

Base £H Method Treatment Viscositv After Peak Breakdown

(BU)

Waxy 9.5 - - 1260 320 75% Maize*

Waxy 9.5 FD - 1240 320 74% Maize**

T-I Waxy 9.5 FD 160°C/6 hrs. 340 465 rising curve Maize

T-I Waxy 9.5 FD 160°C/8 hrs. 285 325 rising curve Maize

Base starch. 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. EXAMPLE 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 different, presented simultaneously. None of the samples is identified as the standard. Control and experimental treatments were systematically varied so that each was presented in odd and identical sample positions an equal number of times. The judge determined which of the three samples differed from the other two. A forced choice was required. Statistical analysis was used to determine whether a significant 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 10 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. Nine out of the twelve judges chose the one different 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 sample as having a blander, cleaner flavor with less aftertaste.

EXAMPLE 7 This example describes the effect of the 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 90 min at 160°C in a fluidized bed) was compared to the thermally-inhibited 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 Responses¹ ( 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 α values were determined from a statistical table. An α 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.

Claims

WHAT IS CLAIMED IS:

1. A process for preparing a thermally- inhibited starch or flour which comprises the steps of:

(a) non-thermally dehydrating a granular starch or flour to substantially anhydrous or anhydrous; and (b) heat treating the dehydrated starch or flour at a temperature and for a period of time sufficient to inhibit the starch or flour.

2. The process of Claim 1, wherein the starch or flour is a cereal, root, tuber, legume or fruit starch or flour.

3. The process of Claim 2, wherein the starch or flour is selected from the group consisting of banana, corn, pea, potato, sweet potato, barley, wheat, rice, sago, amaranth, tapioca, sorghum, V.O. hybrid waxy maize, waxy maize, waxy rice, waxy barley, waxy potato, waxy sorghum, and a starch or flour containing greater than 40% amylose.

4. The process of Claim 1, wherein the starch is a modified starch.

5. The process of Claim 4, wherein the modified starch is a derivatized starch, a converted starch, a chemically crosslinked starch, a derivatized and converted starch, a derivatized and chemically crosslinked starch, or a converted and chemically crosslinked starch.

6. The process of Claim 1, wherein the flour is a modified flour.

7. The process of Claim 6, wherein the modified flour is bleached or enzyme-converted.

8. The process of Claim 1, which further comprises the step of adjusting the pH of the granular starch to about 7-9.5 prior to the dehydrating step.

9. The process of Claim 1, further comprising the step of extracting the heat-treated starch or flour with an organic solvent to improve flavor and/or color.

10. The process of Claim 9, wherein the solvent is an alcohol.

11. The process of Claim 1, wherein the non- thermal dehydrating step is carried out by extracting the granular starch with a solvent.

12. The process of Claim 11, wherein the solvent is a hydrophilic solvent.

13. The process of Claim 12, wherein the hydrophilic solvent forms an azeotrope with water.

14. The process of claim 13, wherein the hydrophilic solvent is an alcohol.

15. The process of Claim 1, wherein the non- thermal dehydrating step is carried out by freeze drying the granular starch.

16. The process of Claim 1, wherein the heat treating step is carried out at a temperature of 100°C or greater.

17. The process of Claim 8, wherein the heat treating step is carried out at a temperature of about 120-180°C for up to 20 hours.

18. The process of Claim 10, wherein the pH is about 8-9.5; wherein the dehydrating step is carried out by extracting the starch with ethanol; wherein the heat treating step is carried out at a temperature of about 120-180°C for up to 20 hours; and wherein the alcohol used in the extraction step is ethanol.

19. The process of Claim 17, wherein the heat treating step is carried out in an oven or in a fluidized bed reactor.

20. A thermally-inhibited starch or flour prepared by the process of Claim 1, characterized by its improved flavor and/or color.

21. A thermally-inhibited starch or flour prepared by the process of Claim 9, characterized by its improved flavor and/or color.