This invention relates to pregelatinized granular starches and flours that are cold water soluble or dispersible and to a process for their preparation. The pregelatinized starches and flours are thermally inhibited and may be used in place of chemically crosslinked pregelatinized starches presently used in foods or in industrial products. Native starch granules are insoluble in cold water, when native granules are dispersed in water and heated, however, they become hydrated and swell. Then, with continued heating, shear, or conditions of extreme pH, the gelatinized granules will fragment and the dispersed starch molecules will solubilize in water. It is possible to make a starch in powder form that is cold water soluble or dispersible if the starch is pregelatinized. Depending on the type of starch molecules prevalent in the starch, the pregelatinized starch will exhibit specific texture and viscosity characteristics after the starch is dispersed in water, starches containing amyiose will exhibit a gel-like or noncohesive texture, starches containing high levels of amyiose, for example, over 40%, will set to a very firm gel. Nongranular amyiose containing starches, pregelatinized, for example by drum drying or extrusion, frequently yield a grainy or lumpy texture. starches that contain mainly amylopectin, which are the waxy starches, do not provide the same gel characteristics as amyiose containing starches. Any unmodified pregelatinized amylopectin starches will exhibit a cohesive and runny texture when dispersed in cold water. That texture can be changed, however, if the waxy starches are chemically modified or crosslinked prior to the pregelatinization process. The crosslinks reinforce the associative hydrogen bonds holding the granules together, inhibit the

swelling and hydration of the starch granules during pregelatinization, and consequently, the inhibited starch granules remain intact, when pregelatinized powders made from these granular crosslinked starches are dispersed in water they will show a noncohesive and salve-like texture, which is described as heavy or short. Nevertheless, in some applications, chemically altered starches are unacceptable or undesirable.

The present invention provides cold water dispersible, granular, pregelatinized starches that avoid the problems of prior art pregelatinized starches. When dispersed in cold water, the amyiose containing starches display a smooth, uniform texture, and the amylopectin containing starches display a smooth, noncohesive, and salve-like texture.

These starches and flours are pregelatinized so that a majority of the starch granules are swollen, but remain intact, and are thermally inhibited in a process that results in the starch or flour assuming the characteristics of a chemically crosslinked starch, without the addition of chemical reagents. These pregelatinized and thermally inhibited starches or flours are dispersible in cold water and possess a noncohesive and salve¬ like texture if amylopectin containing, or a smooth and uniform gel-like texture if amyiose containing. The starches and flours may be pregelatinized and subsequently thermally inhibited, or they first may be thermally inhibited and subsequently pregelatinized. if the pregelatinization process is performed first, a granular starch or flour is slurried in water, typically in a ratio of 1.5 to 2.0 parts to 1.0 part starch, and optionally, the pH is adjusted to neutral or greater. As used herein, neutral covers the range of pH values around pH 7 and is meant to include from about pH 6.5 to about pH 7.5. The slurry is simultaneously pregelatinized and dried and the dried starch or flour is thermally

inhibited. The thermal inhibition process comprises the steps of dehydrating the pregelatinized starch until it is anhydrous or substantially anhydrous, which for purposes herein means containing less than 1% moisture by weight, and then heat treating the anhydrous or substantially anhydrous starch or flour at a temperature and for a period of time effective to cause inhibition.

Alternatively, if the thermal inhibition process is performed first, the starch or flour is slurried in water; optionally, the pH of the starch or flour is adjusted to neutral or greater; and the starch or flour is dried to about 2-15% moisture. The starch or flour is then dried to anhydrous or substantially anhydrous, and heat treated at a temperature and for a period of time effective to cause inhibition. The inhibited starch or flour is reslurried in water, optionally pH adjusted, and simultaneously pregelatinized and dried. After both the pregelatinization and thermal inhibition, the product can be washed by any known methods that will maintain granular integrity.

The preferred pH is at least 7, typically the ranges are pH 7.5 to 10.5, preferably 8 to 9.5, and most preferably greater than pH 8. At a pH above 12, gelatin ization more easily occurs; therefore, pH adjustments below 12 are more effective.

Buffers, such as sodium phosphate, may be used to maintain pH if needed. An alternative method of raising the pH consists of spraying a solution of a base onto the starch or pregelatinized starch until the starch attains the desired pH, either during the heat treatment step or prior to heat treatment. Another method consists of infusing an alkaline gas, such as NH _S , into the starch, preferably during the heat treatment step.

if the starch is not going to be used in a food, any workable or suitable inorganic or organic base that can raise the pH of starch may be used.

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 may include any other base approved for food use under Food and Drug Administration laws or other food regulatory laws. Bases not approved for food use under these regulations may also be used, provided they can be washed from the starch so that the final product conforms to good manufacturing practices for food use. The preferred food grade base is sodium carbonate. It may be noted that 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.

By varying the process conditions, including the initial pH of the starch or flour or of the pregelatinized starch or flour, the dehydrating and heat treating temperatures, and the heat treating times, the level of inhibition can be varied to provide different viscosity characteristics in the final product, inasmuch as the dehydrating and heat treating process parameters can be a function of the particular apparatus used for dehydrating and heat treating, the choice of apparatus will also be a factor in the control of the level of inhibition. in one embodiment, the dehydrating and heat treating steps occur simultaneously. The process steps may be carried out as part of a

continuous process including the extraction of the starch or flour from a plant material.

These pregelatinized and thermally inhibited starches and flours are granular and can be derived from any native source. The native source can be corn, pea, potato, sweet potato, barley, wheat, rice, sago, amaranth, tapioca, sorghum, waxy maize, waxy rice, waxy barley, waxy potato, waxy sorghum 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. References to starch are also meantto include starch containing protein, whether the protein is endogenous protein, or added protein from an animal for plant source, such as, zein, albumin, and soy protein.

AS used herein, a native starch is one as it is found in nature. The starches may be native starches, or the starches may be modified by enzymes, heat or acid conversion, oxidation, phosphorylation, etherif ication (particularly, hydroxyalkylation ⁾ , esterif ication, and chemical crosslinking.

Pregelatinization steps. The starches can be pregelatinized according to any of the known pregelatinization processes that result in the maintenance of intact granules. Exemplary processes are disclosed in us patents numbers 4,280,851; 4,465,702; 5,037,929; and 5,149,799. us 4,280,851 (issued 28 July 1981 to Pitchon et al.) describes a dual- atomization spray-drying process for preparing granular pregelatinized starches, in this process a mixture of the granular starch In an aqueous solvent is injected through an atomizatlon aperture in a nozzle assembly to form a finely divided spray. A heating medium is injected through a second aperture in the nozzle assembly into the spray of atomized starch

to heat the starch to its gelatinization temperature. An enclosed chamber surrounds the atomization and heating medium injection apertures and defines a vent aperture positioned to enable the heated spray of starch to exit the chamber. The arrangement is such that the lapsed time between passage of the spray of starch through the chamber from the atomizatiom aperture to the vent aperture defines the gelatinization time of the starch. The resulting spray-dried pregelatinized starch comprises uniformly gelatinized starch granules in the form of indented spheres, with a majority of the granules being whole and unbroken and swelling upon rehydration.

An apparatus for carrying out this dual-atomization process is disclosed in US 4,600,472 (issued 13 July 1986 to Pitch on et al.). Nozzles suitable for use in the prepartion of these starches are described in US 4,610,760 (issued 9 September 1986 to Kirkpatrick et al.). us 4,847,371 (issued 11 July 1989 to schara et al.) discloses a dual-atomization process and apparatus similar to those of the Pitchon et al. patents. us 4,465,702 (issued 14 august 1984) to Eastman) discloses a process for preparing a cold-water-swelling granular corn starch. An ungelatinized starch at 10-25 parts by weight is slurried in an aqueous C- - C ₅ alkanol, 50- 75 parts by weight, and about 13-20 parts water (provided that the alkanol and water mixture contains about 15-35 weight percent water including the water in the starch). The starch slurry is heated in a confined zone to a temperature of about 300°-360°F for about one to about 30 minutes. The pregelatinized granular starch is then recovered from the slurry. us 5,037,929 (issued 6 August 1991 to Rajagopalan et al.) discloses a process for preparing cold-water-soluble granular starches. The starch granules are slurried in water and a polyhydric alcohol, such as, 1,3- propanediol, butanediol, or glycerol. The slurry is heated to 80°-130°C for

about 3-30 minutes to convert the crystalline structure of the granules to single helix crystals or to an amorphous state while maintaining the granular integrity of the starch. The starch is recovered from the liquid phase. us 5,149,799 (issued 22 September 1992 to Rubens) discloses a single atomization spray-drying process and an apparatus for preparing granular pregelatinized starches. The starch is slurried in an aqueous medium and a stream of the starch slurry is fed into an atomizing chamber within a spray nozzle at a pressure from about 50 to 200 psig. steam is forced into the atomizing chamber at a pressure of 50 to 250 psig, and the starch is then simultaneously cooked and atomized as the steam forces the starch through a vent at the bottom of the chamber. The process takes place in a two-fluid, internal mix, spray nozzle. The process and the apparatus supply sufficient heat and moisture to the starch as it is being atomized to gelatinize the starch uniformly. The atomized starch is dried with a minimum of heat or shear effects as it exits the atomization chamber.

The amount of pregelatinization, and consequently, whether the starch will display a high or a low initial viscosity when dispersed in water, can be regulated by the pregelatinization procedures, which are known In the art. in general, if spray drying is used for the pregelatinization, the longer the residence time in the spray nozzle and the higher the ratio of steam to starch, the higher the initial viscosity of the pregelatinized starch when it is subsequently dispersed in water, conversely, the lower the residence time, and the lower the amount of heat and moisture, the lower the viscosity.

Thermal inhibition steps, in the first step of the process to achieve thermal inhibition, the starch or the pregelatinized starch (hereinafter starch) is dehydrated for a time and at a temperature sufficient to render

the starch anhydrous or substantially anhydrous, in the second step, the anhydrous or substantially anhydrous starch is heat treated for a time and at a temperature sufficient to inhibit the starch.

When starches are subjected to heat in the presence of water, hydrolysis or degradation of the starch can occur. Hydrolysis or degradation will impede or prevent inhibition; therefore, the conditions for the dehydration of the starch need to be chosen so that inhibition is favored over hydrolysis or degradation. Although, any conditions meeting that criteria can be used, suitable conditions consist in dehydrating at low temperatures, or raising the pH of the starch before dehydrating. The preferred conditions consist in a combination of low temperature and neutral to basic pH.

Preferably, the temperatures to dehydrate the starch are kept at

125°c or lower, and more preferably at temperatures, or a range of temperatures, between 100> to 120°C. The dehydrating temperature can be lower than 100>C, but a temperature of at least I00oc will be more effective in removing moisture.

After the starch is dehydrated, it is heat treated for a time and at a temperature, ora range of temperatures, effective to inhibit the starch. The preferred heating ranges are temperatures or a range of temperatures greater than 100°C. For practical purposes, the upper limit of the heat treating temperature is usually in the range of 200°c, at which temperature highly inhibited starches can be obtained. Typically the heat treating is carried outatl20°-l80°c, preferably i40°-l60- _\ more preferably 160°C. The time and temperature profile will depend on the level of inhibition desired.

For most industrial applications, the dehydrating and heat treating steps will be continuous and be accomplished by the application of heat

to the starch beginning from ambient temperature, in the majority of cases, the moisture will be driven off and the starch will be anhydrous before the temperature reaches about 125°c. After the starch reaches an anhydrous state, and heating is continued, some level of inhibition will be attained simultaneously, or even before, the final heat treating temperature is reached. if moisture is present during the heat treating step, and especially if the heat treating step will be performed at elevated temperatures, the pH is adjusted to greater than pH 8 to achieve inhibition. The source of the starch, the dehydrating conditions, the heating time and temperature, the initial pH, and whether or not moisture is present during the process steps, are all interrelated variables that control the level of inhibition and the textural and viscosity characteristics of the inhibited products. The starches may be inhibited individually, or more than one may be inhibited at the same time. The starches also may be inhibited in the presence of other materials or ingredients that would not interfere with the thermal inhibition process or alter the properties of the thermally inhibited product. The process may be performed at normal pressures, under vacuum or under pressure, and may be accomplished using any means known to practitioners, although the preferred method is by the application of dry heat in air or in an inert gaseous environment

The dehydrating and 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. The heat treating step can be accomplished in the same apparatus in which the dehydrating step occurs, and most conveniently is continuous with the dehydrating step. When the dehydrating step is continuous with the heat treating step, and particularly when the apparatus used is a fluidized bed reactor or drier, the dehydrating step occurs simultaneously while bringing the equipment up to the final heat treating temperature.

The pregelatinized and thermally inhibited starches having high viscosities with low percentage breakdown in viscosity are obtained in shorter times in the fluidized bed reactor than can be achieved using 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. Characterization of inhibition by Brabender curves

For pregelatinized starches, the level of viscosity when dispersed in cold water will be dependent on the extent to which the starch was initially cooked out during the pregelatinization process, if the granules are not fully swollen and hydrated during pregelatinization, gelatinization will continue when the starch is dispersed in water and heated, inhibition is determined by a measurement of the starch viscosity when the starch is dispersed at 4.6% solids in water at pH 3 and heated to 95°c. The instrument used to measure the viscosity is a Brabender (manufactured by c.w. Brabender instruments, inc., Hackensack, NJ). The vιsco\Amylo\CRAPH records the torque required to

balance the viscosity that develops when a starch slurry is subjected to a programmed heating cycle.

When the pregelatinized starch has a high initial cold viscosity, meaning it was highly cooked out in the pregelatinization process, the resulting Brabender traces will be as follows: for a highly inhibited starch the trace will be a flat curve, indicating that the starch is already very swollen and is so inhibited that it is resisting any further gelatinization, or the trace will be a rising curve, indicating that further gelatinization is occurring at a slow rate and to a limited extent; for a less inhibited starch, the trace will show a dropping curve, indicating that some of the granules are fragmenting, but the overall breakdown in viscosity will be lower than that for a noninhibited control, or will show a second peak, but the breakdown in viscosity will be lower than that for a noninhibited control.

When the pregelatinized starch has a low initial cold viscosity, meaning it was not highly cooked out in the pregelatinization process and more cooking Is needed to reach the initial peak viscosity, the resulting

Brabender traces will be as follows: for a highly inhibited starch, the trace will be a rising curve, indicating that further gelatinization is occurring at a slow rate and to a limited extent; for a less inhibited starch, the trace will show a peak viscosity as gelatinization occurs, and then a drop in viscosity, but with a lower percentage breakdown in viscosity than a control. sample Preparation

All the starches and flours used were granular and except where indicated, were provided by National starch and Chemical Company of Bridge-water, New Jersey.

The controls for the test samples were from the same native sources as the test samples, were unmodified or modified as the test samples, 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 samples was raised by slurrying the 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.

The slurries were pregelatinized in a pilot size spray drier, Type l- KA#4F, from APV crepaco, inc., Dreyer Division, of Attle boro Falls, Massachusetts, using a spray nozzle, Type 1/2 J, from spraying systems company of Wheaton, Illinois. The spray nozzle had the following configuration: fluid cap, 251376, and air cap, 4691312. The low initial cold viscosity samples were sprayed at a steam : starch ratio of 3.5-4.5 : 1, and the high initial cold viscosity samples were sprayed at a steam : starch ratio

Of 5.5-6.5 : 1.

Moisture content of all samples after spray drying and before the dehydration step in the thermal inhibition process was 4-10%.

Except where a conventional oven or dextrin izer is specified, the test samples were dehydrated and heat treated in a fluidized bed reactor, model number FDR-100, manufactured by Procedyne corporation of New Brunswick, New Jersey. The cross-sectional are of the fluidized bed reactor was 0.05 sq meter. The starting bed height was 0.3 to 0.8 meter, but usually 0.77 meter. The fluidizing gas was air except where otherwise indicated and was used at a velocity of 15-21 meter/ min. The sidewalls of the reactor panels were heated with hot oil, and the fluidizing gas was heated with an electric heater. The samples were loaded to the reactor and then the fluidizing gas introduced, or were loaded while the fluidizing gas was being introduced. No difference was noted in the samples in the order of loading. The samples were brought from ambient temperature to 125°C until the samples became anhydrous, and were further heated to

the specified heat treating temperatures. When the heat treating temperature was 160°C, the time to reach that temperature was less than three hours.

The moisture level of the samples at the final heating temperature was 0%, except where otherwise stated. Portions of the samples were removed and tested for inhibition at the temperatures and times indicated in the tables.

These samples were tested for inhibition using the following Brabender Procedure. Brabender Procedure

The pregelatinized thermally inhibited granular starch to be tested was slurried in a sufficient amount of distilled water to give a 4.6% anhydrous solids starch slurry at pH 3 as follows: I32.75g sucrose, 26.55g starch, io.8rams acetic acid, and 405.9g water, were mixed for three minutes in a standard home Mixmaster blender at setting #1. The slurry was then introduced to the sample cup of a Brabender vιsco\Amylo\CRAPH fitted with a 350 cm/gram cartridge and the viscosity measured as the slurry was heated to 30°c and held for ten minutes. The viscosity at 30°c and ten minutes after hold at 30°c were recorded. The viscosity data at these temperatures are a measurement of the extent of pregelatinization. The higher the viscosity data at 30oC, the greater the extent of granular swelling and hyd ration during the pregelatinization process.

Heating was continued up to 95°c, and held at that temperature for 10 minutes. The peak viscosity and viscosity ten minutes after 95°c were recorded in Brabender units (BU) and used to calculate the percentage breakdown in viscosity according to the formula:

% Breakdown = peak - (95°c + 10') x 100 peak where "peak" is the peak viscosity in Brabender Units, and "(95°c + 10')" is the viscosity in Brabender units at ten minutes after 95°c. if no peak viscosity was reached, that is, the data indicated a rising curve or a flat curve, the viscosity at 95°c and the viscosity at 10 minutes after attaining 95°c were recorded.

Example

The thermally inhibited pregelatinized granular starches and controls in the following example were prepared as described above and are defined in relation to data taken from Brabender curves using the above procedure. using data from Brabender curves, inhibition was determined to be present if during the Brabender heating cycle (i) the Brabender curve showed continuous rising viscosity with no peak viscosity, indicating the pregelatinized starch was highly inhibited and resisted further gelatinization; or (ii) the Brabender curve showed a second peak viscosity or a lower percentage breakdown in viscosity from peak viscosity compared to a control, indicating the starch had achieved some level of inhibition. samples of waxy maize were adjusted to pH 6.0, 8.0 and 10.0, and pregelatinized to both a high and a low initial viscosity, as described above. The starches were evaluated for inhibition and the results are set out in the following tables. The data show some thermal inhibition was attained in all cases, and that increasing the initial pH and the time of heating increased the level of inhibition. For the samples at pH 6.0, at 0 and 30 minutes, the recorded peak is actually a second peak obtained after the initial high viscosity began to breakdown. For some of the examples

at pH 10, no peak viscosity was reached, indicating a highly inhibited starch.

Pregel* Viscosity in Brabender units % Bkdn waxy + 2% maize 30°C 30°C + peak 95°C 95oC +

PH 6.0 10' 10' control 1280 960 — 170 90 —

160°C

Time (min)

0 700 980 700 610 370 47

30 600 910 720 690 370 49

90 450 780 915 740 400 56

150 360 590 925 800 500 46

*Hιgh initial cold viscosity

Pregel % Bkdn waxy Viscosity in Brabender units _+ 2% maize

PH 6.0* 30°C 30«C + peak 95°C 95oC + 10' 10' control 230 250 750 340 100 87

160°C

Time (min)

30 100 130 600 370 210 65

60 100 140 730 500 260 64

120 100 130 630 430 260 59

180 90 120 550 390 240 56

*Lc w initial < :oιo viscosi ty

Pregel % Bkdn waxy Viscosity in Brabender Units ± 2% maize

PH 8.0* 30°C 30°C + Peak 95°C 95°C + 10" 10" control 1400 1020 — 270 100 __

160°C Time (min)

0 700 1060 1050 760 280 73

60 260 600 1340 1200 780 42

90 240 440 1280 1240 1000 22

120 280 420 1320 1320 1280 3

150 120 200 860 860 820 7

180 180 260 980 980 920 8

"High initial coic viscosity

Pregel % Bkdn waxy viscosity in Brabender units _+ 2%

Maize

PH 8.0* 30°C 30°C + eak 95°C 95°C + 10' 10' control 250 250 820 340 130 84

160°C

Time (min)

0 50 100 690 460 270 61

60 40 50 840 590 320 62

120 20 30 720 650 450 38

180 20 30 590 570 450 24

*Lc w initial c :oια viscosi cy

Pregel % Bkdn waxy Viscosity in Brabender units ± 2% maize

PH 10* 30°C 30°C + peak 95°C 95°C + 10' 10' control 1010 740 — 300 160 —

°C\min

140/0 550 850 1280 1080 750 41

150/0 270 420 1680 1680 1540 8

160/0 170 240 — 1180 1440 ris.visc.

160/30 80 85 — 410 650 ris.visc.

160/60 60 60 — 150 300 ris.visc.

160/90 50 50 — 80 140 ris.visc.

160/120 40 40 _ 80 130 ris.visc.

160/150 40 40 — 60 90 ris.visc.

160/180 40 40 — 45 70 ris.visc.

^♦ High initial coiα viscosity

* Lovι initial c -old viscosi ty ** ris.visc. - rising vise osity

statement of utility

The thermally inhibited pregelatinized granular starches prepared by this process can be used in food products requiring a cold water soluble starch that will set up to a smooth, uniform gel, or a heavy, smooth, salve-like texture. The starch may be blended with other starches, either unmodified or modified, or with food ingredients, to be mixed with water to make baby foods, sauces and gravies, soups, salad dressings and mayonnaise, yoghurt, sour cream, pudding and hot cereals.

These starches are also useful in industrial applications where pregelatinized chemically crosslinked granular starches are known to be useful.