DE1197400B - Process for fractionating starch, such as corn starch - Google Patents

Description

Process for fractionating starch, such as common corn starch As is well known, starch consists of two types of glucose polymers Amylose (often referred to as fraction "A") and amylopectin (often also referred to as fraction Marked "B").

The respective proportions of amylose and amylopectin depend on Origin of strength different. The amylose molecule is called a long, linear one Viewed chain of anhydroglucose units. The amylopectin molecule, on the other hand, exists from a larger, more branched chain of tree-like structure in which many branches can be branched further.

A discussion of the vastly different properties of these two starch proportions can be found at Ker r, Chemistry and Industry of Starch, Academic Press (1950) suggests that the amylose molecule is a relatively small one Molecular weight (several hundred anhydroglucose units, with only one non-reducing end group per molecule), amylopectin, on the other hand, has a high Molecular weight (more than a thousand anhydroglucose units, with a non-reducing End group of twenty to thirty glucose residues each).

The separation of these starch fractions has long been the subject of Work and experiments have been given in the above-cited book by Kerr, p. 181 ff., and in a comprehensive article by Schoch in Advances in Carbohydrate Chemistry, 1, pp. 247-277 (1945).

Neither of these methods of separating the starch fractions has proven successful proven to be really successful in an economic sense, and each of these procedures has disadvantages. The amylopectin obtained from waxy maize is because of the the care required to breed and treat this hybrid species is expensive. at the chemical process of separation is a chemical complex of fractions, and especially the amylose, produced, or using a fractional salting out process, in which a complexing agent can also be used. Also this chemical Processes are unsatisfactory because of the recovery, separation or Difficulties arise in the application of the materials used.

That none of these methods are entirely satisfactory is one Signs of the difficulty in developing an economically justifiable process, in which both amylose and amylopectin are obtained from common natural starches will. According to the invention, an economic separation is now method found in which amylose and amylopectin in high purity and in good yields without adding any reactant other than water.

In the present specification, the term "strength" is used in general Sense used to denote a strength that amylose in a considerable amount Contains proportion. Any type of starch or any starch mixture can be used according to the invention be used, e.g. B. corn, rice, wheat, tapioca, sago, sorghum and potato starch and the like. However, with some of these types of starch the working conditions of the Procedure have to be changed somewhat. According to the invention, a strength are used, which are pre-supplied according to a conventional process and the roller or has been spray dried, d. i.e., a strength can be used that often referred to as cold water swelling or cold water soluble starch. So can the starch can be gelatinized by a conventional method by adding the starch slurry is heated to a temperature below the boiling point of this slurry, whereupon the paste processed without cooling according to the method according to the invention will. As the starch obtained from waxy maize is amylose in the is essentially free, this can of course be added to that proposed according to the invention Procedures are not used. Something modified or something converted into dextrins Starch or starch that forms a derivative with a lower degree of substitution Before or after gelling has been implemented, native starch can be used instead can be used provided that their paste properties are similar to those of native Strength practically match. However, such starch products are expensive, and furthermore the starch fractions have a lower purity and the yield will be the separation decreases as the effect on the starch is increased.

Since cold water swelling or pregelatinized starch in the inventive Process offers no advantage, but rather is disadvantageous if a high molecular weight Product is to be produced, is preferred in the method according to the invention granular native starch used. Are granular native starch slurries also easier to handle. When using granular native starch, it is However, it is very important that the molecular weight of the fractions has the highest value, because the starch has not previously been treated by any procedure that resulted in degradation the molecular weight could have occurred.

According to the invention, the fractionation of starch, such as corn starch, Carried out in such a way that a flowable solution of the starch in water through Heating to a temperature of 121 to about 17700 produces this solution up cooled to a temperature below the boiling point at normal pressure and above 490C and the concentration of the starch is adjusted so that the starch dry matter in this cooled solution is greater than about 2.5 percent by weight, then the Solution within the temperature range between about 490C and the boiling point Normal pressure for one to stabilize the solution and deposition and training an amylose-rich solid fraction is held for a sufficient period of time and this Fraction is separated from the stable solution.

The viscosity of the solution becomes below the boiling point during cooling kept at a value below 1500cP at normal pressure. The stabilization of the solution and the separation of the amylose-rich particles requires a time of at least about 8 hours. Furthermore, an effective separation is made much easier, if the growth of the amylose-rich particles is allowed to proceed so far that at least 50 percent by weight thereof have a diameter greater than 20 microns.

The drawings serve to explain the present invention. In Fig. 1 shows the flow diagram of the method according to the invention; F i G. 2 is a graph showing the effects of some of the following Examples of the observed cooling rates are illustrated after the method of the invention characterized above becomes a non-solidifying one Starch solution is produced and amylose is deposited from it as a solid phase, which is then deposited can be separated from the solution relatively easily. This he- results are made through a carefully regulated sequence of heating and cooling of starch and achieved water.

In the proposed method of the present invention, the slurry of starch in water initially heated to a temperature of 121 to 1770 C. if the temperature of the mixture of starch and water is further increased, takes place initially a very strong increase in viscosity, so that the starch paste has little flowability is. This poorly flowable state exists even above the boiling point until the temperature has been raised to a certain value depending on the nature of the Strength, heating rate and the like is determined. At one temperature above about 12100 there is a sudden change to a flowable, mobile and usually fairly clear liquid, which in the present Description is referred to as: * solution «. It has been found that a separation amylose is not possible and that this solution usually thickens when it cools, unless such a conversion has taken place.

If the solution is then according to the method proposed according to the invention is cooled, it is stabilized and does not thicken even when it is is finally cooled to room temperature. The viscosity properties are has been stabilized to such an extent that the flowable solution repeats can be heated and cooled, at a temperature below the boiling point at normal pressure their viscosity at any given temperature essentially is always the same and a starch cone is not formed even if this is done after Type of starch used might be expected. On the other hand, if the flowable Do not solution at a temperature above 490C for the required length of time is held, this solution, like the usual starch pastes of a certain Type of starch, converted back on cooling, d. i.e., it forms a gel.

The solidification is initially due to an increase in viscosity to recognize; in the further course the apparent viscosity increases and the solution becomes more and more cloudy. The material then takes on a lump-like appearance Texture, then becomes ointment-like and finally rigid. This course is irreversible, d. i.e., the gel can be removed by reheating to a temperature cannot be made flowable again below i210C. Once the If gel formation has started, the amylose can no longer be separated off.

Gel formation or retrogradation is not simply an increase in viscosity; a gel of this type differs in type from most viscous liquids. A starch gel has many properties that are comparable to those of a solid substance are. It is often rigid and can have a certain shape. This particular quality of starch solutions or starch pastes is based on the formation of an embedded network of arbitrarily oriented linear molecules.

When carrying out the method proposed according to the invention the starch solution is changed in such a way that it does not change back or on cooling a gel forms and growth the amylose-rich Fraction is such that separation is facilitated.

If in the proposed method of a dry strength is assumed, the starch is first determined by any suitable method suspended in water for suspension.

The starch suspension is expediently quickly to about 121 Heated to 1770 C, for which purpose a device is preferably used that is in the Description of U.S. Patent 3,110,284. In this device is Uninterrupted steam under excess pressure with the starch suspension in the mouth mixed with a steam nozzle. After this procedure, the suspension actually becomes Immediately brought to the desired temperature, with the starch within less Seconds to boil to a flowable solution. In the above device flows the suspension heated by steam downwards into and through a dwell zone, in which the hot suspension is at an elevated temperature for a selectable period of time is held. This device is arranged and dimensioned such that in the Residence zone practically no mixing occurs, so that from the bottom of the residence zone withdrawn starch solution for an even period of time on a constant Temperature can be maintained. Other forms of this type of device can be used can also be used for heating such as those in U.S. Patents 2,871,146, 2582 198 and 2805966 devices described.

Other methods can be used to heat the starch mixture and water can be used. As described later, according to the invention, a Mixture of starch and water heated in an autoclave and then through a heat exchanger be pumped out of a coiled pipe in an environment with constant Temperature, and such a heating process produces the same results can be obtained.

When heated to the specified temperature, the starch suspension becomes preferably stirred.

The final temperature above 1210 C to which the solution is heated will, and the time at this temperature have an influence on the to be obtained Products. Within the specified limits have relatively high temperatures and long residence times appear to have a beneficial effect on viscosity and the stability of the solution after cooling and the feasibility of the Separation. However, the higher the temperature or the longer the residence time at this Temperature, the greater the tendency for the starch to degrade, i.e. H. to a decrease in molecular weight. The starch solution must be at least like this be kept at a temperature of 121 to about 1770 C for a long time until the entire Starch has been converted evenly. When the temperature increases or else the time is extended at a temperature above 1210 C, the Time or temperature factor can be reduced. When the suspension is on 121 to 1770 C has been heated in less than 5 minutes, the mass is at this temperature hold for another 30 minutes. The best results have been obtained when the mixture of starch and water is at temperatures between about 138 and 16QO C heated practically immediately and after an uninterrupted process and this temperature Has been held for 0.5 to 15 minutes. Temperatures of 1770 C should be avoided because the starch is then degraded too quickly, but this temperature limit can vary by about 6 to 110 C depending on the type of starch used.

The solution is preferably very quickly to the boiling point cooled at normal pressure by quickly bringing the solution to normal pressure in the device according to US Pat. No. 3,110,284 is relaxed or by being quenched. if the solutions can also be slowly cooled to the boiling point at normal pressure, such an embodiment is preferably not used, so that a degradation or hydrolysis of the starch is avoided as far as possible. When it cools down quickly the boiling point of the solution will get an amylose with a higher molecular weight, so this embodiment is preferred.

The type of further cooling is essential.

According to the invention it has been found that in order to stabilize the Dissolution and formation of the amylose particles the solution for a time between a Temperature of 490 C and the boiling point under normal pressure must be kept preferably the solution is slowly cooled between these temperatures.

The two basic types of strength, namely the root or knot strength and the corn starch, behave quite well at this stage of the process different. The root starches, like tapioca and potato starch, thicken not as light as the corn starches. The latter, like corn, rice and wheat starch, tend to retrogradation very quickly. If in the proposed according to the invention Method using tapioca or potato starch is done even then only a slight thickening when the solution rapidly moves from its boiling point to room temperature, z. B. is cooled within 1.5 hours.

If, on the other hand, corn, rice or wheat starch with the same Speed or even a little more slowly cooled to the same temperature the solution is always thickened and separation is made impossible. Even though the solutions of root starches are not solidified during rapid cooling, the amylose particles do not grow to a size that allows separation.

These particles pass in a rapidly cooled solution of Root thickness does not average about 5 microns in diameter, but if so the solutions of root starches according to the method proposed according to the invention be cooled in such a way as required to when using corn starches To avoid solidification then the required amount of time is the root starch amylose particles need to grow to a detachable size, roughly equal to the length of time which is needed to grow the starch amylose particles.

It has also been found that a corn starch suspension from the boiling point at normal pressure to a temperature below 490 C in less than 8 hours can not be cooled if a thickening is avoided target.

However, it is preferred for the purpose of further increase the Particle size of the amylose fraction used a longer period of time. In order to be more effective Separation of the amylose particles should be at least 50 percent by weight Have diameters greater than 20 microns; this is stated in the above least time achieved if cornstarch is used and the solution is slow is cooled to a temperature of 490 C. It should be noted that after the slow Cooling to 490 C can form other particles and that these even when Cool down to a temperature below 490 C and continue to grow.

After slow cooling to a temperature between the boiling point and above about 490 C the solution must then be held for a period of time until Stabilization of the solution and formation of the amylose particles is required. the end unknown reasons, however, is the speed with which this is maintained at a constant rate Temperature takes place, much lower than when slowly cooling the solution within the specified temperature range. In addition, these particles are smaller and more difficult to separate.

The time it takes to stabilize a quickly to 400 C cooled solution is required is very different; the time is shorter if the temperature is higher, at a temperature of 490 C the required Cornstarch time can exceed 48 hours. A large proportion of the amylose particles on the other hand, does not seem to grow as quickly at a higher temperature than at a lower temperature, with a much greater risk of hydrolyzing the starch is at a high temperature. For these various reasons the solution is between the boiling point at normal pressure and the critical temperature preferably slowly, at least in 8 hours, cooled at 490 C.

After the solution has been stabilized, it can optionally be cooled further.

The size of the amylose particles after the same amount of time obtained by this method is not the same for all starches. In order to achieve of the desired particle size, namely 50 percent by weight of the particles with a Diameter above 20 microns, is often a longer time than the smallest 8 hours time required. According to the invention, a particle size distribution can be easily achieved, e.g. B. Average diameter between 25 and 30 Microns, with less than 20 weight percent less than 20 microns in diameter. Under the best of conditions, corn amylose particles with a diameter in the On the order of 70 to 80 microns and above have been obtained.

During the cooling step, the solution should be stirred as much as possible kept weak as excessive stirring will result in the formation of a rigid gel or lead to the production of small, difficult to separate particles, or both can. After the temperature has been lowered to a value below the boiling point the solution can be mixed with amylose, for example by adding an aqueous suspension of Amylose to be vaccinated.

When heated, the concentration of starch in water can be so great be that they are still handled advantageously in the device used can. If you work economically, you should the concentration less than be about 2.5 weight percent starch dry matter. During the cool down period between the boiling point at normal pressure and around 490 C the concentration is more important. After cooling the solution to the boiling point at normal pressure, the viscosity should of the solution, which in this process depends to a considerable extent on the content depends on the type of starch used, to a value below 1500 cP are kept. The viscosity of such starch solutions is not only influenced by the content of the type of starch used, but also of the pretreatment of the heating rate and the final temperature and the like. It has found that z. B. the practical upper limit during this stage of the process for commercially available native corn starch at around 15 percent dry starch substance lies. However, the heating step can be carried out at a high concentration whereupon the solution after cooling to a temperature below the boiling point at normal pressure with water to achieve a viscosity below 1500 cP can be diluted.

Because of the viscosity of the solution when it cools down, the growth rate the amylose particle is affected, the viscosity preferably becomes so low kept as possible. That in addition to maintaining a low viscosity required water must later, however, from both the amylose and from the Amylopectin fraction are removed, drying the amylopectin fraction is relatively expensive. To compensate for this, the optimal range is therefore between about 7 and 13 percent by weight starch dry matter. A small amount e.g. B. one A protective agent, such as 0.05 g phenyl mercury acetate per liter, can add to the starch solutions be added.

The solid amylose-rich phase can be separated by any method using a high-speed centrifuge. When there is sufficient particle growth has been achieved, a gravity separator can be used which z. B. works like a "Dorr" thickener.

After separation, the moist amylose cake is washed. this can by slurrying the cake in a relatively small amount of water and separating the solid components from the washing water by centrifugation.

The cake obtained is then e.g. B. by spray drying, roller drying, Dry in vacuo or other methods to quickly remove water dried. When the moist amylose is slowly dried in the air, it becomes hard and horn-like and is relatively difficult to grind. However, it can Can be air-dried relatively slowly if the properties of the dried amylose particles are of little concern. The amylopectin fraction can be dried using the same methods.

The solid fraction can be separated off at room temperature (approx 300 C) can be done satisfactorily at viscosities between 400 and 600 cP, although such separations with a high-speed centrifuge even with viscosities of about 1500 cP can be done. However, since the viscosity increases with increasing temperature becomes lower and the Viscosity properties of the solution according to the Proposed processes have been stabilized, the separation of the solid Fraction can be eased if the solution is centrifuged while hot.

The viscosity values given here are Ir. With a Brockfield viscometer was measured at a spindle speed of 20 revolutions per minute. the Spindle # 1 is for viscosities up to 500 cP and spindle # 2 is for viscosities used above 500 cP.

After a very simple experiment it can be determined whether the inventive Solution is stable and whether the amylose can be separated on it. A sample the solution is quickly stirred in an ice bath to a temperature of 300 C or any other temperature near room temperature. The viscosity is then measured immediately with the Brockfield viscometer. The solution is doing this kept at a constant temperature, taking measurements for a time be repeated at regular intervals for at least 5 hours. If the solution is stable, practically no increase in viscosity is found during the measurement can be. If it is not consistent, the measurements will be sudden and sharp increases and a further increase in viscosity can be observed. If the solution is inconsistent there will usually be at least a 250% increase viscosity within 5 hours and usually within 2 hours. If, According to this attempt, the solution is fickle, is a separation of the amylose fraction not possible in a satisfactory purity and yield. For corn starches can be determined by this experiment, the shortest period of time during which the solution was kept between a temperature of about 490 C and the boiling point must become.

With root strengths where the resistance to solution is not that great Difficulty, the shortest period of time is better determined according to the extent in which the particles grow. In order to achieve an effective separation, this should be Particle growth must be such that at least 50 weight percent greater than 20 microns are.

The separated amylose can be cast from the solution as a film, which is particularly useful for packaging foodstuffs and as sausage casings, since amylose can be digested by humans. Amylose, which is similar to cellulose is, and likewise many of its derivatives are thermoplastic. Amylose and Their derivatives, like the acetates, are therefore used in the manufacture of fibers and shaped Cellulosic type products useful. The amylopectin fraction can be used in the same way as the starch obtained from the waxy Corn species is obtained from maize. Amylopectin is used to make adhesives used for printing and finishing fabrics, for thickening and stabilizing of pie fillings, salads and canned foods.

The results obtained by the method of the invention are especially exceptional when using starch from ordinary corn. from all types of starch are particularly prone to Cornstarch to a convert back on cooling after heating in water to a temperature at or above the paste formation temperature. When a solution of corn starch in water according to the proposed method up a temperature above 490 C is held for at least 8 hours, the Retrogradation avoided. This is particularly advantageous because strength predominates is made from corn.

1 shows a flow diagram of the method according to the invention. 10 means an open mixing tank with a stirrer 12, in which water and granular Starch can be mixed to create a suspension. The tank is of more common use Design and has a conical lower part with an outlet line 14 at the tip of the cone and an outlet valve 15 for regulating the flow rate. The line 14 is connected to the inlet of a pump 16 for delivery through the slurry feed line 18 serves. The conduit 18 is provided with a heater 20 according to the United States patent 3 101 284 connected for the slurry.

This consists of a steam nozzle 22, which is on a pressure vessel 26, which is referred to as the holding tank, is attached. The steam nozzle 22 is connected to a steam line 24 and the pump delivery line 18. In the The starch slurry enters the nozzle under pressure in the axial direction, during the Water vapor enters the throat of the nozzle from nozzles attached to the circumference, allowing thorough and rapid heating of the starch slurry to a temperature takes place, which is easily regulated by the water vapor pressure and the flow rate will. The steam nozzle 2Z conveys directly into the holding tank 26. The holding tank is provided with a discharge line 28 with a pressure regulating valve 30, whereby the pressure can be regulated in the holding tank.

More water vapor can enter the empty space above the Liquid can be brought into the holding tank to compensate for heat losses.

At the lower part of the holding tank 26 is an outlet line 32 for the starch paste attached, the line 32 with a valve 33 for regulating the residence time is equipped in the holding tank. The outlet line 32 is provided with a separation vessel 34 connected, which can simply be a tank under normal pressure. The separation vessel has a jacket 36, through the heating or cooling liquids with the help of the lines 38 and 40 can be pumped around and therefore the cooling rate of the starch solution can be regulated.

The vessel 34 has an outlet line 42 at the bottom, which is connected to the inlet port a centrifuge 44 is connected. A pump can be switched into the line 42 be, or the device can be arranged so that the liquid flows by gravity. In the centrifuge, an aqueous, amylopectin-rich Solution and a moist, firm, amylose-rich cake is produced. The amylopectin solution is through line 46 to a spray dryer 48 for the purpose of producing a dry amylopectin-enriched product. In this drying device the liquid is sprayed into an ascending stream of hot air so that the spray-dried Product after falls down as it dries, but also others Types of drying devices that can be used in starch production are common. In order to reduce the load on the dryer, the Amylopectin solution concentrated in a conventional evaporator before drying will.

The moist cake obtained by centrifugation is then washed. The device used for washing consists of a simple mixing tank 52 with a stirrer 54 and a water inlet 56. The tank shown in the drawing 52 is connected to the centrifuge 44 by a line 50.

The method of conveying the moist, firm cake to the washing device however, it is determined by the need for solids content. In some In some cases it can be useful to wash the solid substances out of the centrifuge or to operate the centrifuge in such a way that a pumpable solid phase is obtained will. In each embodiment, the solid phase in tank 52 is mixed with water and then partially dewatered in a second centrifuge 60. The mixed drink 52 is through line 58 to the feed inlet of a second centrifuge tied together.

The centrifuge 60 is connected to the mixing tank 10 by the line 62, so that the wash water to avoid loss of amylose fine particles or can be returned from amylopectin in the wash water. The wet one Solid cake from the centrifuge 60 is then dried using the centrifuge through a line 64 is connected to the drying device 66. For conveying the centrifuge cake again, any suitable method can be used to the drying apparatus. The drying device can consist of a spray dryer or another embodiment from a series of tanks and filters and finally from a suitable dryer consist in which the amylose is dehydrated or treated with methanol (or another organic solvent) to displace the water will. In the last-mentioned embodiment, the organic solvent is removed using standard and simpler drying methods. The organic solvent can be recovered for further use by known methods.

In the following examples, the invention is proposed according to Process explained without being affected by the details and embodiments given there the scope of the invention is to be limited. The examples are only commercially available Varieties of starch have been used.

In the examples, the "blue value" of the separated fractions is given been. The "blue value" is an analytical determination, a distinction between amylose and amylopectin. Amylose has a high blue value, whereby Commercially available corn amylose has a blue value of 0.7 or less. Values of even 1.34 have been given for high molecular weight potato amylose.

A blue value of 0.37 has been given for defatted corn starch.

Amylopectin has a blue value of 0.20 or less. The blue value amylose becomes habitual Lich determined by their molecular weight, this value becomes smaller with decreasing molecular weight, although not necessarily directly Relationship. With corn starch and its fractions, the blue value becomes when degreasing increased by about 10 or 15 per cent. The blue values given in the following description were determined as follows: a sample of 0.1 g strength (weighed to the nearest 0.1 mg) is placed in a 100 cc flask. This sample is mixed with 1 cc of ethanol, 10 cc water and 2 cc 100 / above sodium hydroxide mixed. The sample will then Heated until a clear solution, cooled and diluted with water to a volume of 100 ccm filled up. 5 cc of this solution are then transferred to a 500 cc flask brought into which 100 cc of water and finally 3 drops of 6N hydrochloric acid are added will. After mixing by shaking, 5 cc iodine solution (0.2eo iodine and 2 0 / o potassium iodide) is added, whereupon it is made up to 500 ccm. The optical density this solution is then measured at a wavelength of 680 mF in a Beckman spectrophotometer determined in a 2 cm cell in comparison to a blank sample, which in the same way, however, was made without the carbohydrate. When multiplying the measured optical density by 0.2 and dividing by the weight of the sample then becomes the Preserved blue value.

In another embodiment, the sample is not in a sithanol-sodium hydroxide mixture dissolved, but is dissolved in 5 ccm of 1N sodium hydroxide solution without heating.

Since the blue value depends on both the molecular weight of the amylose and is determined by the amylose content and also by the fatty acid content of the starch, is in some cases the intrinsic viscosity of the separated fractions as a measure of the molecular weight has been determined. These measurements were made as with K er r is shown on p. 675, at a temperature of 350 C in a 1N sodium hydroxide solution as a solvent. With a certain solvent-polymer system, the Structural viscosity decreases with decreasing molecular weight.

Example 1 A suspension of granular, native corn starch in water with a density of 5.60 Be and a pH of 6.5 was obtained by heating in a The device described in U.S. Patent 3,110,284 into a flowable Solution converted. The sample was held in the holding tank for 6 minutes. Of the Water vapor pressure in the nozzle mixer was 5.4 kg / qcm, with the starch suspension was introduced into the nozzle mixer under a pressure of 6.65 kglqcm. In the holding tank, the water vapor pressure was kept at a value of 3 9 kg / qcm, while the measured temperature in the tank was 1470 ° C.

When the starch solution was removed from the holding tank, it had that Appearance of a clear solution.

When the pressure was released to normal pressure, the temperature of the sample was noticeable a value below the boiling point of water (around 980 C). The one with a Brockfield viscometer the measured viscosity had a value of 102 cP at a temperature of 97.80 C, while a sample measured at 96.70 C a viscosity value of 105 cP. The pH of the solution was 6.7.

The sample was cooled at various speeds divided into three parts. The speeds are shown in FIG. 2 shown graphically. In order to achieve the different cooling rates, the proportions were this sample was allowed to cool in three differently insulated containers. As a container were made of a stainless steel cup with no insulation, one with a fibrous one Insulation of an insulated camping container or a Dewar vessel used.

The cooling rates obtained through the release of heat to the surrounding air have been indicated in Fig. 2 with 1, 2 and 3, respectively. From this representation it can be inferred that the solution cooled at speed 1 in a little more than 4 hours assumed a temperature below 490 C. At the speeds 2 and 3 this temperature was reached in 11 and 32 hours, respectively. It was found that the solution cooled after the first cooling curve formed a rigid gel, while the other two samples, cooled according to curves 2 and 3, persisted stayed. In each experiment, the solution turned into a solid, particulate Phase deposited, which was then removed from the solution by centrifugation. The rigid gel (made in the stainless steel beaker) had to be made by means of a high-speed mixer in water to be crushed before the solid substance could be won. The solid substance obtained in each experiment was under vigorous stirring dispersed in water and centrifuged again, whereupon this Wash cycle was repeated.

The washed solid phase was then dehydrated by dissolving it in methanol stirred and then washed twice in methanol and twice in acetone. the The dehydrated solid matter was finally made thorough by heating at 1100 ° C dried. The product was a white powder.

The blue values given in Table 1 were then determined. Despite the thorough washing contained the solid matter separated from the rigid gel (Cooling speed 1) a large amount of amylopectin.

Table 1 Cool down | Amylose fraction amylopectin fraction speed blue value blue value 2 1,000 * 0.122 ** 3 0.896 0.320 Structural viscosity -1.45.

Intrinsic viscosity - 1.47.

Example 2 The procedure described in Example 1 was repeated, only the solution was at a temperature of 148.30 C for 12 minutes in the holding tank held. According to the cooling curve 1 in FIG. 2 cooled solution formed again a rigid gel, while the other solutions remained stable.

The results obtained are shown in Table 2. The viscosity the solution was 80 cP a temperature of 97.80 C, with a second sample had a value of 90 cP at a temperature of 96.70 ° C. The pH of the solution was 6.7.

Table 2 Cooling amylose fraction amylopectin speed blue value fraction Blue value 2 1.020 * 0.140 X e 3 0.944 0.314 Intrinsic viscosity - 1.46, ** intrinsic viscosity -1.48.

In Examples 1 and 2, after the Temperature had only fallen to 60.00 C, samples removed. If the solutions like it preferably happens to be further cooled to 48.90 C, the results are about the same or slightly better than when it cooled down after speed 2 will.

Example 3 The procedure described in Example 1 was followed in all essential details repeated, with the proviso, however, that the time in the tank 9 minutes and the native corn starch replaced by native starch from other sources was replaced. The cooling rate corresponded to that in FIG. 2 cooling curve shown 2. The results obtained are shown in Table 3. The stated yield is based on the weight of the starch used and not on the amylose content of the native Starch related. The solution ultimately obtained was stable in every attempt.

Table 3 Solution yield blue value blue value viscosity amylose- that of the arny- Starch cP with fraction amylose- lopectin- 96.70 CO / o fraction fraction Potato .. 157 18.5 1.38 0.111 Tapioca. . . 87 16.3 1.38 0.026 Sago ..... 82 27.7 1.13 0.056 Rice ...... 103 20.0 1.13 0.117 Wheat . . . . 119 32.2 * 1.05 Arrowroot 162 17.2 1.20 - This value is significantly higher than the stated amylose content of wheat starch; nevertheless, the blue value indicates that the amylose fraction has a high purity.

Example 4 A mixture of native granular corn starch and potato starch in a ratio of 3: 1 was according to the method described in Example 1 in water heated and held for 8.5 minutes at the temperature specified there. The slurry had a pH of 6.0. When cooling after the in F i g. 2 given cooling curve a stable solution was obtained from which 21.8 g of amylose per 100 g of starch were separated became. The amylose had a blue value above 1.1.

Similar results were obtained with mixtures Corn- and potato starch in the ratio of 1: 1, 7: 1 and 1: 9.

Although in all of the examples given above the heating with With the help of a steam nozzle, the heating stage can also be used after a other procedures can be carried out. The following examples show the results which were obtained on heating in a different way.

Example 5 A granular native corn starch slurry with a starch content of about 9.5 o was constant at room temperature with Speed is pumped through a coiled pipe, which is always heated to 148.90 C Immersed heating bath.

The pumping speed was such that the strength and the water remained in the bath for 2 minutes. The one formed under these conditions Solution was placed under normal pressure in an insulated container in which the Solution with a slightly slower cooling rate than that of curve 2 could be cooled in Fig.2. After cooling to a temperature below the solution was stable at 490 ° C., from which 27.7 g of amylose with a blue value were then obtained of 0.96 per 100 g of the starch charge could be obtained.

This procedure was repeated with gradually increasing temperatures. Above about 1770 C the starch degradation was so rapid that it diminished specific viscosity of starch - a measure of the molecular weight of starch - has been reduced to almost 60e / o.

Example 6 200 g of corn starch were suspended in 21 water. The mixture was 45 minutes using a steam bath and submerged heater heated with stirring. The temperature was 96.10 C, although on the surface of the Immersion heater low boiling occurred.

About 1.5 liters of the clear starch paste formed were placed in an autoclave poured, whereupon the autoclave was closed and electrically heated. After about half an hour the temperature had risen to about 152.20 C; then left to cool down.

After another 65 minutes after the temperature has reached about the boiling point had fallen at normal pressure, the autoclave was opened. A portion of the starch solution was then poured into a tightly capped Dewar flask to cool.

The solution reached and stayed at room temperature after about 2 days resistant. On microscopic examination of the solution, it was found that large high amylose particles were present.

A substantial proportion of these amylose particles had a diameter from about 50 to 75 microns. Daw high amylose material could be obtained by centrifugation easily separated from the amylopectin-rich liquid phase.

Another portion of the solution treated in the autoclave was added cooled in a non-insulated beaker, the solution within 24 Solidified for hours into a very rigid, opaque gel. In this stare Gel became some Particles observed, however, only have a diameter of about 5 microns, i.e. H. much smaller than the average size of cornstarch granules was. This is for the particles formed upon retrogradation of the starch paste significant.

Example 7 As example 1, but with a time in the tank of 10 minutes, a large volume of corn starch solution was made while cooling the amylose fraction was carefully separated from the boiling point. The cooling rate was dimensioned to allow about 36 hours to reach a temperature of 490 C were needed. Small samples were taken as the solution cooled. Each sample was centrifuged under the same conditions, whereupon the ratio the volume of the solid cake was determined to the volume of the liquid. Approximately a third of the amylose-rich solids had turned up in the first 10 hours (at about 690 C) deposited. When a temperature of 490 C was reached a sudden and sharp increase in the amylose-rich solid phase until more than 25 / o of the starch solids deposited as amylose.

Example 8 A corn starch solution was made according to that described in Example 1 Process made and then divided into 7 parts. Six parts that covered each other Containers were then immediately placed in separate ovens, one on top of the other constant temperature of 70.0, 60.0, 55, 49.4, 47.2 or

37.80 C. The other portion was on its own at room temperature let cool down.

When left to stand overnight, they were at 47.2, 37.80 C and the samples cooled to room temperature solidified. When left to stand overnight of the sample kept at 700 ° C. and after leaving all other samples to stand for 48 hours contained these amylose particles which are easily separated by centrifugation could. The thickened samples did not contain separable amylose particles Size.

In the above description, the temperatures given are approximate Values. It should also be noted that the beginning and the completion of the separation the fixed faction are difficult to observe.

Claims (9)

Claims: 1. Process for fractionating starch, such as corn starch, characterized in that a flowable solution of starch in water by heating to a temperature of about 121 to about 1770 C, this solution to a Cooled temperature below the boiling point at normal pressure and above 490 C. the concentration of the dry starch substance in this cooled solution is greater than about 2.5 weight percent, the solution is within the temperature range between about 490 C and the boiling point at normal pressure for one to stabilize the solution and to separate and form an amylose-rich fixed fraction is held for a sufficient period of time and this fraction from the stable solution is separated. 2. The method according to claim 1, characterized in that this solution is kept in this temperature range for more than 8 hours. 3. The method according to claim 1 or 2, characterized in that the concentration of dry starch in this cooled solution is lower than the concentration at which the cooled solution has a viscosity greater than than 1500 cP. 4. The method according to claims 1 to 3 or one of these claims, characterized in that from the separated amylopectin-containing solution an amylopectin-rich solid fraction is produced by removing the water. 5. The method according to claim 1, characterized in that the solution first cooled to the boiling point at normal pressure and then from this temperature slowly to one Temperature of about 490 C cooled at such rate becomes that this temperature will only be reached in more than 8 hours. 6. The method according to claims 1 to 5 or one of these claims, characterized in that the flowable solution is initially at a temperature is heated between about 138 and 1600 C. 7. The method according to claims 1 to 5 or one of these claims, characterized in that the solution is initially at a temperature between about 121 and 1770 C for a time of about 30 minutes. 8. The method according to claim 7, characterized in that the flowable Solution at the beginning under positive pressure with steam to a temperature between approx 121 and 1770 C is heated quickly. 9. The method according to claims 1 to 8 or one of these claims, characterized in that the amylose-rich solid fraction is separated after at least 50 percent by weight of the particles are larger than 20 microns.