Method for producing allulose crystals

Abstract

To provide a method for producing allulose crystals.SOLUTION: This method comprises the steps: cooling and agitating a first admixture composed of a first portion of allulose syrup and allulose seed crystals; and initiating crystallization of allulose dissolved in the allulose syrup, thereby forming a first massecuite comprising allulose crystals and a first mother liquor containing residual dissolved allulose, the cooling and agitating being continued until a first preselected target yield of allulose crystals is achieved.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 414,280, filed on October 28, 2016, the entire disclosure of which is incorporated herein by reference for all purposes.

[0003] Field of the Technology

[0004] The present invention relates to the production of allulose crystals from allulose - containing syrup.

Background Art

[0005] Consideration of the Prior Art

[0006] Many food and beverage products contain nutritive sweeteners such as sucrose (commonly referred to as "sugar" or "table sugar"), glucose, fructose, corn syrup, high - fructose corn syrup, etc. Although favorable in terms of taste and functional properties, the excessive intake of nutritive sweeteners such as sucrose has long been associated with an increase in diet - related health problems such as obesity, heart disease, metabolic disorders, and dental problems. Due to such concerning trends, consumers have adopted a healthier lifestyle and there has been an increased awareness of the importance of reducing the level of nutritive sweeteners in their diet.

[0007] In recent years, particular focus has been placed on the development of low - calorie or zero - calorie sweeteners, and the development of nutritive sweetener substitutes has been progressing. One proposed substitute for nutritive sweeteners is allulose (also known as D - psicose). Allulose is known as a "rare sugar" because it occurs naturally in extremely small amounts. Allulose is about 70% as sweet as sucrose but provides only about 5% of sucrose calories (about 0.2 kcal / g). Thus, allulose can be considered essentially a "zero - calorie" sweetener.

[0008] Given its scarcity in nature, the production of allulose relies on the epimerization of readily available fructose. Ketohexose-3-epimerase can interconvert fructose and allulose, and various ketohexose-3-epimerases for such conversions are known. Such epimerization reactions are typically carried out initially using an aqueous medium in which fructose is dissolved, and the allulose-containing product obtained as a result of the epimerization is in the form of an aqueous allulose solution. Further processing and purification of the reaction product can be carried out according to known procedures, thereby producing an allulose syrup containing allulose with a fairly high concentration and purity. Such an allulose syrup can be used in many consumer products, including food and beverages, as an alternative to conventional "sugary" syrups such as glucose syrup and high fructose corn syrup.

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, in other applications, it is preferable to utilize "dry", free-flowing, crystalline allulose, i.e., allulose in a form generally similar to that of table sugar. Although several attempts have been reported to develop methods for producing crystalline allulose (see, for example, U.S. Patent No. 8,524,888 and WO2016 / 064087), allulose is generally recognized as a sugar that is difficult to crystallize in an efficient manner such that crystals of appropriate shape and size can be reliably obtained in high yield. Thus, improving the crystallization method of allulose remains a significant concern.

Means for Solving the Problems

[0010] Various aspects of the present invention can be summarized as follows: Aspect 1: A method for producing allulose crystals, the method comprising the following steps: a) Cooling and stirring a first mixture consisting of a first portion of allulose syrup and allulose seed crystals to initiate crystallization of allulose dissolved in the allulose syrup, thereby forming a first massecuite containing allulose crystals and a first mother liquor containing the remaining dissolved allulose, wherein the cooling and stirring continue until the allulose crystals achieve a preselected first target yield; b) Optionally, separating the first massecuite into a first portion (which can perform further processing steps such as separating the allulose crystals from the mother liquor portion and washing and / or drying the separated allulose crystals) and a second portion; c) Optionally, combining a second portion of allulose syrup and the second portion of the first massecuite to form a second mixture; and d) Optionally, cooling and stirring the second mixture to initiate crystallization of allulose dissolved in the second portion of the allulose syrup, thereby forming a second massecuite containing allulose crystals and a second mother liquor containing the remaining dissolved allulose, wherein the cooling and stirring continue until the allulose crystals achieve a preselected second target yield.

[0011] In various embodiments of aspect 1, at least steps a) and b) are performed, at least steps a) - c) are performed, or at least steps a) - d) are performed.

[0012] Aspect 2: The method according to aspect 1, wherein the first mixture is obtained by combining a first portion of the allulose syrup and dry allulose crystals.

[0013] Aspect 3: The method according to aspect 1, wherein the first mixture is obtained by combining a first portion of the allulose syrup and a heel consisting of allulose crystals and mother liquor.

[0014] Aspect 4: When the above-mentioned first mixture and second mixture are used in step d), in steps a) and d), the method according to any one of Aspects 1 to 3, wherein a stirrer having a tip speed of 0.02 to 2 m / sec is used for stirring.

[0015] Aspect 5: The method according to any one of Aspects 1 to 4, wherein step a) further includes a step of blending at least one further portion of the allulose syrup with the above-mentioned first mixture after the start of crystallization of allulose dissolved in the above-mentioned allulose syrup.

[0016] Aspect 6: The method according to any one of Aspects 1 to 5, wherein the cooling in step a) includes a step of reducing the temperature of the above-mentioned first mixture from within an initial temperature range to within a second temperature range and a step of maintaining the temperature of the above-mentioned first mixture within the second temperature for a certain period of time.

[0017] Aspect 7: The method according to any one of Aspects 1 to 6, wherein step d) is carried out, and the cooling in step d) includes a step of reducing the temperature of the above-mentioned second mixture from within an initial temperature range to within a second temperature range and a step of maintaining the temperature of the above-mentioned second mixture within the second temperature range for a certain period of time.

[0018] Aspect 8: The method according to any one of Aspects 1 to 7, wherein the above-mentioned allulose syrup has a dry solid content of 70 wt% to 95 wt%, 75 wt% to 90 wt%, or 80 wt% to 85 wt%.

[0019] Aspect 9: The method according to any one of Aspects 2 to 8, wherein the above-mentioned allulose syrup has an allulose purity of at least 70%, at least 75%, at least 80%, at least 85%, or at least 90%.

[0020] Aspect 10: The method according to any one of aspects 1 to 9, further comprising the step of separating allulose crystals from the first mother liquor in the first part below the first white.

[0021] Aspect 11: The method according to aspect 10, wherein the separation is at least partially carried out by one or more physical separation methods selected from the group consisting of centrifugation, filtration, decantation, membrane separation, and combinations thereof.

[0022] Aspect 12: The method according to aspect 10 or 11, wherein the allulose crystals separated from the first mother liquor are washed at least once in i) water, an organic solvent, a blend of organic solvents, a blend of water and organic solvent(s), or an aqueous solution comprising at least one carbohydrate (e.g., allulose); ii) dried; or a combination thereof.

[0023] Aspect 13: The method according to any one of aspects 1 to 12, wherein steps b) to d) are carried out and repeated at least once.

[0024] Aspect 14: A method for producing allulose crystals, the method comprising the following steps: a). i) A feed syrup containing water and dissolved allulose, and ii) a recycled white mass containing allulose crystals and a recycled white mass mother liquor containing dissolved allulose, to form a feed syrup / recycled white mass mixture (wherein the feed syrup / recycled white mass mixture is cooled within a first crystallization temperature range), passing the feed syrup / recycled white mass mixture through a first step crystallization region, wherein the feed syrup / recycled white mass mixture is agitated, the feed syrup / recycled white mass mixture is maintained within the first crystallization temperature range, and crystallization of the allulose dissolved in the feed syrup and the recycled white mass mother liquor is initiated, thereby forming a first white mass containing allulose crystals and a first mother liquor containing dissolved residual allulose, and discharging the first white mass that has reached a preselected first target yield from the first step crystallization region; b). Optionally, cooling the first white mass discharged from the first step crystallization region within a second crystallization temperature range and transferring the first white mass to a second step crystallization region; c). Optionally, passing the first white mass through the second step crystallization region, wherein the first white mass is agitated, the first white mass is maintained within the second crystallization temperature range, and crystallization of the allulose dissolved in the first mother liquor is initiated, thereby forming a second white mass containing allulose crystals and a second mother liquor containing dissolved residual allulose, and discharging the second white mass that has achieved a preselected second target yield from the second step crystallization region; and d). Optionally, repeating steps b and c at least once to obtain a final white mass and a final mother liquor containing allulose crystals.

[0025] In various embodiments of aspect 14, at least steps a) and b) are performed, at least steps a) - c) are performed, or at least steps a) - d) are performed.

[0026] Aspect 15: The method according to aspect 14, wherein steps a) to d) are carried out and further comprising a step of separating the allulose crystals and the final mother liquor within at least a part of the final white liquor.

[0027] Aspect 16: The method according to aspect 14 or 15, wherein steps a) to d) are carried out and a part of the final white liquor is used as the recycled white liquor.

[0028] Aspect 17: The method according to any one of aspects 14 to 16, obtained by mixing the feed syrup / recycled white liquor mixture in a mixing vessel with the feed syrup and the recycled white liquor containing the recycled white liquor composed of allulose crystals and dissolved allulose and the recycled white liquor mother liquor, and transferring the feed syrup / recycled white liquor mixture from the mixing vessel to the first step crystallization region.

[0029] Aspect 18: The method according to any one of aspects 14 to 17, wherein when step c) is carried out, the first mixture and the second mixture are stirred using a stirrer having a tip speed of 0.02 to 2 m / sec in steps a) and c) respectively.

[0030] Aspect 19: The method according to any one of aspects 14 to 18, wherein the allulose syrup has a dry solid content of 70 wt% to 95 wt%, 75 wt% to 90 wt%, or 80 wt% to 85 wt%.

[0031] Aspect 20: The method according to any one of aspects 14 to 19, wherein the allulose syrup has an allulose purity of at least 70%, at least 75%, at least 80%, at least 85%, or at least 90%.

[0032] Aspect 21: The method according to embodiment 15, wherein said separation is carried out at least in part by one or more physical separation methods selected from the group consisting of centrifugation, filtration, decantation, membrane separation and combinations thereof.

[0033] Embodiment 22: The method according to embodiment 15 or 21, wherein the allulose crystals separated from the final mother liquor are washed at least once in: i) water, an organic solvent, a blend of organic solvents, a blend of water and organic solvent(s) or an aqueous solution comprising at least one carbohydrate (e.g., allulose); ii) dried; or a combination thereof.

[0034] Embodiment 23: The method according to any one of embodiments 14 - 22, wherein the feed syrup / recycled white underflow mixture passes through the first step crystallization zone in a plug flow mode and / or, when performing steps b) and c), the first white underflow passes through the second step crystallization zone in a plug flow mode.

[0035] Embodiment 24: The method according to any one of embodiments 1 - 23, wherein the method is carried out continuously.

[0036] Embodiment 25: Allulose crystals obtained by the method according to any one of embodiments 1 - 24.

[0037] Embodiment 26: A consumer product comprising or manufactured using allulose crystals according to embodiment 25 and at least one further component other than allulose crystals.

[0038] Embodiment 27: A method for manufacturing a consumer product, comprising the step of using allulose crystals according to embodiment 25.

[0039] Embodiment 28: The mother liquor obtained by the method according to any one of embodiments 1 - 24.

[0040] Aspect 29: The mother liquor according to aspect 28, which is suitable for use as a product consumable by humans or animals or as a component in a dosage form of a product consumable by humans or animals.

Brief Description of the Drawings

[0041]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0042] Detailed description of specific embodiments of the present invention

[0043] Allulose syrup

[0044] The present invention utilizes at least one allulose syrup as a starting material for the crystallization process, where the allulose present in dissolved form in the syrup is converted to a crystalline form. Methods for obtaining allulose syrup are well known in the art and are described, for example, in the following patent documents, the disclosures of each of which are incorporated herein by reference in their entirety for all purposes: WO 2016 / 135458; US 2015 / 0210996; US 5,411,880; US 8,735,106; and US 8,030,035.

[0045] For example, allulose syrup can be produced by a process comprising contacting an aqueous fructose solution with an allulose (D-psicose) epimerase enzyme under conditions effective to convert at least a portion of the fructose to allulose, purifying the obtained reaction product, and then concentrating the purified reaction product to a desired dry solid content. The purification step can include one or more techniques such as deproteination, decolorization (treatment with decolorizing agent(s)), decontamination, ion exchange chromatography (using one or more ion exchange resins such as anion exchange resin, cation exchange resin, etc.), column chromatography, fractionation, etc. to remove impurities from the reaction product.

[0046] As described in more detail below, the allulose syrup should have a dry solid content that is sufficiently effective to crystallize allulose when the syrup is cooled in the presence of seed crystals. For example, in various embodiments, the dry solid content of the allulose syrup can be at least 50 wt%, at least 55 wt%, at least 60 wt%, at least 65 wt%, at least 70 wt%, at least 75 wt% or at least 80 wt%. However, it will generally be preferred that the dry solid content of the allulose is sufficiently low such that the syrup exists as a free-flowing solution without seed crystals at the temperature at which the syrup is held before crystallization is initiated by the introduction of seed crystals. Thus, in various embodiments of the present invention, the allulose syrup has a dry solid content not exceeding 90% or not exceeding 85%. The desired dry solid content can be achieved by the evaporation or concentration process of a dilute solution of allulose, in which volatile components (e.g., water) are removed from the solution and only the more concentrated syrup remains. The evaporation / concentration conditions can advantageously be selected such that the degree to which allulose is denatured is initiated or reduced; for example, a relatively low evaporation temperature can be employed.

[0047] The purity of allulose syrup can vary, but it would typically be preferred that allulose makes up the majority (by weight) of the non-volatile substances present in the allulose syrup. Thus, the allulose purity of the syrup can be at least 60 wt%, at least 65 wt%, at least 70 wt%, at least 75 wt%, at least 80 wt%, at least 85 wt% or at least 90 wt% in various embodiments of the present invention. The term "allulose purity" as used herein with respect to allulose syrup means the weight percentage of allulose in the syrup based on the total weight of the dry solids in the syrup.

[0048] Seed crystals of allulose

[0049] The present invention employs seed crystals of allulose (e.g., in the form of allulose-containing solid crystals that were previously present in solution in allulose syrup, mother liquor, or the like) to assist in promoting the initiation of further crystallization of allulose from a solution. In certain embodiments, the allulose seed crystals are present in dry form (e.g., dry crystals of allulose recovered from a previously performed crystallization) and / or in the form of a heel, such as a portion of the white bottom consisting of allulose crystals and mother liquor. The exact amount of allulose seed crystals is not considered to be particularly critical; for example, it can be used in an amount that occupies about 0.1% to about 5% of the total amount of allulose present in the crystallization vessel or crystallization region, which will be described in more detail below. Generally speaking, it is preferred to use allulose seed crystals of relatively high purity; for example, the allulose seed crystals can have an allulose purity of at least 90%, at least 95% or at least 99 wt% in various embodiments of the present invention. The term "allulose purity" as used herein with respect to allulose crystals means the weight percentage of allulose in the crystals based on the total weight of the dry solids in the crystals.

[0050] Description of various exemplary embodiments of the crystallization process

[0051] In one embodiment of the invention, the batch crystallization of allulose can be carried out in a jacketed vessel equipped with a stirrer by lowering the temperature of the cooling medium (e.g., water or other heat transfer liquid) in the jacket to lower the white temperature and thereby induce crystallization. The following series of steps can be performed: 1. The vessel is partially filled with an appropriate allulose syrup. 2. The temperature of the cooling medium is set to a desired initial temperature. 3. The stirrer is operated and set to an RPM effective to provide a desired tip speed. 4. The temperature of the allulose syrup in the vessel is appropriately changed with the temperature of the cooling medium and lowered to a desired temperature. 5. A desired amount of seed crystals (e.g., dry seed crystals) is added to the vessel (this addition can be made before the time when the allulose syrup reaches the temperature set in step 2). 6. Using an appropriate stirrer tip speed, the seed crystals and the allulose syrup are mixed. The stirrer tip speed can be selected to minimize or avoid breakage of not only the seed crystals but also the allulose crystals that are subsequently formed during crystallization. In certain embodiments, the stirrer tip speed is faster when initially mixing the seed crystals and the allulose syrup than when proceeding with subsequent crystallization step(s). 7. Then, the temperature of the allulose syrup / seed crystal mixture is lowered to a desired temperature effective to achieve crystallization of a portion of the allulose dissolved in the allulose syrup. This temperature can vary, for example, depending on the concentration of allulose in the syrup, but will typically not exceed about 40°C and will not be lower than about 0°C. 8. Crystallization can continue with an appropriate degree of stirring until a desired yield of allulose crystals is achieved (this can be confirmed by periodically sampling from the vessel and measuring the dry solid content of the mother liquor). 9. To achieve the desired yield of allulose crystals, the white temperature can be continuously lowered or lowered in one or more steps. 10. Once the desired yield of allulose crystals is achieved, the mother liquor is blended with a further portion of allulose syrup (e.g., to fill the container). Then, steps 7-9 are repeated. 11. After introducing the further portion of allulose syrup into the container, once the desired yield of allulose crystals is achieved, a portion (e.g., about 1 / 4 to 3 / 4) of the mother liquor is removed from the container while retaining the remainder of the mother liquor in the container to serve as a source of seed crystals for subsequent batches of mother liquor. In this way, multiple batches of mother liquor can be produced. 12. After separating the allulose crystals from the mother liquor by one or more physical separation methods selected from the group consisting of centrifugation, filtration, decantation, membrane separation, and combinations thereof, for the portion(s) of mother liquor removed from the container, one or more desired processing steps such as washing and / or drying the separated allulose crystals can be performed.

[0052] In another embodiment of the present invention, crystallization can be carried out in a continuous manner involving multiple steps (e.g., 3 or 4 steps). Such a process is shown in schematic form in Figure 1 and can be carried out using the system described in more detail below.

[0053] Appropriate purity allulose syrup is introduced into evaporator 2 via line 1, and in that evaporator the dry solid content of the syrup is increased to the desired level. Next, the allulose syrup is pumped (using pump 3) via line 4 into allulose syrup feed storage tank 5. From tank 5, the allulose syrup is pumped (using pump 6) via line 7 and introduced into heat exchanger 8, where the temperature of the allulose syrup is adjusted to the desired value before being supplied via line 9 to mixing tank 10. In mixing tank 10, the allulose syrup is blended while being vigorously mixed with the mother liquor from crystallization region 22, which is supplied to mixing tank 10 using line 25. The mixture of allulose syrup and mother liquor (which serves as a source of seed crystals) is discharged from mixing tank 10 and introduced into crystallization region 12. Crystallization region 12 may be inside a suitable tank or other container equipped with an agitator. Any type of agitator known in the art can be used; in particular, the agitator can be any type of mechanical device recognized as being useful for agitating the solution / seed crystal mixture that can be used in the crystallization process. In one embodiment, the agitator in the crystallization region can cause its agitation effect horizontally but not vertically. In order to prevent or reduce the turbulence formed during crystallization and the breakage / damage of the crystals, the agitation may preferably proceed at a low speed. The agitator can be arranged and operated to prevent allulose crystals from adhering to the wall(s) and / or bottom of the container constituting crystallization region 12. According to one aspect of the present invention, the mixture of allulose syrup and mother liquor does not perform concentration within crystallization region 12. The allulose syrup / mother liquor mixture can move through crystallization region 12 in a plug flow manner, at which time the tip speed of the agitator is appropriately adjusted to promote the crystallization of allulose dissolved in the liquid phase mixture and to produce allulose crystals of the desired size and shape. In one embodiment, the process parameters are controlled such that the allulose syrup / mother liquor mixture is a downward continuous flow and passes through the container containing crystallization region 12.The flow rate of the mixture passing through the crystallization zone 12 and thereby the residence time of the mixture in the crystallization zone 12 are controlled such that the mixture leaving the crystallization zone 12 via line 14 has the desired content of allulose crystals (i.e., the desired yield of allulose crystals is achieved by the time the mixture is discharged from the crystallization zone 12). In one embodiment, the temperature of the allulose syrup / white syrup mixture is held constant or essentially constant as the mixture passes through the crystallization zone 12. For example, the temperature of the mixture can be controlled such that the temperature of the mixture at the time it is introduced into the crystallization zone 12 differs by less than 5°C, less than 4°C, less than 3°C, less than 2°C, or less than 1°C from the temperature of the mixture when it exits or is discharged from the crystallization zone 12.

[0054] The white syrup obtained from the crystallization zone 12 is further cooled to a desired temperature using a heat exchanger 15 (e.g., it may be about 1°C to about 10°C lower than the temperature when the white syrup exits the crystallization zone 12) and introduced into the crystallization zone 17 via line 16. According to one embodiment of the present invention, the white syrup obtained from the crystallization zone 12 does not undergo concentration before or after being introduced into the crystallization zone 17. The crystallization zone 17 may be inside a suitable tank or other container equipped with a stirrer. The white syrup can move through the crystallization zone 17 in a plug flow manner, at which time the tip speed of the stirrer is appropriately adjusted to promote the crystallization of allulose still dissolved in the liquid phase (mother liquor) of the white syrup. The flow rate of the mixture passing through the crystallization zone 17 and thereby the residence time of the mixture in the crystallization zone 17 are controlled such that the mixture leaving the crystallization zone 17 via line 18 has the desired content of allulose crystals (i.e., the desired yield of allulose crystals is achieved by the time the mixture is discharged from the crystallization zone 17), but the desired content of allulose crystals is higher than the content of the white syrup discharged from the crystallization zone 12. The white syrup in the crystallization zone 17 does not undergo concentration according to one embodiment of the present invention.

[0055] The white magma obtained from the crystallization zone 17 is further cooled to a desired temperature using a heat exchanger 20 (for example, it may be about 1 °C to about 10 °C lower than the temperature when the white magma leaves the crystallization zone 17) and introduced into the crystallization zone 22 via line 21. According to one embodiment of the present invention, the white magma obtained from the crystallization zone 17 does not perform concentration before or after being introduced into the crystallization zone 22. The crystallization zone 22 may be inside a suitable tank or other container equipped with a stirrer. The white magma can move through the crystallization zone 22 in a plug flow manner, and at this time, the tip speed of the stirrer is appropriately adjusted to promote the crystallization of allulose still dissolved in the liquid phase (mother liquor) of the white magma. The flow rate of the mixture passing through the crystallization zone 22 and thereby the residence time of the mixture in the crystallization zone 22 are controlled such that the mixture leaving the crystallization zone 22 via line 23 has a desired content of allulose crystals (that is, the desired yield of allulose crystals is achieved by the time the mixture is discharged from the crystallization zone 22), but the desired content of allulose crystals is higher than the content of the white magma discharged from the crystallization zone 17. According to one embodiment of the present invention, the white magma in the crystallization zone 22 does not perform concentration.

[0056] If so desired, one or more additional crystallization zones (not shown), operating in a manner similar to the crystallization zones 12, 17, and 22, can be introduced, in which the white magma leaving the crystallization zone 22 will be further cooled and crystallized. According to a particular embodiment of the present invention, such further steps proceed without any concentration of the white magma.

[0057] Once the white magma with the desired final target yield of allulose crystals is produced, a portion of it can be recycled and used as the source of the seed crystals described above (transported to the mixing tank 10 via line 25), and the remaining portion can pass through the heat exchanger 27 and be supplied to the white magma storage tank 29 via line 28. The white magma from the white magma storage tank 29 can perform separation of allulose crystals from the mother liquor using centrifugation 30, and then the obtained allulose crystal cake is washed before being dried in a rotary dryer 31.

[0058] Generally speaking, a high allulose crystal concentration can have a high viscosity and may consequently tend to result in a white bottom that makes further processes difficult. Therefore, it would be preferable to control the crystallization conditions so that the final white bottom (i.e., the white bottom from which allulose crystals are recovered, including separation from the mother liquor components of the white bottom) does not have an overly high allulose crystal content. Thus, in various embodiments of the present invention, the allulose crystal yield in the final white bottom is 60% or less, 55% or less, 50% or less, or 45% or less. At the same time, it is preferable that the allulose crystal yield achieved in the final white bottom is sufficiently high to reduce the manufacturing cost. Thus, in various embodiments, the allulose crystal yield in the final white bottom is at least 20%, at least 25%, at least 30%, at least 35%, or at least 40%.

[0059] The mother liquor(s) separated from allulose crystals according to various embodiments of the present invention can be further processed and / or used in different ways. For example, the mother liquor recovered from the separation step can be used to manufacture consumer products or simply used as is (e.g., in the form of a solution or syrup) as a source of allulose in dosage form. If so desired, the mother liquor can be subjected to one or more processing steps such as concentration (evaporation) and / or treatment to remove impurities (using an adsorbent or the like). In still other embodiments, the recovered mother liquor can be recycled by returning to a crystallization process of the type described herein and thus can act as a source (in whole or in part) of the allulose syrup starting material. Before such recycling, the mother liquor can be subjected to one or more processing steps such as concentration and / or purification.

[0060] Further Processing of Allulose Crystals

[0061] In various embodiments of the present invention, the method can include one or more additional steps, where, after separation from the mother liquor portion below the white layer by centrifugation, filtration, decantation, membrane separation or other such physical separation methods, the allulose crystals present within the white layer will undergo further processing. For example, allulose crystals separated from the mother liquor generally have some mother liquor on the external surface of the crystals. Since the mother liquor generally contains some impurities (substances other than allulose), the purity of the recovered crystals can be improved by performing one or more washing steps in which the separated allulose crystals are washed with one or more volumes of a suitable liquid. The washing step(s) can be performed in any suitable manner using techniques known in the art, such as passing the washing liquid through a bed of allulose crystals or slurrying the separated allulose crystals in a predetermined volume of washing liquid and then performing physical separation steps such as centrifugation, decantation, membrane separation and / or filtration to recover the allulose crystals washed from the washing liquid. Any suitable washing liquid can be used, such as water, an organic solvent (e.g., an alcohol such as ethanol), a blend of water and one or more organic solvents, a blend of two or more organic solvents, and / or an aqueous solution consisting of at least one carbohydrate (e.g., allulose). In one embodiment, the allulose crystals are washed even with the recovered mother liquor having a higher purity (relative to allulose) than the purity of the initial mother liquor present within the allulose syrup or the crystals being washed.

[0062] The allulose crystals separated from the mother liquor below the white layer can be subjected to a drying step to reduce the moisture content of the crystals. The drying step can proceed, for example, after a washing step or a series of washing steps. Drying of the crystals can be performed in a fluidized bed dryer, a rotary dryer, a vacuum dryer or other such apparatus. For example, in the drying step, the allulose crystals can be dried using an air temperature not exceeding about 100°C, preferably not exceeding 80°C, for about 20 minutes to about 24 hours, more preferably for about 20 minutes to about 6 hours.

[0063] Compared with the conventionally known crystallization process of allulose, the present invention can produce relatively large, dried, free-flowing allulose crystals at a lower manufacturing cost (by better utilization of equipment). Such larger crystals have a better appearance than small allulose crystals that appear powdery and flocculent. The larger crystals have fewer fines, which will ultimately reduce dusting. Fines (i.e., small crystals) can fill the space between the larger crystals, but will probably cause not only poor flow characteristics but also caking problems. Furthermore, small allulose crystals have a larger surface area compared to larger crystals; this results in faster moisture absorption, which can also contribute to caking. The type of dried, free-flowing allulose crystals that can be economically produced using the present invention does not require special handling equipment and can be handled by customers (e.g., food manufacturers).

[0064] The process according to the present invention can produce allulose crystal products having an average particle size of, for example, at least 100 microns, at least 150 microns, at least 200 microns, or at least 250 microns, or larger (e.g., 250 - 350 microns) in various embodiments of the present invention. The average particle size can be determined using a laser diffraction particle size analyzer such as the LS 13 320 model manufactured by Beckman Coulter. According to a specific aspect of the present invention, 25% or less of the obtained allulose crystal product has a size less than 75 microns.

[0065] The present invention can be carried out to obtain allulose crystals having a preferred form in which the allulose crystals have a clearly defined three-dimensional shape rather than the shape of needles or flat sheets. Figure 2 is a microscopic image of white sub-allulose crystals having such a preferred form.

[0066] The allulose crystals produced according to at least certain embodiments of the present invention, for example, have a bulk density of greater than 30 lb / ft 3 and more preferably greater than 35 lb / ft 3 which can be advantageous.

[0067] Use of allulose crystals

[0068] The allulose crystals produced by the method of the present invention can be used in products for human and / or animal consumption. Such uses are particularly beneficial for products having a low moisture content. In some embodiments, the product can be a food product, a beverage product, a pharmaceutical product, a nutritional product, a sports product, or a cosmetic product. For example, if the product is a food product, the food product can be selected from the group consisting of confectionery products (including chocolate products), dessert products, cereal products, baked goods, frozen dairy products (e.g., ice cream), meats, dairy products (e.g., yogurt), seasonings, snack bars, energy bars, nutritional bars, soups, dressings, mixes, prepared foods, baby foods, diet formulations, syrups, food coatings, dried fruits, sauces, gravies, and jams / jellies. In some embodiments, the food product can contain allulose crystals produced by the method of the present invention in the form of a coating or frosting formed on the surface of the product. Alternatively, if the product is a beverage product, the beverage product can be selected from the group consisting of carbonated beverages, non-carbonated beverages, fruit-flavored beverages, fruit juices, tea, milk, coffee, and the like. A food product containing allulose crystals produced according to the present invention can also be a tabletop sweetener.

[0069] The allulose crystals produced according to the present invention can be used in combination with one or more other food or beverage ingredients, including any food and beverage ingredients known in the art. Such additional food and beverage ingredients include, but are not limited to, flavors other than allulose, colorants, sweeteners (other carbohydrates such as sucrose, fructose, allulose, tagatose and other rare carbohydrates, high-potency synthetic sweeteners such as sucralose, acesulfame K, saccharin, aspartame, high-potency natural sweeteners including steviol glycosides and mogrosides such as those containing steviol glycosides and mogrosides (e.g., rebaudioside A, rebaudioside B, rebaudioside C, rebaudioside D, rebaudioside E, rebaudioside F, rebaudioside G, rebaudioside H, rebaudioside I, rebaudioside J, rebaudioside K, rebaudioside L, rebaudioside M (also known as rebaudioside X), rebaudioside N, rebaudioside O, stevioside, steviol monoside, steviol bioside, glucoside A, glucoside B, rubusoside, glycosylated steviol glycosides, enzyme-modified steviol glycosides, mogroside IIA, mogroside IIB, 7-oxomogroside IIE, 11-oxomogroside A, mogroside IIIA2, 11-deoxymogroside III, 11-oxomogroside IVA, 7-oxomogroside V, 11-oxomogroside V, mogroside V, mogroside VI and the like, and combinations thereof), dietary fiber (including soluble dietary fiber such as soluble corn fiber and polydextrose), acidulants, water, etc. The allulose crystals can be mixed or blended with such other components in a dried form. In other embodiments, the allulose crystals may be coated with one or more other components; for example, a solution containing one or more other components (such as a combination of high-potency sweeteners, high-potency sweeteners, and / or one or more other carbohydrates) can be applied to the allulose crystals by spraying or other such procedures and then dried.

Claims

1. A method for producing allulose crystals, comprising the following steps: a) cooling and stirring a first mixture consisting of a first portion of allulose syrup and allulose seed crystals, and initiating crystallization of allulose dissolved in the allulose syrup, thereby forming a first white precipitate containing allulose crystals and a first mother liquor containing dissolved residual allulose, wherein the cooling and stirring continue until the allulose crystals achieve a preselected first target yield; b) optionally, separating the first white precipitate into a first portion and a second portion; c) optionally, combining a second portion of allulose syrup and the second portion of the first white precipitate to form a second mixture; and d) optionally, cooling and stirring the second mixture and initiating crystallization of allulose dissolved in the second portion of allulose syrup, thereby forming a second white precipitate containing allulose crystals and a second mother liquor containing dissolved residual allulose, wherein the cooling and stirring continue until the allulose crystals achieve a preselected second target yield.

2. The method according to claim 1, wherein at least steps a) and b) are carried out.

3. The method according to claim 1, wherein at least steps a), b) and c) are carried out.

4. The method according to claim 1, wherein at least steps a), b), c) and d) are carried out.

5. The method according to claim 1, wherein the first mixture is obtained by combining a first portion of the allulose syrup and dry allulose crystals.

6. The method according to claim 1, wherein the first mixture is obtained by combining a first portion of the allulose syrup and a heel consisting of allulose crystals and mother liquor.

7. If step d) is carried out for the first and second mixtures, in steps a) and d), the mixtures are stirred using a stirrer having a tip speed of 0.02 to 2 m / sec respectively. The method according to claim 1.

8. The method according to claim 1, wherein step a) further comprises combining at least one additional portion of allulose syrup and the first mixture after initiation of crystallization of allulose dissolved in the allulose syrup.

9. The method according to claim 1, wherein the cooling in step a) comprises reducing the temperature of the first mixture from within an initial temperature range to within a second temperature range and maintaining the temperature of the first mixture within the second temperature range for a certain period of time.

10. The method according to claim 1, wherein steps a) to d) are carried out, and the cooling in step d) comprises reducing the temperature of the second mixture from within an initial temperature range to within a second temperature range and maintaining the temperature of the second mixture within the second temperature range for a certain period of time.

11. The method according to claim 1, wherein the allulose syrup has a dry solid content of 70% to 95% by weight, 75% to 90% by weight, or 80% to 85% by weight.

12. The method according to claim 1, wherein the allulose syrup has an allulose purity of at least 70%, at least 75%, at least 80%, at least 85%, or at least 90%.

13. The method according to claim 1, further comprising the step of separating allulose crystals from the first mother liquor in the first part of the first white liquor.

14. The method according to claim 13, wherein the separation is at least partially carried out by one or more physical separation methods selected from the group consisting of centrifugation, filtration, decantation, membrane separation, and combinations thereof.

15. The method according to claim 13, wherein the allulose crystals separated from the first mother liquor are washed at least once in: i) water, an organic solvent, a blend of organic solvents, a blend of water and organic solvent(s), or an aqueous solution consisting of at least one carbohydrate; ii) dried; or a combination thereof.

16. The method according to claim 1, wherein steps b) to d) are carried out and repeated at least once.

17. A method for producing allulose crystals, comprising the following steps: a). i) A feed syrup containing water and dissolved allulose, and ii) a recycled white liquor containing recycled white liquor and dissolved allulose containing allulose crystals, a feed syrup / recycled white liquor mixture (wherein the feed syrup / recycled white liquor mixture is cooled within a first crystallization temperature range) is passed through a first step crystallization region, the feed syrup / recycled white liquor mixture is stirred, the feed syrup / recycled white liquor mixture is maintained within the first crystallization temperature range, crystallization of allulose dissolved in the feed syrup and recycled white liquor mother liquor is initiated, thereby forming a first white liquor containing allulose crystals and a first mother liquor containing dissolved residual allulose, and discharging the first white liquor reaching a preselected first target yield from the first step crystallization region; b). Optionally, cooling the first white liquor discharged from the first step crystallization region within a second crystallization temperature range and transferring the first white liquor to a second step crystallization region; c). Optionally, a step of passing the first white liquor through the second step crystallization region, the first white liquor is stirred, the first white liquor is maintained within the second crystallization temperature range, crystallization of allulose dissolved in the first mother liquor is initiated, thereby forming a second white liquor containing allulose crystals and a second mother liquor containing dissolved residual allulose, and discharging the second white liquor achieving a preselected second target yield from the second step crystallization region; and d). Optionally, repeating steps b and c at least once to obtain a final white liquor and a final mother liquor containing allulose crystals.

18. The method according to claim 17, wherein at least steps a) and b) are carried out.

19. The method according to claim 17, wherein at least steps a), b) and c) are carried out.

20. The method according to claim 17, wherein at least steps a), b), c) and d) are carried out.

21. The method according to claim 17, wherein steps (a) to (d) are carried out and further comprising a step of separating the allulose crystals and the mother liquor in at least a part of the final mother liquor.

22. The method according to claim 17, wherein steps (a) to (d) are carried out and a part of the final mother liquor is used as the recycled mother liquor.

23. The feed syrup / recycled mother liquor mixture is obtained by mixing the feed syrup with the recycled mother liquor containing the recycled mother liquor composed of allulose crystals and dissolved allulose in a mixing vessel to provide the feed syrup / recycled mother liquor mixture and transferring the feed syrup / recycled mother liquor mixture from the mixing vessel to the first step crystallization region. The method according to claim 17.

24. The method according to claim 17, wherein at least steps (a) to (c) are carried out, and the first mixture and the second mixture are each stirred in steps (a) and (c) using a stirrer having a tip speed of 0.02 to 2 m / sec.

25. The method according to claim 17, wherein the allulose syrup has a dry solid content of 70% to 95% by weight, 75% to 90% by weight, or 80% to 85% by weight.

26. The method according to claim 17, wherein the allulose syrup has an allulose purity of at least 70%, at least 75%, at least 80%, at least 85%, or at least 90%.

27. The method according to claim 21, wherein the separation is at least partially carried out by one or more physical separation methods selected from the group consisting of centrifugation, filtration, decantation, membrane separation, and combinations thereof.

28. The allulose crystals separated from the final mother liquor are washed at least once in (i) water, an organic solvent, a blend of organic solvents, a blend of water and organic solvent(s), or an aqueous solution consisting of at least one carbohydrate; (ii) dried; or a combination thereof. The method according to claim 21.

29. The feed syrup / recycled underflow mixture passes through the first-step crystallization region in a plug flow mode and / or if steps b) and c) are carried out, the first underflow passes through the second-step crystallization region in a plug flow mode, the method according to claim 17.

30. The method according to any one of claims 1 to 29, wherein the method is carried out continuously.

31. An allulose crystal obtained by the method according to any one of claims 1 to 30.

32. A consumer product comprising the allulose crystal according to claim 31 and at least one further component other than the allulose crystal, or manufactured using the same.

33. A method for manufacturing a consumer product, comprising the step of using the allulose crystal according to claim 31.

34. A mother liquor obtained by the method according to any one of claims 1 to 30.

35. The mother liquor is suitable for use as a product consumable by humans or animals or as an ingredient in a dosage form product consumable by humans or animals.

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