Allulose crystal particles with Anti-caking properties

Abstract

The present invention provides allulose crystal particles exhibiting a particle size distribution in which 80-95 wt% of the total crystal particles have a size of 300 μm or greater and 0.1-5 wt% have a size of less than 212 μm, and having an average aspect ratio (the ratio of major axis length to minor axis length) of 1 to 3 and an average particle size of 400-520 μm. The allulose crystal particles according to the present invention exhibit low hygroscopicity and high anti-caking properties. Accordingly, the allulose crystal particles of the present invention can be stored and distributed for extended periods without degradation in quality.

Description

Allulose crystal particles with solidification resistance

[0001] The present invention relates to allulose crystal particles, and more specifically, to D-allulose crystal particles having low hygroscopicity and high caking resistance.

[0002] D-allulose is an epimer of the 3rd carbon of fructose and is also called D-psicose. D-allulose has a sweetness level of 70% compared to sugar (Oshima, 2006) but only 0.3% of the energy, making it a functional monosaccharide applicable as a low-calorie sweetener for diet foods (Matsuo et al., 2002). In addition, D-allulose has the function of inhibiting glucose absorption and blood sugar levels, so it can be applied to food products for diabetic patients. It can also be used in various functional foods, such as health foods, because it inhibits abdominal fat accumulation by inhibiting the activity of enzymes involved in lipid synthesis in the liver (Matsuo et al. 2001; Iida et al. 2008; Hayashi et al. 2010; Hossain et al. 2011).

[0003] Due to the characteristics mentioned above, allulose is a good source for replacing sugar, but because it is a rare sugar—a monosaccharide that exists extremely rarely in nature—an efficient method for producing allulose is required for its application in the food industry. The most efficient method for producing allulose for industrialization is to convert fructose into allulose using D-allulose 3-epimerase. Since the reaction solution containing D-allulose produced by the enzymatic reaction is a low-purity product containing about 30% (w / w) of D-allulose solids, it is required to prepare a high-purity allulose-containing mother liquor using chromatography to produce high-purity D-psychose crystals with a purity of 98% (w / w) or higher.

[0004] Generally, methods for crystallizing sugars are broadly classified into two types: the first is concentration crystallization, and the second is cooling crystallization. Both methods utilize the principle of inducing crystal growth within the metastable zone of a supersaturated state.

[0005] D-allulose exhibits characteristics where the crystal formation and growth rates show almost no change even within the supersaturated concentration range, so it can be classified as a sugar that is difficult to crystallize under particle size growth conditions. Generally, crystal particle size is known to be an important factor in the sugar crystallization industry. When fine crystals are produced in a mass production system, the separation of crystals and mother liquor in the crystal centrifuge equipment is not easily achieved due to the viscosity in the supersaturated concentration range. Consequently, the purity of the final product decreases due to the influence of the remaining mother liquor. Furthermore, the remaining mother liquor causes crystals to clump together during drying, resulting in reduced packaging volume or decreased marketability. Therefore, such fine crystals are not suitable for mass production methods.

[0006] Regarding technology for controlling the size and shape of D-allulose crystals, Chinese Registered Patent Publication No. 112574263 discloses a method for producing allulose crystals by sequentially using a isothermal concentration crystallization method and a cooling crystallization method. Since the allulose crystal production method presented in the prior art primarily generates crystal nuclei during the isothermal concentration crystallization step and crystal growth primarily occurs during the cooling crystallization step, the produced allulose crystals have limited particle size, exhibit caking during long-term storage, and show somewhat high hygroscopicity; consequently, they are not suitable for commercialization.

[0007] In addition, regarding a technology for improving the hygroscopicity of D-allulose crystals and mitigating solidification, Korean Registered Patent Publication No. 10-2616151 discloses an allulose crystal having an X-ray powder diffraction pattern in which the 2θ diffraction angles in X-ray powder diffraction (XRD) analysis include peaks of 18.8±0.5°, 15.2±0.5°, and 19.5±0.5°.

[0008] The present invention is derived from the prior art background, and the objective of the present invention is to provide D-allulose crystal particles having low hygroscopicity and high caking resistance.

[0009] The inventors of the present invention prepared D-allulose crystal particles from a D-allulose-containing mother liquor through various methods and prepared allulose crystal particles having a specific particle size distribution through sieve separation. Subsequently, the inventors evaluated the hygroscopicity and caking resistance of the allulose crystal particles. As a result, they confirmed that the allulose crystal particles exhibit low hygroscopicity and high caking resistance when they satisfy a particle size distribution within a predetermined range, an average aspect ratio (ratio of the major axis length to the minor axis length) within a predetermined range, and an average particle size within a predetermined range, thereby completing the present invention.

[0010]

[0011] The term "supersaturated state" as used in this specification refers to an unstable state in which a solute is dissolved beyond the solvent's dissolving capacity, meaning a state in which the solute can precipitate as a solid. Therefore, a supersaturated state is essential for separating a solute in a solution by crystallization. Generally, the supersaturated state of a solution can be affected by external conditions, impurities, temperature, concentration, pH, pressure, etc.

[0012] The term "supersaturated state of the metastable zone" as used in this specification refers to a state in which the concentration of a solution is in the range from the saturation concentration to the lowest supersaturation concentration at which crystals spontaneously precipitate. At the concentration in this region, crystallization phenomena such as crystal nucleation do not occur; however, since it is a supersaturated concentration, if a crystal is introduced from the outside, spontaneous crystal growth occurs and the crystal size increases. That is, when a seed crystal is introduced into a solution with a concentration above the saturation concentration to produce a crystal, the seed crystal grows in the metastable zone to form a large crystal.

[0013] In this specification, Brix, a unit of sugar solid content concentration of an allulose-containing solution or an allulose-containing mother liquor, can be used interchangeably with weight%.

[0014]

[0015] To solve the above problem, one example of the present invention provides allulose crystal particles having a particle size distribution in which particles with a particle size of 300 μm or more comprise 80 to 95 weight% and particles with a particle size of less than 212 μm comprise 0.1 to 5 weight%, an average length-to-short length ratio (ratio of the major axis length to the minor axis length) of the total crystal particles comprises 1 to 3, and an average particle size of the total crystal particles comprises 400 to 520 μm. The allulose crystal particles according to one example of the present invention are an aggregate of crystal particles having various particle sizes and correspond to a powder. The upper limit of the particle size of 300 μm or more is not significantly restricted, and, for example, represents a particle size of 300 μm or more to less than 1,000 μm, preferably 300 μm or more to less than 900 μm, and more preferably 300 μm or more to less than 800 μm. The above particle size of less than 212㎛ is not significantly limited to a lower limit, and for example, represents a particle size of 1㎛ or more to less than 212㎛, preferably 5㎛ or more to less than 212㎛, more preferably 10㎛ or more to less than 212㎛.

[0016] According to a preferred example of the present invention, the allulose crystal particles have a particle size distribution in which 80 to 95 weight percent of the total crystal particles have a particle size of 300 μm or more and less than 800 μm, and 0.1 to 5 weight percent of the total crystal particles have a particle size of less than 212 μm, and the average length-to-short length ratio (ratio of the length of the major axis to the length of the minor axis) of the total crystal particles is 1 to 2.8, and the average particle size of the total crystal particles is 400 to 510 μm.

[0017] In addition, the allulose crystal particles according to a preferred example of the present invention have a particle size distribution in which 82 to 90 weight percent of the total crystal particles have a particle size of 300 μm or more, 7 to 16 weight percent have a particle size of 212 μm or more and less than 300 μm, and 0.5 to 3 weight percent have a particle size of less than 212 μm, and the average length-to-short length ratio (ratio of the length of the major axis to the length of the minor axis) of the total crystal particles is 1 to 2.5, and the average particle size of the total crystal particles is 410 to 500 μm.

[0018] In addition, the allulose crystal particles according to a more preferred example of the present invention have a particle size distribution in which 83 to 89 weight% of the total crystal particles have a particle size of 300 μm or more and less than 710 μm, 9 to 15 weight% have a particle size of 212 μm or more and less than 300 μm, and 0.6 to 2.5 weight% have a particle size of less than 212 μm, the average length-to-short length ratio (ratio of the length of the major axis to the length of the minor axis) of the total crystal particles is 1.1 to 2.4, and the average particle size of the total crystal particles is 420 to 500 μm.

[0019] In addition, when the allulose crystal particles according to one example of the present invention are stored for 24 hours under conditions of 30°C and 75% relative humidity, the moisture absorption rate of the total crystal particles is 0.4% or less, preferably 0.3% or less, and more preferably 0.2% or less.

[0020]

[0021] Allulose crystal particles according to one example of the present invention can be manufactured by a method that sequentially combines cooling crystallization under reduced pressure conditions and cooling crystallization under atmospheric pressure conditions. Specifically, allulose crystal particles according to one example of the present invention can be manufactured by a manufacturing method comprising: (a) a step of adding allulose seeds to an allulose-containing mother liquor, then maintaining a reduced pressure condition of 10 to 100 millibars (mb) and proceeding with a first crystallization reaction under a temperature gradient condition in which the temperature of the allulose-containing mother liquor is gradually reduced; (b) a step of releasing the reduced pressure condition when the allulose crystal precipitation rate of the first crystallization reaction becomes 12% or more, and proceeding with a second crystallization reaction under a temperature gradient condition in which the temperature of the D-allulose-containing mother liquor is gradually reduced while maintaining a supersaturated state in the metastable zone; and (c) a step of washing and dehydrating the allulose-containing mother liquor and drying it to obtain allulose crystal particles after the second crystallization reaction is completed.

[0022] Considering the smooth crystallization of D-allulose, the size of D-allulose crystal particles, and the economic efficiency of the crystallization reaction, the initial sugar solid content of the allulose-containing mother liquor is preferably 70 to 85 Brix, and more preferably 74 to 82 Brix. In addition, considering the smooth crystallization of D-allulose, the size of D-allulose crystal particles, the economic efficiency of the crystallization reaction, and the solidification resistance of crystal particles, the initial allulose content of the allulose-containing mother liquor is preferably 96 to 99 weight% based on the total weight of sugars in the mother liquor, and more preferably 97 to 99 weight%. For example, the sugar composition of the allulose-containing mother liquor may consist of 97 to 99 weight% allulose, 0.1 to 2 weight% fructose, 0.01 to 1 weight% glucose, and the remainder being other sugars, based on the total weight of sugars in the mother liquor. The allulose-containing mother liquor used as a starting material in the present invention can be prepared by various known methods. For example, the allulose-containing mother liquor can be prepared by reacting fructose syrup with D-allulose 3-epimerase to produce an allulose-containing solution, and then undergoing decolorization, desalination, fractionation by chromatography, and concentration processes.

[0023] The above allulose seed is a fine crystal composed of high-purity D-allulose, and the purity of the D-allulose in the allulose seed is preferably 99 to 100% (w / w), and more preferably 99.5 to 100% (w / w). In addition, the average particle size of the allulose seed is not significantly limited and can be selected from 100 to 500 μm, and is preferably 150 to 400 μm. The amount of the allulose seed added is not significantly limited, and considering the size of the D-allulose crystal particles and the economic feasibility of the crystallization reaction, it is preferably 0.1 to 4.0% (w / w) relative to the total weight of the sugar solids in the allulose-containing mother liquor, and more preferably 0.2 to 2.0% (w / w).

[0024]

[0025] Step of proceeding with the primary crystallization reaction

[0026] The step of carrying out the above primary crystallization reaction corresponds to cooling crystallization under reduced pressure conditions.

[0027] When carrying out the above primary crystallization reaction, the temperature gradient condition is the temperature of the allulose-containing mother liquor T a From T b It consists of reducing to the initial temperature T of the above primary crystallization reaction. a The temperature can be selected within various ranges depending on the sugar solid content concentration of the allulose-containing mother liquor, reduced pressure conditions, etc., and considering the smooth crystallization of D-allulose, the size of D-allulose crystal particles, and the economic feasibility of the crystallization reaction, it is preferable to select a temperature of 40–55°C, and preferably a temperature of 45–54°C. The above initial temperature T a If α is below 40℃, the crystallization yield decreases, which may cause difficulties in industrial application. In addition, the above initial temperature T a If α exceeds 55℃, the sugar solid content concentration of the allulose-containing mother liquor required to satisfy the supersaturation state becomes too high, which may hinder the smooth operation of processes such as stirring. Additionally, the final temperature T of the above primary crystallization reaction b is the initial temperature T a It can be selected at a temperature 2 to 10°C lower than the initial temperature T a It is preferable to select a temperature 2 to 8°C lower. Since the primary crystallization reaction is carried out under reduced pressure conditions close to a vacuum of 10 to 100 millibars (mb), the final temperature T of the primary crystallization reaction b initial temperature T a Even if selected at a temperature 2 to 5°C lower, large and uniform crystal grains can be obtained.

[0028] At least a portion of the above primary crystallization reaction process includes temperature conditions corresponding to a supersaturated state in the metastable zone. To induce the primary crystallization reaction, the temperature of the allulose-containing mother liquor is set to an initial temperature T a At the final temperature T b The temperature gradient that reduces includes temperature conditions corresponding to a supersaturated state in at least the metastable zone, and preferably consists of temperature conditions for maintaining a supersaturated state in the metastable zone for most of the time during which the primary crystallization reaction is carried out. In the step of carrying out the primary crystallization reaction, the allulose-containing mother liquor preferably enters a supersaturated state in the metastable zone from the time turbidity occurs in the mother liquor and maintains a supersaturated state in the metastable zone until the primary crystallization reaction is completed.

[0029] The reduced pressure conditions when carrying out the above first crystallization reaction are preferably selected from 20 to 80 millibars (mb), and more preferably from 30 to 70 millibars (mb). When the first crystallization reaction is carried out under reduced pressure conditions close to a vacuum and cooling conditions in which the temperature is gradually reduced, crystal nucleation and crystal growth proceed simultaneously, producing crystal particles with large particle size and a uniform particle size distribution.

[0030] The above first crystallization reaction time is not significantly limited, and considering the size of the D-allulose crystal particles and the economic feasibility of the crystallization reaction, it is preferably selected from 15 to 35 hours, and more preferably from 18 to 32 hours.

[0031]

[0032] Step of proceeding with the secondary crystallization reaction

[0033] The step of carrying out the above secondary crystallization reaction corresponds to cooling crystallization under atmospheric pressure conditions.

[0034] In a method for manufacturing allulose crystal particles, the point at which the first crystallization reaction is terminated and the second crystallization reaction is started is when the allulose crystal precipitation rate of the first crystallization reaction becomes 12% or higher, preferably 15% or higher. For example, the point at which the second crystallization reaction is started may be when the allulose crystal precipitation rate of the first crystallization reaction becomes 12-20%, preferably 15-18%.

[0035] When carrying out the above secondary crystallization reaction, the temperature gradient condition is the temperature of the allulose-containing mother liquor T c From T d It consists of reducing to . In the present invention, since the secondary crystallization reaction is carried out under atmospheric pressure conditions with the reduced pressure condition released and under conditions maintaining a supersaturated state in the metastable zone, the initial temperature T of the secondary crystallization reaction c T is the final temperature of the first crystallization reaction. b It is selected at a lower temperature. For example, the initial temperature T of the secondary crystallization reaction. c T is the final temperature of the first crystallization reaction. b It can be selected at a temperature 4 to 15°C lower, and preferably at a temperature 5 to 12°C lower to stably maintain the supersaturated state of the metastable zone. Specifically, the initial temperature T of the secondary crystallization reaction is c Considering the smooth growth of D-allulose, the size of D-allulose crystal grains, and the economic feasibility of the crystallization reaction, it is preferable to select a temperature of 30–45°C, and more preferable to select a temperature of 35–43°C. In addition, the final temperature T of the secondary crystallization reaction is d Considering the smooth growth of D-allulose, the size of D-allulose crystal grains, and the economic feasibility of the crystallization reaction, the initial temperature T cIt can be selected at a temperature 10–30°C lower than, and the initial temperature T c It is preferable to select a temperature 15 to 28°C lower.

[0036] The above secondary crystallization reaction time is not significantly limited, and is preferably selected from 45 to 100 hours, and more preferably from 50 to 90 hours, considering the size of D-allulose crystal particles, crystallization yield, and the economic feasibility of the crystallization reaction.

[0037]

[0038] Step of obtaining allulose crystal particles

[0039] The step of obtaining the allulose crystal particles described above consists of removing the liquid phase from the allulose-containing mother liquor after the crystallization reaction is completed and obtaining the resulting solid crystal particles. The process of washing and dewatering the allulose-containing mother liquor in the step of obtaining the allulose crystal particles can be implemented by various known methods, such as centrifugation or vacuum filtration using filter paper or filter cloth. Additionally, the drying process in the step of obtaining the allulose crystal particles can be implemented by various known methods, such as hot air drying, spray drying, or fluidized bed drying.

[0040]

[0041] A method for producing allulose crystal particles according to an example of the present invention may preferably further include the step of (d) separating the obtained allulose crystal particles with a sieve. Through sieve separation with a predetermined sieve mesh size, an allulose crystal particle fraction can be obtained having a particle size distribution in which particles with a particle size of 300 μm or more account for 80 to 95 weight% of the total crystal particles and particles with a particle size of less than 212 μm account for 0.1 to 5 weight%.

[0042] The allulose crystal particles according to the present invention have low hygroscopicity and high resistance to solidification. Therefore, the allulose crystal particles according to the present invention can be stored and distributed for a long time without deterioration of quality.

[0043] Figure 1 is a photograph showing the solidification characteristics of D-allulose crystal particles prepared in an embodiment of the present invention.

[0044] The present invention will be described in detail below through the following examples. However, the following examples are intended only to clearly illustrate the technical features of the present invention and do not limit the scope of protection of the present invention.

[0045]

[0046] 1. D-allulose containing mother liquor

[0047] (1) D-allulose containing mother liquor (AL 95%)

[0048] A D-allulose-containing mother liquor (AL 95%) was prepared by concentrating an allulose-containing solution, which has a sugar solid content concentration of about 30 Brix and a sugar composition of 95.4 wt% allulose, 1.7 wt% fructose, 0.1 wt% glucose, and 2.66 wt% other sugars based on the total weight of the sugar solids, to a sugar solid content concentration of about 78 Brix.

[0049]

[0050] (2) D-allulose containing mother liquor (AL 97%)

[0051] A D-allulose containing mother liquor (AL 97%) was prepared by concentrating an allulose-containing solution, which has a sugar solid content concentration of about 30 Brix and a sugar composition of 97.5 wt% allulose, 0.8 wt% fructose, 0.1 wt% glucose, and 1.6 wt% other sugars based on the total weight of the sugar solid content, to a sugar solid content concentration of about 78 Brix.

[0052]

[0053] (3) D-allulose containing mother liquor (AL 99%)

[0054] A D-allulose-containing mother liquor (AL 99%) was prepared by concentrating an allulose-containing solution, which has a sugar solid content concentration of about 30 Brix and a sugar composition of 99.0 wt% allulose, 0.4 wt% fructose, 0.0 wt% glucose, and 0.6 wt% other sugars based on the total weight of the sugar solid content, to a sugar solid content concentration of about 78 Brix.

[0055]

[0056] 2. D-allulose seed crystal

[0057] Allulose crystal particles having a sugar composition of 99.7 wt% allulose and 0.3 wt% fructose based on the total weight of the sugars, an average particle size of about 300 μm, and a moisture content of about 0.2 wt% were used as D-allulose seeds.

[0058]

[0059] 3. D-Allulose Crystallization Experiment Using Combinations of Various Conditions and Steps

[0060] (1) D-allulose crystallization using a sequential combination of vacuum cooling crystallization and atmospheric pressure cooling crystallization

[0061] Crystallization Example 1.

[0062] D-allulose containing mother liquor (AL 97%) was placed in a crystallizer equipped with a system for controlling stirring speed, temperature, and pressure, and the temperature of the mother liquor was adjusted to 52°C. Then, D-allulose seed crystal particles were added to the crystallizer in an amount of 0.3% (w / w) relative to the total weight of the sugar solids in the D-allulose containing mother liquor, and the mixture was stirred to evenly disperse the D-allulose seed crystal particles. Subsequently, the stirring speed of the crystallizer was set to 30 rpm and the pressure inside the crystallizer was set to a reduced pressure condition of 50 mbar. Then, the first crystallization reaction was carried out by gradually lowering the temperature inside the crystallizer from 52°C to 49°C over a period of 24 hours. In the first crystallization reaction step described above, the D-allulose-containing mother liquor entered a supersaturated state in the metastable zone as turbidity occurred, and subsequently maintained a supersaturated state in the metastable zone. The precipitation rate of D-allulose crystals in the first crystallization reaction step was approximately 16.9%. Subsequently, the pressure inside the crystallizer was set to atmospheric pressure and the temperature inside the crystallizer was adjusted to 40°C. Then, a second crystallization reaction was carried out by lowering the temperature inside the crystallizer over 70 hours from 40°C to 15°C under a temperature gradient condition that maintained the metastable zone. Afterward, the mother liquor from which the second crystallization reaction was carried out was washed and dehydrated using centrifugation and dried at approximately 50°C to obtain D-allulose crystal particles. The final yield of D-allulose crystal particles obtained through the second crystallization reaction step was approximately 48.9%. Afterwards, D-allulose crystal particles were placed on a standard sieve with a mesh size of 25 (sieve size: 710 μm), and after vibrating the sieve, only the D-allulose crystal particles that passed through the sieve were used in subsequent experiments.

[0063]

[0064] Crystallization Example 2.

[0065] D-allulose crystal particles having a predetermined particle size distribution were obtained under the same conditions and method as in Crystallization Example 1, except that a D-allulose-containing mother liquor (AL 99%) was used instead of a D-allulose-containing mother liquor (AL 97%). The precipitation rate of D-allulose crystals in the first crystallization reaction step was approximately 17.1%, and the final yield of D-allulose crystal particles obtained through the second crystallization reaction step was approximately 49.7%.

[0066]

[0067] Crystallization Example 3.

[0068] D-allulose crystal particles having a predetermined particle size distribution were obtained under the same conditions and method as in Crystallization Example 1, except that a D-allulose-containing mother liquor (AL 95%) was used instead of a D-allulose-containing mother liquor (AL 97%). The precipitation rate of D-allulose crystals in the first crystallization reaction step was about 16.5%, and the final yield of D-allulose crystal particles obtained through the second crystallization reaction step was about 47.8%.

[0069]

[0070] Crystallization Example 4.

[0071] In Crystallization Example 1, D-allulose crystal particles that passed through a 25-mesh standard sieve (sieve size: 710 μm) were separated using a 50-mesh standard sieve (sieve size: 300 μm) and a 70-mesh standard sieve (sieve size: 212 μm) in stages. The fraction of D-allulose crystal particles that passed through the 25-mesh standard sieve but did not pass through the 50-mesh standard sieve was named "N3", the fraction of D-allulose crystal particles that passed through the 50-mesh standard sieve but did not pass through the 70-mesh standard sieve was named "N23", and the fraction of D-allulose crystal particles that passed through the 70-mesh standard sieve was named "N2".

[0072]

[0073] (2) Crystallization of D-allulose using a sequential combination of vacuum isothermal concentration crystallization and atmospheric pressure cooling crystallization

[0074] Crystallization Example 5.

[0075] D-allulose containing mother liquor (AL 97%) was placed in a crystallizer equipped with a system for controlling stirring speed, temperature, and pressure, and the temperature of the mother liquor was adjusted to 50°C. Then, D-allulose seed crystal particles were added in an amount of 0.3% (w / w) relative to the total weight of the sugar solids in the D-allulose containing mother liquor, and the D-allulose seed crystal particles were evenly dispersed by stirring. Subsequently, the stirring speed of the crystallizer was set to 30 rpm and the pressure inside the crystallizer was set to a reduced pressure condition of 50 mbar. Then, the first crystallization reaction was carried out for 24 hours while maintaining the temperature inside the crystallizer at 50°C. In the first crystallization reaction step, as turbidity occurred in the D-allulose containing mother liquor, it entered a supersaturated state in the metastable zone and subsequently maintained a supersaturated state in the metastable zone. The precipitation rate of D-allulose crystals in the first crystallization reaction step was approximately 7.5%. Subsequently, the pressure inside the crystallizer was set to atmospheric pressure, and the temperature inside the crystallizer was adjusted to 40°C. Then, a second crystallization reaction was carried out by lowering the temperature inside the crystallizer over 70 hours under a temperature gradient condition that maintained a metastable region from 40°C to 15°C. Afterward, the mother liquor from the second crystallization reaction was washed and dehydrated using centrifugation and dried at approximately 50°C to obtain D-allulose crystal particles. The final yield of D-allulose crystal particles obtained through the second crystallization reaction step was approximately 47.2%. Subsequently, the D-allulose crystal particles were placed on a standard sieve with a mesh size of 25 (sieve size: 710 μm), and the sieve was vibrated; only the D-allulose crystal particles that passed through the sieve were used for subsequent experiments.

[0076]

[0077] Crystallization Example 6.

[0078] D-allulose crystal particles having a predetermined particle size distribution were obtained under the same conditions and method as in Crystallization Example 5, except that a D-allulose-containing mother liquor (AL 99%) was used instead of a D-allulose-containing mother liquor (AL 97%). The precipitation rate of D-allulose crystals in the first crystallization reaction step was about 7.6%, and the final yield of D-allulose crystal particles obtained through the second crystallization reaction step was about 47.9%.

[0079]

[0080] Crystallization Example 7.

[0081] D-allulose crystal particles having a predetermined particle size distribution were obtained under the same conditions and method as in Crystallization Example 5, except that a D-allulose-containing mother liquor (AL 95%) was used instead of a D-allulose-containing mother liquor (AL 97%). The precipitation rate of D-allulose crystals in the first crystallization reaction step was about 7.3%, and the final yield of D-allulose crystal particles obtained through the second crystallization reaction step was about 46.2%.

[0082]

[0083] (3) Crystallization of D-allulose using atmospheric pressure cooling method

[0084] Crystallization Example 8.

[0085] A D-allulose-containing mother liquor was prepared by concentrating an allulose-containing solution, which had a sugar solid content of approximately 30 Brix and a sugar composition of 97.5 wt% allulose, 0.8 wt% fructose, 0.1 wt% glucose, and 1.6 wt% other sugars based on the total weight of the sugar solids, to a sugar solid content of approximately 80 Brix. The D-allulose-containing mother liquor was placed in a crystallizer equipped with a system for controlling stirring speed, temperature, and pressure, and the temperature of the mother liquor was adjusted to 40°C. Then, D-allulose seed crystal particles were added to the mother liquor in an amount of 3% (w / w) relative to the total weight of the sugar solids of the D-allulose-containing mother liquor, and the mixture was stirred to evenly disperse the D-allulose seed crystal particles. Subsequently, the stirring speed of the crystallizer was set to 30 rpm and the pressure inside the crystallizer was set to atmospheric pressure. Then, the crystallization reaction was carried out by lowering the temperature inside the crystallizer over 70 hours from 40°C to 15°C under a temperature gradient condition that maintained a metastable region. Afterward, the mother liquor from which the crystallization reaction proceeded was washed and dehydrated using centrifugation and dried at approximately 50°C to obtain D-allulose crystal particles. The final yield of the D-allulose crystal particles obtained through the above crystallization reaction was approximately 44.8%. Subsequently, the D-allulose crystal particles were placed on a standard sieve with a mesh size of 25 (sieve opening: 710 μm), and after vibrating the sieve, only the D-allulose crystal particles that passed through the sieve opening were used for subsequent experiments.

[0086]

[0087] 4. Analysis of particle size distribution of D-allulose crystal particles

[0088] The particle size distribution of D-allulose crystal particles that passed through a standard sieve with a mesh size of 25 in Crystallization Examples 1 to 3 and Crystallization Examples 5 to 8 was analyzed. In addition, the particle size distribution of D-allulose crystal particle fractions "N3", "N23", and "N2" obtained in Crystallization Example 4 was also analyzed. Specifically,

[0089] Standard sieves of 50 mesh (mesh size: 300 µm), 70 mesh (mesh size: 212 µm), and 140 mesh (mesh size: 106 µm) were arranged sequentially from the top. After placing D-allulose crystal particles on the 50 mesh standard sieve, vibrations of 80 times per minute were applied using a vibrator for 5 minutes. Subsequently, the weight of the sample remaining on each standard sieve was measured, and the particle size distribution was analyzed. The results of the particle size distribution analysis of D-allulose crystal particles are summarized in Table 1 below.

[0090] D-Allulose Crystal Particle Sample Classification Content by Particle Size (Weight %) Approx. 300 µm or more Approx. 212 µm or more to less than Approx. 300 µm Approx. 106 µm or more to less than Approx. 212 µm Approx. 106 µm or less Crystallization Example 187.610.81.50.2 Crystallization Example 285.013.41.50.2 Crystallization Example 386.010.13.80.2 Crystallization Example 4: N387.212.00.60.3 Crystallization Example 4: N231.276.222.00.7 Crystallization Example 4: N20.11.276.022.8 Crystallization Example 512.953.632.60.9 Crystallization Example 615.750.930.33.1 Crystallization Example 75.250.737.26.9 Crystallization Example 880.315.24.20.4

[0091]

[0092] 5. Measurement of average particle size, average aspect ratio (ratio of major axis length to minor axis length; aspect ratio), moisture content, and hygroscopicity of D-allulose crystal particles

[0093] For the D-allulose crystal particles that passed through a standard sieve with a mesh size of 25 in Crystallization Examples 1 to 3 and Crystallization Examples 5 to 8, and for the D-allulose crystal particle fractions "N3", "N23", and "N2" obtained in Crystallization Example 4, the average particle size, average aspect ratio (ratio of the major axis length to the minor axis length; aspect ratio), moisture content, and moisture absorption rate were measured, and the results are summarized in Table 2 below.

[0094] D-Allulose Crystal Particles Sample Classification Average Particle Size (㎛) Average Length-to-Length Ratio Moisture Content (Wt%) Hygroscopicity (%) Crystallization Example 1 496.42.20.10.1 Crystallization Example 2 457.01.20.20.1 Crystallization Example 3 410.03.50.30.2 Crystallization Example 4: N3 421.82.20.10.1 Crystallization Example 4: N23 314.62.20.10.3 Crystallization Example 4: N21 70.92.10.10.4 Crystallization Example 5 254.02.10.20.3 Crystallization Example 6 276.61.50.10.3 Crystallization Example 7 220.33.80.20.6 Crystallization Example 8 372.74.70.30.7

[0095] * Average particle size: Measured using a particle size distribution analyzer (Model: Microtrac S3500; Supplier: Microtrac Inc, USA)

[0096] * Average Length-to-Shortness Ratio: Acquired images of D-allulose crystal particles and calculated using image analysis software

[0097] * Moisture content: Measured using the Karl Fischer method

[0098] Moisture absorption rate: Calculated by placing allulose crystal particles in a constant temperature and humidity chamber set to 30°C and 75% relative humidity and storing them for 24 hours, then measuring the increase in weight.

[0099]

[0100] As shown in Table 2 above, the D-allulose crystal particles with low moisture absorption were found to be the D-allulose crystal particles obtained in Crystallization Examples 1 to 3, and the D-allulose crystal particle fraction "N3" obtained in Crystallization Example 4.

[0101]

[0102] 6. Measurement of Caking Characteristics of D-Allulose Crystal Grains

[0103] 90g of allulose crystal particles were placed into a transparent plastic cylinder with a diameter of 60mm to fill about half of the cylinder, and then the upper layer of the allulose crystal particles was covered with circular wood chips with a diameter of 60mm and a thickness of 4mm. Subsequently, a weight with a diameter of 55mm and a weight of 1kg was placed on the wood chips to apply pressure, and the mixture was stored in a hot air dryer at 35℃ for 6 weeks while maintaining the pressure conditions. Afterward, the allulose crystal particles were removed from the transparent plastic cylinder, and the degree of caking was visually checked.

[0104] Figure 1 is a photograph showing the measured solidification characteristics of D-allulose crystal particles prepared in an embodiment of the present invention. In addition, the solidification characteristics of D-allulose crystal particles were evaluated based on the size of the solidified lumps and the number of solidified lumps, and the results are summarized in Table 3 below.

[0105] D-Allulose Crystal Particle Sample Classification D-Allulose Crystal Solidification Lump Size D-Allulose Crystal Solidification Lump Water Crystallization Example 1 ++Crystallization Example 2 ++Crystallization Example 3+++++++Crystallization Example 4: N3 ++Crystallization Example 4: N23++++++++Crystallization Example 4: N2++++++++Crystallization Example 5 ++++++++Crystallization Example 6 ++++++++Crystallization Example 7 +++++++++Crystallization Example 8+++++++

[0106] * Size of solidified lump

[0107] + : Composed of very small particles (no clumps); ++ : Small clumps exist; +++ : Medium-sized clumps exist; ++++ : Many large clumps exist; +++++ : A few very large clumps exist

[0108] * Number of noble lumps

[0109] + : No lumps; ++ : 1–3 lumps present; +++ : 4–6 lumps present; ++++ : 7–10 lumps present; ++++ : More than 10 lumps

[0110]

[0111] As shown in Figure 1 and Table 3 above, the D-allulose crystal particles with high solidification resistance were found to be the D-allulose crystal particles obtained in Crystallization Example 1 and Crystallization Example 2, and the D-allulose crystal particle fraction "N3" obtained in Crystallization Example 4.

[0112]

[0113] 7. Conclusion

[0114] It was confirmed that the hygroscopicity and solidification resistance of D-allulose crystal particles are influenced by the particle size distribution, average particle size, and average aspect ratio (ratio of the major axis length to the minor axis length; aspect ratio) of the crystal particles. D-allulose crystal particles exhibited low hygroscopicity and high solidification resistance when the particle size distribution showed that 80–95 wt% of the total particles had a particle size of 300 µm or more and 0.1–5 wt% had a particle size of less than 212 µm, the average aspect ratio was 1–3, and the average particle size was 400–520 µm.

[0115]

[0116] Although the present invention has been described above through the embodiments, the invention is not necessarily limited thereto, and it is understood that various modifications are possible within the scope and spirit of the invention. Accordingly, the scope of protection of the present invention should be interpreted to include all embodiments falling within the scope of the claims attached to the present invention.

Claims

1. Among the total crystal grains, the particle size distribution shows that particles with a particle size of 300㎛ or larger account for 80~95 wt% and particles with a particle size of less than 212㎛ account for 0.1~5 wt%, and The average length-to-mind ratio (ratio of major axis length to minor axis length) of the entire crystal grain is 1 to 3, and Allulose crystal particles with an average particle size of 400 to 520 μm.

2. In Paragraph 1, The particle size distribution shows that among the total crystal particles, particles with a particle size of 300㎛ or more to less than 800㎛ account for 80 to 95 weight% and particles with a particle size of less than 212㎛ account for 0.1 to 5 weight%, and The average length-to-minor ratio (ratio of major axis length to minor axis length) of the entire crystal grain is 1 to 2.8, and Allulose crystal particles with an average particle size of 400 to 510 μm.

3. In Paragraph 1, The particle size distribution shows that among the total crystal particles, particles with a particle size of 300㎛ or larger account for 82 to 90 weight%, particles with a particle size of 212㎛ or larger but less than 300㎛ account for 7 to 16 weight%, and particles with a particle size less than 212㎛ account for 0.5 to 3 weight%. The average length-to-mind ratio (ratio of major axis length to minor axis length) of the entire crystal grain is 1 to 2.5, and Allulose crystal particles with an average particle size of 410 to 500 µm.

4. In Paragraph 1, The particle size distribution shows that among the total crystal particles, particles with a particle size of 300㎛ or more and less than 710㎛ make up 83~89% by weight, particles with a particle size of 212㎛ or more and less than 300㎛ make up 9~15% by weight, and particles with a particle size of less than 212㎛ make up 0.6~2.5% by weight. The average length-to-minor ratio (ratio of major axis length to minor axis length) of all crystal grains is 1.1 to 2.4, and Allulose crystal particles with an average particle size of 420 to 500 µm.

5. In Paragraph 1, Allulose crystal particles characterized by having a moisture absorption rate of 0.4% or less of the total crystal particles when stored for 24 hours under conditions of 30℃ and 75% relative humidity.

6. Allulose crystal particles according to claim 1, characterized by being manufactured by a manufacturing method comprising the following steps: (a) a step of adding allulose seeds to an allulose-containing mother liquor, and then proceeding with a primary crystallization reaction under a temperature gradient condition in which the temperature of the allulose-containing mother liquor is gradually reduced while maintaining a reduced pressure of 10 to 100 millibars (mb); (b) a step of releasing the reduced pressure condition when the allulose crystal precipitation rate of the first crystallization reaction becomes 12% or more, and proceeding with a second crystallization reaction under a temperature gradient condition in which the temperature of the D-allulose-containing mother liquor is gradually reduced while maintaining a supersaturated state in the metastable zone; and (c) A step of washing and dehydrating the allulose-containing mother liquor and drying it to obtain allulose crystal particles after the secondary crystallization reaction is completed. The initial sugar solid content concentration of the allulose-containing mother liquor is 70 to 85 Brix, and the initial allulose content of the allulose-containing mother liquor is 96 to 99 weight% based on the total weight of sugars in the mother liquor, and at least part of the primary crystallization reaction process includes temperature conditions corresponding to a supersaturated state in the metastable zone.

7. In paragraph 6, when proceeding with the primary crystallization reaction, the temperature gradient condition is the temperature of the allulose-containing mother liquor T a From T b It consists of reducing to, and when proceeding with the secondary crystallization reaction, the temperature gradient condition is the temperature of the allulose-containing mother liquor T c From T d It consists of reducing to, and the above T c is T b Allulose crystal particles characterized by being selected at a temperature 4 to 15°C lower.

8. In Paragraph 7, the above T a is selected at 40~55℃ and T b is T a Allulose crystal particles characterized by being selected at a temperature 2 to 10°C lower.

9. In Paragraph 7, the above T c is selected at 30~45℃ and T d is T c Allulose crystal particles characterized by being selected at a temperature 10 to 30°C lower.

10. Allulose crystal particles according to claim 6, wherein the manufacturing method further comprises the step of (d) separating the obtained allulose crystal particles with a sieve.

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