Production method of high-fluidity crystal maltitol

Abstract

The invention relates to the technical field of sugar alcohol crystallization, and discloses a high-fluidity crystal maltitol production method which comprises the following steps: pre-concentrating a maltitol solution; performing vacuum evaporation and concentration to a supersaturated state, adding a seed crystal, and maintaining evaporation and crystallization under the conditions of keeping vacuum and temperature; then transferring to a crystallizer, growing crystal at constant temperature, and then carrying out slow-to-fast stage cooling to finish cooling crystallization; and finally, centrifuging and drying to obtain a finished product. According to the invention, a vacuum evaporation and segmented cooling coupling crystallization technology is adopted, and explosive nucleation and fine powder generation are effectively inhibited by accurately controlling crystallization kinetics in an organic-solvent-free system. The obtained product is regular in crystal form, uniform in particle size distribution, small in repose angle, excellent in fluidity, high in crystallization yield and high in purity, and the technical problems that a traditional water phase crystallization product is prone to caking and poor in fluidity are solved.

Description

Technical Field

[0001] This invention relates to the field of sugar alcohol crystallization technology, specifically to a method for producing highly fluid crystalline maltitol. Background Technology

[0002] Maltitol, as a functional sugar alcohol, is widely used in food, pharmaceuticals, and health products due to its low calorie content, non-cariogenicity, and similar taste and processing characteristics to sucrose. In practical applications, high-purity crystalline maltitol, compared to liquid syrup, exhibits higher chemical stability, lower hygroscopicity, and a higher melting point, making it the preferred raw material form for high-end end products. Therefore, developing efficient and high-quality maltitol crystallization processes has always been a hot research topic in the industry.

[0003] Currently, the industrial production of crystalline maltitol mainly employs organic solvent crystallization and direct aqueous phase crystallization. Organic solvent crystallization typically involves adding organic solvents such as ethanol to a concentrated maltitol solution, using the solvent to reduce the system's viscosity and solubility, thus precipitating crystals. However, this process has limitations in practical production. Due to the use of large quantities of flammable and explosive organic solvents, the production process poses significant safety hazards, requiring extremely high explosion-proof standards for production equipment. Furthermore, solvent recovery and distillation processes increase energy consumption and production costs. More importantly, the solvent method cannot completely eliminate trace amounts of solvent residue in the product, which severely limits its application in fields with extremely high safety requirements, such as infant formula and high-end pharmaceutical excipients.

[0004] To mitigate the risk of solvent residue, the industry has attempted to employ direct aqueous crystallization without adding organic solvents. However, maltitol aqueous solutions have extremely high viscosity, resulting in significant mass transfer resistance and hindering molecular diffusion during crystallization. In traditional cooling crystallization processes, the lack of effective supersaturation control means that high-viscosity systems are prone to localized excessive supersaturation in the initial cooling phase, triggering explosive nucleation and leading to the instantaneous formation of numerous fine crystals. These tiny crystals not only have a large specific surface area and strong adsorption capacity for the mother liquor, making subsequent centrifugation difficult and easily clogging filters or causing filter breakage, but also result in a wide particle size distribution and excessively high fine powder content in the final dried product. Excessive fine powder directly leads to a decrease in the product's bulk density, an increase in the angle of repose, and extremely poor flowability. During packaging, storage, and transportation, they are highly susceptible to moisture absorption, bridging, and clumping, severely impacting the product's commercial value and downstream user experience. Furthermore, due to the hindered mass transfer caused by high viscosity, the crystallization yield of traditional aqueous crystallization processes is typically low, making efficient solute recovery difficult and resulting in low production efficiency and resource waste. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for producing high-flowability crystalline maltitol, which solves the problems of solvent residue and safety hazards in the organic solvent method of existing maltitol crystallization processes, and the high fine powder content, poor flowability and low crystallization yield of the traditional aqueous method due to easy nucleation explosion.

[0006] To achieve the above objectives, the present invention provides a method for producing highly fluid crystalline maltitol, comprising the following steps: S1. Pre-concentrate the maltitol solution to obtain a concentrated solution with a Brix concentration of 70-75%; S2. The concentrate is concentrated to a supersaturated state by vacuum evaporation, maltitol seed crystals are added, the vacuum degree is adjusted, and evaporation is maintained for 2-4 hours under vacuum and temperature conditions, after which the vacuum is released. S3. Transfer the material obtained in step S2 to a pre-temperature-controlled crystallizer, first perform constant-temperature crystal growth, and then perform a phased cooling process that starts slowly and then accelerates to complete the cooling crystallization. S4. After the material in step S3 has cooled down, centrifuge it to separate the crystals. S5. Dry the collected crystals to obtain crystalline maltitol product.

[0007] By employing the above technical solution, this invention utilizes the coupled synergistic effect of vacuum evaporation and segmented cooling to achieve precise control of maltitol crystallization kinetics in a solvent-free system. The specific mechanism is as follows:

[0008] First, in the vacuum evaporation maintenance stage of step S2, this invention constructs a supersaturation maintenance system at an isothermal temperature. By continuously removing the solvent (water) in a vacuum environment, the solution maintains a stable supersaturation without lowering the temperature. This process locks the solution state in the middle of the metastable region, and the main driving force is used to induce the added seed crystals to undergo preliminary growth and lattice repair, rather than to generate new crystal nuclei, thereby establishing a regular crystal framework before cooling.

[0009] Second, in the cooling stage of step S3, a three-stage strategy of isothermal cooling followed by slow cooling and then rapid cooling is adopted. First, isothermal crystal growth further eliminates high-energy sites on the surface of the seed crystals; then, slow cooling is adopted in the high-temperature, high-concentration region to suppress explosive nucleation caused by the surge in supersaturation and avoid the formation of fine crystals; finally, rapid cooling is adopted in the low-temperature region to quickly precipitate the remaining solute by utilizing the difference in solubility, thereby improving the crystallization yield.

[0010] In summary, this method effectively solves the problems of diffusion obstruction and easy nucleation resulting in a large amount of fine powder in traditional aqueous phase crystallization due to high viscosity. The final product has a uniform particle size distribution, low fine powder content, excellent flowability and high crystallization yield.

[0011] Preferably, the maltitol content in the dry matter of the maltitol solution in step S1 is greater than 92.0%, more preferably 95.0%-96.0%.

[0012] By adopting the above technical solution and selecting high-purity raw materials as starting materials, the interference and hindrance of impurity molecules (such as sorbitol and maltitol) on the crystal growth of maltitol are reduced, which is conducive to obtaining a finished product with a more perfect crystal form and improving the single-pass crystallization yield.

[0013] Preferably, step S2 is implemented as follows: the maltitol solution is vacuum evaporated to a dry matter concentration of 78-86 wt%, and seed crystals are added when the material temperature is controlled at 70-75°C; the vacuum degree is adjusted to -0.4 ± 0.2 MPa.

[0014] By employing the above technical solution, controlling the dry matter concentration at 78-86 wt% and maintaining a vacuum of -0.4 ± 0.2 MPa is crucial for achieving evaporative crystal growth. If the concentration is too low, insufficient supersaturation leads to easy dissolution of the seed crystals; if the concentration is too high, the system viscosity increases dramatically, easily causing agglomeration. Within this process window, the evaporation rate of water and the crystal growth rate reach a dynamic equilibrium, ensuring sufficient crystal growth during the crystal growth stage and providing a good nucleation basis for subsequent cooling crystallization.

[0015] Preferably, in step S2, the amount of maltitol seed crystals added is 1-3‰ of the total dry matter mass in the maltitol solution; the particle size of the maltitol seed crystals is 100-200 mesh.

[0016] By adopting the above technical solution, limiting the particle size and addition amount of seed crystals is to control the specific surface area and particle size distribution of the final product. Seed crystals with a specific surface area of ​​100-200 mesh have a moderate amount of surface area, which can provide sufficient crystallization centers to shorten the induction period, while avoiding the problems of excessive fine powder in the final product due to excessively fine seed crystals (>200 mesh) or slow crystallization rate and low yield due to excessively coarse seed crystals (<100 mesh).

[0017] Preferably, the maltitol seed crystals are prepared by the following method: high-purity maltitol crystals are taken, crushed, and sieved to collect particles with a particle size distribution in the range of 100-200 mesh.

[0018] By adopting the above technical solution, seed crystals are prepared by mechanical crushing and strict sieving of homogeneous high-purity crystals, which ensures the consistency between the seed crystals and the crystal form of the target product, eliminates the uncontrollable factors of heterogeneous nucleation, and ensures the stable progress of the crystallization process.

[0019] Preferably, in step S3, the specific process parameters for the constant temperature crystal growth are: temperature controlled at 60-70℃, and constant temperature time of 2-4h.

[0020] By adopting the above technical solution, constant temperature crystal growth is performed after material transfer. The Ostwald ripening effect is used to dissolve and redeposit the tiny crystal nuclei on the surface of the large crystal, repairing the mechanical damage caused to the crystal during transportation and improving the integrity and mechanical strength of the crystal.

[0021] Preferably, in step S3, the slow-then-fast staged cooling includes a slow cooling stage and a fast cooling stage; the process parameters for the slow cooling stage are: cooling from the constant temperature to 40-50℃ at a cooling rate of 0.2-0.5℃ / h; the process parameters for the fast cooling stage are: cooling from 40-50℃ to 30-35℃ at a cooling rate of 1-2℃ / h. By adopting the above technical solution, the dynamic control logic of the segmented cooling is clarified.

[0022] Slow cooling phase (60-70℃ to 40-50℃): During this phase, the system is in a high-concentration, high-temperature state and is extremely sensitive to changes in supersaturation. By controlling an extremely low cooling rate of 0.2-0.5℃ / h, the supersaturation is strictly controlled within the metastable region, forcing solute molecules to accumulate orderly mainly on the surface of existing crystal nuclei, thereby significantly reducing the proportion of microcrystals formed. This is the core step in ensuring the high fluidity of the product.

[0023] Rapid cooling phase (40-50℃ to 30-35℃): As the temperature decreases, crystal growth enters a stable period and the system viscosity increases. At this time, increasing the cooling rate to 1-2℃ / h can increase the driving force of supersaturation, promote the rapid precipitation of the remaining solute, improve the crystallization yield without introducing new crystal nuclei, and shorten the production cycle.

[0024] Preferably, in step S3, continuous stirring is maintained during the cooling and crystallization process, and the stirring speed is 30-60 rpm.

[0025] By adopting the above technical solution, appropriate low-speed stirring can maintain the uniformity of temperature and concentration fields in the system, enhance the mass transfer process, and avoid crystal breakage due to excessive shear force, thus maintaining the integrity of crystal morphology.

[0026] Preferably, in step S4, the centrifugal separation is carried out after the material temperature drops to 30-35℃, and the centrifugal speed is 1500-3000 rpm; in step S5, the drying is carried out using a fluidized bed dryer, the inlet air temperature is controlled at 50-60℃, and the product moisture content is dried to less than 0.3wt%.

[0027] By adopting the above technical solutions, solid-liquid separation and low-temperature fluidized bed drying are carried out at a certain temperature, avoiding product surface melting or clumping caused by high temperature, ensuring low moisture content and good particle dispersion of the final product, and further guaranteeing the excellent flowability of the product.

[0028] This invention provides a method for producing highly fluid crystalline maltitol. It has the following beneficial effects: 1. This invention maintains the synergistic effect of crystal growth and segmented cooling crystallization through vacuum evaporation. In the early stages of crystallization, supersaturation is maintained by solvent removal rather than cooling. During the cooling stage, a slow-then-fast rate control suppresses secondary nucleation. This kinetic control strategy effectively avoids the problem of excessive local supersaturation leading to the formation of numerous fine crystals in traditional aqueous crystallization. This results in a final product with a concentrated and uniform particle size distribution and regular crystal morphology, thus giving the product excellent flowability and reducing the risk of moisture absorption and clumping during storage and transportation. 2. This invention overcomes the problem of low crystallization yield caused by the high viscosity and difficult diffusion of maltitol aqueous solutions. By continuously evaporating water during the crystallization stage and employing a rapid cooling strategy at the end of the cooling period, the crystallization potential of the system is fully explored, allowing a large amount of solute to transfer from the liquid phase to the solid phase, thus improving the single-pass crystallization yield. Simultaneously, the isothermal crystallization and slow growth process helps repair lattice defects and eliminate impurities, ensuring that the product still possesses excellent purity without the use of organic solvents for purification, meeting the needs of high-end applications. 3. Compared to traditional organic solvent crystallization methods, this invention does not use flammable and explosive organic solvents such as ethanol. This not only eliminates the possibility of solvent residue in the product, ensuring safety in food and pharmaceutical applications, but also eliminates explosion hazards in the production environment. Furthermore, it eliminates the need for complex solvent recovery and distillation equipment, significantly reducing energy consumption and production costs, aligning with the industrial development trend of green manufacturing. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments and comparative examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] Preparation Examples 1-3: Preparation Example 1: This preparation example is used to prepare maltitol seed crystals that conform to the preferred particle size range of the present invention.

[0031] Take 2000g of commercially available high-purity maltitol crystals and place them in a universal grinder for grinding. Set the grinder speed to 3000rpm and the grinding time to 1-2 minutes. The ground powder is then sieved using a standard sieve assembly containing 100-mesh (150μm pore size) and 200-mesh (75μm pore size) standard sieves. Collect the particles that remain on the 200-mesh sieve but pass through the 100-mesh sieve; this yields maltitol seed crystal A with a particle size distribution between 100-200 mesh. Seal and store for later use.

[0032] Preparation Example 2: This preparation example is used to prepare maltitol seed crystals with excessively fine particle size, which are intended for subsequent comparative examples to verify the negative impact of fine seed crystals on product flowability.

[0033] Take 1000g of the commercially available high-purity maltitol crystals and place them in a universal grinder for an extended grinding time of up to 5 minutes to obtain a finer powder. The ground powder is then sieved using a 200-mesh (75μm aperture) standard sieve. Collect the particles that pass through the 200-mesh sieve, obtaining fine seed crystals B with a particle size greater than 200 mesh (less than 75μm), and seal them for later use.

[0034] Preparation Example 3: This preparation example is used to prepare maltitol seed crystals with a relatively large particle size, which are intended to be used in subsequent comparative examples to verify the effect of coarse seed crystals on crystallization efficiency.

[0035] Take 1000g of commercially available high-purity maltitol crystals, lightly crush them, and then sieve them using a standard sieve set containing 60-mesh (250μm pore size) and 80-mesh (180μm pore size) standard sieves. Collect the particles that are trapped on the 80-mesh sieve but pass through the 60-mesh sieve, which yields coarse seed crystals C with a particle size between 60-80 mesh. Seal and store for later use.

[0036] Example 1: This example provides a method for producing highly fluid crystalline maltitol, including the following steps: (1) Pre-concentration: Take maltitol raw material solution with a dry basis purity of 95.0%, pump it into an evaporator and heat it to concentrate until the solution has a viscosity of 75%; (2) Evaporation and crystallization: Continue to concentrate the above maltitol solution by vacuum evaporation until the dry matter mass concentration of the solution reaches 83%. At this time, adjust the material temperature to 72°C, add the maltitol seed crystal A obtained in Preparation Example 1, and add 2‰ of the total dry matter mass in the maltitol solution. After adding the seed crystal, adjust the vacuum degree to -0.4MPa, maintain the evaporation at this vacuum degree and temperature for 2 hours, and then release the vacuum. (3) Cooling and crystallization: The material is quickly transferred to a preheated and constant-temperature crystallizer and kept at 62°C for 2 hours; then it enters the slow cooling stage, controlling the cooling rate at 0.5°C / h, and cooling down to 40°C; finally, it enters the rapid cooling stage, controlling the cooling rate at 2.0°C / h, and cooling down to 30°C. (4) Separation and drying: After cooling, the crystallization liquid is sent to a centrifuge for solid-liquid separation. The collected wet crystals are sent to a fluidized bed dryer and dried at an air inlet temperature of 55°C until the moisture content is less than 0.3%, thus obtaining the finished product.

[0037] Example 2: This example provides a method for producing highly fluid crystalline maltitol, including the following steps: (1) Pre-concentration: Take maltitol raw material solution with a dry basis purity of 92.0%, pump it into an evaporator and heat it to concentrate until the solution has a viscosity of 72%; (2) Evaporation and crystallization: Continue to concentrate the above maltitol solution by vacuum evaporation until the dry matter mass concentration of the solution reaches 78%. At this time, adjust the material temperature to 70°C, add the maltitol seed crystal A obtained in Preparation Example 1, and add 1‰ of the total dry matter mass in the maltitol solution. After adding the seed crystal, adjust the vacuum degree to -0.45MPa, maintain the evaporation at this vacuum degree and temperature for 2 hours, and then release the vacuum. (3) Cooling and crystallization: The material is quickly transferred to a preheated and constant-temperature crystallizer and kept at 65°C for 2 hours; then it enters the slow cooling stage, controlling the cooling rate at 0.3°C / h, and cooling down to 40°C; finally, it enters the rapid cooling stage, controlling the cooling rate at 1.5°C / h, and cooling down to 35°C. (4) Separation and drying: After cooling, the crystallization liquid is sent to a centrifuge for solid-liquid separation. The collected wet crystals are sent to a fluidized bed dryer and dried at an air inlet temperature of 50°C until the moisture content is less than 0.3%, thus obtaining the finished product.

[0038] Example 3: This example provides a method for producing highly fluid crystalline maltitol, including the following steps: (1) Pre-concentration: Take maltitol raw material solution with a dry basis purity of 96.0%, pump it into an evaporator and heat it to concentrate until the solution has a viscosity of 70%; (2) Evaporation and crystallization: Continue to concentrate the above maltitol solution by vacuum evaporation until the dry matter mass concentration of the solution reaches 86%. At this time, adjust the material temperature to 75°C, add the maltitol seed crystal A obtained in Preparation Example 1, and add 3‰ of the total dry matter mass in the maltitol solution. After adding the seed crystal, adjust the vacuum degree to -0.5MPa, maintain the evaporation at this vacuum degree and temperature for 3 hours, and then release the vacuum. (3) Cooling and crystallization: The material is quickly transferred to a preheated and constant-temperature crystallizer and kept at 60°C for 2 hours; then it enters the slow cooling stage, controlling the cooling rate at 0.2°C / h, and cooling down to 50°C; finally, it enters the rapid cooling stage, controlling the cooling rate at 1.0°C / h, and cooling down to 33°C. (4) Separation and drying: After cooling, the crystallization liquid is sent to a centrifuge for solid-liquid separation. The collected wet crystals are sent to a fluidized bed dryer and dried at an air inlet temperature of 60°C until the moisture content is less than 0.3%, thus obtaining the finished product.

[0039] Example 4: This example provides a method for producing highly fluid crystalline maltitol, including the following steps: (1) Pre-concentration: Take maltitol raw material solution with a dry basis purity of 95.0%, pump it into an evaporator and heat it to concentrate until the solution reaches a viscosity of 74%; (2) Evaporation and crystallization: Continue to concentrate the above maltitol solution by vacuum evaporation until the dry matter mass concentration of the solution reaches 82%. At this time, adjust the material temperature to 74°C, add the maltitol seed crystal A obtained in Preparation Example 1, and add 2.5‰ of the total dry matter mass in the maltitol solution. After adding the seed crystal, adjust the vacuum degree to -0.3MPa, maintain evaporation at this vacuum degree and temperature for 4 hours, and then release the vacuum. (3) Cooling and crystallization: The material is quickly transferred to a preheated and constant-temperature crystallizer and kept at 68°C for 4 hours; then it enters the slow cooling stage, controlling the cooling rate at 0.4°C / h, and cooling down to 45°C; finally, it enters the rapid cooling stage, controlling the cooling rate at 1.8°C / h, and cooling down to 32°C. (4) Separation and drying: After cooling, the crystallization liquid is sent to a centrifuge for solid-liquid separation. The collected wet crystals are sent to a fluidized bed dryer and dried at an air inlet temperature of 55°C until the moisture content is less than 0.3%, thus obtaining the finished product.

[0040] Comparative Examples 1-5: Comparative Example 1: Compared with Example 1, the main difference is the use of an organic solvent-assisted crystallization process. Specifically, in step (2), the solution is concentrated to 80% of the dry matter concentration and then evaporation is stopped without vacuum crystallization maintenance; in step (3), after being kept at 60°C, the temperature is lowered at a rate of 0.2°C / h, and ethanol solvent is added at a rate of 5 mL / h during the cooling process. The remaining parameters and steps are basically the same as in Example 1.

[0041] Comparative Example 2: Compared with Example 1, the difference is that the vacuum crystallization process in step (2) is omitted. Specifically, after adding the seed crystals, the vacuum is immediately released and the material is transferred to the crystallizer for cooling and crystallization, instead of maintaining a vacuum evaporation operation for 2 hours. The remaining steps and parameters are the same as in Example 1.

[0042] Comparative Example 3: Compared with Example 1, the difference is that the segmented cooling strategy was not adopted in the cooling and crystallization stage in step (3). Specifically, after the constant temperature of 62°C was completed, the slow cooling stage and the fast cooling stage were not distinguished. Instead, the temperature was directly reduced to 30°C at a constant rate of 1.5°C / h. The remaining steps and parameters were the same as in Example 1.

[0043] Comparative Example 4: Compared with Example 1, the difference lies in the different specifications of the seed crystals used in step (2). Specifically, the added seed crystal is the fine seed crystal B (particle size greater than 200 mesh) obtained in Preparation Example 2, instead of the seed crystal A obtained in Preparation Example 1. The remaining steps and parameters are the same as in Example 1.

[0044] Comparative Example 5: Compared with Example 1, the difference lies in the different specifications of the seed crystals used in step (2). Specifically, the added seed crystal is the coarse seed crystal C (particle size of 60-80 mesh) obtained in Preparation Example 3, instead of the seed crystal A obtained in Preparation Example 1. The remaining steps and parameters are the same as in Example 1.

[0045] Test Example 1-2: Test Example 1: Verification of Product Physicochemical Properties and Process Feasibility This test case aims to verify the basic physicochemical properties of the maltitol crystals prepared in Examples 1-4, confirm whether they meet the quality standards for high-purity crystalline maltitol, and verify the industrial feasibility of the solvent-free coupled crystallization process described in this invention.

[0046] Experimental methods: Take 500g of each of the dried crystal samples prepared in Examples 1-4, and perform the following index determinations respectively:

[0047] Appearance characteristics: Place the sample on a white background and observe it visually under natural light.

[0048] Main content determination: High performance liquid chromatography (HPLC) was used for detection. Chromatographic conditions were: Sugar-Pak TM One column was used at a temperature of 85°C, with ultrapure water as the mobile phase and a flow rate of 0.5 mL / min. A differential refractive index detector (RID) was employed. The normalized peak area was calculated.

[0049] Moisture content: Take 2.0g of the ground sample and determine the moisture content using a Karl Fischer coulometric analyzer.

[0050] Melting range: determined using a fully automated video melting point apparatus. The heating rate was 1.0℃ / min, and the initial melting point and final melting point were recorded.

[0051] Bulk density: Loose density and compacted density were measured separately. Loose density was determined using the natural packing method, and compacted density was determined using the vibrating table method (vibration frequency 300 times / min, vibration time 5min).

[0052] Experimental results: Table 1. Summary of Physicochemical Property Test Data of Products from Examples

[0053] Results analysis: As shown in Table 1, the products obtained in Examples 1-4 all achieved excellent levels in various physicochemical indicators. The main maltitol content was consistently above 99.1%, reaching a maximum of 99.35%; the moisture content was controlled below 0.3%, and the melting range was narrow (around 1.5℃), which is consistent with the standard melting point characteristics of anhydrous maltitol (around 148-151℃).

[0054] This result validates the mechanistic advantages of the vacuum evaporation-segmented cooling coupled crystallization process: during the evaporation stage, by maintaining vacuum and temperature, the supersaturation driving force formed by continuous moisture removal allows seed crystals to initially grow and repair surface defects under controlled conditions, constructing a complete crystal lattice framework; the subsequent segmented cooling strategy avoids lattice defects and mother liquor encapsulation caused by rapid solute precipitation. This staged supersaturation control method enables the final product to maintain extremely high purity and extremely low moisture residue without the use of organic solvents for purification, confirming the feasibility and reliability of this solvent-free production scheme in industrial applications.

[0055] Test Example 2: Performance Comparison and Process Mechanism Verification of the Example and Comparative Examples This test case compares the key performance indicators of the products obtained from Examples 1-4 and Comparative Examples 1-5, focusing on crystallization yield, product purity, flowability, particle size distribution, and solvent residue, to verify the technical advantages of the vacuum evaporation and segmented cooling coupling process described in this invention compared to traditional solvent methods and single control methods.

[0056] Experimental methods: The dried crystal samples prepared in Examples 1-3 and Comparative Examples 1-5 were analyzed according to the following methods: Crystallization yield calculation: Flowability determination: The angle of repose method is used. The sample is allowed to flow naturally down a funnel to form a cone, and the base angle of the cone is measured. The smaller the angle of repose, the better the flowability (generally...). (Considered as having good liquidity).

[0057] Particle size distribution: Use standard test sieves (30 mesh, 50 mesh, 80 mesh, 100 mesh, 200 mesh) for sieving, weigh the mass of the material retained in each sieve layer, and calculate the percentage.

[0058] Solvent residue: For comparative examples using organic solvents, the amount of ethanol residue was determined by gas chromatography headspace method.

[0059] Experimental results: Table 2. Comparison of comprehensive performance indicators of each embodiment and comparative example product

[0060] Table 3. Particle size distribution data (%) of products from the examples and comparative examples

[0061] Results analysis: Based on the data in Tables 2 and 3, and in conjunction with the technical mechanism of this invention, the following analysis is performed: (1) Comparison with solvent method (Comparative Example 1): The crystallization yield of the products in Examples 1-3 reached over 90% without the use of any organic solvents, which is higher than the 75.52% of Comparative Example 1. Meanwhile, the purity of the products in the examples was all above 99%, with no risk of solvent residue. This indicates that through precise control of the physical field (vacuum and temperature coupling), the role of chemical solvents in reducing system viscosity and promoting molecular diffusion can be replaced, achieving green and efficient production. (2) Effect of vacuum evaporation crystal growth step (compared with Comparative Example 2): Comparative Example 2 omitted the vacuum evaporation maintenance step after seeding, resulting in an increase in the content of 100-200 mesh fine powder in the product from 6.74% in Example 1 to 23.31%, and an increase in the angle of repose to 43.6°. The mechanism is explained as follows: maintaining a certain vacuum evaporation in the early stage of seeding can continuously remove solvent, maintain the supersaturation of the system in the middle of the metastable region, and allow the seed crystals to obtain sufficient growth time and repair lattice defects before cooling. If this step is omitted, the crystal skeleton will not develop fully, and it is easy to break or undergo secondary nucleation during subsequent cooling; (3) Effect of segmented cooling strategy (compared with Comparative Example 3): Comparative Example 3 adopted linear rapid cooling, which led to a surge in the fine powder content of the product to 38.51%, a deterioration of the angle of repose to 46.8°, and extremely poor fluidity. This confirms the necessity of the strategy of isothermal to slow cooling and then rapid cooling: slow cooling in the high temperature zone effectively inhibits explosive nucleation and ensures that the solute is mainly deposited on the surface of existing crystal nuclei; rapid cooling in the low temperature zone ensures the yield. Linear cooling cannot balance nucleation control and growth rate, resulting in a wide crystal size distribution, too many fine crystals, and seriously affecting fluidity; (4) Influence of seed crystal size (compared with Comparative Examples 4 and 5): Using fine seed crystals (Comparative Example 4) resulted in a high content of fine powder in the final product and poor flowability; using coarse seed crystals (Comparative Example 5), although the flowability was acceptable, the insufficient specific surface area led to a prolonged crystallization induction period, a slight decrease in yield, and an excessively high proportion of coarse crystals, which affected the dissolution rate. In the example, 100-200 mesh seed crystals were selected, and coupled with the crystallization process, the proportion of 50-80 mesh in the final product reached more than 55%, achieving the optimal balance between packing density and flowability.

[0062] In summary, this invention successfully achieved kinetic control of the maltitol crystallization process through the coupled synergistic effect of vacuum evaporation and segmented cooling, resulting in a crystalline product with no solvent residue, high purity, high yield, and concentrated particle size distribution (high fluidity).

Claims

1. A process for the production of a high flowability crystalline maltitol, characterized in that, The method comprises the following steps: S1, pre-concentrating a maltitol solution to obtain a concentrated solution with a degree of polymerization of 70-75%; S2, concentrating the concentrated solution to a supersaturated state by vacuum evaporation, adding maltitol seed crystals, adjusting the vacuum degree, and maintaining evaporation under the conditions of maintaining vacuum and temperature for 2-4 h, and then releasing the vacuum; S3, transferring the material obtained in step S2 to a crystallizer that has been kept at a constant temperature, first performing constant temperature seed crystal growth, and then performing slow-to-fast staged temperature reduction to complete cooling crystallization; S4, centrifugally separating the material after temperature reduction in step S3, and collecting the crystals; S5, drying the collected crystals to obtain a crystal maltitol product.

2. A process for the production of a high flowability crystalline maltitol according to claim 1, characterized in that, The mass content of maltitol in the dry matter of the maltitol solution in step S1 is greater than 92.0%, and is preferably 95.0%-96.0%.

3. A process for the production of a high flowability crystalline maltitol according to claim 1, characterized in that, The specific implementation of step S2 is as follows: The maltitol solution is vacuum evaporated to a dry matter mass concentration of 78-86 wt%, and the seed crystals are added when the material temperature is controlled at 70-75℃; The vacuum degree is controlled at -0.4±0.2 MPa.

4. A process for the production of a high flowability crystalline maltitol according to claim 1, characterized in that, In step S2, the addition amount of the maltitol seed crystals is 1-3 ‰ of the total mass of the dry matter in the maltitol solution; The particle size of the maltitol seed crystals is 100-200 mesh.

5. A process for the production of a high flowability crystalline maltitol according to claim 4, characterized in that, The maltitol seed crystals are prepared by the following method: High-purity maltitol crystal finished products are taken, crushed, and then screened to collect the particle part with a particle size distribution in the range of 100-200 mesh.

6. A process for the production of a high flowability crystalline maltitol according to claim 1, characterized in that, In step S3, the specific process parameters for constant temperature seed crystal growth are as follows: The temperature is controlled at 60-70℃, and the constant temperature time is 2-4 h.

7. A process for the production of a high flowability crystalline maltitol according to claim 1, characterized in that, In step S3, the slow-to-fast staged temperature reduction comprises a slow temperature reduction stage and a fast temperature reduction stage; The process parameters for the slow temperature reduction stage are as follows: the temperature is reduced from the constant temperature temperature to 40-50℃ at a reduction rate of 0.2-0.5℃ / h; The process parameters for the fast temperature reduction stage are as follows: the temperature is reduced from 40-50℃ to 30-35℃ at a reduction rate of 1-2℃ / h.

8. A process for the production of a high flowability crystalline maltitol according to claim 1, characterized in that, In step S3, continuous stirring is maintained during the cooling crystallization process, and the stirring speed is 30-60 rpm.

9. A process for the production of a high flowability crystalline maltitol according to claim 1, characterized in that, In step S4, the centrifugal separation is performed after the material temperature is reduced to 30-35℃, and the centrifugal speed is 1500-3000 rpm.

10. A process for the production of a high flowability crystalline maltitol according to claim 1, characterized in that, In step S5, the drying is performed using a fluidized bed dryer, the inlet air temperature is controlled at 50-60℃, and the drying is performed until the product moisture content is less than 0.3 wt%.

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