Preparation method of lactose microcrystals based on asymmetric field flow separation and high-pressure homogenization

Abstract

The invention provides a preparation method of lactose microcrystals based on asymmetric field flow separation and high-pressure homogenization. The invention provides a method for separating and purifying lactose. The method comprises a step of separating and purifying lactose from a lactose-containing mixture by utilizing asymmetric field flow separation. The invention also provides a preparation method of lactose microcrystals. The preparation method comprises the step of separating and purifying lactose from a lactose-containing mixture by using the method for separating and purifying lactose. The invention also provides the lactose microcrystal prepared by the preparation method, a method for reducing the particle size distribution of the lactose microcrystal, a method for adjusting the particle size of the lactose microcrystal and related application.

Description

Technical Field

[0001] This invention pertains to the field of lactose preparation, and more specifically, it relates to a method for preparing lactose microcrystals based on asymmetric field flow separation and high-pressure homogenization. Background Technology

[0002] Lactose is a major byproduct of the dairy industry, typically derived from whey. Recovering lactose from whey and processing it into high-value-added products not only brings economic benefits but also addresses the serious environmental problems caused by direct whey discharge. For example, the chemical oxygen demand (COD) of whey is typically 60-70 g / L, which can lead to eutrophication of water bodies. Currently, industrial lactose recovery mainly relies on crystallization, with cold crystallization being the most common process, achieving a typical yield of 45-55%. However, existing lactose crystallization technologies generally suffer from the following drawbacks: (1) The crystallization process is slow and uncontrollable: Lactose crystallizes slowly and has a wide metastable zone width (MSZW). Traditional processes often require 20-48 hours to complete one crystallization cycle, resulting in low production efficiency and high energy consumption.

[0003] (2) Wide crystal size distribution: Traditional stirred crystallizers (STC) often use high-intensity stirring to ensure mass and heat transfer, which easily induces secondary nucleation and crystal breakage. As a result, the crystal size distribution is wide (PSD Span value is usually > 2.0), which affects filtration and drying efficiency and the quality of the final product, such as easy agglomeration.

[0004] (3) Unstable product quality: Uncontrollable nucleation and growth often lead to a high proportion of amorphous lactose production, making the product prone to moisture absorption and clumping, and it is easy to stick to the wall during spray drying, resulting in limited yield.

[0005] (4) Limitations on raw material purity: Large molecular impurities such as proteins, peptides, and polysaccharides remaining in whey permeate can inhibit crystal growth, which is an important reason for crystallization difficulties and poor product quality. Traditional filtration methods (such as ultrafiltration) are difficult to completely remove these trace impurities.

[0006] To address the aforementioned issues and control lactose crystallization, existing technologies primarily employ the following techniques: Seed crystal method: Seed crystals are added to a supersaturated solution to induce crystallization. The quality, quantity, and size of the seed crystals have a decisive impact on the final product. However, using seed crystals made from commercially ground lactose can lead to uncontrollable secondary nucleation due to the tiny particles and fragmented structure attached to their surface, resulting in a smaller particle size in the final product.

[0007] Antisolvent crystallization: By adding antisolvents such as ethanol or acetone (20–60% v / v) to reduce lactose solubility and accelerate crystallization, the yield can be significantly improved (to 55–65%). However, on a macroscopic scale, the mixing uniformity of the antisolvent is difficult to control, which can easily lead to excessive local supersaturation, resulting in severe crystal agglomeration and uncontrollable particle size.

[0008] Energy field-assisted crystallization: Energy fields such as ultrasound (20-40 kHz) can induce nucleation, but uneven energy distribution and excessively high local energy can easily lead to crystal breakage. Although continuous crystallization techniques such as the MSMPR crystallizer can improve efficiency, the treatment of acid whey permeate still presents challenges, and high lactic acid content can easily lead to insufficient purification.

[0009] Therefore, there is an urgent need in this field to explore a new method for preparing lactose in order to solve the above problems. Summary of the Invention

[0010] The purpose of this invention is to solve the technical problems existing in current lactose crystallization processes, such as long crystallization cycles, wide particle size distribution (PSDSpan value > 3.0), easy product agglomeration, and low yield. This invention provides a method for preparing lactose microcrystals based on asymmetric field flow separation and high-pressure homogenization. This method removes crystal growth inhibitors through deep purification and combines this with high-pressure homogenization to induce explosive nucleation, achieving precise control of lactose crystal particle size and a significant improvement in yield.

[0011] A first aspect of the present invention provides a method for separating and purifying lactose, the method comprising the step of separating and purifying lactose from a mixture containing lactose using asymmetric field flow separation.

[0012] In one or more embodiments, the asymmetric field flow separation employs an open channel structure, the channel comprising an impermeable upper wall and a lower wall serving as an accumulation wall.

[0013] In one or more embodiments, the accumulation wall consists of a porous support and a filter membrane covering it.

[0014] In one or more embodiments, the filter membrane is an organic or ceramic membrane with a molecular weight cutoff (MWCO) of 1-10 kDa.

[0015] In one or more embodiments, the method further includes the step of separating and purifying lactose from a lactose-containing mixture using nanofiltration.

[0016] In one or more embodiments, the nanofiltration is performed using a nanofiltration membrane.

[0017] In one or more embodiments, the nanofiltration membrane has a molecular weight cutoff of 150-300 Da.

[0018] In one or more embodiments, the step of separating and purifying lactose from a lactose-containing mixture using asymmetric field flow separation precedes the step of separating and purifying lactose from a lactose-containing mixture using nanofiltration.

[0019] In one or more embodiments, the method sequentially includes the steps of separating and purifying lactose from a lactose-containing mixture using asymmetric field flow separation and separating and purifying lactose from the lactose-containing mixture using nanofiltration.

[0020] A second aspect of the present invention provides a method for preparing lactose microcrystals, the method comprising the step of separating and purifying lactose from a mixture containing lactose using the method for separating and purifying lactose described in any embodiment of the present invention.

[0021] In one or more embodiments, the method for preparing the lactose microcrystals includes the following steps: (1) Using the method for separating and purifying lactose described in any embodiment of the present invention, lactose is separated and purified from a mixture containing lactose to obtain a purified lactose solution; (2) Concentrate the lactose purification solution described in (1) to a supersaturated state to obtain a lactose supersaturated solution; (3) Homogenize the lactose supersaturated solution described in (2) to obtain a lactose homogenized solution; (4) Crystallize the lactose homogenized solution described in (3) to obtain lactose microcrystals.

[0022] In one or more embodiments, in step (3), the homogenization process is high-pressure homogenization or high-speed dispersion shearing.

[0023] In one or more embodiments, the homogenization process is a high-pressure homogenization process.

[0024] In one or more embodiments, the pressure of the high-pressure homogenization is 40 MPa or higher, more preferably 80 to 200 MPa, and / or the number of cycles of the high-pressure homogenization is 1 to 5.

[0025] In one or more embodiments, in step (2), the concentration is to concentrate the lactose purification solution to a solid content of 50 wt% or more, and / or the concentration of lactose in the concentrated lactose supersaturated solution is 500 g / L or more.

[0026] In one or more embodiments, the crystallization in step (4) is cooling crystallization.

[0027] In one or more embodiments, the cooling crystallization is achieved by reducing the temperature from 65-75°C to 10-15°C.

[0028] In one or more embodiments, the cooling crystallization is a staged cooling crystallization, wherein the first stage temperature is reduced from 65~75℃ to 45~50℃ and the residence time is 20~40 min, the second stage temperature is reduced to 30~35℃ and the residence time is 20~40 min, and the third stage temperature is reduced to 10~15℃ and the residence time is 20~40 min.

[0029] In one or more embodiments, the cooling crystallization is a stirred cooling crystallization, a multi-stage series continuous cooling crystallization, or a mixed suspension mixed product discharge (MSMPR) crystallizer cooling crystallization.

[0030] In one or more embodiments, the method further includes the steps of separating and / or drying the lactose microcrystals of (4).

[0031] In one or more embodiments, the separation is a solid-liquid separation, more preferably a centrifugal separation.

[0032] In one or more embodiments, the drying is selected from any one or more of hot air drying, vacuum drying, airflow drying, static drying under negative pressure and fluidized bed drying, preferably fluidized bed drying.

[0033] In one or more embodiments, the moisture content in the dried lactose microcrystals is ≤5.5 wt%.

[0034] In one or more embodiments, the particle size distribution of lactose microcrystals is reduced by high-pressure homogenization, such that the obtained lactose microcrystals have a particle size distribution PSD Span value of less than or equal to 2.0.

[0035] In one or more embodiments, the purified solution containing lactose is treated with high-pressure homogenization, and the particle size of lactose microcrystals is adjusted by regulating the pressure of the high-pressure homogenization.

[0036] In one or more embodiments, when the pressure of high-pressure homogenization is above 40 MPa and below 80 MPa (40 MPa ≤ P ≤ 80 MPa), the average particle size D50 of the obtained lactose microcrystals is greater than 45 μm; when the pressure of high-pressure homogenization is greater than 80 MPa and below 200 MPa (80 MPa < P ≤ 200 MPa), the average particle size D50 of the obtained lactose microcrystals is less than or equal to 45 μm.

[0037] In one or more embodiments, using a homogenization pressure greater than 80 MPa and less than 200 MPa (80 MPa < P ≤ 200 MPa) to homogenize the lactose-containing purified solution can result in a lactose microcrystal size distribution PSDSpan value of less than or equal to 2.

[0038] In one or more embodiments, the lactose-containing mixture includes whey, whey permeate, preferably whey permeate; and / or, in the lactose-containing mixture, the dry weight percentage of lactose is 50% or more, preferably 50-90%.

[0039] A third aspect of the present invention provides lactose microcrystals, which are prepared using the preparation method described in any embodiment of the present invention.

[0040] In one or more embodiments, the particle size distribution PSD Span value of the lactose microcrystals is less than or equal to 2.0.

[0041] A fourth aspect of the present invention provides a method for reducing the particle size distribution of lactose microcrystals, the method comprising: a step of treating a lactose-containing purified solution with high pressure homogenization, preferably the high pressure homogenization treatment as described in any embodiment of the present invention.

[0042] A fifth aspect of the present invention provides a method for adjusting the particle size of lactose microcrystals, the method comprising: treating a lactose-containing purified solution with high-pressure homogenization, and adjusting the particle size of lactose microcrystals by adjusting the pressure of the high-pressure homogenization.

[0043] In one or more embodiments, when the pressure of high-pressure homogenization is above 40 MPa and below 80 MPa (40 MPa ≤ P ≤ 80 MPa), the average particle size D50 of the obtained lactose microcrystals is greater than 45 μm; when the pressure of high-pressure homogenization is greater than 80 MPa and below 200 MPa (80 MPa < P ≤ 200 MPa), the average particle size D50 of the obtained lactose microcrystals is less than or equal to 45 μm.

[0044] In one or more embodiments, using a homogenization pressure greater than 80 MPa and less than 200 MPa (80 MPa < P ≤ 200 MPa) to homogenize the lactose-containing purified solution can result in a lactose microcrystal size distribution PSDSpan value of less than or equal to 2.

[0045] A sixth aspect of the present invention provides applications selected from the following: (1) Application of asymmetric field flow separation in lactose separation and purification, preparation of lactose microcrystals, and / or improvement of lactose recovery rate; (2) Application of asymmetric field flow separation and nanofiltration in lactose separation and purification, preparation of lactose microcrystals, and / or improvement of lactose recovery rate; (3) Application of high pressure homogenization in the preparation of lactose microcrystals, reducing the particle size distribution of lactose microcrystals, and / or adjusting the particle size of lactose microcrystals.

[0046] In one or more embodiments, the method for separating and purifying lactose is as described in any embodiment of the present invention, and / or the method for preparing lactose microcrystals is as described in any embodiment of the present invention, and / or the method for reducing the particle size distribution of lactose microcrystals is as described in any embodiment of the present invention, and / or the method for adjusting the particle size of lactose microcrystals is as described in any embodiment of the present invention.

[0047] Other aspects of the invention will be apparent to those skilled in the art from the disclosure herein. Attached Figure Description

[0048] Figure 1 The particle size distribution of the larger lactose microcrystals prepared using the method in Example 1 was measured.

[0049] Figure 2 The particle size distribution of the smaller lactose microcrystals prepared using the method in Example 2 was measured.

[0050] Figure 3 The particle size distribution of the larger-sized lactose microcrystals obtained by the method in Example 3 was measured.

[0051] Figure 4 The particle size distribution of the smaller lactose microcrystals prepared using the method in Example 4 was measured.

[0052] Figure 5 The particle size distribution of the larger-sized lactose microcrystals obtained by the method in Example 5 was measured.

[0053] Figure 6 The particle size distribution of the smaller lactose microcrystals prepared using the method in Example 6 was measured.

[0054] Figure 7 The particle size distribution of the larger-sized lactose microcrystals prepared using the method in Example 7 was measured.

[0055] Figure 8 The particle size distribution of the smaller lactose microcrystals prepared using the method in Example 8 was measured.

[0056] Figure 9 The particle size distribution of the larger-sized lactose microcrystals prepared using the method in Example 9 was measured.

[0057] Figure 10 The particle size distribution of the smaller lactose microcrystals prepared using the method of Example 10 was measured.

[0058] Figure 11 The particle size distribution of lactose microcrystals prepared using the method in Example 11 was measured.

[0059] Figure 12 The particle size distribution of lactose microcrystals prepared using the method in Example 12 was measured.

[0060] Figure 13 The particle size distribution of lactose microcrystals prepared using the method in Example 13 was measured.

[0061] Figure 14 The particle size distribution of lactose microcrystals prepared using the method in Example 14 was measured. Detailed Implementation

[0062] Through in-depth research, the inventors have creatively introduced asymmetric field flow separation (AF4) technology, commonly used for the analysis and separation of biological macromolecules (such as proteins), into the lactose preparation process. This technology can gently and efficiently remove trace macromolecular impurities such as protein aggregates, peptides, and polysaccharide colloids from whey permeate. These impurities are key factors that are difficult to remove with traditional membrane filtration and severely inhibit crystal growth. By using AF4 for deep purification, combined with subsequent nanofiltration desalination to remove small molecule impurities such as lactic acid, citric acid, and calcium ions, the purity and crystallization yield of the lactose solution are significantly improved.

[0063] Furthermore, this invention combines asymmetric field flow separation technology with high-pressure homogenization (HPH). In a pure, supersaturated solution system, the strong shear force and cavitation effect generated by high-pressure homogenization break the nucleation energy barrier, resulting in the explosive generation of a large number of uniform nucleation sites, replacing uncontrollable spontaneous nucleation. Through this synergistic control of "purification-homogenization-crystallization," high-quality lactose microcrystals with extremely narrow particle size distribution (PSD Span value ≤ 2.0) and regular crystal morphology can be obtained.

[0064] the term

[0065] Unless otherwise indicated or defined, all terms used have their ordinary meaning in the art as would be understood by those skilled in the art. Furthermore, unless otherwise stated, all methods, steps, techniques, and operations not specifically detailed herein can and have been performed in a manner known per se as would be understood by those skilled in the art.

[0066] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0067] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0068] The terms "above" and "below" both include the stated number.

[0069] Unless otherwise specified, percentages refer to weight percentages and proportions refer to weight ratios in this article.

[0070] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0071] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0072] The term "lactose" refers to a disaccharide composed of one molecule of glucose and one molecule of galactose linked by a β-1,4-glycosidic bond, with the chemical formula […]. Since lactose (which contains no water of crystallization) has a molecular weight of 342.30, it is classified as a small molecule sugar.

[0073] The term "lactose microcrystals" refers to lactose with a crystalline structure and an average particle size in the micrometer range. The term "larger particle size lactose microcrystals" refers to lactose microcrystals with an average particle size D50 value of 45 μm or greater (e.g., 45–120 μm). The term "smaller particle size lactose microcrystals" refers to lactose microcrystals with an average particle size D50 value of 45 μm or less (e.g., 5–45 μm). The term "average particle size" refers to the average diameter of all microcrystals in a lactose microcrystal. The average particle size of lactose microcrystals can be reflected by the D50 value. The "D50 value" refers to the particle size of lactose microcrystals measured using equipment such as a laser particle size analyzer, and is the particle size corresponding to the 50% position of the cumulative distribution curve.

[0074] The term "lactose-containing mixture" refers to a raw material used in the production or preparation of lactose, typically a mixture containing lactose. The lactose-containing mixture may include whey or whey permeate. In some embodiments, the lactose in the lactose-containing mixture has a dry weight percentage of 50% or more, 55% or more, 60% or more, 70% or more, or 75% or more, for example, 50-80%, 55-75%, or 60-75%. In some specific embodiments, the lactose-containing mixture is a whey permeate.

[0075] The term "whey" refers to the mixture formed during the production of cheese or casein. It is usually a liquid and its main components include lactose, soluble proteins (such as β-lactoglobulin and α-lactalbumin), minerals (calcium, phosphorus, etc.), and trace amounts of fat.

[0076] The term "whey permeate" refers to a mixture formed during the lactose preparation process from whey, typically containing about 20% dry matter, of which 60% to 75% lactose, 15% to 25% minerals (or ash), 5% to 15% protein, and trace amounts of other whey components. In some embodiments, whey permeate can be prepared from whey by membrane separation (e.g., ultrafiltration, microfiltration, etc.).

[0077] The terms "asymmetric flow field-flow separation," "asymmetrical flow field-flow separation," and "AF4" are used interchangeably, all referring to a separation method based on fluid dynamics and diffusion behavior, which separates samples through asymmetric flow. The asymmetric flow typically includes vertical crossflow (crossflow) and laminar flow within channels (channel flow or tangential flow).

[0078] The term "high-pressure homogenization" refers to a physical processing technique that uses high mechanical pressure to force a sample through a narrow slit (homogenization valve), utilizing shear force, cavitation effect, and turbulence to break particles or droplets down to the nanometer / micrometer scale, achieving uniform dispersion, emulsification, or cell disruption. In some implementations, the pressure for high-pressure homogenization is 40-200 MPa.

[0079] Methods for the isolation and purification of lactose

[0080] The present invention provides a method for separating and purifying lactose from a mixture containing lactose, the method comprising the step of separating and purifying lactose from the mixture containing lactose using asymmetric field flow separation.

[0081] One advantage of this invention lies in the use of asymmetric field flow separation (AF4) to separate and purify lactose from a mixture containing lactose. Through the hydrodynamic separation mechanism of asymmetric field flow, under the combined action of tangential and perpendicular cross-flow, large molecular impurities such as residual proteins, peptides, polysaccharides, and colloidal aggregates in the solution are pushed towards the accumulation wall and discharged as waste liquid, while smaller lactose molecules pass through the channel with the mainstream solvent. This process gently and efficiently removes trace amounts of micron- to nanometer-sized large molecular impurities (crystal growth inhibitors) that are difficult to remove with traditional ultrafiltration. Furthermore, by combining it with nanofiltration (NF) technology, efficient desalination can be achieved, removing small molecular impurities such as lactic acid, citric acid, phosphate, and calcium ions, significantly improving the purity of lactose.

[0082] In some embodiments, the ratio of the channel velocity to the cross velocity in asymmetric field flow separation is typically controlled between 1:1 and 10:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or any combination thereof, more specifically, 2:1 to 9:1, 3:1 to 8:1, 4:1 to 7:1, 5:1 to 7:1, to ensure effective separation resolution. In some embodiments, the channel velocity for asymmetric field flow separation is 6.0 ± 1.0 mL / min. In some embodiments, the cross velocity for asymmetric field flow separation is 1.0 ± 0.3 mL / min.

[0083] The asymmetric flow separation employs an open channel with an impermeable upper wall (such as polycarbonate or stainless steel) and a porous support and filter membrane forming an accumulation wall. In some embodiments, the filter membrane is an organic or ceramic membrane with a molecular weight cutoff (MWCO) of 1-10 kDa (e.g., 1 kDa, 2 kDa, 3 kDa, 5 kDa, 9 kDa, 10 kDa, or any combination thereof). The term "Da" refers to the molecular weight cutoff, i.e., the molecular weight of molecules retained by the filter membrane. It should be understood that "a certain value + Da" indicates that the molecular weight cutoff is greater than or equal to that value. For example, a 1 kDa organic membrane means that when applied for filtration, the molecular weight cutoff is ≥1 kDa. Therefore, taking a 1000 Da organic membrane as an example, a 1-10 kDa organic membrane means that when applied for filtration, the molecular weight cutoff is in the range of ≥1 kDa to ≤10 kDa.

[0084] In some embodiments, the method for separating and purifying lactose from a lactose-containing mixture further includes the step of separating and purifying lactose from the lactose-containing mixture using nanofiltration. In some embodiments, the nanofiltration uses a nanofiltration membrane to further separate and purify the lactose solution separated by asymmetric field flow. In some embodiments, the molecular weight cutoff of the nanofiltration membrane is 150-300 Da, for example, 150 Da, 160 Da, 180 Da, 200 Da, 220 Da, 240 Da, 260 Da, 280 Da, 300 Da, or any combination thereof.

[0085] In some embodiments, the method for separating and purifying lactose from a lactose-containing mixture includes the steps of separating and purifying lactose from the lactose-containing mixture using asymmetric flow separation and nanofiltration. In some embodiments, the asymmetric flow separation step and the nanofiltration step are performed sequentially. The nanofiltration step can remove salts and small molecule impurities from the lactose solution after asymmetric flow separation, thereby obtaining a further purified lactose solution.

[0086] Preparation method of lactose microcrystals

[0087] This invention provides a method for preparing lactose microcrystals from a lactose-containing mixture, the method comprising the lactose separation and purification steps described in any embodiment of this invention. In some embodiments, the lactose separation and purification steps are steps of separating and purifying lactose from the lactose-containing mixture using asymmetric field flow separation and nanofiltration, preferably the asymmetric field flow separation step and the nanofiltration step are performed sequentially.

[0088] In some embodiments, the method for preparing lactose microcrystals from a lactose-containing mixture further includes a step of concentrating the purified lactose solution. In some embodiments, the concentration may bring the purified lactose-containing solution to a supersaturated state. In some embodiments, the concentration of the lactose solution to a supersaturated state can be determined by the solids content in the lactose solution; for example, the solids content in the concentrated lactose supersaturated solution may be above 50 wt%, above 55 wt%, or above 60 wt% (more specifically, 55-65 wt%, 56-64 wt%, 57-63 wt%, 58-62 wt%, or 59-61 wt%). In some embodiments, the lactose concentration in the concentrated lactose supersaturated solution may be above 500 g / L, above 520 g / L, or above 550 g / L, for example, 550-650 g / L. The concentration may be performed using concentration methods known in the art, such as, but not limited to, evaporation concentration. For example, the evaporation concentration temperature may be 65-75°C.

[0089] In some embodiments, the method for preparing lactose microcrystals from a lactose-containing mixture further includes a step of homogenizing a concentrated, supersaturated lactose solution. In some embodiments, the homogenization is high-pressure homogenization or high-speed shear dispersion.

[0090] One of the core advantages of this invention is the application of high-pressure homogenization to nucleation control in supersaturated lactose-containing solutions. The instantaneous pressure drop, shearing, and cavitation during homogenization force lactose molecules to overcome the nucleation energy barrier, forming numerous highly uniform molecular aggregates at the nanoscale. These aggregates provide a large number of uniform nucleation sites for lactose crystallization. By precisely controlling the homogenization pressure and the number of cycles, the average size and concentration of crystal nuclei can be adjusted, thereby obtaining lactose microcrystals with uniform particle size distribution and improving the quality of the lactose microcrystals.

[0091] In some embodiments, the pressure of the high-pressure homogenization is above 40 MPa, for example 40~200 MPa, 40~150 MPa or 80~120 MPa.

[0092] In some implementations, the high-pressure homogenization cycle is repeated more than once, more than twice, more than three times, or even more than five times, for example, 1 to 5 times.

[0093] In some embodiments, the high-pressure homogenization is a staged high-pressure homogenization. In some specific embodiments, the staged high-pressure homogenization includes a first-stage high-pressure homogenization and a second-stage high-pressure homogenization, wherein the pressure of the first-stage high-pressure homogenization is above 120 MPa (e.g., 120-150 MPa), and the pressure of the second-stage high-pressure homogenization is below 120 MPa (e.g., 80-100 MPa). It should be understood that the terms "first-stage" and "second-stage" in this invention have a specific order, i.e., first then second. However, the first and second stages do not necessarily mean only two high-pressure homogenizations. The first-stage high-pressure homogenization can be performed once, twice, three times, or more, and the second-stage high-pressure homogenization can also be performed once, twice, three times, or more. The higher homogenization pressure in the first stage ensures sufficient lactose nucleation, while the lower pressure in the second stage stabilizes and refines the lactose crystal nuclei, preventing excessive aggregation.

[0094] In this invention, the high-pressure homogenization can be performed using high-pressure homogenization equipment known in the art, such as a staged high-pressure homogenization device. In some embodiments, the high-pressure homogenization can be monitored and controlled online to further control the uniformity of lactose crystal size. For example, online process analysis technology (PAT), such as focused beam reflectance measurement (FBRM), can be integrated at the outlet of the high-pressure homogenization instrument (e.g., its high-speed shear reactor) to monitor the crystal size distribution in real time.

[0095] In some embodiments, the high-speed shear dispersion can be performed using a high-speed shear disperser. In some embodiments, the high-speed shear dispersion speed is 8000 rpm or higher, for example, 9000 rpm or higher, 10000 rpm or higher. In some embodiments, the high-speed shear dispersion treatment time can be 1 to 10 minutes, for example, 2 to 8 minutes, 3 to 7 minutes or 4 to 6 minutes.

[0096] In some embodiments, the method for preparing lactose microcrystals from a lactose-containing mixture further includes a crystallization step. In some embodiments, the crystallization can be performed by cooling a homogenized lactose-containing liquid. It should be understood that the cooling crystallization can be carried out by various methods such as stirring cooling and crystallizer cooling. In some embodiments, the crystallization can be performed using an MSMPR crystallizer, for example, by using multi-stage series continuous cooling crystallization. By using multi-stage series continuous cooling crystallization, different temperature gradients can be set for each stage, allowing for programmed and precise control of the lactose crystal growth process. For example, a staged cooling strategy can be used to balance the crystal growth rate and the limitations of vortex dynamics: the first stage temperature is lowered to 45-50°C, with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage temperature is lowered to 30-35°C, with a residence time of 20-40 min; the third stage temperature is lowered to 10-15°C, with a residence time of 20-40 min, minimizing lactose solubility through deep cooling.

[0097] In some embodiments, the method for preparing lactose microcrystals from a lactose-containing mixture further includes the steps of separating and / or drying the crystallized lactose microcrystals. The separation can be a solid-liquid separation, such as, but not limited to, centrifugal separation. In some specific embodiments, the centrifugal separation can be performed using vacuum filtration or a horizontal screw centrifuge. The drying can be performed using methods known in the art, such as hot air drying, vacuum drying, airflow drying, static drying under negative pressure, fluidized bed drying, etc. In some specific embodiments, the drying is fluidized bed drying. In some embodiments, the moisture content in the dried lactose microcrystals is less than or equal to 5.5 wt%, preferably 5.0 wt% to 5.5 wt%.

[0098] In some embodiments, the method for preparing lactose microcrystals from a lactose-containing mixture comprises the following steps in sequence: (1) Lactose was separated and purified from a mixture containing lactose by using asymmetric field flow separation (AF4) and nanofiltration to obtain a lactose purified solution; (2) Concentrate the lactose purification solution described in (1) to a supersaturated state to obtain a lactose supersaturated solution; (3) The lactose supersaturated solution described in (2) is subjected to high-pressure homogenization to obtain a lactose homogenized solution; (4) Crystallize the lactose homogenized solution described in (3) to obtain lactose microcrystals.

[0099] In some embodiments, the asymmetric field flow separation, nanofiltration, concentration, high-pressure homogenization, and / or crystallization are as described in any embodiment of the present invention.

[0100] In some embodiments, step (1) includes: separating and purifying lactose from a mixture containing lactose using asymmetric field flow separation (AF4), and then further separating and purifying lactose using nanofiltration to obtain a lactose purified solution.

[0101] In some embodiments, the method for preparing lactose microcrystals from a lactose-containing mixture further includes an optional step (5): separating and / or drying the crystallized lactose microcrystals. In some embodiments, the separation and / or drying is as described in any embodiment of the present invention.

[0102] Lactose microcrystals

[0103] The present invention also provides lactose microcrystals prepared by the method for preparing lactose microcrystals from a mixture containing lactose as described in any embodiment of the present invention.

[0104] In some embodiments, the lactose recovery rate obtained by the method of the present invention is high, for example, the lactose recovery rate is above 60%, above 70%, above 74%, above 76%, above 80%, above 81%, above 82% or higher.

[0105] In some embodiments, the lactose crystallites prepared by the method of the present invention exhibit a normally distributed particle size distribution. In some embodiments, the PSD Span value of the lactose crystallites prepared by the method of the present invention is less than or equal to 2, less than or equal to 1.5, less than or equal to 1.2, or lower.

[0106] Methods to reduce lactose crystallite size distribution and methods to adjust lactose crystallite size

[0107] The present invention also provides a method for reducing the particle size distribution of lactose microcrystals, the method comprising: treating a lactose-containing purified solution using high-pressure homogenization. In some embodiments, the high-pressure homogenization is as described in any embodiment of the present invention.

[0108] The present invention also provides a method for adjusting the particle size of lactose microcrystals, the method comprising: treating a lactose-containing purified solution with high pressure homogenization, and adjusting the particle size of lactose microcrystals by adjusting the pressure of the high pressure homogenization.

[0109] In some embodiments, when the high-pressure homogenization pressure is above 40 MPa and below 80 MPa (40 MPa ≤ P ≤ 80 MPa), the average particle size D50 of the obtained lactose microcrystals is greater than 45 μm. In some embodiments, when the high-pressure homogenization pressure is greater than 80 MPa and below 200 MPa (80 MPa < P ≤ 200 MPa), the average particle size D50 of the obtained lactose microcrystals is less than or equal to 45 μm.

[0110] In some implementations, using a homogenization pressure greater than 80 MPa and less than 200 MPa (80 MPa < P ≤ 200 MPa) to homogenize the lactose-containing purified solution can result in a lactose microcrystal PSD Span value of less than or equal to 2, less than or equal to 1.5, less than or equal to 1.2, or lower.

[0111] application

[0112] This invention provides applications selected from the following: (1) Application of asymmetric field flow separation in lactose separation and purification, preparation of lactose microcrystals, and / or improvement of lactose recovery rate; (2) Application of asymmetric field flow separation and nanofiltration in lactose separation and purification, preparation of lactose microcrystals, and / or improvement of lactose recovery rate; (3) Application of high pressure homogenization in the preparation of lactose microcrystals and / or reduction of lactose microcrystal size distribution.

[0113] The advantages of this invention include: (1) Achieving deep purification of the crystal growth environment: By using asymmetric field flow separation (AF4) combined with nanofiltration technology, trace amounts of macromolecular crystal growth inhibitors (such as protein aggregates) and multivalent ions in the whey permeate are reduced to low levels. This deep purification makes the supersaturation window of the subsequent crystallization process more stable, eliminates the causes of crystal distortion and secondary nucleation, and improves the stability of the process.

[0114] (2) Achieve source control of the nucleation process: Through high-pressure homogenization, a large number of uniform lactose nanoscale molecular aggregates are directly induced to form nucleation sites in a supersaturated solution, which is significantly better than the traditional uncontrollable spontaneous nucleation or external seeding method, and determines the number of crystals and particle size distribution from the source.

[0115] (3) Achieve efficient and controllable crystal growth process: The crystal nuclei grow rapidly and uniformly in a continuous crystallizer with low shear and high mass transfer, shortening the traditional batch crystallization cycle of tens of hours to a few hours, which significantly improves production efficiency.

[0116] (4) Achieve customized control of particle size: By adjusting parameters such as homogenization pressure, the final average particle size (D50) of lactose microcrystals can be controlled as needed in the range of 20-120 μm, and a narrow distribution can be maintained (PSD Span value ≤2.0) to meet the needs of different downstream applications.

[0117] (5) Improve raw material utilization and green process level: Using whey permeate as raw material, the purity of raw material is improved by combining asymmetric field flow and nanofiltration membrane purification, which ultimately improves lactose recovery rate and reduces the use of chemicals.

[0118] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0119] Experimental Materials and Methods

[0120] Experimental materials

[0121] The raw material used in this experiment was whey permeate. This raw material was obtained from whey, a byproduct of cheese production, after pasteurization, defatting, and ultrafiltration (MWCO 10-50 kDa) pretreatment. The main indicators of the raw material were: solids content of approximately 18-20%, of which lactose (dry weight percentage) was approximately 70-90%.

[0122] Asymmetric field flow separation (AF4) instrument: The preparative AF4 separation system is built based on the principle of asymmetric field flow separation and is manufactured by Wyatt Technology Corp. (with a widened trapezoidal channel to meet the needs of preparation).

[0123] Channel parameters: Widened trapezoidal channel, length 350 mm, inlet and outlet widths 20 mm and 5 mm respectively.

[0124] Accumulated wall membrane materials: Organic membrane: PES membrane produced by Synder Filtration, with a MWCO of 1 kDa.

[0125] Nanofiltration membrane (NF): Using DuPont FilmTec™ NF270 nanofiltration membrane elements, with a molecular weight cutoff of approximately 150-300 Da, it is used for desalination and removal of small molecule organic acids.

[0126] High-pressure homogenizer: The APV-2000 high-pressure homogenizer (SPX FLOW) is used, with a maximum working pressure of 200 MPa and a temperature control jacket.

[0127] Cooling crystallizer: A three-stage series continuous cooling crystallizer is built using the EasyMax automated crystallization workstation manufactured by Mettler Toledo of Switzerland, equipped with precision temperature control and stirring paddle.

[0128] Experimental methods

[0129] 1. Particle size detection of lactose microcrystals

[0130] The particle size distribution is inverted by measuring the angular distribution of the scattered light intensity through laser diffraction, utilizing the scattering characteristics of laser light by particles suspended in a liquid dispersant.

[0131] The Dandong Baite BT-9300H laser particle size analyzer, equipped with a wet dispersion module, was used. Analytical grade anhydrous ethanol was selected as the dispersant. The lactose sample to be tested was dissolved in anhydrous ethanol, ultrasonically dispersed, and then added dropwise to the sample cell until a 10-30% masking rate was obtained. The size of the sample was measured, and the instrument automatically collected data and calculated D10, D50, and D90.

[0132] Particle size distribution span (PSD Span value): Calculated by the instrument software using the formula Span = (D90-D10) / D50 using a Dandong Baite BT-9300H laser particle size analyzer.

[0133] 2. Methods for detecting the moisture content of lactose

[0134] The water content of lactose was determined using the Karl Fischer method.

[0135] The moisture content was determined using an automated Karl Fischer moisture analyzer equipped with a heated stirring table. The sample mass was input, and the titration program was started. Methanol-formamide (2:1) was used as the titration solvent, and the instrument automatically titrated to the endpoint (potential jump point), calculating the moisture content based on the volume of titrant consumed.

[0136] 3. Methods for detecting lactose recovery rate

[0137] The lactose recovery rate from raw materials to finished product was calculated using a gravimetric method combined with HPLC purity correction. Calculation formula: Lactose recovery rate (%) = [ M product × P product ×(1- W water )] / (C material ×V material )]×100%; M product : The total mass (g) of the final dried lactose product obtained; P product The lactose purity (%) of the finished lactose was determined by HPLC. W water The moisture content (%) of the finished lactose was determined by the Karl Fischer method. C material The lactose concentration (g / L) in the sample feed solution (whey permeate) was determined by HPLC. V material : Total volume of the sample feed solution (L).

[0138] Example 1: Preparation of large-particle-size lactose microcrystals using AF4 and high-pressure homogenization

[0139] The pretreated whey permeate was pumped into an asymmetric field flow separation (AF4) system. The AF4 channel flow rate was 6.0 mL / min, and the crossflow rate was 1.0 mL / min. The accumulating membrane was a PES organic membrane with a molecular weight cutoff (MWCO) of 1 kDa. The AF4 effluent entered a nanofiltration system (membrane MWCO approximately 150-300 Da) for desalting and removal of small molecule impurities, yielding a purified lactose solution.

[0140] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a supersaturated solution.

[0141] The supersaturated solution was pumped into a high-pressure homogenizer, homogenized at a pressure of 80 MPa, and circulated once. The temperature of the solution was controlled to be kept below 70°C to induce the formation of an appropriate amount of crystal nuclei.

[0142] The homogenized slurry was pumped into a three-stage series continuous cooling crystallizer. A staged cooling strategy was employed to balance the crystal growth rate and the constraints of vortex kinetics: the first stage temperature was lowered to 45-50℃ with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage temperature was lowered to 30-35℃ with a residence time of 20-40 min; and the third stage temperature was lowered to 10-15℃ with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time for the entire crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 250-300 rpm to ensure suspension and mass transfer of the high-solids-content slurry.

[0143] The crystal slurry in the crystallizer is separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0144] Detection results: The average particle size (D50) was 67.02 μm, D10 was 16.83 μm, and D90 was 145.5 μm. The particle size distribution was normally distributed, and the PSD Span value of the lactose microcrystals was 1.92. The lactose recovery rate was 80.2%. Figure 1 ).

[0145] Example 2: Preparation of small-particle-size lactose microcrystals using AF4 and high-pressure homogenization

[0146] The pretreated whey permeate was pumped into an asymmetric field flow separation (AF4) system. The AF4 channel flow rate was 6.0 mL / min, and the crossflow rate was 1.0 mL / min. The accumulating membrane was a PES organic membrane with a molecular weight cutoff (MWCO) of 1 kDa. The AF4 effluent entered a nanofiltration system (membrane MWCO approximately 150-300 Da) for desalting and removal of small molecule impurities, yielding a purified lactose solution.

[0147] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a lactose supersaturated solution.

[0148] The supersaturated solution was pumped into a high-pressure homogenizer, homogenized at a pressure of 120 MPa, and cyclically repeated three times. The temperature of the homogenized solution was controlled to maintain a temperature not exceeding 70°C. This high-pressure, multi-cycle condition was designed to induce the explosive generation of a large number of tiny crystal nuclei to prepare small-particle-size samples.

[0149] The homogenized slurry was pumped into a three-stage series continuous cooling crystallizer. A staged cooling strategy was employed to balance crystal growth rate and vortex kinetics constraints: the first stage temperature was lowered to 45-50°C with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage temperature was lowered to 30-35°C with a residence time of 20-40 min; and the third stage temperature was lowered to 10-15°C with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time for the entire crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 450-500 rpm to ensure suspension and mass transfer of the high-solids-content slurry.

[0150] The crystal slurry in the crystallizer is separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0151] Detection results: The average particle size (D50) was 25.64 μm, D10 was 6.216 μm, and D90 was 52.63 μm. The particle size distribution was normally distributed, and the PSD Span value of the lactose microcrystals was 1.81. The lactose recovery rate was 82.5%. Figure 2 ).

[0152] Example 3: Preparation of large-particle-size lactose microcrystals using nanofiltration and high-pressure homogenization

[0153] The pretreated whey permeate was placed in a high-speed refrigerated centrifuge and centrifuged at 12,000 rpm for 30 min at 4°C. The supernatant was then fed into a nanofiltration system (membrane MWCO approximately 150-300 Da) for desalting and removal of small molecule impurities to obtain a purified lactose solution.

[0154] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a supersaturated solution.

[0155] The supersaturated solution was pumped into a high-pressure homogenizer, homogenized at a pressure of 80 MPa, and circulated once. The temperature of the solution was controlled to be kept below 70°C to induce the formation of an appropriate amount of crystal nuclei.

[0156] The homogenized slurry was pumped into a three-stage series continuous cooling crystallizer. A staged cooling strategy was employed to balance the crystal growth rate and the constraints of vortex kinetics: the first stage temperature was lowered to 45-50℃ with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage temperature was lowered to 30-35℃ with a residence time of 20-40 min; and the third stage temperature was lowered to 10-15℃ with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time for the entire crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 250-300 rpm to ensure suspension and mass transfer of the high-solids-content slurry.

[0157] The crystal slurry in the crystallizer is separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0158] The test results showed that the average particle size (D50) was 52.74 μm, D10 was 7.509 μm, D90 was 140.9 μm, the PSD Span value was 2.53, and the lactose recovery rate was 66.8%. Figure 3 ).

[0159] Example 4: Preparation of small-particle-size lactose microcrystals using nanofiltration and high-pressure homogenization

[0160] The pretreated whey permeate was placed in a high-speed refrigerated centrifuge and centrifuged at 12,000 rpm for 30 min at 4°C. The supernatant was then fed into a nanofiltration system (membrane MWCO approximately 150-300 Da) for desalting and removal of small molecule impurities to obtain a purified lactose solution.

[0161] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a lactose supersaturated solution.

[0162] The supersaturated solution was pumped into a high-pressure homogenizer, homogenized at a pressure of 120 MPa, and cyclically repeated three times. The temperature of the homogenized solution was controlled to maintain a temperature not exceeding 70°C. This high-pressure, multi-cycle condition was designed to induce the explosive generation of a large number of tiny crystal nuclei to prepare small-particle-size samples.

[0163] The homogenized slurry was pumped into a three-stage series continuous cooling crystallizer. A staged cooling strategy was employed to balance crystal growth rate and vortex kinetics constraints: the first stage temperature was lowered to 45-50°C with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage temperature was lowered to 30-35°C with a residence time of 20-40 min; and the third stage temperature was lowered to 10-15°C with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time for the entire crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 450-500 rpm to ensure suspension and mass transfer of the high-solids-content slurry.

[0164] The crystal slurry in the crystallizer is separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0165] The test results showed that the average particle size (D50) was 38.44 μm, D10 was 10.03 μm, D90 was 96.59 μm, the PSD span value was 2.25, and the lactose recovery rate was 72.5%. Figure 4 ).

[0166] Example 5: Preparation of large-particle-size lactose microcrystals using AF4 and high-speed shear dispersion

[0167] The pretreated whey permeate was pumped into an asymmetric field flow separation (AF4) system. The AF4 channel flow rate was 6.0 mL / min, and the crossflow rate was 1.0 mL / min. The accumulating membrane was a PES organic membrane with a molecular weight cutoff (MWCO) of 1 kDa. The AF4 effluent entered a nanofiltration system (membrane MWCO approximately 150-300 Da) for desalting and removal of small molecule impurities, yielding a purified lactose solution.

[0168] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a supersaturated solution.

[0169] The supersaturated solution was pumped into a high-speed shear disperser (such as IKA 2000) at a speed of 10,000 rpm and circulated for 5 min.

[0170] The homogenized slurry was pumped into a three-stage series continuous cooling crystallizer. A staged cooling strategy was employed to balance the crystal growth rate and the constraints of vortex kinetics: the first stage temperature was lowered to 45-50℃ with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage temperature was lowered to 30-35℃ with a residence time of 20-40 min; and the third stage temperature was lowered to 10-15℃ with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time for the entire crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 250-300 rpm to ensure suspension and mass transfer of the high-solids-content slurry.

[0171] The crystal slurry in the crystallizer is separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0172] The test results showed that the average particle size (D50) was 54.06 μm, D10 was 7.606 μm, D90 was 148.3 μm, the PSD span value was 2.6, and the lactose recovery rate was 65.8%. Figure 5 ).

[0173] Example 6: Preparation of small-particle-size lactose microcrystals using AF4 and high-speed shear dispersion

[0174] The pretreated whey permeate was pumped into an asymmetric field flow separation (AF4) system. The AF4 channel flow rate was 6.0 mL / min, and the crossflow rate was 1.0 mL / min. The accumulating membrane was a PES organic membrane with a molecular weight cutoff (MWCO) of 1 kDa. The AF4 effluent entered a nanofiltration system (membrane MWCO approximately 150-300 Da) for desalting and removal of small molecule impurities, yielding a purified lactose solution.

[0175] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a lactose supersaturated solution.

[0176] The supersaturated solution was pumped into a high-speed shear disperser (such as IKA 2000) at 10,000 rpm and circulated for 5 min.

[0177] The high-shear slurry was pumped into a three-stage series continuous cooling crystallizer. A staged cooling strategy was employed to balance crystal growth rate and vortex kinetics constraints: the first stage lowered the temperature to 45-50°C with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage lowered the temperature to 30-35°C with a residence time of 20-40 min; and the third stage lowered the temperature to 10-15°C with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time for the entire crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 450-500 rpm to ensure suspension and mass transfer of the high-solids-content slurry.

[0178] The crystal slurry in the crystallizer is separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0179] The test results showed that the average particle size (D50) was 24.36 μm, D10 was 4.156 μm, D90 was 72.62 μm, the PSD Span value was 2.81, and the lactose recovery rate was 68.4%. Figure 6 ).

[0180] Example 7: Preparation of larger-diameter lactose microcrystals by stirring and cooling crystallization

[0181] The pretreated whey permeate was pumped into an asymmetric field flow separation (AF4) system. The AF4 channel flow rate was 6.0 mL / min, and the crossflow rate was 1.0 mL / min. The accumulating membrane was a PES organic membrane with a molecular weight cutoff (MWCO) of 1 kDa. The AF4 effluent entered a nanofiltration system (membrane MWCO approximately 150-300 Da) for desalting and removal of small molecule impurities, yielding a purified lactose solution.

[0182] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a lactose saturated solution.

[0183] The above lactose solution was pumped into a jacketed stirred cooling crystallizer and the temperature was controlled to linearly decrease from 65-70℃ to 10-20℃. The total crystallization time was set to 8 h. When the solution temperature dropped to 45℃, 0.05% (w / w) of lactose seed crystals were added at the inlet of the crystallizer and the crystallization speed was maintained at 300 rpm.

[0184] The crystal slurry in the crystallizer is separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0185] The test results showed that the average particle size (D50) was 85.29 μm, D10 was 8.849 μm, D90 was 232.1 μm, the PSD Span value was 2.62, and the lactose recovery rate was 55.4%. Figure 7 ).

[0186] Example 8: Preparation of small-particle-size lactose microcrystals by stirring and cooling crystallization

[0187] The pretreated whey permeate was pumped into an asymmetric field flow separation (AF4) system. The AF4 channel flow rate was 6.0 mL / min, and the crossflow rate was 1.0 mL / min. The accumulating membrane was a PES organic membrane with a molecular weight cutoff (MWCO) of 1 kDa. The AF4 effluent entered a nanofiltration system (membrane MWCO approximately 150-300 Da) for desalting and removal of small molecule impurities, yielding a purified lactose solution.

[0188] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a lactose saturated solution.

[0189] The above lactose solution was pumped into a jacketed stirred cooling crystallizer, and the temperature was controlled to linearly decrease from 65-70℃ to 10-20℃. The total crystallization time was set to 8 h. When the solution temperature dropped to 45℃, 0.20% (w / w) of lactose seed crystals were added at the inlet of the crystallizer, and the crystallization speed was maintained at 500 rpm.

[0190] The crystal slurry in the crystallizer is separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0191] The test results showed that the average particle size (D50) was 26.15 μm, D10 was 7.509 μm, D90 was 58.35 μm, the particle size distribution PSD span value was 1.94, and the lactose recovery rate was 59.6%. Figure 8 ).

[0192] Example 9: Preparation of large-particle-size lactose microcrystals by static drying under negative pressure

[0193] The pretreated whey permeate was pumped into an asymmetric field flow separation (AF4) system. The AF4 channel flow rate was 6.0 mL / min, and the crossflow rate was 1.0 mL / min. The accumulating membrane was a PES organic membrane with a molecular weight cutoff (MWCO) of 1 kDa. The AF4 effluent entered a nanofiltration system (membrane MWCO approximately 150-300 Da) for desalting and removal of small molecule impurities, yielding a purified lactose solution.

[0194] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a supersaturated solution.

[0195] The supersaturated solution was pumped into a high-pressure homogenizer, homogenized at a pressure of 80 MPa, and circulated once. The temperature of the solution was controlled to be kept below 70°C to induce the formation of an appropriate amount of crystal nuclei.

[0196] The homogenized slurry was pumped into a three-stage series continuous cooling crystallizer. A staged cooling strategy was employed to balance the crystal growth rate and the constraints of vortex kinetics: the first stage temperature was lowered to 45-50℃ with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage temperature was lowered to 30-35℃ with a residence time of 20-40 min; and the third stage temperature was lowered to 10-15℃ with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time for the entire crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 250-300 rpm to ensure suspension and mass transfer of the high-solids-content slurry.

[0197] The crystal slurry in the crystallizer is filtered through a plate and frame filter press to obtain a wet filter cake. The wet filter cake is then placed in a vacuum drying oven and statically dried for 12 h at 50-60℃ and a negative pressure of 0.1 MPa. After pulverization, a dried lactose crystal sample is obtained.

[0198] The test results showed that the average particle size (D50) was 48.88 μm, D10 was 8.046 μm, D90 was 128.7 μm, the PSD span value was 2.47, and the lactose recovery rate was 67.8%. Figure 9 ).

[0199] Example 10: Preparation of small-particle-size lactose microcrystals by static drying under negative pressure

[0200] The pretreated whey permeate was pumped into an asymmetric field flow separation (AF4) system. The AF4 channel flow rate was 6.0 mL / min, and the crossflow rate was 1.0 mL / min. The accumulating membrane was a PES organic membrane with a molecular weight cutoff (MWCO) of 1 kDa. The AF4 effluent entered a nanofiltration system (membrane MWCO approximately 150-300 Da) for desalting and removal of small molecule impurities, yielding a purified lactose solution.

[0201] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a lactose supersaturated solution.

[0202] The supersaturated solution was pumped into a high-pressure homogenizer, homogenized at a pressure of 120 MPa, and cyclically repeated three times. The temperature of the homogenized solution was controlled to maintain a temperature not exceeding 70°C. This high-pressure, multi-cycle condition was designed to induce the explosive generation of a large number of tiny crystal nuclei to prepare small-particle-size samples.

[0203] The homogenized slurry was pumped into a three-stage series continuous cooling crystallizer. A staged cooling strategy was employed to balance the crystal growth rate and the limitations of vortex kinetics: the first stage temperature was lowered to 45-50°C with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage temperature was lowered to 30-35°C with a residence time of 20-40 min; and the third stage temperature was lowered to 10-15°C with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time of the entire crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 450-500 rpm to ensure the suspension and mass transfer of the high-solids-content slurry.

[0204] The crystal slurry in the crystallizer is filtered through a plate and frame filter press to obtain a wet filter cake. The wet filter cake is then placed in a vacuum drying oven and statically dried for 12 h at 50-60℃ and a negative pressure of 0.1 MPa. After pulverization, a dried lactose crystal sample is obtained.

[0205] The test results showed that the average particle size (D50) was 30.8 μm, D10 was 6.246 μm, D90 was 67.66 μm, the PSD span value was 1.99, and the lactose recovery rate was 68.3%. Figure 10 ).

[0206] Example 11: Lactose preparation by crystallization and drying using AF4 combined with nanofiltration without high-pressure homogenization.

[0207] In this embodiment, the supersaturated lactose solution purified and concentrated by AF4 was directly crystallized and dried without high-pressure homogenization to induce nucleation.

[0208] The pretreated whey permeate was pumped into an asymmetric field flow separation (AF4) system. AF4 parameters: channel flow rate 6.0 mL / min, crossflow rate 1.0 mL / min. A PES organic membrane with a molecular weight cutoff (MWCO) of 1 kDa was used to remove large protein aggregates. The AF4 effluent was then fed into a nanofiltration system (membrane MWCO approximately 150-300 Da) for desalting and removal of small molecule impurities, yielding a purified lactose solution.

[0209] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a lactose supersaturated solution.

[0210] A supersaturated lactose solution was pumped into a three-stage, series-connected continuous cooling crystallizer. A staged cooling strategy was employed to balance crystal growth rate and vortex kinetics constraints: the first stage lowered the temperature to 45-50°C with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage lowered the temperature to 30-35°C with a residence time of 20-40 min; and the third stage lowered the temperature to 10-15°C with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time throughout the crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 450-500 rpm to ensure suspension and mass transfer of the high-solids-content slurry.

[0211] The crystal slurry in the crystallizer is separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0212] The test results showed that the average particle size (D50) was 37.77 μm, D10 was 5.115 μm, D90 was 114.6 μm, the PSD Span value was 2.90, and the lactose recovery rate was 56.2%. Figure 11 ).

[0213] Example 12: Lactose preparation by ultrafiltration combined with nanofiltration followed by high-pressure homogenization, crystallization, and drying without AF4 purification.

[0214] In this embodiment, an ultrafiltration (UF) combined with nanofiltration (NF) method is used to separate and purify lactose.

[0215] The pretreated whey permeate was pumped into an ultrafiltration system using a PES spiral wound ultrafiltration membrane with a molecular weight cutoff (MWCO) of 1 kDa. Tangential flow filtration was performed at a transmembrane pressure of 0.5 MPa to remove most of the protein. The solution then entered a nanofiltration system (MWCO 150-300 Da) for desalting and removal of small molecule impurities, yielding a purified lactose solution.

[0216] The lactose purification solution is heated to 65-70℃ and concentrated by multi-effect evaporation until the solid content reaches 55-60wt%, forming a lactose supersaturated solution.

[0217] The supersaturated solution was pumped into a high-pressure homogenizer, homogenized at a pressure of 120 MPa, and circulated 3 times. The temperature of the solution was controlled to be kept below 70°C to induce the formation of an appropriate amount of crystal nuclei.

[0218] The homogenized slurry was pumped into a three-stage series continuous cooling crystallizer. A staged cooling strategy was employed to balance the crystal growth rate and the limitations of vortex kinetics: the first stage temperature was lowered to 45-50℃ with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage temperature was lowered to 30-35℃ with a residence time of 20-40 min; and the third stage temperature was lowered to 10-15℃ with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time for the entire crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 450-500 rpm to ensure suspension and mass transfer of the high-solids-content slurry.

[0219] The crystal slurry in the crystallizer is separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0220] The test results showed that the average particle size (D50) was 24.22 μm, D10 was 3.740 μm, D90 was 70.76 μm, the PSD span value was 2.77, and the lactose recovery rate was 51.5%. Figure 12 ).

[0221] Example 13: Lactose was prepared by nanofiltration separation and purification, crystallization and drying, without using AF4 purification and high-pressure homogenization.

[0222] In this embodiment, the prior art (US20180148803A) is adopted, and only nanofiltration is used to separate and purify lactose.

[0223] The pretreated whey permeate was pumped directly into a nanofiltration system without passing through AF4 or ultrafiltration. A spiral wound nanofiltration membrane (MWCO 150-300 Da) was used for desalting and removing small molecule impurities to obtain a purified lactose solution.

[0224] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a lactose supersaturated solution.

[0225] The lactose supersaturated solution was pumped into a three-stage series continuous cooling crystallizer. A staged cooling strategy was employed to balance the crystal growth rate and the constraints of vortex kinetics: the first stage lowered the temperature to 45-50℃ with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage lowered the temperature to 30-35℃ with a residence time of 20-40 min; and the third stage lowered the temperature to 10-15℃ with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time throughout the crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 450-500 rpm to ensure suspension and mass transfer of the high-solids-content slurry.

[0226] The crystal slurry in the crystallizer is then separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0227] The test results showed that the average particle size (D50) was 23.53 μm, D10 was 6.561 μm, D90 was 119.3 μm, the PSD span value was 4.79, and the lactose recovery rate was 48.5%. Figure 13 ).

[0228] Example 14: Lactose was prepared by purification using AF4 without nanofiltration, combined with high-pressure homogenization, crystallization, and drying.

[0229] The pretreated whey permeate was pumped into an asymmetric field flow separation (AF4) system. AF4 parameters: channel flow rate 6.0 mL / min, crossflow rate 1.0 mL / min. Accumulation of the wall membrane: A PES organic membrane with a molecular weight cutoff (MWCO) of 1 kDa was used to remove large protein aggregates, yielding a purified lactose solution.

[0230] The lactose purification solution is heated to 65-70℃ and concentrated by vacuum evaporation until the solid content reaches 55-60wt%, forming a lactose supersaturated solution.

[0231] The supersaturated solution was pumped into a high-pressure homogenizer, homogenized at a pressure of 80 MPa, and circulated once. The temperature of the solution was controlled to be kept below 70°C to induce the formation of an appropriate amount of crystal nuclei.

[0232] The homogenized slurry was pumped into a three-stage series continuous cooling crystallizer. A staged cooling strategy was employed to balance the crystal growth rate and the constraints of vortex kinetics: the first stage temperature was lowered to 45-50℃ with a residence time of 20-40 min, utilizing the rapid vortex rate at high temperature to promote crystal nucleus stability and initial growth; the second stage temperature was lowered to 30-35℃ with a residence time of 20-40 min; and the third stage temperature was lowered to 10-15℃ with a residence time of 20-40 min, minimizing lactose solubility through deep cooling. The total residence time for the entire crystallization process was controlled at 90-120 min, and the stirring speed was maintained at 250-300 rpm to ensure suspension and mass transfer of the high-solids-content slurry.

[0233] The crystal slurry in the crystallizer is then separated into solid and liquid phases by vacuum filtration. The separated wet crystals are then sent to a fluidized bed for drying to obtain a dried lactose crystal sample.

[0234] The test results showed that the average particle size (D50) was 46.19 μm, D10 was 12.80 μm, D90 was 117.7 μm, the PSD span value was 2.27, and the lactose recovery rate was 57.8%. Figure 14 ).

[0235] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims. Furthermore, all documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference.

Claims

1. A method for separating and purifying lactose, characterized in that, The method includes the step of separating and purifying lactose from a mixture containing lactose using asymmetric field flow separation; Preferably, the asymmetric field flow separation adopts an open channel structure, which includes an impermeable upper wall and a lower wall serving as an accumulation wall; More preferably, the accumulation wall consists of a porous support and a filter membrane covering it; More preferably, the filter membrane is an organic membrane or a ceramic membrane with a molecular weight cutoff (MWCO) of 1-10 kDa.

2. The method as described in claim 1, characterized in that, The method further includes the step of separating and purifying lactose from a mixture containing lactose using nanofiltration; Preferably, the nanofiltration is performed using a nanofiltration membrane; More preferably, the nanofiltration membrane has a molecular weight cutoff of 150-300 Da; More preferably, the step of separating and purifying lactose from the lactose-containing mixture using asymmetric field flow separation precedes the step of separating and purifying lactose from the lactose-containing mixture using nanofiltration.

3. A method for preparing lactose microcrystals, characterized in that, The preparation method includes the step of separating and purifying lactose from a lactose-containing mixture using the method of claim 1 or 2.

4. The preparation method according to claim 3, characterized in that, The preparation method includes the following steps: (1) Using the method of claim 1 or 2, lactose is separated and purified from a mixture containing lactose to obtain a purified lactose solution; (2) Concentrate the lactose purification solution described in (1) to a supersaturated state to obtain a lactose supersaturated solution; (3) Homogenize the lactose supersaturated solution described in (2) to obtain a lactose homogenized solution; (4) Crystallize the lactose homogenized solution described in (3) to obtain lactose microcrystals.

5. The preparation method according to claim 4, characterized in that, In step (3), the homogenization process is either high-pressure homogenization or high-speed dispersion shearing. Preferably, the homogenization process is a high-pressure homogenization process; More preferably, the pressure of the high-pressure homogenization is 40 MPa or higher, more preferably 80 to 200 MPa, and / or the number of cycles of the high-pressure homogenization is 1 to 5.

6. The preparation method according to claim 4 or 5, characterized in that, In step (2), the concentration is to concentrate the lactose purification solution to a solid content of 50 wt% or more, and / or the concentration of lactose in the concentrated lactose supersaturated solution is 500 g / L or more.

7. The preparation method according to any one of claims 4-6, characterized in that, In step (4), the crystallization is cooling crystallization; Preferably, the cooling crystallization is performed by reducing the temperature from 65-75°C to 10-15°C; More preferably, the cooling crystallization is a staged cooling crystallization, wherein the first stage temperature is reduced from 65~75℃ to 45~50℃ and the residence time is 20~40 min, the second stage temperature is reduced to 30~35℃ and the residence time is 20~40 min, and the third stage temperature is reduced to 10~15℃ and the residence time is 20~40 min. More preferably, the cooling crystallization is a stirred cooling crystallization, a multi-stage series continuous cooling crystallization, or a mixed suspension mixed product discharge (MSMPR) crystallizer cooling crystallization.

8. The preparation method according to any one of claims 4-7, characterized in that, The preparation method further includes the steps of separating and / or drying the lactose microcrystals described in (4); Preferably, the separation is a solid-liquid separation, more preferably centrifugal separation, and / or, the drying is selected from any one or more of hot air drying, vacuum drying, airflow drying, static drying under negative pressure and fluidized bed drying, more preferably fluidized bed drying; Preferably, the moisture content in the dried lactose microcrystals is ≤5.5 wt%.

9. The preparation method according to any one of claims 4-8, characterized in that, High-pressure homogenization reduces the particle size distribution of lactose microcrystals, resulting in a PSD Span value of less than or equal to 2.0 for the obtained lactose microcrystals.

10. The preparation method according to any one of claims 4-9, characterized in that, The purified solution containing lactose was treated by high-pressure homogenization, and the particle size of lactose microcrystals was adjusted by regulating the pressure of the high-pressure homogenizer. Preferably, when the high-pressure homogenization pressure is above 40 MPa and below 80 MPa (40 MPa ≤ P ≤ 80 MPa), the average particle size D50 of the obtained lactose microcrystals is greater than 45 μm; when the high-pressure homogenization pressure is greater than 80 MPa and below 200 MPa (80 MPa < P ≤ 200 MPa), the average particle size D50 of the obtained lactose microcrystals is less than or equal to 45 μm; more preferably, by using a homogenization pressure greater than 80 MPa and below 200 MPa (80 MPa < P ≤ 200 MPa) to treat the lactose-containing purified solution with high-pressure homogenization, the PSD Span value of the lactose microcrystals can be less than or equal to 2.

11. The method according to claim 1 or 2, or the preparation method according to any one of claims 3-10, characterized in that, The lactose-containing mixture includes whey, whey permeate, preferably whey permeate; and / or, in the lactose-containing mixture, the dry weight percentage of lactose is 50% or more, preferably 50-90%.

12. A type of lactose microcrystals, characterized in that, The lactose microcrystals were prepared using the preparation method described in any one of claims 3-11; Preferably, the particle size distribution PSD Span value of the lactose microcrystals is less than or equal to 2.

0.

13. Selected from the following applications: (1) Application of asymmetric field flow separation in lactose separation and purification, preparation of lactose microcrystals, and / or improvement of lactose recovery rate; (2) Application of asymmetric field flow separation and nanofiltration in lactose separation and purification, preparation of lactose microcrystals, and / or improvement of lactose recovery rate; (3) Application of high-pressure homogenization in the preparation of lactose microcrystals, reducing the particle size distribution of lactose microcrystals, and / or adjusting the particle size of lactose microcrystals; Preferably, the method for separating and purifying lactose is as described in claim 1 or 2, and / or the method for preparing the lactose microcrystals is as described in any one of claims 3-11.

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