Powder manufacturing method

Abstract

To provide a method for producing powder in which, when spray-drying a substance that is highly hygroscopic and difficult to pulverize (difficult-to-pulverize substance), a powder with high yield, narrow particle size distribution width, and hard to solidify even in high humidity is obtained.SOLUTION: The present invention is a method for producing powder that is characterized by spray-drying a stock solution containing a difficult-to-pulverize substance and hydroxypropylcellulose.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing a powder by spray-drying a highly hygroscopic substance (a substance difficult to be powdered).

Background Art

[0002] As one of the methods for powdering liquid products, a spray-drying method using a spray dryer is known. Spray drying is a method in which finely divided droplets are sprayed into hot air by a high-pressure nozzle or a disk, etc., and the solvent is instantaneously evaporated to obtain a powder. This method is widely used in the production of powdered milk, instant coffee, etc. However, when producing a raw material containing a highly hygroscopic substance in spray drying, there are problems such as a large amount of adhesion to the spray drying equipment (a decrease in yield), and the produced powder is likely to agglomerate. As methods for solving the above problems, the following methods, etc. have been known so far, but sufficient effects have not been obtained.

[0003] For example, a method has been proposed in which a liquid, which is a mixture of a solution or suspension of a powder material and an emulsified oil and fat, is spray-dried to solve problems in the dispersibility, solubility, fluidity, jet flowability, caking property, etc. of the powder (Patent Document 1). Since this method uses an emulsified oil and fat, there is a possibility of impairing the original quality of the powder material, and there is a concern that it may particularly affect the flavor and the liquid property when dissolved.

[0004] Also, a method has been proposed in which ethanol is added to a water-containing raw material containing monosaccharides, disaccharides, polysaccharides, etc. and then spray-dried (Patent Document 2). However, since ethanol is an organic solvent, it must be handled with care for safety, and a closed-type spray drying equipment must be adopted, and the solvent must be recovered by circulating nitrogen gas, resulting in a problem of high equipment cost.

[0005] A method has also been proposed in which a solution containing starch hydrolysates in 1,5-D-anhydrofructose (sometimes abbreviated as 1,5-AF), one of the substances that is difficult to powderize, is spray-dried (Patent Document 3). The yield of the powder obtained by this spray-drying method is easily affected by humidity, and there is room for improvement in the particle size distribution of the resulting powder.

[0006] A method has also been proposed to stably obtain fixed flavorings (fragrance-containing spray-dried products) by spray-drying a mixture composed of difficult-to-powder substances such as monosaccharides and disaccharides, high molecular weight thin-film-forming carbohydrates, and maltodextrin (Patent Document 4). However, this method uses a large proportion of high molecular weight thin-film-forming carbohydrates, which may impair the original quality of the materials (solubility, flavor, etc.), and the proportion of the target component is reduced. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2002-28467 [Patent Document 2] Japanese Patent Publication No. 2009-207477 [Patent Document 3] Japanese Patent Publication No. 2005-263770 [Patent Document 4] Special Publication No. 2003-514104 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Therefore, the objective of the present invention is to obtain a powder with a high yield, a narrow particle size distribution, and resistance to caking even in high humidity environments when spray-drying a component that is highly hygroscopic and difficult to powder (a substance that is difficult to powder). [Means for solving the problem]

[0009] The inventors of the present invention have discovered that when hydroxypropyl cellulose (HPC) is used as a powdering aid in the spray drying of difficult-to-powder materials, it is possible to obtain a powder that is less affected by humidity, has a high yield, and has a narrow particle size distribution, thereby completing the present invention.

[0010] This invention encompasses the following inventions. 1. A method for producing powder, characterized by spray-drying a stock solution containing a difficult-to-powder substance and hydroxypropyl cellulose. 2. The method for producing the product according to paragraph 1, wherein the substance that is difficult to powderize is at least one selected from the group consisting of 1,5-D-anhydrofructose, honey, soy sauce, and miso. 3. The manufacturing method according to item 1 or 2 above, wherein the stock solution contains a starch hydrolysate. 4. The manufacturing method according to paragraph 3 above, wherein the starch hydrolysate is maltodextrin. 5. The manufacturing method according to any one of items 1 to 4 above, wherein the content of hydroxypropyl cellulose in the stock solution is 0.0005 to 0.05 parts by mass per 1 part by mass of the difficult-to-powder substance. 6. The manufacturing method according to any one of paragraphs 3 to 5 above, wherein the content of the starch hydrolysate in the stock solution is 0.1 to 9 parts by mass per 1 part by mass of the difficult-to-powder substance. 7. The manufacturing method according to any one of items 1 to 6 above, wherein the temperature of the hot air used in spray drying is 70 to 200°C. 8. The manufacturing method according to any one of items 1 to 7 above, wherein the powder has an average particle size of 10 to 70 μm and a CV value of 0.45 or less. 9. A powder obtained by the manufacturing method described in any one of items 1 to 8 above. [Effects of the Invention]

[0011] According to the present invention, even in high-humidity environments, less adhesion to spray drying equipment is achieved, and powder can be obtained with a high yield. Furthermore, the obtained powder is less likely to clump together. In addition, according to the present invention, powder with a narrow particle size distribution and excellent uniformity can be obtained. Furthermore, according to the present invention, powder that is less likely to clump together even in high-humidity environments can be obtained. [Brief explanation of the drawing]

[0012] [Figure 1] It is a diagram showing the relationship between relative humidity and solid yield in the examples and comparative examples. [Figure 2] It is a diagram showing the particle size distribution of the powders obtained in the examples and comparative examples. [Figure 3] It is a diagram showing the relationship between each condition and the solid yield. [Figure 4] It is a diagram showing the particle size distribution of the powders obtained in the examples and comparative examples. [Figure 5] It is a diagram showing the relationship between each condition and the solid yield. [Figure 6] It is a diagram showing the particle size distribution of the powders obtained in the examples and comparative examples. [Figure 7] It is a diagram showing the relationship between each condition and the solid yield.

MODE FOR CARRYING OUT THE INVENTION

[0013] <substance difficult to be powdered> The substance difficult to be powdered is preferably at least one selected from the group consisting of monosaccharides, disaccharides and trisaccharides. Examples of monosaccharides include glucose and fructose. Examples of disaccharides include sucrose, maltose and lactose. Among them, monosaccharides are preferred. Examples of the substance difficult to be powdered include 1,5-D-anhydrofructose. Also, honey mainly composed of glucose and fructose, soy sauce, miso, etc. can be mentioned. The substance difficult to be powdered can be said to be a substance whose solid yield becomes as low as 60% or less in an environment where the relative humidity of the aspirated air is 50% or more even when it contains 1.1 parts by mass of maltodextrin per 1 part by mass.

[0014] <hydroxypropyl cellulose> In the present invention, hydroxypropyl cellulose (HPC) is used as a powdering aid. Hydroxypropyl cellulose (HPC) is a nonionic cellulose ether obtained by using cellulose (pulp) that widely exists in nature as a raw material, treating it with sodium hydroxide, and then reacting it with an etherifying agent such as propylene oxide. In Japan, it is listed in the second part of the Japanese Pharmacopoeia and is used as a lubricant, coating agent, disintegrant, binder, suspension / stabilizing agent for syrup, thickening agent for poultice, base for ointment, jelly base, etc. for tablets and granules.

[0015] The viscosity of hydroxypropyl cellulose (HPC) in a 2% aqueous solution at 20°C is preferably 2.0 to 4,000 mPa·s, more preferably 2.0 to 10 mPa·s, and even more preferably 2.0 to 2.9 mPa·s. The average molecular weight of hydroxypropyl cellulose (HPC) is preferably 30,000 to 1,000,000, more preferably 30,000 to 200,000, and even more preferably 30,000 to 50,000. When hydroxypropyl cellulose (HPC) with a viscosity of 2.0 to 2.9 mPa·s and an average molecular weight of 30,000 to 50,000 is used, a powder with a small CV value and a narrow particle size distribution width can be obtained.

[0016] <Starch hydrolyzate> The starch hydrolyzate is obtained by using corn starch or potato starch as a raw material and reducing the molecular weight of starch by chemical or enzymatic methods. Examples of the starch hydrolyzate include dextrin, maltodextrin, and starch syrup. The starch hydrolyzate is preferably maltodextrin. It is graded according to the degree of molecular weight reduction, and the dextrose equivalent (DE) is used as an index. DE is a relative measure when the reducing power of dextrose (glucose) is set to 100. The closer it is to 0, the closer it is to the characteristics of starch. The closer it is to 100, the more the hydrolysis of starch progresses, the average molecular weight decreases, and the characteristics become similar to those of glucose. Dextrin has a DE of 10 or less. The range of 10 < DE < 20 is maltodextrin, and DE > 20 is called starch syrup. Its structure is the same as that of starch, which is a polymer of α-glucose linked by glycosidic bonds.

[0017] <Stock solution> The content of hydroxypropyl cellulose in the stock solution is preferably 0.0005 to 0.05 parts by mass, more preferably 0.001 to 0.01 parts by mass, and still more preferably 0.002 to 0.004 parts by mass with respect to 1 part by mass of the difficult-to-powder substance. The content of the starch degradation product in the stock solution is preferably 0.1 to 9 parts by mass, more preferably 0.2 to 4 parts by mass, and still more preferably 0.3 to 3 parts by mass with respect to 1 part by mass of the difficult-to-powder substance. The stock solution can be prepared by dissolving the difficult-to-powder substance, hydroxypropyl cellulose, and, if necessary, the starch degradation product in water. The content of the solid matter in the stock solution is preferably 20 to 60% by mass, more preferably 30 to 50% by mass.

[0018] <Spray drying> As the spray dryer used for drying, a device generally used for spray drying, such as a nozzle type or a rotary disk type, can be used. The temperature of the hot air blown into the spray dryer is preferably 70 to 200 °C, more preferably 110 to 160 °C, considering that the difficult-to-powder substance is converted or decomposed into other compounds during drying or the coloring of the product.

[0019] <Powder> The average particle size of the powder obtained by the method of the present invention is preferably 10 to 70 μm, more preferably 35 to 50 μm. The powder obtained by the method of the present invention preferably has a CV value of 0.45 or less, more preferably 0.42 or less, and still more preferably 0.35 or less. The CV value is obtained from the standard deviation ÷ average particle size × 100, and a lower value means a sharper particle size distribution.

Examples

[0020] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0021] <Evaluation Method> (Yield) After the temperature and liquid supply in the dryer stabilized (approximately 1 hour later), the collection pot was replaced, and the weight of the powder collected per unit time was measured to evaluate the yield. Since the yield also fluctuates depending on the moisture content of the powder, the moisture content was measured using a vacuum oven dryer (75°C, 5 hours or more), and the yield converted to solid content (solid yield) was evaluated. Solid yield = Solid content in recovered powder / Solid content in supplied liquid × 100 (%) Here, the mass of solids in the recovered powder = mass of recovered powder × (100 - moisture content (%)) / 100)

[0022] (Particle size distribution measurement) The particle size distribution was measured using a laser diffraction particle size analyzer (Mastersizer3000), and the median diameter (D50) and the CV value (correlation coefficient), which indicates particle uniformity, were compared. The CV value is calculated as standard deviation ÷ mean particle diameter × 100, and a lower value indicates a sharper particle size distribution.

[0023] <Example 1-1> (Difficult to powder) As a difficult-to-powder substance, 1,5-D-anhydrofructose (1,5-AF) was used. Specifically, "Anhydros®," manufactured by Sanas Co., Ltd., which contains 35-42% by mass of 1,5-D-anhydrofructose (1,5-AF) and 38-42% by mass of maltodextrin, was used.

[0024] (Powdering aid) HPC-L (hydroxypropyl cellulose, Wako Pure Chemical Industries, viscosity 2.0-2.9 mPa·s, molecular weight 40,000) was used as a powdering aid. A powdering aid solution (concentration 1% by mass) was prepared in advance by dissolving HPC-L. The powdering aids used are summarized in Table 1.

[0025] (Preparation of the stock solution) The amount of maltodextrin in the stock solution was 1.1 parts by mass per 1 part by mass of 1,5-AF. The amount of HPC-L in the stock solution was 0.005 parts by mass per 1 part by mass of 1,5-AF. The amount of dilution water was prepared so that the solid content concentration of the stock solution was 40% by mass. The solid content concentration was determined by measuring the Brix using an Abbe refractometer, and this value was taken as the solid content concentration.

[0026] (spray drying) A spray experiment apparatus (L-8i type) manufactured by Okawara Chemical Machinery Co., Ltd. was used. The relative humidity of the air drawn into the dryer was set to 30-85%. The relative humidity of the air was measured using an Assmann psychrometer (model: Y-5001) manufactured by Yoshino Keisoku Co., Ltd. The undiluted solution was supplied to the dryer at a rate of 32 g / min. The dryer's hot air temperature was adjusted to 135°C, the disk rotation speed to 15,000 rpm, and the exhaust fan output to 50 Hz, and the solid yield of the spray-dried powder was measured. The spray drying conditions are shown in Table 2. Figure 1 shows the relationship between the relative humidity of the air drawn into the dryer and the solid yield.

[0027] [Table 1]

[0028] [Table 2]

[0029] <Examples 1-2 to 1-16> Spray drying was performed under the same conditions as in Example 1, except that the relative humidity of the air drawn into the dryer was changed as shown in Table 3, and the solid yield was measured. Figure 1 shows the relationship between relative humidity and solid yield under each condition.

[0030] [Table 3]

[0031] <Examples 2-1 to 2-2> The same method as in Example 1 was used for spray drying, and the solid yield was measured, except that HPC-H (hydroxypropyl cellulose, Wako Pure Chemical Industries, viscosity 1,000-5,000 mPa·s, molecular weight 1,000,000) was used instead of HPC-L as a powdering aid, and the relative humidity of the air drawn into the dryer was changed as shown in Table 4. The relationship between relative humidity and solid yield under each condition is shown in Figure 1.

[0032] [Table 4]

[0033] <Comparative Example 1-1 to Comparative Example 1-7> The same method as in Example 1 was used for spray drying and solid yield measurement, except that no powdering aid was used and the relative humidity of the air drawn into the dryer was changed as shown in Table 5. Figure 1 shows the relationship between relative humidity and solid yield under each condition.

[0034] [Table 5]

[0035] <Comparative Example 2-1 to Comparative Example 2-9> The same method as in Example 1 was used for spray drying and measurement of the solid yield, except that CMC (carboxymethylcellulose, Kimika Co., Ltd., grade name: F-2, viscosity 150-350 mPa·s, degree of etherification 0.5-0.9) was used instead of HPC-L as a powdering aid, and the relative humidity of the air drawn into the dryer was changed as shown in Table 6. Figure 1 shows the relationship between relative humidity and solid yield under each condition.

[0036] [Table 6]

[0037] (Relationship between relative humidity of air drawn into a dryer and solid yield) Compared to the results of Comparative Examples 1-1 to 1-7, which did not use a powdering aid, the addition of HPC-L (Examples 1-1 to 1-16) and HPC-H (Examples 2-1 to 2-2) as powdering aids allowed for stable powder production even under high humidity conditions. On the other hand, in Comparative Examples 2-1 to 2-9, where CMC was added as a powdering aid, the yield was high at relative humidity of 55% or less, but at high humidity of 65% or more, the yield decreased sharply, resulting in the same results as the sample without the powdering aid.

[0038] (Powder properties) Table 7 and Figure 2 show the measurement results of the particle size distribution. Compared to Comparative Examples 1-4, which did not use a powdering aid, and Comparative Example 2-4, which used CMC as a powdering aid, the sample in Example 1-10, to which HPC-L was added as a powdering aid, had the smallest CV value. This is presumed to be the result of stable powdering without moisture absorption or caking during spray drying. On the other hand, the powders in Comparative Examples 1-4 (without powdering aid) and 2-4 (with CMC as the powdering aid) tended to have high CV values, and some of the powder particles were observed to have partially solidified into clumps, resulting in an apparent D50 value that was larger.

[0039] [Table 7]

[0040] (Moisture absorption properties) Each sample was prepared by placing different saturated salt solutions (K2CO3, Mg(NO3)2) in separate desiccators to create environments with predetermined humidity levels (43.3%RH, 54.6%RH). The samples were then placed in glass weighing bottles with the lids open and left to stand for a predetermined time (0h to 24h) at 30°C in each humidity environment. The hygroscopic properties over time were evaluated by checking whether or not the surface solidified. As an evaluation method, the weighing bottle was inverted and shaken up and down; if powder fell out, it was marked as "○", and if the surface solidified and no powder fell out, it was marked as "×".

[0041] As shown in Table 8, under a relative humidity of 43.2%, the surface of both Comparative Examples 1-4 (without additives) and Comparative Examples 2-4 (with CMC added as a powdering aid) solidified in 18 hours, while the surface of Example 1-10 (with HPC-L added as a powdering aid) solidified in 24 hours. Furthermore, under a relative humidity of 51.3%, the surface of both Comparative Examples 1-4 (without additives) and Comparative Examples 2-4 (with CMC added as a powdering aid) solidified in 4 hours, while the surface of Example 1-10 (with HPC-L added as a powdering aid) solidified in 18 hours. It was confirmed that the addition of HPC could suppress the rate of moisture absorption and improve moisture resistance.

[0042] [Table 8]

[0043] <Example 3-1> (Difficult to powder) Honey was used as a difficult-to-powder substance. Specifically, pure honey from China, specifically "Kumade no Hachimitsu" (Rake Honey), was used.

[0044] (Powdering aid) HPC-L (hydroxypropyl cellulose, Wako Pure Chemical Industries, viscosity 2.0-2.9 mPa·s, molecular weight 40,000) was used as a powdering aid. A powdering aid solution (concentration 1% by mass) in which HPC-L was dissolved was prepared in advance.

[0045] (Preparation of the concentrate) 1.5 parts by mass of MD-200 (maltodextrin DE16-18 manufactured by Sanas Co., Ltd.) was added to 1 part by mass of honey. In addition, HPC-L was added to a ratio of 0.002 parts by mass per 1 part by mass of honey. The amount of dilution water was adjusted so that the solid content concentration of the stock solution was 40% by mass. The solid content concentration was determined by measuring the Brix using an Abbe refractometer, and this value was taken as the solid content concentration.

[0046] (spray drying) A spray experiment apparatus (L-8i type) manufactured by Okawara Chemical Machinery Co., Ltd. was used. The relative humidity of the air drawn into the dryer was set to 45-65%. The relative humidity of the air was measured using a thermometer / hygrometer (model: HN-CFA3) manufactured by Chino Corporation. The undiluted solution was supplied to the dryer at a rate of 31 g / min. The dryer's hot air temperature was adjusted to 135°C, the disk rotation speed to 15,000 rpm, and the exhaust fan output to 50 Hz. The solid yield of the spray-dried powder was measured. The spray drying conditions are shown in Table 9. The solid yield results are shown in Figure 3.

[0047] [Table 9]

[0048] <Examples 3-1 to 3-6> Spray drying was performed under the conditions shown in Table 9, except that the relative humidity of the air drawn into the dryer was changed as shown in Table 10, and the solid yield was measured. The results of the solid yield under each condition are shown in Figure 3.

[0049] [Table 10]

[0050] <Examples 4-1 to 4-6> As dextrin, CD (DE3 cluster dextrin manufactured by Glico Nutrition Foods Co., Ltd.) was used instead of MD-200. HPC-L was used as a powdering aid, and the same method as in Example 3 was used for spray drying and measurement of the solid yield, except that the relative humidity of the air drawn into the dryer was changed as shown in Table 11. The solid yield results for each condition are shown in Figure 3.

[0051] [Table 11]

[0052] <Comparative Examples 3-1 to 3-3> The solid yield was measured by spray drying in the same manner as in Example 3, except that only MD-200 was added, the powdering aid HPC-L was not used, and the relative humidity of the air drawn into the dryer was changed as shown in Table 12. The solid yield results for each condition are shown in Figure 3.

[0053] [Table 12]

[0054] <Comparative Examples 4-1~4-2> The solid yield was measured by spray drying in the same manner as in Example 4, except that only CD was added, the powdering aid HPC-L was not used, and the relative humidity of the air drawn into the dryer was changed as shown in Table 13. The solid yield results for each condition are shown in Figure 3. [Table 13]

[0055] (Relationship between each condition and solid yield) Comparing the results of Comparative Examples 3-1 to 3-3 and 4-1 to 4-2, which did not use the powdering aid HPC-L, Examples 3-1 to 3-6 and 4-1 to 4-6, which used the powdering aid HPC-L, were able to obtain powder with a consistently higher yield.

[0056] (Powder properties) Table 14 and Figure 4 show the measurement results of the particle size distribution. Compared to Comparative Examples 3-3 and 4-1, which did not use the powdering aid HPC-L, the samples in Examples 3-1 and 4-1 to which HPC-L was added as a powdering aid had smaller CV values. This is presumed to be a result of stable powdering without moisture absorption or caking during spray drying. On the other hand, the powders in Comparative Examples 3-3 and 4-1 tended to have high CV values, and some of the powder particles were observed to have partially solidified into clumps, resulting in an apparent increase in D50.

[0057] [Table 14]

[0058] (Moisture absorption properties) Each sample was prepared by placing different saturated salt solutions (MgCl2, K2CO3) in separate desiccators to create environments with predetermined humidity levels (33.0%RH, 43.0%RH). The samples were then placed in glass weighing bottles with the lids open and left to stand for a predetermined time (0h to 24h) at 30°C in each humidity environment. The hygroscopic properties over time were evaluated by checking whether or not the surface solidified. As an evaluation method, the weighing bottle was inverted and shaken up and down; if powder fell out, it was marked as "○", and if the surface solidified and no powder fell out, it was marked as "×".

[0059] As shown in Table 15, under a relative humidity of 33.0%, the surface of Comparative Example 3-3, which did not use the additive HPC-L, solidified in 4 hours, while the surface of Example 3-1, to which HPC-L was added as a powdering aid, solidified in 24 hours. Furthermore, under a relative humidity of 43.0%, the surface of Comparative Example 3-3, which did not use the additive aid, solidified in 1 hour, and Comparative Example 4-1 solidified in 24 hours, while the surface of Example 3-1, to which HPC-L was added, solidified in 4 hours, and Example 4-1 solidified in 48 hours. It was confirmed that the rate of moisture absorption could be suppressed by adding HPC, and that the resistance to moisture absorption was improved.

[0060] [Table 15]

[0061] <Example 5-1> (Difficult to powder) Soy sauce was used as a difficult-to-powder substance. Specifically, Kikkoman Corporation's dark soy sauce (naturally brewed) was used.

[0062] (Powdering aid) HPC-L (hydroxypropyl cellulose, Wako Pure Chemical Industries, viscosity 2.0-2.9 mPa·s, molecular weight 40,000) was used as a powdering aid. A powdering aid solution (concentration 1% by mass) in which HPC-L was dissolved was prepared in advance.

[0063] (Preparation of the concentrate) HPC-L was added in a ratio of 0.005 parts by mass per 1 part by mass of soy sauce. The amount of dilution water for the stock solution was adjusted so that the solid content concentration was 20% by mass. The solid content concentration was determined by measuring the Brix value using an Abbe refractometer.

[0064] (spray drying) A spray experiment apparatus (L-8i type) manufactured by Okawara Chemical Machinery Co., Ltd. was used. The relative humidity of the air drawn into the dryer was set to 20-70%. The relative humidity of the air was measured using a thermometer / hygrometer (model: HN-CFA3) manufactured by Chino Corporation. The undiluted solution was supplied to the dryer at a rate of 30 g / min. The dryer's hot air temperature was adjusted to 135°C, the disk rotation speed to 15,000 rpm, and the exhaust fan output to 55 Hz. The solid yield of the spray-dried powder was then measured. The spray drying conditions are shown in Table 16. The solid yield results are shown in Figure 5.

[0065] [Table 16]

[0066] <Examples 5-1 to 5-6> Spray drying was performed under the conditions in Table 16, except that the relative humidity of the air drawn into the dryer was changed as shown in Table 17, and the solid yield was measured. The results of the solid yield under each condition are shown in Figure 5.

[0067] [Table 17]

[0068] <Comparative Examples 5-1 to 5-8> The powdering aid HPC-L was not used, and the relative humidity of the air drawn into the dryer was changed as shown in Table 18, but the same method as in Example 5 was used for spray drying and the solid yield was measured. The solid yield results for each condition are shown in Figure 5.

[0069] [Table 18]

[0070] (Relationship between each condition and solid yield) Compared to the results of Comparative Examples 5-1 to 5-8, which did not use the powdering aid HPC-L, Examples 5-1 to 5-6, which used the powdering aid HPC-L, were able to obtain powder with a stable and high yield without being affected by humidity.

[0071] (Powder properties) Table 19 and Figure 6 show the measurement results of the particle size distribution. Compared to Comparative Example 5-1, which did not use the powdering aid HPC-L, the sample in Example 5-1 to which HPC-L was added as a powdering aid had a smaller CV value. This is presumed to be a result of stable powdering without moisture absorption or caking during spray drying. On the other hand, the powder in Comparative Example 5-1 tended to have a high CV value, and some of the powder particles were observed to have partially solidified into clumps, resulting in an apparent D50 value that was large.

[0072] [Table 19]

[0073] (Moisture absorption properties) Each sample was prepared by placing different saturated salt solutions (MgCl2, K2CO3) in separate desiccators to create environments with predetermined humidity levels (33.0%RH, 43.0%RH). The samples were then placed in glass weighing bottles with the lids open and left to stand for a predetermined time (0h to 24h) at 30°C in each humidity environment. The hygroscopic properties over time were evaluated by checking whether or not the surface solidified. As an evaluation method, the weighing bottle was inverted and shaken up and down; if powder fell out, it was marked as "○", and if the surface solidified and no powder fell out, it was marked as "×".

[0074] As shown in Table 20, under a relative humidity of 33.0%, the surface of Comparative Example 5-1, which did not use the additive HPC-L, solidified in 18 hours, while the surface of Example 5-1, which had HPC-L added as a powdering aid, solidified in 22 hours. Furthermore, under a relative humidity of 43.0%, the surface of Comparative Example 5-1, which did not use the additive, solidified in 8.5 hours, while the surface of Example 5-1, which had HPC-L added as a powdering aid, solidified in 18 hours. It was confirmed that the rate of moisture absorption could be suppressed by adding HPC, and that the resistance to moisture absorption was improved.

[0075] [Table 20]

[0076] <Example 6-1> (Difficult to powder) Miso was used as a difficult-to-powder substance. Specifically, Marukome's rice miso (white miso) was used.

[0077] (Powdering aid) HPC-L (hydroxypropyl cellulose, Wako Pure Chemical Industries, viscosity 2.0-2.9 mPa·s, molecular weight 40,000) was used as a powdering aid. A powdering aid solution (concentration 1% by mass) in which HPC-L was dissolved was prepared in advance.

[0078] (Preparation of the concentrate) The amount of HPC-L was adjusted to 0.010 parts by mass per 1 part by mass of miso. The amount of dilution water was adjusted so that the solid content concentration of the stock solution was approximately 25% by mass. The actual solid content concentration was calculated from the moisture content of the miso and the amount of water added, which were measured in advance.

[0079] (Moisture content measurement of miso) Approximately 2 g of the sample was placed in a constantly weighed aluminum dish and dried at 70°C for 5 hours using a rectangular vacuum low-temperature dryer (DP300) manufactured by Yamato Scientific Co., Ltd., before measurement.

[0080] (spray drying) A spray experiment apparatus (L-8i type) manufactured by Okawara Chemical Machinery Co., Ltd. was used. The relative humidity of the air drawn into the dryer was set to 60-70%. The relative humidity of the air was measured using a thermometer / hygrometer (model: HN-CFA3) manufactured by Chino Corporation. The undiluted solution was supplied to the dryer at a rate of 30 g / min. The dryer's hot air temperature was adjusted to 135°C, the disk rotation speed to 15,000 rpm, and the exhaust fan output to 55 Hz. The solid yield of the spray-dried powder was measured. The spray drying conditions are shown in Table 21. The solid yield results are shown in Figure 7.

[0081] [Table 21]

[0082] <Examples 6-1 to 6-4> Spray drying was performed under the conditions in Table 21, except that the relative humidity of the air drawn into the dryer was changed as shown in Table 22, and the solid yield was measured. The solid yield results for each condition are shown in Figure 7.

[0083] [Table 22]

[0084] <Comparative Examples 6-1 to 6-4> The powdering aid HPC-L was not used, and the relative humidity of the air drawn into the dryer was changed as shown in Table 23, but the same method as in Example 6 was used for spray drying and the solid yield was measured. The solid yield results for each condition are shown in Figure 7.

[0085] [Table 23]

Claims

1. A method for producing powder, characterized by spray-drying a stock solution containing at least one difficult-to-powder substance selected from the group consisting of 1,5-D-anhydrofructose, honey, soy sauce, and miso, and hydroxypropyl cellulose, wherein the hydroxypropyl cellulose content is 0.0005 to 0.05 parts by mass per 1 part by mass of the difficult-to-powder substance.

2. The manufacturing method according to claim 1, wherein the stock solution contains a starch hydrolysate.

3. The manufacturing method according to claim 2, wherein the starch hydrolysate is maltodextrin.

4. The manufacturing method according to claim 2, wherein the content of the starch hydrolysate in the stock solution is 0.1 to 9 parts by mass per 1 part by mass of the difficult-to-powder substance.

5. The manufacturing method according to claim 1, wherein the temperature of the hot air used in spray drying is 70 to 200°C.

6. The manufacturing method according to claim 1, wherein the powder has an average particle size of 10 to 70 μm and a CV value of 0.45 or less.

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