Method for producing pregelatinized starch

Abstract

To provide a method for producing pregelatinized starch by using starch as a raw material.SOLUTION: A method for producing pregelatinized starch includes a process of shearing and crushing starch at the temperature of 5°C or higher and 160°C or lower and under a condition satisfying the following formula. W<0.00012Q-25 20×104<Q-25<W≤80 [in the formula, W denotes a moisture reduction rate (%) expressed by [{moisture content (mass%) of starch immediately before pulverization-moisture content (mass%) of starch immediately after pulverization} / moisture content (mass%) of starch immediately before pulverization×100], and Q denotes [retention time (sec) of raw material starch in producing pregelatinized starch which includes a process of shearing and crushing]×[the maximum shear speed (1 / sec.)]].SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for producing pregelatinized starch. [Background technology]

[0002] Generally, starch swells and becomes hydrated when it gelatinizes (alpha-gelatinizes) through heating with water. Alpha-gelatinized starch, obtained by drying while maintaining its alpha-gelatinized state, has the property of being easily hydrated even with cold water. Therefore, because alpha-gelatinized starch exhibits physical properties such as water retention, thickening, binding, and shape retention without heating, it has the advantage of eliminating the heating process industrially, and it can impart starch properties even in processes where heating is not possible. For this reason, it is widely used in industrial applications as a thickener and adhesive, and in food applications as a quality improver such as a thickener and water retention agent, as well as in instant foods and baby food.

[0003] Conventional pregelatinized starch is produced by suspending raw starch in water, heating and gelatinizing it, and then dehydrating and drying it using a dryer such as a drum dryer. In this method, pregelatinized starch has high viscosity and cannot be produced at high concentrations, making it very inefficient. Furthermore, evaporating large amounts of water and drying consumes large amounts of electricity and steam, resulting in high processing costs and a high environmental burden. In addition, the process is long, involving suspension, gelatinization, drying, sizing, and humidity control, making it difficult to introduce into existing facilities. On the other hand, a method has been proposed for producing pregelatinized starch by feeding raw grains into a millstone-type grinder and grinding the raw grains under shear conditions while heating them to a temperature of 80°C or higher, particularly 100-200°C (Patent Documents 1 to 3). Furthermore, research on the amorphous formation of tapioca starch using a shearing and heating pulverizer has been reported (Non-Patent Literature 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-038368 [Patent Document 2] Japanese Patent Publication No. 2007-075104 [Patent Document 3] Japanese Patent Publication No. 2010-215861 [Non-patent literature]

[0005] [Non-Patent Document 1] Starch,2021,Vol 74,Issue 1-2,p.2100159 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, because starch has a particle size of several micrometers to tens of micrometers, it is more difficult to pulverize under shear conditions compared to grains. Therefore, even when the methods proposed in Patent Documents 1 to 3 are applied to starch, it is difficult to obtain starch with the same degree of gelatinization (degree of gelatinization) as the starch in the gelatinized starch powder obtained by these methods. Moreover, the methods proposed in Patent Documents 1 to 3 are methods for producing gelatinized starch powder containing gelatinized starch by pulverizing and gelatinizing grains, and Patent Documents 1 to 3 do not propose a method for producing gelatinized starch from starch in the first place. Furthermore, Non-Patent Document 1 only describes that tapioca starch can be amorphous using a shearing and heating pulverizer, but it does not describe or suggest the relationship between Q, which is the product of the maximum shearing rate and the residence time of the raw starch in the production of pregelatinized starch, including the shearing and pulverizing process, the moisture reduction rate of the raw starch, and the degree of pregelatinization of the starch.

[0007] The object of the present invention is to provide a method for producing pregelatinized starch using starch as a raw material. [Means for solving the problem]

[0008] In order to solve the above problems, the inventors conducted experiments and research to find the conditions necessary for producing pregelatinized starch from starch. As a result, they discovered that under a predetermined grinding temperature, the ratio of Q to the moisture reduction rate of the raw starch greatly affects the degree of gelatinization of the starch, and thus completed the present invention. Furthermore, by using alkali-treated starch as the raw material starch, it has been found that a gelatinized starch with a higher degree of gelatinization and / or a suspension with high transparency can be produced when mixed with water compared to untreated starch, and the present invention has been completed.

[0009] That is, the present invention relates to a method for producing gelatinized starch, which includes a step of shear pulverizing starch at a temperature of 5°C or higher and 160°C or lower under conditions satisfying the following formula. W < 0.00012Q - 25 20×10

[0011] , 4 <Q -25 < W ≤ 80 [In the formula, W represents the water reduction rate (%) represented by [{(moisture content (%) of starch immediately before pulverization - moisture content (%) of starch immediately after pulverization) / moisture content (%) of starch immediately before pulverization × 100}], Q = [(residence time (seconds) of raw material starch in the production of gelatinized starch including the step of shear pulverization)] × [(maximum shear rate (1 / second))] [[ID=2​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​According to the present invention, a method for producing pregelatinized starch from starch without adding water can be provided. Furthermore, according to the present invention, it is possible to provide pregelatinized starch that has a high degree of gelatinization of 80% or more, and / or can produce a highly transparent suspension when mixed with water. Furthermore, according to the present invention, by using alkali-washed starch as the raw material starch, it is possible to provide pregelatinized starch that has a higher degree of gelatinization and / or produces a highly transparent suspension when mixed with water, compared to untreated starch. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a schematic diagram showing an example of an apparatus configuration for carrying out the method of the present invention [(a) side view, (b) top view]. [Figure 2] Figure 2 is a cross-sectional view of the main part of the device shown in Figure 1. [Figure 3] Figure 3 is a graph showing the relationship between Q, the moisture loss rate W, and the degree of gelatinization of starch (the percentage values ​​in the graph represent the degree of gelatinization). [Figure 4] Figure 4 is a graph showing the relationship between the degree of gelatinization and the degree of crystallinity of pregelatinized starch obtained in the examples, comparative examples, and reference examples. [Modes for carrying out the invention]

[0018] The present invention relates to a method for producing pregelatinized starch, which includes a step of shearing and grinding starch at a temperature of 5°C to 160°C and under conditions that satisfy the following formula. W<0.00012Q-25 20×10 4 -twenty five <W≦80 [In the formula, W represents the percentage of moisture loss, expressed as [{Moisture content of starch immediately before grinding (mass%) - Moisture content of starch immediately after grinding (mass%)} / Moisture content of starch immediately before grinding (mass%) × 100]. Q = [Residence time of raw starch in the production of pregelatinized starch, including the shearing and crushing process (seconds)] × [Maximum shear rate (1 / second)] ​

[0019] The starch used in the present invention is not particularly limited and includes potato starch, bean starch such as pea starch and mung bean starch, waxy corn starch, high-amylose corn starch, corn starch, tapioca starch, sweet potato starch, rice starch, sago starch, wheat starch, high-amylose wheat starch, and modified starches obtained by chemically, physically, or enzymatically processing these starches. Potato starch, pea starch, waxy corn starch, and tapioca starch are preferred, and potato starch is more preferred. The starch may be used alone or in combination of two or more types. The particle size of the starch used in the present invention is not particularly limited. For example, the particle size of potato starch is, for example, 5 μm to 100 μm, the particle size of pea starch is, for example, 5 μm to 75 μm, the particle size of waxy corn starch is, for example, 3 μm to 30 μm, and the particle size of tapioca starch is, for example, 5 μm to 35 μm. The starch particle size is measured using a laser diffraction scattering particle size distribution analyzer.

[0020] Furthermore, the starch used in the present invention may or may not undergo treatment such as washing with water, or it may be alkaline washed. From the viewpoint of obtaining a pregelatinized starch that can have a higher degree of gelatinization and / or a pregelatinized starch that can produce a more transparent suspension when mixed with water, it is preferable that the starch used in the present invention is alkaline washed starch.

[0021] The method of alkaline washing is not particularly limited and may include a step of dispersing starch in water to prepare a slurry (suspension), a step of mixing the slurry with an alkaline aqueous solution to perform alkaline washing, a step of washing the alkali-washed slurry, and a step of drying the washed starch. In the alkaline washing process, examples of alkaline aqueous solutions include sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium carbonate aqueous solution, potassium carbonate aqueous solution, and sodium bicarbonate aqueous solution. The pH of the alkaline aqueous solution is preferably greater than 7.0 and 14.0 or less, preferably between 7.5 and 13.0, and more preferably between 7.5 and 12.0. Furthermore, the mixing time between the slurry and the alkaline aqueous solution is preferably between 10 minutes and 180 minutes, and between 30 minutes and 90 minutes. In the washing process, washing methods include filtering the alkali-washed starch slurry and washing the solids on the filter paper with water until the pH of the water reaches 7.0, or neutralizing the alkali-washed starch slurry with an acid such as hydrochloric acid or sulfuric acid, filtering the neutralized starch slurry, and washing the solids on the filter paper with water.

[0022] In this invention, shear pulverization does not simply mean pulverizing by compression, but rather pulverizing by applying a shear force to an object, in other words, pulverizing by causing the two sides of the object to slide against each other along a certain surface inside the object. This can be carried out using a crusher, and examples of shear crushers include die-type crushers, roll crushers, cutter mills, sculptors, ring mills, extruders, roller mills, ball mills, rotary mills, vibratory mills, planetary mills, attritors, and bead mills, with die-type crushers being preferred.

[0023] In the present invention, the shear pulverization of starch is carried out at a temperature of 5°C to 160°C, preferably 10°C to 120°C, more preferably 10°C to less than 80°C, and even more preferably 10°C to 40°C. The present invention makes it possible to produce pregelatinized starch not only at high temperatures of 80°C or above, but also at low temperatures of less than 80°C, and especially at low temperatures of 40°C or below.

[0024] In the present invention, the shear pulverization of starch is carried out under the condition that the water content reduction rate W and Q satisfy the following formula. W < 0.00012Q - 25 20 × 10 4 <Q -25 < W ≤ 80

[0025] In the present invention, Q is defined as [the residence time (seconds) of the raw starch in the production of pregelatinized starch including the step of shear pulverization] × [the maximum shear rate (1 / second)]. The residence time (seconds) is defined as the production amount of the pregelatinized starch produced through the shear pulverization process. Furthermore, the maximum shear rate (1 / second) is the shear rate at the location where the gap between two relatively moving members of the shear pulverizer (such as a mortar-type pulverizer or a two-shaft kneading pulverizer) is the smallest, and is defined as the circumferential speed (mm / second) / gap (mm). Even if the gap is 0 mm, when the raw starch passes between the two members and is shear pulverized, for the sake of convenience, the gap is set to 1 μm, and the maximum shear rate (1 / second) is calculated. Q is 20 × 10 4 super, and 50 × 10 4 above 3000 × 10 4 below is preferable, and 50 × 10 4 above 2000 × 10 4 below is more preferable, and 70 × 10 4 above 1500 × 10 4 below is even more preferable, and 70 × 10 4 above 1000 × 10 4 below is particularly preferable.

[0026] In the present invention, the water content reduction rate W (%) is defined as [({the water content of the starch before pulverization (mass%) - the water content of the starch after pulverization (mass%)} / the water content of the starch before pulverization (mass%) × 100)]. The water content reduction rate W is more than -25% and 80% or less, preferably 0% or more and 80% or less, more preferably 5% or more and 75% or less, and even more preferably 45% or more and 75% or less. The water content of the starch immediately before grinding is, for example, 5.00% by mass or more and 20.00% by mass or less, preferably 6.50% by mass or more and 18.50% by mass or less, and more preferably 8.00% by mass or more and 17.00% by mass or less. The water content of the starch immediately after grinding is, for example, 4.00% by mass or more and 14.00% by mass or less, preferably 3.50% by mass or more and 13.50% by mass or less, and more preferably 3.00% by mass or more and 13.00% by mass or less. The moisture content (mass%) of the starch immediately before grinding and the moisture content (mass%) of the starch immediately after grinding are values ​​measured using a heated drying type moisture meter (MX-50, manufactured by A&D Co., Ltd.).

[0027] The pregelatinized starch obtained by the production method of the present invention preferably has a degree of gelatinization of 80% or more, and more preferably 85% or more, as measured by the β-amylase-pullulanase (BAP) method. It is more preferable that it be 90% or more, even more preferable that it be 95% or more.

[0028] When the pregelatinized starch obtained by the manufacturing method of the present invention is mixed with pure water, the absorbance of the 1% suspension (720 nm) is lower than that of the untreated starch (720 nm), and preferably the turbidity reduction rate is, for example, 35% to 100%, and more preferably 40% to 100%. Since a higher turbidity reduction rate results in higher transparency of the suspension, in the present invention, a suspension with a turbidity reduction rate of 40% or more is considered a highly transparent suspension. The absorbance of a 1% suspension (at 720 nm) can be obtained by the measurement method described in the examples. The turbidity reduction rate can be calculated using the following formula. Turbidity reduction rate (%) = [{Absorbance of 1% suspension of untreated starch (720nm)} - {Absorbance of 1% suspension of sample (720nm)}] / {Absorbance of 1% suspension of untreated starch (720nm)} × 100

[0029] Next, the method for manufacturing the present invention will be described. When carrying out the manufacturing method of the present invention, an apparatus for crushing starch by applying shear force can be used, such as a mortar-type pulverizer with the configuration shown in Figure 1, an apparatus configured to crush raw starch by shear as it passes through a minute gap between two relatively rotating rollers, or an apparatus configured to crush raw starch by shear as it passes through a minute gap between the outside of the small-diameter member and the inside of the large-diameter member, with a small-diameter cylindrical or columnar member and a large-diameter cylindrical member arranged concentrically and rotating relative to each other.

[0030] Below, as an example of the apparatus, we will describe a mortar-type grinder with the configuration shown in Figure 1. The millstone grinder 10 has a fixed upper millstone 11 and a lower millstone 12 that is rotatably mounted between the upper millstone 11 and the lower millstone 12 via a predetermined gap 13. The upper millstone 11 is formed in a ring shape with a raw material inlet 14 in the center into which raw starch is introduced. The raw material inlet 14 is connected to the gap 13 at the bottom surface of the upper millstone 11. The lower millstone 12 is formed in a disc shape having approximately the same outer diameter as the upper millstone 11.

[0031] The lower millstone 12 is driven to rotate at a predetermined speed by the motor 15. The gap 13 between the upper millstone 11 and the lower millstone 12 is adjustable within the range of the gap adjustment unit 16, and the set gap can be arbitrarily adjusted within the range of 0 μm to 50 μm (0 mm to 0.05 mm), 5 μm to 40 μm (0.005 mm to 0.04 mm), or 10 μm to 30 μm (0.01 mm to 0.03 mm) depending on the size of the raw starch.

[0032] A temperature controller 17 is provided in the upper millstone 11. The temperature controller 17 is formed in a ring shape with an outer diameter approximately the same as that of the upper millstone 11 and an opening approximately the same diameter as that of the raw material inlet 14. The temperature controller 17 is connected to a temperature controller 19 via a temperature controller cord 18, and the upper millstone 11 is heated or cooled to a temperature set by the temperature controller 19, thereby heating or cooling the entire surface of the upper millstone 11. The computer 22 compares the set temperature from the temperature controller 19 (input from data cable 23) with the measured temperature from a thermocouple (not shown) (input from data cable 21), and provides a control signal for the temperature controller to the temperature controller 19 via a temperature control cable 24.

[0033] Furthermore, the computer 22 provides motor control signals to the motor 15 via the motor control cable 25 to control the rotation speed of the lower millstone 12. The rotation speed of the lower millstone 12 is set so that the maximum shear rate experienced by the starch fed into the gap 13 between the fixed upper millstone 11 and the rotating lower millstone 12 is, for example, between 20,000 [1 / sec] and 750,000 [1 / sec], or between 20,000 [1 / sec] and 75,000 [1 / sec].

[0034] Below the upper millstone 11 and lower millstone 12, a receiving tray 26 is provided, having an inner diameter sufficiently larger than their outer diameters. An opening 27 for pregelatinized starch is provided at the bottom of the receiving tray 26, allowing the pregelatinized starch processed by the millstone grinder 10 to fall from the receiving tray 26 and then be collected in a predetermined container (not shown) via a pregelatinized starch dropping chute 28.

[0035] Figure 2 is a cross-sectional view of the main part of the die-type grinder 10. As shown in Figure 2, the upper millstone 11 has a tapered raw material passage 11c that extends from the inner surface 11a facing the raw material inlet 14 to the bottom surface 11b, which is tapered in cross-sectional view and spiral in plan view. A receiving section 20, enlarged by the tapered raw material passage 11c, is formed at the lower end of the raw material inlet 14. The raw starch introduced into the raw material inlet 14 enters this receiving section 20 just before it enters the gap 13 and is sheared and ground. It is then heated or cooled by heat transfer or heat dissipation from the inner surface 11a of the upper millstone 11, which is heated by the temperature controller 17. The aforementioned thermocouple is inserted into a hole formed from the side of the upper millstone 11 toward the center and approximately indicates the processing temperature when the starch is being sheared and ground in the gap 13 between the upper millstone 11 and the lower millstone 12. On the surfaces facing the gaps 13 of the upper millstone 11 and the lower millstone 12, numerous grooves extending in a direction intersecting the circumferential direction are formed to increase the shear force on the raw starch.

[0036] Next, the manufacturing method of the present invention, which is carried out using this mortar-type grinder 10, will be described. The gap 13 between the upper millstone 11 and the lower millstone 12 is arbitrarily adjusted via the gap adjustment unit 16 according to the size of the raw starch, for example, within the range of 0 μm to 50 μm (0 mm to 0.05 mm), 5 μm to 40 μm (0.005 mm to 0.04 mm), or 10 μm to 30 μm (0.01 mm to 0.03 mm). The temperature controller 19 heats or cools the temperature controller 17 to a predetermined temperature (set within the range of 5°C to 160°C), thereby heating or cooling the upper millstone 11. The motor 15 is driven at a rotational speed controlled by the computer 22, rotating the lower millstone 12 to provide the predetermined maximum shear rate.

[0037] With the preparation of the millstone grinder 10 complete, the raw starch is fed into the raw material inlet 14 to start processing. The temperature controller 17 has already been heated or cooled to a predetermined temperature, and the upper millstone 11 has also been heated or cooled accordingly. As the starch passes through the temperature controller 17 and the raw material inlet 14, and then through the tapered raw material passage 11c or the storage section 20, it is heated or cooled to a temperature corresponding to the heater temperature. Immediately thereafter, it is sent into the gap 13 between the upper millstone 11 and the lower millstone 12, where it is crushed by shear force between the fixed upper millstone 11 and the rotating lower millstone 12. The pregelatinized starch obtained by shear crushing is discharged from the side of the gap 13 and collected in the receiving tray 26, and then collected in a predetermined container (not shown) via the pregelatinized starch drop-off port 27 and the pregelatinized starch drop-off chute 28. [Examples]

[0038] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0039] In the following example, the maximum shear rate, residence time, Q, and moisture loss rate W were measured by the following method. (1) Maximum shear rate The rotational speed of motor 15 and the peripheral velocity were determined from the circumference of the upper and lower mortars 11 and 12. From the value of the gap 13, the maximum shear rate of crushing was defined from the following relationship. In the following example, even when the gap of the millstone grinder used was set to 0 μm (no gap), some raw starch passed between the upper millstone 11 and the lower millstone 12 and was sheared and ground. In such cases, for convenience, the gap was set to 1 μm and the maximum shear rate was calculated. Peripheral speed (mm / sec) = [Rotational speed (rpm) × Circumference (mm)] / 60 Maximum shear rate (1 / sec) = Peripheral speed (mm / sec) / Gap (mm) (2) Time spent The residence time was defined from the following relationship based on the production volume of pregelatinized starch produced through the shearing and grinding process. Residence time (seconds) = 1 / Amount of pregelatinized starch produced through the shearing and grinding process (3)Q Q was found using the following formula. Q = [Residence time of raw starch in the production of pregelatinized starch, including the shearing and crushing process (seconds)] × [Maximum shear rate (1 / second)] (4) Moisture reduction rate W The moisture loss rate W was calculated using the following formula. Moisture reduction rate W (%) = [Moisture content of starch immediately before grinding (mass%) - Moisture content of starch immediately after grinding (mass%)] / Moisture content of starch immediately before grinding (mass%) × 100 The moisture content (mass%) of starch immediately before grinding and the moisture content (mass%) of starch immediately after grinding were measured using a heated drying type moisture meter (MX-50, manufactured by A&D Co., Ltd.).

[0040] In the following example, the degree of gelatinization and crystallinity of pregelatinized starch were measured by the following method. (5) Degree of alphaning The degree of gelatinization of pregelatinized starch was measured using the β-amylase-pullulanase (BAP) method. (i) Pregelatinized starch was crushed in advance and adjusted to a particle size that could pass through a sieve with a mesh size of 0.15 mm according to JIS Z8801-1 standards, and this was used as the measurement sample. (ii) The degree of gelatinization (%) of pregelatinized starch was measured in accordance with the method described in "A New Method for Measuring the Degree of Gelatinization and Retrograde of Starch Using the β-Amylase-Pullulanase (BAP) System" in "Starch Science," Vol. 28, No. 4, pp. 235 to 240 (1981). (6) Degree of crystallinity The crystallinity of pregelatinized starch was determined by separating the peaks from crystalline reflection and amorphous scattering using wide-angle X-ray diffraction measurements. Let Sa be the integral of the amorphous scattering peak, and Sc be the integral of the crystalline reflection peak. The crystallinity of the ground pregelatinized starch was determined from the following relationship. Crystallinity (%)=[(Sc / (Sc+Sa)]×100 The experimental specifications for the wide-angle X-ray diffraction described above are as follows: • Measuring instrument: Rigaku Ultima IV • Measurement conditions X-ray source: Cu-Kα ray Wavelength: 1.54Å Scan speed: 10° / min Measurement angle: 5-35° Tube voltage 40kV Tube current 40mA Proposed method: Reflection method

[0041] In the following example, the transparency of pregelatinized starch was evaluated by the following method. (7) Transparency The transparency of the pregelatinized starch suspension was evaluated by the turbidity reduction rate, which was the decrease in turbidity at 720 nm of the absorbance of a 1% sample suspension compared to untreated starch. High turbidity indicates poor transparency, while low turbidity indicates high transparency. 40 mg of starch was weighed into a 15 mL container and suspended in 3.96 mL of distilled water. The absorbance at 720 nm was measured using a spectrophotometer (Thermo Fisher GENESYS150) while ensuring that the suspension did not settle. The measurement method followed the turbidity measurement method described on page 109 of the Industrial Analysis Methods for Starch and Sugar-Related Products. The turbidity reduction rate was calculated using the following formula. Turbidity reduction rate (%) = [{Absorbance of 1% suspension of untreated starch (720nm)} - {Absorbance of 1% suspension of sample (720nm)}] / {Absorbance of 1% suspension of untreated starch (720nm)} × 100

[0042] [Example 1] Potato starch with a moisture content of 8.12% by mass was used as the raw material starch and was shear-pulverized using a mortar-type pulverizer 10 configured as shown in Figures 1 and 2. In the mortar-type pulverizer 10 used, the upper millstone 11, lower millstone 12, and temperature controller 17 all have an outer diameter of 90 mm (radius 45 mm) and have a raw material inlet 14 with a diameter of 10 mm at its center. The tapered raw material passage 11c of the upper millstone 11 is formed over a range of 5 mm from the inner surface 11a (Figure 2). The gap 13 between the millstones was fixed at 30 μm, the rotation speed of the motor 15 was set to 150 rpm, and the pulverization temperature was set to 120°C. Pregelatinized starch was produced by shear-pulverization. The amount of potato starch input was substantially the same as the amount of pregelatinized starch produced. The degree of gelatinization of the obtained pregelatinized starch is shown in Table 1 and Figure 3. The degree of crystallinity and transparency (turbidity reduction rate) of the obtained pregelatinized starch are also shown in Table 1.

[0043] [Examples 2 to 12, and Comparative Examples 1 to 8] The raw starch was replaced with potato starch having the moisture content shown in Table 1, and the α-starch was produced in the same procedure as in Example 1 except that the gap 13 between the mortars, the rotational speed of the motor 15, and the pulverization temperature were replaced with the conditions shown in Table 1. The degree of gelatinization of the obtained α-starch is shown in Table 1 and FIG. 3. Further, the crystallinity and transparency (turbidity reduction rate) of the obtained α-starch are shown in Table 1.

[0044]

Table 1

[0045] From the results shown in Table 1 and FIG. 3, by subjecting potato starch to shear pulverization at a temperature of 5°C or higher and 160°C or lower and under the condition that the water reduction rates W and Q satisfy the above formula, an α-starch having a degree of gelatinization of 82% or higher was obtained (Examples 1 to 12). Further, the turbidity reduction rate was 51% or higher, and a suspension with high transparency was obtained. On the other hand, under the condition that the relationship between the water reduction rate W and the shearing force is W≧0.00012Q-25 (Comparative Examples 2 and 5), the condition that the water reduction rate W exceeds 80% (Comparative Examples 1, 4 and Comparative Example 7) and the condition that Q is less than 20×10 4 (Comparative Examples 3 and 6), that is, when any one of the above formulas (W<0.00012Q-25, 20×10 4 <Q, -25<W≦80) is not satisfied, starch having a degree of gelatinization of 36% or less was obtained. Further, the turbidity reduction rate was 14% or less, and the transparency of the suspension was considerably lower than that of the suspension in the examples. Therefore, it is clear that the present invention can produce α-starch by subjecting starch to shear pulverization at a temperature of 5°C or higher and 160°C or lower and under the condition that the above formula (W<0.00012Q-25, 20×10 4 <Q, -25<W≦80) is satisfied. Further, in the present invention, even when the pulverization temperature is 40°C or lower, α-starch having a degree of gelatinization of 82% or higher can be produced (Examples 8, 11 and 12).

[0046] [Example 13] Pea starch was used as the raw material and sheared using a mortar-type pulverizer 10 configured as shown in Figures 1 and 2. In the mortar-type pulverizer 10 used, the upper millstone 11, lower millstone 12, and temperature controller 17 all have an outer diameter of 90 mm (radius 45 mm) and have a raw material inlet 14 with a diameter of 10 mm at its center. The tapered raw material passage 11c of the upper millstone 11 is formed over a range of 5 mm from the inner surface 11a (Figure 2). The gap 13 between the millstones was fixed at 10 μm, the rotation speed of the motor 15 was set to 150 rpm, and the pulverizing temperature was set to 120°C. Pregelatinized starch was produced by shearing and pulverizing. The amount of pea starch input was substantially the same as the amount of pregelatinized starch produced. Table 2 shows the degree of gelatinization and transparency (turbidity reduction rate) of the obtained pregelatinized starch.

[0047] [Example 14] Pregelatinized starch was produced using the same procedure as in Example 13, except that the raw starch was replaced with water-washed pea starch. The degree of gelatinization and transparency (turbidity reduction rate) of the obtained pregelatinized starch are shown in Table 2.

[0048] [Example 15] Pregelatinized starch was produced using the same procedure as in Example 13, except that the raw starch was replaced with pea starch washed according to the procedure described below. The degree of gelatinization and transparency (turbidity reduction rate) of the obtained pregelatinized starch are shown in Table 2. <Cleaning> (1) Add 300g of raw starch and 600g of pure water to a 1L beaker and stir with a stirrer to prepare a slurry. (2) While stirring with a stirrer, adjust the pH with a 5% sodium hydroxide solution and a 2% hydrochloric acid solution. (3) Stir with a stirrer and leave at room temperature (25°C) for 1 hour. (4) Adjust the pH to 7 with a 2% hydrochloric acid solution and a 5% sodium hydroxide solution. (5) Filter by suction using filter paper (Kiriyama Funnel Filter Paper No. 5A, manufactured by Kiriyama Seisakusho Co., Ltd.). (6) Collect the solids on the filter paper and suspend them in 1500g of pure water. (7) Filter by suction using filter paper (Kiriyama Funnel Filter Paper No. 5A, manufactured by Kiriyama Seisakusho Co., Ltd.), and dry the solids on the filter paper at 45°C. (8) The dried material is sieved through a 60-mesh sieve to obtain washed starch.

[0049] [Table 2]

[0050] As shown in Table 2, even when pea starch was used as the raw material starch, the present invention was able to produce pregelatinized starch with a degree of gelatinization of 90% or more (Examples 13 to 15). Furthermore, using alkali-washed pea starch as the raw material improved the degree of gelatinization of the pregelatinized starch (Example 15).

[0051] [Example 16] Waxy corn starch was used as the raw material starch and sheared using a mortar-type pulverizer 10 configured as shown in Figures 1 and 2. In the mortar-type pulverizer 10 used, the upper millstone 11, lower millstone 12, and temperature controller 17 all have an outer diameter of 90 mm (radius 45 mm) and have a raw material inlet 14 with a diameter of 10 mm at its center. The tapered raw material passage 11c of the upper millstone 11 is formed over a range of 5 mm from the inner surface 11a (Figure 2). The gap 13 between the millstones was fixed at 10 μm, the rotation speed of the motor 15 was set to 150 rpm, and the pulverizing temperature was set to 120°C. Pregelatinized starch was produced by shearing and pulverizing. The amount of waxy corn starch input was substantially the same as the amount of pregelatinized starch produced. Table 3 shows the degree of gelatinization, crystallinity, and transparency (turbidity reduction rate) of the obtained pregelatinized starch.

[0052] [Examples 17 to 20] Pregelatinized starch was produced using the same procedure as in Example 16, except that the raw starch was replaced with waxy corn starch washed at the pH shown in Table 3. The degree of gelatinization, crystallinity, and transparency (turbidity reduction rate) of the obtained pregelatinized starch are shown in Table 3.

[0053] [Table 3]

[0054] As shown in Table 3, even when waxy corn starch is used as the raw material starch, the present invention was able to produce pregelatinized starch with a degree of gelatinization of 79% or more (Examples 16 to 20). Furthermore, the raw starch is washed, especially with an alkaline aqueous solution with a pH of 7.5 or higher. As a result, the degree of gelatinization of the obtained gelatinized starch was greatly improved (Examples 18 to 20). Furthermore, by alkaline washing the raw starch, the transparency (rate of turbidity reduction) of the obtained pregelatinized starch was improved (Examples 18 to 20).

[0055] [Example 21] Tapioca starch was used as the raw material and sheared using a mortar-type pulverizer 10 configured as shown in Figures 1 and 2. In the mortar-type pulverizer 10 used, the upper millstone 11, lower millstone 12, and temperature controller 17 all have an outer diameter of 90 mm (radius 45 mm) and have a raw material inlet 14 with a diameter of 10 mm at its center. The tapered raw material passage 11c of the upper millstone 11 is formed over a range of 5 mm from the inner surface 11a (Figure 2). The gap 13 between the millstones was set to 10 μm, the rotation speed of the motor 15 was set to 150 rpm, and the pulverizing temperature was set to 80°C. Pregelatinized starch was produced by shearing and pulverizing. The amount of tapioca starch input was substantially the same as the amount of pregelatinized starch produced. Table 4 shows the degree of gelatinization and transparency of the obtained pregelatinized starch.

[0056] [Examples 22 and 23] Pregelatinized starch was produced using the same procedure as in Example 21, except that the gap 13 between the millstones and the grinding temperature were changed to the conditions shown in Table 4. The degree of gelatinization and transparency (turbidity reduction rate) of the obtained pregelatinized starch are shown in Table 4.

[0057] [Table 4]

[0058] As shown in Table 4, even when tapioca starch is used as the raw material starch, the present invention was able to produce pregelatinized starch with a degree of gelatinization of 94% or more (Examples 21 to 23).

[0059] [Reference example 1] Rice grains with a moisture content of 15.00% by mass (polished rice from Yamagata Prefecture, 2018) were shear-pulverized using a mortar-type pulverizer 10 configured as shown in Figures 1 and 2. In the mortar-type pulverizer 10 used, the upper millstone 11, lower millstone 12, and temperature controller 17 all have an outer diameter of 250 mm (radius 125 mm), and have a raw material inlet 14 with a diameter of 190 mm at its center. The tapered raw material passage 11c of the upper millstone 11 is formed from the inner surface 11a (Figure 2). The gap 13 between the millstones was fixed at 0 μm, the rotation speed of the motor 15 was set to 80 rpm, the pulverization temperature was set to 120°C, and the input rate of rice grains was 50 g / min. Pregelatinized starch was produced by shear-pulverization. The degree of gelatinization, degree of crystallinity, and transparency of the obtained pregelatinized starch are shown in Table 5.

[0060] [Reference example 2] 5 kg of commercially available polished rice from Yamagata Prefecture, harvested in 2018, was pulverized using a pin mill that does not apply shear (Nara Machine Works, M-2 free pulverizer: 1 mm filter hole). The moisture content of the polished rice before pulverization was 14.0% by mass. After pulverization, the rice was sieved to obtain 4.5 kg of rice flour with a 50-mesh pass. The moisture content of the obtained rice flour was 18.5% by mass.

[0061] [Reference example 3] 5 kg of commercially available polished rice from Yamagata Prefecture, harvested in 2018, was pulverized using a pin mill that does not apply shear (Nara Machine Works, M-2 free pulverizer: 1 mm filter hole). The moisture content of the polished rice before pulverization was 14.0% by mass. After pulverization, the rice was sieved to obtain 4.5 kg of rice flour with a 50-mesh pass. The moisture content of the obtained rice flour was 18.5% by mass. 2 kg of the obtained rice flour was mixed with 3 kg of water to make a 12 Baume slurry. The slurry was supplied at a flow rate of 42 L / hour to an on-litter (Sakura Seisakusho HAS00503-1) heated to 130°C and thoroughly gelatinized. The inlet temperature at this time was 13.7°C and the outlet temperature was 105.3°C. The gelatinized slurry was dried in a double drum dryer (clearance 0.6 mm, rotation speed 2.5 rpm) heated to a surface temperature of 150°C, and then ground in a pin mill and sieved to obtain drum-dried alpha rice flour with a 50-mesh pass. 5 kg of slurry was added to obtain 1.5 kg of drum-dried alpha rice flour. The moisture content of the obtained drum-dried alpha rice flour was 5.4% by mass.

[0062] [Table 5]

[0063] [Relationship between crystallinity and alpha-adsorption] Relationship between degree of gelatinization and crystallinity of potato starch obtained in the examples and comparative examples, relationship between degree of gelatinization and crystallinity of waxy corn starch obtained in the examples, and degree of gelatinization of rice flour obtained in the reference example. The relationship between the two is shown in Figure 4. As shown in Figure 4, a low degree of crystallinity does not necessarily equate to a low degree of alpha-gelatinization, and no correlation was observed between crystallinity and alpha-gelatinization. [Explanation of symbols]

[0064] 10. Mortar-type grinder 11 Upper millstone 11a Inner Self 11b Bottom 11c Tapered raw material passage 12 Lower acetabulum 13 Gap 14 Raw material input port 15 Motor 16 Gap adjustment section 17 Temperature controller 18 Temperature controller cord 19 Temperature controller 20 Storage Units 21 Data Cables 22 Computers 23 Data Cables 24 Temperature control cables 25 Motor control cable 26. Drip tray 27 Pregelatinized starch fall port 28 Pregelatinized starch drop chute

Claims

1. The process includes a step of shearing and grinding starch at a temperature of 5°C to 160°C and under conditions that satisfy the following formula. The degree of gelatinization of pregelatinized starch, as measured by the BAP method, is 80% or higher. A method for producing pregelatinized starch. W<0.00012Q-25 20×10 ４ <Q -25 < W ≤ 80 [In the formula, W represents the moisture loss rate (%) expressed as [{Moisture content of starch immediately before grinding (mass%) - Moisture content of pregelatinized starch immediately after grinding (mass%)} / Moisture content of starch immediately before grinding (mass%) × 100], Q = [Residence time of raw starch in the production of pregelatinized starch, including the shearing and crushing process (seconds)] × [Maximum shear rate (1 / second)].

2. The aforementioned Q is 50 × 10 ４ 3000 x 10 ４ The manufacturing method according to claim 1, which is as follows:

3. The manufacturing method according to claim 1 or claim 2, wherein the moisture reduction rate W is 0% or more and 80% or less.

4. The manufacturing method according to any one of claims 1 to 3, wherein the temperature is 10°C or more and 120°C or less.

5. The manufacturing method according to any one of claims 1 to 4, wherein the starch is alkali-washed starch.

6. The manufacturing method according to any one of claims 1 to 5, wherein the shearing and grinding step is performed using a mortar-type grinder.

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