Recrystallization method, starch material containing recrystallized starch, and food and feed

Abstract

To recrystallize low crystalline starch by a simple process of only heating without cooling.SOLUTION: A recrystallization method includes the step of heating a starch material containing low crystalline starch, to recrystallize the low crystalline starch, the low crystalline starch produced by crushing the raw material while heating under shear conditions.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a technique for recrystallizing starch. [Background technology]

[0002] With the recent increase in health consciousness, foods containing resistant starch are desired. Resistant starch is known to reduce the absorption of carbohydrates and lipids because it is difficult to be absorbed by the digestive tract. For example, Patent Document 1 discloses a bakery food mix containing resistant starch. Resistant starch can be obtained, for example, by gelatinizing (gelatinizing) starch by heating, and then cooling and recrystallizing it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-92474 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, the production of recrystallized starch (i.e., resistant starch) requires a step of cooling the starch (typically refrigerating or freezing), which poses the problem of time and labor required for the cooling step. Therefore, the present invention provides a recrystallization method for recrystallizing starch through a simpler process. [Means for solving the problem]

[0005] In order to solve the above problems, the recrystallization method of the present invention includes a step of heating a starch material containing low-crystalline starch to recrystallize the low-crystalline starch, and the low-crystalline starch is produced by pulverizing a raw material under shear conditions while heating the raw material. Effect of the Invention

[0006] According to the present invention, low-crystalline starch can be recrystallized by a simple process of only heating without cooling. [Brief description of the drawings]

[0007] [Figure 1] 1 shows the results of wide-angle X-ray diffraction of the rice flour of Reference Example 1. [Diagram 2] 1 shows the results of wide-angle X-ray diffraction of rice flour according to Example 1. [Diagram 3] 1 shows the results of wide-angle X-ray diffraction of rice flour in Comparative Example 1. [Figure 4] 1 shows the results of wide-angle X-ray diffraction of rice flour in Reference Example 2. [Diagram 5] 1 shows the results of wide-angle X-ray diffraction of rice flour according to Example 2. [Figure 6] 1 shows the results of wide-angle X-ray diffraction of rice flour in Comparative Example 2. [Figure 7] FIG. 1 is a schematic diagram showing the recrystallization of low-crystalline starch. [Figure 8] These are the results of wide-angle X-ray diffraction on the dough before baking and the cookies after baking. [Figure 9] These are the results of wide-angle X-ray diffraction before and after heating rice flour made from different ingredients. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The recrystallization method according to the present invention is a method for recrystallizing a starch material containing low-crystalline starch. This method can produce a starch material containing starch recrystallized from low-crystalline starch. The "recrystallization" of low-crystalline starch means that the molecules of the amorphous portion change their higher-order structure by molecular motion and are arranged in a crystalline structure. The recrystallized starch is so-called resistant starch. The starch material containing the recrystallized starch according to the present invention is used in various foods. For example, the starch material containing the recrystallized starch is used in baked goods (e.g., cookies, sponge cakes, scones, etc.), bread, noodles, batter for deep-fried foods, gyoza and shumai skins, rice crackers, and okonomiyaki. Since the recrystallized starch exhibits resistance to digestion, the above-mentioned various foods can be used as diet foods, foods for suppressing blood sugar rise, foods for intestinal regulation, etc. The starch material containing the recrystallized starch according to the present invention can also be used as feed for livestock or pets. Target animals include cows, pigs, chickens, dogs, cats, etc. When used as feed, in addition to the above-mentioned starch material, conventionally known feed ingredients such as hay, vegetables, lactic acid products, bran, oil, protein, amino acids, minerals, vitamins, etc. can be appropriately blended.

[0009] Low-crystalline starch (gelatinized starch) is starch that has a lower degree of crystallinity (i.e., a higher degree of amorphization) than crystalline starch (beta-starch). The crystallinity of low-crystalline starch is, for example, 20% or less, and preferably 10% or less.

[0010] The starch material containing low crystalline starch used in the recrystallization method of the present invention is produced from plants such as grains, millet, pulses, pseudocereals, etc., which contain starch as a main component. Examples of the raw material include plants such as rice, potato, wheat, soybean, red bean, buckwheat, potatoes, beans, and corn. Crystalline starch produced from these plants may also be used as the raw material. For example, tapioca produced from cassava rhizomes may also be used as the raw material. The starch content in the starch material may vary appropriately depending on the raw material and the production method.

[0011] The low-crystalline starch contained in the starch material used in the recrystallization method of the present invention is produced by heating the raw material and pulverizing it under shear conditions. Note that the "shear conditions" do not simply mean compressing and pulverizing, but rather mean conditions that act to displace both sides of the object from each other along a surface inside the object.

[0012] For example, a starch material containing low crystalline starch is produced by a manufacturing method using a mortar-type grinder proposed in Japanese Patent No. 4767128, Japanese Patent No. 5503885, or Japanese Patent Application Laid-Open No. 2009-213472. Specifically, a raw material fed into a mortar-type grinder is heated at 80°C or higher (e.g., 100 to 200°C) and ground under shearing conditions to produce flour. The flour (e.g., rice flour when rice is used as the raw material) is the starch material containing low crystalline starch of the present invention. As described above, a starch material containing low crystalline starch is produced by simultaneously carrying out heating and shearing.

[0013] The above-mentioned manufacturing method using a mortar-type grinder has the advantage that a starch material having a highly low crystallinity can be easily produced without adding water. However, the method for producing a starch material containing low crystallinity starch is not limited to the above examples. For example, a starch material containing low crystallinity starch may be produced by grinding a raw material using a twin-screw extruder equipped with two intermeshing screws.

[0014] The crystallinity of low crystalline starch can be appropriately controlled according to the grinding conditions when grinding the raw material. The crystallinity of starch is calculated by any known technique. For example, the crystallinity of low crystalline starch is determined according to the result of X-ray diffraction intensity. Specifically, a peak representing the amorphous part of starch and a peak representing the crystalline part of starch are extracted from the result of X-ray diffraction intensity. Any known peak separation technique is used to extract each peak. Then, the crystallinity is determined from the ratio of the peak representing the amorphous part to the peak representing the crystalline part. For example, the crystallinity is calculated by substituting the area A of the peak representing the crystalline part (the total area of ​​a plurality of peaks) and the area B of the peak representing the amorphous part into the following formula (1). Crystallinity (%)=100×Area A / (Area A+Area B)...(1) The range of diffraction angles used in formula (1) is adjusted appropriately depending on the raw material and the grinding method used when grinding the raw material.

[0015] The low crystalline starch of the present invention contains amylose and amylopectin. Amylose has a smaller molecular weight than amylopectin and has a linear structure. On the other hand, amylopectin has a larger molecular weight than amylose and has a branched structure. When the total of amylose and amylopectin in the entire low crystalline starch is taken as 100% by mass, it is preferable that amylose is contained in the range of 0 to 45% by mass and amylopectin is contained in the range of 55 to 100% by mass. When amylose and amylopectin are contained in the above ranges, efficient recrystallization is possible. From the viewpoint of making the above effects more prominent, it is preferable that amylose is contained in the range of 0 to 30% by mass and amylopectin is contained in the range of 70 to 100% by mass. However, it is not essential in the present invention that amylose and amylopectin are contained in the above ranges. The present invention also encompasses configurations in which the amylose content is outside the range of 0 to 45% by mass and the amylopectin content is outside the range of 55 to 100% by mass.

[0016] The recrystallization method according to the present invention involves heating a starch material containing low-crystalline starch to recrystallize the low-crystalline starch in the starch material. The conditions for heating the starch material are as follows: Temperature: 100°C to 200°C, preferably 150°C to 180°C Time: 5 to 30 minutes, preferably 10 to 20 minutes For heating the starch material, various heating devices such as an oven, a hot plate, a heater, and an electric furnace are used.

[0017] In the recrystallization method according to the present invention, a method of adding a fatty acid to a starch material containing low crystalline starch and heating the starch material is preferable. Adding a fatty acid to a starch material and heating the starch material allows efficient recrystallization. The fatty acid used in the recrystallization method is, for example, an unsaturated fatty acid. For example, oleic acid, palmitoleic acid, linoleic acid, or α-linolenic acid are examples of unsaturated fatty acids. Alternatively, a saturated fatty acid such as palmitic acid may be used. According to the method of adding oleic acid as the fatty acid, the effect of efficient recrystallization becomes more remarkable. It is to be noted that multiple types of fatty acids may be added to the starch material.

[0018] The fatty acid is preferably added in an amount of 5 to 80 parts by mass per 100 parts by mass of the starch material containing low crystalline starch. By adding a fatty acid to the starch material, it is possible to prepare dough for use in various foods (e.g., cookie dough). By setting the amount of fatty acid added within the above range, it is possible to prepare dough that is highly moldable and has reduced stickiness while efficiently recrystallizing the low crystalline starch when heated. From the viewpoint of making the above effect more pronounced, the fatty acid is preferably added in an amount of 20 to 70 parts by mass, more preferably 30 to 60 parts by mass, per 100 parts by mass of the starch material containing low crystalline starch.

[0019] However, it is not essential in the present invention to add a fatty acid to the starch material. In addition to fatty acids, various other materials may be added depending on the application. For example, when the starch material is used as a dough for food, various seasonings and food additives may be added to the starch material. EXAMPLES

[0020] The present invention will be described in more detail below with reference to examples, comparative examples and reference examples, but the present invention is not limited to the following examples.

[0021] Example 1 (Rice flour containing low crystalline starch) Raw material: Akita No. 63 Amylose content: 20% by mass Manufacturing method: Using a mortar-type grinder equivalent to that proposed in Patent No. 4767128, the raw materials were heated and ground under shear conditions at a grinding temperature of 120°C, a gap of 10 μm, and a rotation speed of 150 rpm. The amylose content is the content when the low crystalline starch is taken as 100% by mass.

[0022] Comparative Example 1 (Rice flour containing low crystalline starch) Commercially available product: Pregelatinized rice (manufactured by Frystar Co., Ltd.) Manufacturing method: By adding water, gelatinizing at high temperature, and then grinding.

[0023] The rice flours of Example 1 and Comparative Example 1 were heated under the following heating conditions. Heating equipment: Gas oven (Ozaki Co., Ltd.: OZ100BOEC) Temperature: 180℃ Time: 15 minutes

[0024] The crystal structure of starch was observed from the results of wide-angle X-ray diffraction before and after heating for the rice flours of Example 1 and Comparative Example 1. The conditions for wide-angle X-ray diffraction were as follows. Equipment: UltimaIV (Rigaku Corporation) X-ray source: Cu-Kα ray Wavelength: 1.54Å Tube voltage: 40kV Tube current: 40mA Scan range: 2θ=5°~35° Scan speed: 10° / min

[0025] Here, wide-angle X-ray diffraction was also performed under similar conditions on rice flour containing crystalline starch as Reference Example 1. The details of Reference Example 1 are as follows. Reference Example 1 (Rice flour containing crystalline starch) Raw material: Akita No. 63 Amylose content: 20% by mass Manufacturing method: Conventional airflow grinding. The amylose content is the content when the starch is taken as 100% by mass.

[0026] FIG. 1 shows the results of wide-angle X-ray diffraction of rice flour according to Reference Example 1. As shown in FIG. 1, in Reference Example 1, the diffraction image is almost unchanged before and after heating, and it can be seen that there is no change in the crystal structure. In Reference Example 1, peaks are shown at diffraction angles (2θ) of approximately 15°, 17°, and 18° before and after heating. These peaks are characteristic of crystallized starch. The peaks indicating crystallization are not limited to those at diffraction angles (2θ) of approximately 15°, 17°, and 18°. The positions of the peaks indicating crystallization may vary depending on the type of raw material.

[0027] Fig. 2 shows the results of wide-angle X-ray diffraction of the rice flour of Example 1. As shown in Fig. 2, it can be seen that in Example 1, the diffraction image changes significantly before and after heating. Specifically, peaks (i.e., peaks approximately the same as the peaks representing the crystal structure) appeared near diffraction angles (2θ) of 15°, 17°, and 18°. These peaks were not observed in Example 1 before heating. In other words, it was clear that the low-crystalline starch in the rice flour of Example 1 was recrystallized.

[0028] Figure 3 shows the results of wide-angle X-ray diffraction of rice flour according to Comparative Example 1. As shown in Figure 3, in Comparative Example 1, the diffraction image remains almost unchanged before and after heating, and it can be seen that no peaks specific to crystallized starch appear. That is, it was revealed that in Comparative Example 1, the crystal structure does not change upon heating and recrystallization does not occur. Note that in Comparative Example 1, peaks were observed at diffraction angles (2θ) of approximately 13° and 20° before heating, whereas in Example 1, these peaks are not observed before heating.

[0029] Here, a method for recrystallizing starch has been known in the past (hereinafter referred to as "conventional example") in which a starch material is gelatinized after heating and then cooled to recrystallize (so-called retrogradation). However, according to the conventional example, a step of cooling after heating must be carried out, which takes time and effort. In contrast, according to the recrystallization method of the present invention, low-crystalline starch in a starch material can be recrystallized by a simple step of heating only, without cooling. On the other hand, low-crystalline starch from a starch material produced by a production method other than pulverizing the raw material under shearing conditions while heating it (low-crystalline starch in Comparative Example 1) does not recrystallize by heating alone.

[0030] Example 2 and Comparative Example 2 will be described. Example 2 is obtained by adding a fatty acid to the rice flour of Example 1, and Comparative Example 2 is obtained by adding a fatty acid to the rice flour of Comparative Example 1. Oleic acid was used as the fatty acid. The rice flours to which the fatty acids of Example 2 and Comparative Example 2 were added were heated. Then, wide-angle X-ray diffraction was performed on Example 2 and Comparative Example 2 before and after heating.

[0031] Wide-angle X-ray diffraction was also performed on Reference Example 2, in which fatty acids were added to the rice flour of Reference Example 1. FIG. 4 shows the results of wide-angle X-ray diffraction on Reference Example 2. As shown in FIG. 4, in Reference Example 2, similar to Reference Example 1, there is no change in the crystal structure before and after heating, and peaks are observed at diffraction angles (2θ) of approximately 15°, 17°, and 18°. That is, in Reference Example 2, similar to Reference Example 1, peaks specific to crystallized starch are observed before and after heating. In reality, the addition of fatty acids may cause the positions of the peaks to shift slightly from the vicinity of 15°, 17°, and 18°.

[0032] FIG. 5 shows the results of wide-angle X-ray diffraction of rice flour according to Example 2. As shown in FIG. 5, in Example 2, it can be seen that the diffraction image changes greatly before and after heating. Specifically, similar to Example 1, peaks appeared at diffraction angles (2θ) of 15°, 17°, and 18°. However, in Example 2, the change in the diffraction image after heating is even greater than in Example 1. From the fact that a diffraction image almost identical to that of Reference Example 2 after heating was observed in Example 2 after heating, it can be confirmed that the degree of recrystallization is greater than that of Example 1. As can be understood from the above explanation, it has become clear that efficient recrystallization occurred in Example 2 to which fatty acids were added.

[0033] Figure 6 shows the results of wide-angle X-ray diffraction of the rice flour according to Comparative Example 2. As shown in Figure 6, it can be seen that in Comparative Example 2, there is no significant change in the diffraction pattern before and after heating, and no peaks specific to crystallized starch appear. In other words, it was revealed that in Comparative Example 2, like Comparative Example 1, the crystal structure did not change upon heating and recrystallization did not occur.

[0034] FIG. 7 is a schematic diagram showing low-crystalline starch in the starch material of the present invention (i.e., produced by pulverizing a raw material under shearing conditions while heating it). Specifically, the double helix structure of amylopectin is illustrated. As illustrated in FIG. 7, the amylopectin in the starch material before heating has its double helix open. Therefore, when fatty acids are added to the starch material, they enter the double helix of amylopectin, and the fatty acids and amylopectin are complexed. Then, when the material is heated in a state where the fatty acids have entered the double helix, the fatty acids are expelled from the double helix. As a result, it is believed that the double helix is ​​closed and the amylopectin is efficiently recrystallized.

[0035] <Cookie making> Cookies were made from five different types of rice flour, 1 to 5, which are made from different varieties of rice. The ingredients of rice flours 1 to 5 are as follows. Rice flours 1 to 5 were made by heating the rice and grinding it under shear conditions. Rice flour 1 A6 type rice (amylose content: 45% by mass) Rice flour 2 Akita Sarari (amylose content: 30% by mass) Rice flour 3 Akita No. 63 (amylose content: 20% by mass) Rice flour 4 Milky Queen: (Amylose content: 8% by mass) Rice flour 5 Himenomochi (amylose content: 0% by mass) The amylose content is the content when the starch content is taken as 100% by mass.

[0036] The ingredients for the cookies are as follows: Rice flour 1~5 50g Oleic acid 30g 20g sugar

[0037] The above ingredients were mixed at low speed for 2 minutes, then mixed at medium speed for 4 minutes to prepare the dough. Then, the dough was cut into a mold with a diameter of 45 mm and a thickness of 6 mm. The molded dough was then baked in an oven at 180°C for 15 minutes to prepare cookies.

[0038] Figure 8 shows the results of wide-angle X-ray diffraction of the dough before baking and the cookies after baking for rice flours 1 to 5. As shown in Figure 8, it can be seen that for all rice flours 1 to 5, peaks specific to crystallization (peaks around 15°, 17°, and 18°) that were not observable before baking appeared after baking. In other words, the low-crystalline starch in the rice flour was recrystallized in all rice flours 1 to 5. Note that when low-crystalline starch is recrystallized by adding fatty acid and heating, the degree of recrystallization is more remarkable than when recrystallization is performed by the conventional method (heating and cooling).

[0039] For rice flours 1 to 5, wide-angle X-ray diffraction was performed before and after heating without adding fatty acids. Figure 9 shows the results of wide-angle X-ray diffraction for rice flours 1 to 5 before and after heating. As shown in Figure 9, peaks specific to crystallization (peaks near 15°, 17°, and 18°) appear after heating for all rice flours 1 to 5. In other words, regardless of the type of raw rice, it was observed that rice flours produced by heating the raw material and grinding it under shearing conditions recrystallized when heated.

[0040] As can be understood from the above description, the low-crystalline starch in the starch material is recrystallized by the recrystallization method according to the present invention. Therefore, it is possible to recrystallize the low-crystalline starch in the starch material by a simple process of only heating without cooling.

[0041] In the examples, rice flour is used as the starch material, but starch materials of other types of raw materials will also recrystallize when heated if they are pulverized under shear conditions while being heated. Whether low-crystalline starch in a starch material has recrystallized can be determined by whether a peak specific to crystallization appears after heating in wide-angle X-ray diffraction. The peak specific to starch crystallization varies depending on the raw material.

[0042] The present invention can also be conceived as a starch material containing recrystallized starch and a method for producing the same. Specifically, the present invention is a method for producing a starch material containing starch obtained by recrystallizing low-crystalline starch, which includes a step of heating a starch material containing low-crystalline starch to recrystallize the low-crystalline starch, and the low-crystalline starch is produced by grinding a raw material under shear conditions while heating it. In other words, the present invention can also be conceived as a method for producing resistant starch. The present invention can also be conceived as a starch material containing starch recrystallized by the recrystallization method according to the present invention, and as a food (e.g., cookies according to the examples) and feed containing the starch material containing the recrystallized starch.

Claims

1. The method includes a step of heating a starch material containing low-crystalline starch produced by pulverizing a raw material under shear conditions while heating the raw material, thereby recrystallizing the low-crystalline starch. Recrystallization method.

2. Adding a fatty acid to the starch material and heating it to recrystallize the low crystallinity starch. The recrystallization method of claim 1.

3. The fatty acid is oleic acid. The recrystallization method according to claim 2.

4. The fatty acid is added in an amount of 5 to 80 parts by weight per 100 parts by weight of the starch material. The recrystallization method according to claim 2 or 3.

5. The raw material is rice. The recrystallization method according to any one of claims 1 to 4.

6. The low-crystalline starch contains amylose and amylopectin. The recrystallization method according to any one of claims 1 to 5.

7. The low-crystalline starch contains 0 to 45% by mass of the amylose when the low-crystalline starch is taken as 100% by mass. The recrystallization method according to claim 6.

8. A starch material comprising starch recrystallized by the recrystallization method according to any one of claims 1 to 7.

9. 9. A food product containing a starch material comprising the recrystallized starch of claim 8.

10. 9. A feed containing a starch material comprising the recrystallized starch of claim 8.

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