Manufacturing method for grain powder with increased resistant starch content

Abstract

A method for producing grain powder with increased resistant starch content using RS2 or RS3 type grains is disclosed. The present invention provides a method for producing grain powder with increased resistant starch content comprising: (a) a step of steaming washed grains to gelatinize them; (b) a step of primary drying the gelatinized grains; (c) a step of rolling the primary dried grains; (d) a step of secondary drying the rolled grains; (e) a step of roasting the secondary dried grains; and (f) a step of grinding the roasted grains.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing grain powder, and more specifically, to a method for manufacturing grain powder with increased resistant starch content. Background Technology

[0002] As dietary habits become Westernized, grain consumption decreases and fat intake increases, and as the prevalence of adult obesity has continuously increased over the past decade (increasing from 32.8% in 2012 to 37.2% in 2021, Korea Disease Control and Prevention Agency, “National Health and Nutrition Examination Survey”, 2022), the risk of developing various adult diseases such as diabetes, hypertension, and myocardial infarction has also increased, and research on discovering dietary materials and identifying factors to improve obesity is active.

[0003] Recently, starch that is resistant to digestion and possesses physiological characteristics similar to dietary fiber is being developed as a functional material that helps health. Starch that is resistant to digestion includes slowly digestible starch (SDS) and resistant starch (RS), which exhibit relatively hard amorphous or crystalline structures. As a result, the content of resistant starch is high in unprocessed natural starch or partially retrograded starch, and during cooking or processing, most of this resistant starch is converted into rapidly digestible starch (RDS).

[0004] Resistant starch is further classified into four types: RS1, RS2, RS3, and RS4. RS1 is a type of starch surrounded by a matrix that is not broken down by enzymes, making it physically difficult for digestive enzymes to access the starch. RS2 is a natural starch that exhibits resistance to enzymes and is abundant in potatoes and bananas. In particular, commercially developed and sold resistant starch derived from high-amylose corn (e.g., Novelose 240, Manufacturer: National Starch, USA) is produced by utilizing RS2 type resistant starch. RS2 is converted into easily digestible starch upon heat treatment. RS3 is produced when starch (amylose and amylopectin) is heat-treated and then dried; as starch molecules aggregate, hydrogen bonding occurs between adjacent molecules, leading to partial crystallization and recrystallization. This process is called starch retrogradation, and RS3 type resistant starch is generated through this retrogradation. RS4 refers to chemically modified starch produced through chemical treatment, specifically processed starch that is difficult for digestive enzymes to act upon. Therefore, RS4 is a starch that cannot be obtained from natural foods.

[0005] Since cooking is fundamentally a process designed to increase the digestibility of nutrients with low digestibility (primarily starch) to make them easier to consume, it is a natural phenomenon for resistant starch to decrease during cooking. RS1 is resistant starch formed by physical and spatial disturbances, so it is easily destroyed even during normal cooking or processing. RS2 tends to be completely destroyed when sufficient gelatinization occurs (meaning the starch expands and transforms into a high-viscosity paste through heating in steam or treatment with solvents such as alkaline solutions). RS3 is resistant starch formed by recrystallization during drying or storage after heat treatment, so it does not easily change due to cooking or processing; however, the RS3 content may decrease under conditions of sufficient gelatinization (heating under high moisture conditions). RS4 is a chemically modified starch that is resistant starch that does not easily change due to cooking or processing.

[0006] Most commercially available cereals are produced through multiple stages, such as drying and pressing processes, baking with hot air, adding sugars and various additives to enhance palatability, or grinding grains, puffing them in an extruder, molding them, heat-treating the resulting puffed product through a roaster, coating the puffed product with sugar syrup, and drying it in a hot-air dryer. However, the more complex the manufacturing process, the greater the loss of resistant starch RS1 and RS2 for the reasons mentioned above, and the higher the content of digestible starch and various sugar additives, which poses a problem as it is not suitable as a functional material for improving obesity and adult diseases. The problem to be solved

[0007] The present invention aims to provide a method for producing grain powder with increased resistant starch content using RS2 or RS3 type grains. means of solving the problem

[0008] To solve the above problem, the present invention provides a method for manufacturing grain powder with increased resistant starch content, comprising: (a) a step of steaming washed grains to gelatinize them; (b) a step of first drying the gelatinized grains; (c) a step of rolling the first dried grains; (d) a step of secondarily drying the rolled grains; (e) a step of roasting the secondarily dried grains; and (f) a step of grinding the roasted grains.

[0009] In addition, the above method is characterized in that step (a) is performed for 15 to 35 minutes with steam at 100 to 150 ℃.

[0010] In addition, the above method is characterized in that step (b) is performed until the grain surface temperature reaches 25 to 45 ℃.

[0011] In addition, the method is characterized in that the rolling in step (c) is performed to a thickness of 1 to 5 mm.

[0012] In addition, the above method is characterized in that step (d) is performed at 50 to 70 ℃ for 5 to 15 hours.

[0013] In addition, the above (e) step is performed at 110 to 250 ℃ for 10 to 30 minutes, and a method is provided. Effects of the invention

[0014] The present invention can provide a method for producing grain powder with an increased resistant starch content compared to existing grains by specializing a series of processes such as steaming, rolling, roasting, and drying for RS2 or RS3 type grains. Specific details for implementing the invention

[0015] Preferred embodiments of the present invention are described in detail below. In describing the present invention, detailed descriptions of related prior art are omitted if it is determined that such detailed descriptions may obscure the essence of the present invention. Throughout the specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0017] The present invention discloses a method for producing grain powder with increased resistant starch content, comprising: (a) a step of steaming washed grains to gelatinize them; (b) a step of primary drying the gelatinized grains; (c) a step of rolling the primary dried grains; (d) a step of secondary drying the rolled grains; (e) a step of roasting the secondary dried grains; and (f) a step of grinding the roasted grains.

[0018] In the present invention, the grain is not specifically limited to any type as long as it is a conventional grain capable of containing resistant starch, but preferably, it may be selected from RS2 type Dodam rice, RS3 type black rice, whole wheat, oats, and barley.

[0019] In step (a) above, steaming refers to a cooking method in which the material is heated or heat-treated in water, and in the present invention, it is preferable to perform this with steam at 100 to 150 ℃ for 15 to 35 minutes.

[0020] In addition, the above gelatinization refers to the process in which starch expands and transforms into a high-viscosity paste by heating in water (steaming) or treating with a solvent such as an alkaline solution. This is because starch molecules, which have a dense micelle structure that is difficult for water molecules to penetrate, melt sequentially from the outside due to steaming, causing gaps to form and allowing water molecules to penetrate through them.

[0021] Resistant starch, which is abundant in cereals, is of the RS2 type. When complete gelatinization occurs, the resistant starch tends to be completely destroyed and converted into digestible starch, and it exhibits gelatinization characteristics in which gelatinization occurs from the outside of the starch and moves toward the center. In the present invention, by steaming within a range of temperature and time conditions that minimize the loss of resistant starch, processing is performed to make the starch edible for consumers, while inducing incomplete gelatinization instead of complete gelatinization to minimize the reduction in resistant starch content.

[0022] In step (b) above, the first drying refers to the removal of heat that causes a change to a lower temperature. In the present invention, the first drying can be performed until the grain surface temperature reaches 25 to 45 ℃, and, for example, can be performed by a forced suction method of steam.

[0023] In step (c) above, rolling refers to a process of placing the material to be rolled between an upper plate and a lower plate and applying pressure to the upper plate and the lower plate to spread the material to be rolled thinly. In the present invention, the rolling can be performed to a thickness of 1 to 5 mm. Through the rolling, the physical structure of the starch is transformed into RS1 type resistant starch, which is difficult for starch digestive enzymes to access, thereby being advantageous for increasing the resistant starch content.

[0024] In step (d) above, secondary drying means evaporating water molecules contained in the material to be dried to lower the moisture content. Drying methods include natural drying, hot air drying, freeze-drying, etc., and preferably, drying by far-infrared treatment may be used, but is not limited thereto.

[0025] Drying by the far-infrared treatment described above has high thermal efficiency and a fast drying speed because the far-infrared rays are conducted into the interior of the object to be dried, drying both the exterior and the interior simultaneously. It minimizes the reduction of resistant starch in the object to be dried. The longer the contact time between heat and moisture, the higher the likelihood of digestive enzyme action (e.g., reduction of resistant starch and increase of digestible starch) through starch gelatinization; since far-infrared treatment has high thermal efficiency and a fast drying speed for the reasons mentioned above, it can minimize the reduction of resistant starch in the object to be dried. In the present invention, it is preferable that the secondary drying be performed at 50 to 70 ℃ for 5 to 15 hours.

[0026] In step (e) above, roasting is a cooking method that removes as much moisture contained in the raw material as possible through heat treatment. In the present invention, the roasting lowers the moisture content in the rolled grain, contributing to the promotion of starch retrogradation and recrystallization of the starch structure, and increases the content of RS3 through starch retrogradation. The retrogradation and recrystallization of starch occur when heat-treated starch is left at a low temperature, causing hydrogen bonds between adjacent starch molecules, resulting in partial crystallization and recrystallization. This phenomenon of crystallization and recrystallization is called starch retrogradation, and the starch converted by retrogradation is called β-starch.

[0027] Step (f) above is a step of grinding the roasted grain to finally obtain a grain powder with increased resistant starch content. The grinding method for obtaining the powder form is not particularly limited and can be performed using a commonly used grain grinder.

[0028] The present invention will be explained in more detail below through examples.

[0030] Experimental Example

[0031] Dodam rice, whole wheat, barley, black rice, and oats were each washed three times and divided into three groups. They were then gelatinized by steaming at 100°C for 15, 25, and 35 minutes, respectively. Subsequently, the grains were dried in a first drying step until the surface temperature reached 35°C, and the dried grains were placed between an upper and lower plate and rolled to a thickness of 2 mm. Afterward, they were dried in a second drying step at 60°C for 8 hours and then placed in a roasting machine to be roasted at 150°C for 20 minutes. Finally, the roasted grains were ground using a grain grinder to produce the final grain powder. Resistant starch analysis was performed on the prepared grain powder using the method described below, and the results are shown in Table 3. The results of the resistant starch content analysis for each grain are expressed as Mean ± SD.

[0032] [Resistant Starch Analysis Method]

[0033] For resistant starch analysis, a pretreatment was performed to separate protein from the raw material using the following alkaline method: 5 g of the sample was placed in 15 ml of 0.2% NaOH and dispersed at 25 °C for 1 hour. Subsequently, the sample was centrifuged at 1,800 ×g for 10 minutes, 15 ml of 0.2% NaOH was added to the precipitate to turbidize it, and centrifugation (×4) was performed at 1,800 ×g for 10 minutes. Afterward, the final precipitate was mixed with 100 ml of distilled water and neutralized to pH 7.0 using 0.1 N HCl. Subsequently, the residue was centrifuged at 1,800 ×g for 10 minutes and washed twice with distilled water. Finally, the sample was washed with 100 ml of 95% ethanol, and the centrifuged precipitate was dried (overnight) at 40 °C.

[0034] To analyze the digestion resistance of the pre-treated samples, rapidly digested starch (RDS), slow digested starch (SDS), and undigested resistant starch (RS) were classified and analyzed according to the following method (see Table 1 below): 30 mg of the pre-treated sample was dispersed in 0.75 ml of sodium acetate buffer (pH 5.2) and left for 10 minutes. Then, 0.75 ml of enzyme solution was added and reacted at 37 ℃ for 10 minutes and 240 minutes. The enzyme solution was prepared by adding 2 g of pancreatin to 24 ml of distilled water and stirring. Afterward, centrifugation was performed at 1,500 ×g for 10 minutes, and 20 ml of the supernatant was mixed with 0.4 ml of amyloglucosidase (60 U / ml) and 3.6 ml of distilled water. Afterward, the enzymatic reaction was stopped and the mixture was centrifuged at 12,000 ×g for 5 minutes, and the glucose in the supernatant was measured using the GOD-POD method (see Table 2 below). From this, starch digested within 20 minutes was classified as rapidly digestible starch (RDS), starch digested within 120 minutes as slow-digestible starch (SDS), and starch that was not digested even after 240 minutes as indigestible starch (RS) (see Equation 1 below).

[0035] [Mathematical Formula 1]

[0036] RDS = (G20-FG) × 0.9 × 100

[0037] SDS = (G120-G20) × 0.9 × 100

[0038] RS = (TG-FG) × 0.9 × 100 - (RDS + SDS)

[0039] Test method ingredient standard Englyst (1985) pancreatin from porcine pancreas (P7545, Sigma-aldrich, Inc.St.Louis, MO. USA) 8 USP (200 U / ml) Amyloglucosidase solution from Aspergillus niger (A9913, Sigma-aldrich, Inc.St.Louis, MO. USA) 10 ml (60 U / ml) sodium acetate buffer pH 5.2 Glucose-oxidase peroxidase (GOD-POD) K-GLUC (Megazyme, Bray, Ireland) 660 assays per kit

[0040] division Blank Standard Test GOD-POD Reagent 1 ml 1 ml 1 ml Distilled water 10 μl - - Glucose standard - 10 μl - Sample - - 10 μl

[0041] division Steaming time (minutes) Starch content (%) RDS(Mean±SD) SDS(Mean±SD) RS(Mean±SD) Dodam rice raw materials 17.88±0.94 24.76±1.45 3.52±0.76 15 41.25±1.72 16.37±2.59 1.03±2.87 25 47.44±1.70 6.89±1.98 1.29±0.22 35 48.86±1.99 9.04±0.71 0.79±0.45 whole wheat raw materials 56.29±1.97 17.95±1.76 11.56±0.95 15 38.34±0.43 0.44±0.61 4.29±0.48 25 38.35±1.02 1.36±2.26 1.78±1.13 35 38.12±0.77 2.78±1.54 2.51±1.84 barley raw materials 53.97±1.33 26.75±1.94 2.84±2.67 15 69.79±1.40 16.24±0.69 -0.86±0.77 25 68.85±1.35 9.44±1.01 1.90±1.66 35 73.34±1.38 7.40±1.74 3.12±2.20 black rice raw materials 46.51±2.37 28.42±4.74 4.17±1.05 15 49.43±0.18 8.49±0.99 -0.65±1.32 25 54.37±0.04 4.04±1.33 2.76±1.85 35 52.90±1.56 5.02±2.49 1.86±0.49 oats raw materials 29.60±25.75 12.20±10.60 3.06±3.07 15 33.08±0.00 1.59±0.00 3.84±0.00 25 34.56±0.00 4.60±0.00 3.35±0.00 35 34.30±0.00 7.36±0.00 -0.94±0.00

[0043] Referring to Table 3, all samples except whole wheat showed a tendency for the content of RDS to increase and the content of SDS to decrease as processing was performed. Since the amount of rapidly digested starch increases with processing and the amount of slowly digested starch decreases as processing time increases, it can be seen that processing time affects starch digestibility.

[0044] In the case of whole wheat, the processed sample was analyzed without pretreatment and showed a different trend, indicating that the processing facilitates the swelling of starch, thus not exhibiting an effect that inhibits digestion. Compared to the raw material, the processed sample showed a tendency for both the amount of slowly digestible starch and the amount of indigestible resistant starch to decrease.

[0045] Slowly digestible starch (SDS) for each sample was highest in Dodam rice processed for 15 minutes (16.37±2.59%), whole wheat processed for 35 minutes (2.78±1.54%), barley processed for 15 minutes (16.24±0.69%), black rice processed for 15 minutes (8.49±0.99%), and oats processed for 35 minutes (7.36±0.00%). Undigested resistant starch (RS) was highest in Dodam rice processed for 15 minutes (1.03±2.87%), whole wheat processed for 15 minutes (4.29±0.48%), barley processed for 35 minutes (3.12±2.20%), black rice processed for 25 minutes (2.76±1.85%), and oats processed for 15 minutes (3.84±0.00%).

[0047] Preferred embodiments of the present invention have been described in detail above. The description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention.

[0048] Accordingly, the scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning, scope, and equivalent concepts of the claims should be interpreted as being included within the scope of the present invention.

Claims

Claim 1 A method for producing grain powder with increased resistant starch content, comprising: (a) a step of steaming washed grains to gelatinize them; (b) a step of first drying the gelatinized grains; (c) a step of rolling the first dried grains; (d) a step of secondarily drying the rolled grains; (e) a step of roasting the secondarily dried grains; and (f) a step of grinding the roasted grains. Claim 2 A method according to claim 1, characterized in that step (a) is performed for 15 to 35 minutes with steam at 100 to 150 ℃. Claim 3 A method according to claim 1, characterized in that step (b) is performed until the grain surface temperature reaches 25 to 45 ℃. Claim 4 A method according to claim 1, characterized in that, in step (c), the rolling is performed to a thickness of 1 to 5 mm. Claim 5 A method according to claim 1, characterized in that step (d) is performed at 50 to 70 ℃ for 5 to 15 hours. Claim 6 A method according to claim 1, characterized in that step (e) is performed at 110 to 250 ℃ for 10 to 30 minutes.

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