Method for producing modified resistant starch

Abstract

The present invention addresses the problem of providing modified resistant starch which improves a rough texture which is a problem peculiar to a food containing resistant starch, and with which when the modified resistant starch is used for a food for the purpose of reducing carbohydrates, a supple and smooth texture of the food inherent in the food is not impaired. The method for producing modified resistant starch (first production method) according to the present invention involves: a step for obtaining a starch slurry by adding 100-300 parts by mass of water to 100 parts by mass of resistant starch, which is raw material starch; and a stirring step for stirring the starch slurry. In the stirring step, the product temperature of the starch slurry under stirring is maintained at 50°C or higher and below the gelatinization onset temperature of the starch in the starch slurry. The method for producing modified resistant starch (second production method) according to the present invention involves a first step for preparing resistant starch, and a second step for subjecting the prepared resistant starch to a modification treatment, wherein the second step is the same as the stirring step.

Description

Method for producing modified resistant starch

[0001] The present invention relates to a technology for improving resistant starch.

[0002] Carbohydrates are one of the three major nutrients, along with lipids and proteins. However, consuming large amounts of carbohydrates can contribute to an increase in body fat, and if consuming large amounts of carbohydrates raises blood sugar levels, it can become a risk factor for diabetes. For these reasons, there has been a growing demand for low-carbohydrate foods in recent years.

[0003] Dough foods, such as bakery foods and noodles, are typically produced using dough, which is a mixture of powder ingredients such as cereal flour and starch with liquid ingredients such as water, as an intermediate product, and contain a large amount of carbohydrates. Therefore, in order to reduce the carbohydrate content of dough foods, the cereal flour (carbohydrate) contained in dough foods has traditionally been replaced with dietary fiber, and examples of such dietary fiber include resistant starch, resistant dextrin, and inulin. However, the inclusion of dietary fiber in dough foods creates a rough texture, which deteriorates the taste and texture of the dough foods, resulting in a loss of palatability as a food. This tendency is particularly pronounced when resistant starch is used.

[0004] Patent Document 1 describes a method for producing dietary fiber starch, which is starch with a total dietary fiber content of 50% or more, comprising steps of heat-treating starch at a temperature below its gelatinization temperature, phosphorylating it, and then heat-treating it again at a high temperature, and describes heat-treating conditions for the phosphorylated starch as heat-treating it at a temperature above its gelatinization temperature, 80 to 95°C, with shaking for 1 to 30 minutes. Patent Document 2 describes another method for producing the dietary fiber starch, which comprises steps of performing high-temperature heat treatment and ultrasonic treatment while cross-linking rice starch, and describes high-temperature heat-treating conditions as heat-treating it at 80 to 95°C with shaking for 1 to 10 minutes. The production methods described in Patent Documents 1 and 2 were developed in consideration of the problem that when modified starch such as phosphate-crosslinked starch is applied to liquid foods such as mayonnaise, it tends to separate due to its low emulsifying power, and it is said that this production method can produce dietary fiber starch with enhanced emulsifying power.

[0005] Patent Document 3 describes yet another method for producing the dietary fiber starch, which comprises a step of phosphorylating and heat-moisture treating starch, followed by a further heat-moisture treatment, and describes conditions for the latter heat-moisture treatment (i.e., heat-moisture treatment of phosphorylated starch) as follows: the moisture content of the starch to be treated is adjusted to about 10 to 80% by weight, based on the weight of the starch in a dry state, and then the starch is heat-treated at a temperature of about 65 to 160° C. for 0.25 to 24 hours. The production method described in Patent Document 3 was devised in view of the problem that the dietary fiber content is significantly reduced when dietary fiber starch is subjected to extrusion treatment using an extruder, and it is claimed that this production method can produce dietary fiber starch that can maintain a total dietary fiber content of 50% or more even after extrusion treatment.

[0006] US Patent Application Publication No. 2012 / 0132197 US Patent Application Publication No. 2011 / 0129579 European Patent No. 1836903

[0007] An object of the present invention is to provide a modified resistant starch that improves the rough texture that is a problem specific to foods containing resistant starch, and that does not impair the inherent smooth texture with a pleasant feel to the tongue of the food when used in foods for the purpose of reducing carbohydrate content.

[0008] The present invention provides a method for producing a modified resistant starch (first production method), which includes a step of adding 100 to 300 parts by mass of water to 100 parts by mass of a raw material starch to obtain a starch slurry, and a stirring step of stirring the starch slurry, wherein the raw material starch is a resistant starch, and during the stirring step, the product temperature of the starch slurry is maintained at 50°C or higher and below the gelatinization onset temperature of the starch in the starch slurry.

[0009] The present invention also provides a method for producing a modified resistant starch, comprising a first step of preparing a resistant starch and a second step of modifying the prepared resistant starch, wherein the first step comprises: a 1-1 step of adding 100 to 300 parts by mass of water to 100 parts by mass of raw starch to obtain a starch slurry and adjusting the pH of the starch slurry to 10.0 to 12.0; a 1-2 step of adding one or more phosphate crosslinkers selected from sodium trimetaphosphate and phosphorus oxychloride to the starch slurry that has undergone the 1-1 step to react with the starch slurry; and a 1-3 step of adding water to the starch slurry that has undergone the 1-2 step to wash the reactant in the starch slurry, and then adjusting the concentration of the reactant in the starch slurry to 25 to 50% by mass without drying the reactant; and the second step comprises a stirring step of stirring the starch slurry that has undergone the 1st step. In this method for producing a modified resistant starch (second production method), the temperature of the starch slurry during stirring is maintained at 50°C or higher and below the gelatinization onset temperature of the starch in the starch slurry.

[0010] The production methods of the present invention include a method in which resistant starch is used as raw starch (starting material) and the resistant starch is subjected to a predetermined modification treatment (hereinafter also referred to as the "first production method"), and a method in which non-digestible starch is used as raw starch (starting material), a resistant starch is prepared from the non-digestible starch, and the resistant starch is subjected to a predetermined modification treatment (hereinafter also referred to as the "second production method").

[0011] First, the first production method of the present invention will be described. In the first production method, the resistant starch used as the raw starch (starting material) is a starch that is resistant to digestion by digestive enzymes and is a type of dietary fiber. As used herein, "dietary fiber" refers to a food component that is not digested by human digestive enzymes. Starch is a polymer in which many glucose units are bonded together via α(1,4) and α(1,6) bonds, and biologically derived starch is generally degraded by digestive enzymes. However, even if the starch is biologically derived, starches that have a specific structure in part or entirely, or starches that have been chemically modified, become resistant to digestive enzymes.

[0012] Resistant starches are generally classified into four types, RS1 to RS4, as follows. RS1 is a type of resistant starch that is easily digestible but physically protected by an outer skin or other barrier, making it resistant to digestion by digestive enzymes. It is mainly found in whole grains, seeds, legumes, etc. RS2 is a type of resistant starch that is resistant to digestion due to the special crystalline structure of the starch granules. Examples of RS2 include potato starch that has been subjected to moist heat treatment under low moisture conditions and unripe banana starch. High-amylose starch, which contains a large amount of linear amylose, is also classified as RS2. RS3 is a type of resistant starch that is resistant to digestion due to a change in structure caused by starch retrogradation that makes it less susceptible to digestive enzymes. Examples of RS3 include retrograded starch (beta-starch) obtained by first gelatinizing (gelatinizing) the starch by heating and then cooling it. RS4 is a resistant starch that is highly chemically modified and therefore resistant to digestion, and examples of RS4 include cross-linked starch that has been subjected to a strong cross-linking treatment, and etherified and / or esterified starch.

[0013] The resistant starch used in the first production method may be natural starch (unprocessed starch) or processed starch. The source of the resistant starch is not particularly limited, and it may be derived from any plant, such as tapioca starch or potato starch. In the first production method, the resistant starch may be one selected from the above-mentioned RS1 to RS4, or two or more of them may be used in combination.

[0014] As can be seen from the above description of RS1 to RS4, resistant starch may contain impurities (substances that cannot be completely removed by refining the resistant starch). From the perspective of ensuring low-sugar foods and dietary fiber enrichment, the resistant starch used in the first production method preferably has few impurities, i.e., high purity. More specifically, the resistant starch used in the first production method preferably has a dietary fiber content of 75% by mass or more, calculated on a starch dry matter basis. The aforementioned RS4, particularly phosphate-crosslinked starch, is preferred because its dietary fiber content is increased by chemical modification (such as phosphate crosslinking) under appropriate conditions. Many RS4s, particularly phosphate-crosslinked starches, have a dietary fiber content of 75% by mass or more, calculated on a starch dry matter basis. The term "phosphate-crosslinked starch" as used herein refers to processed starch that has been subjected to at least phosphate crosslinking, and may also be subjected to processing other than phosphate crosslinking (e.g., pregelatinization).

[0015] In this specification, the term "dietary fiber content" refers to a value determined based on AOAC 2011.25. For example, the dietary fiber content can be measured using a commercially available measurement kit, such as a dietary fiber measurement kit (Wako Pure Chemical Industries, Ltd.).

[0016] In the first production method, commercially available products can be used as the raw material resistant starch. For example, commercially available examples of RS2 products include Nisshoku Roadster (manufactured by Nippon Shokuhin Kako Co., Ltd.), Himaizu 1043 (manufactured by Nippon NSC Co., Ltd.), and Actistar 11700 (manufactured by Cargill Japan Co., Ltd.). Commercially available examples of RS4 products include Pine Starch RT (manufactured by Matsutani Chemical Industry Co., Ltd.), Novelose (manufactured by Ingredion Inc.), Fibergym RW (manufactured by Matsutani Chemical Industry Co., Ltd.), and Actistar RT 75330 (manufactured by Cargill Japan Co., Ltd.).

[0017] The form of the resistant starch is not particularly limited, and may be what is generally referred to as powder, fine grains, granules, etc. Furthermore, the particle size of the resistant starch is also not particularly limited, and may be appropriately selected depending on the intended use of the resulting modified resistant starch, etc. For example, from the viewpoint of the balance between the handleability of the modified resistant starch and the texture of foods using it, the average particle size of the resistant starch used as a raw material is preferably 5 to 30 μm, more preferably 15 to 25 μm.

[0018] In this specification, the "average particle size" refers to the particle size at which the cumulative amount, starting from the smallest particle, is 50% of the total in a cumulative volumetric particle size distribution curve of resistant starch measured by a dry laser diffraction / scattering method. The average particle size can be measured in accordance with a standard method using, for example, a commercially available laser diffraction particle size distribution analyzer (e.g., Microtrac MT3300EXII, manufactured by Nikkiso Co., Ltd.).

[0019] The first production method includes a step of adding water to a raw material starch, resistant starch, to obtain a starch slurry (slurry preparation step), and a stirring step of stirring the starch slurry.

[0020] In the slurry preparation step, 100 to 300 parts by mass, preferably 120 to 200 parts by mass, and more preferably 130 to 180 parts by mass of water is added to 100 parts by mass of raw starch (resistant starch) to obtain a starch slurry. The starch slurry is typically a suspension in which starch particles are stably mixed in water, and has fluidity at room temperature and normal pressure (ambient temperature 20°C, 1 atmosphere). If the amount of water added relative to the raw starch is less than 100 parts by mass or more than 300 parts by mass, the aforementioned intended object of the present invention cannot be achieved. The starch slurry may contain components other than the raw starch and water, provided that the intended object of the present invention is not impaired.

[0021] In the stirring step, the temperature of the starch slurry during stirring is maintained at 50°C or higher and below the gelatinization onset temperature of the starch in the starch slurry. In the present invention, the "gelatinization onset temperature" refers to the temperature at which a rapid increase in viscosity begins when starch is suspended in water and the temperature of the suspension is gradually increased while stirring. More specifically, starch has the property of undergoing gelatinization (gelatinization) and swelling when heated with water, resulting in an increase in viscosity. Generally, the viscosity of starch does not change significantly at relatively low temperatures at the beginning of the temperature increase, but begins to increase rapidly at a certain temperature, reaches a peak (maximum viscosity), and then decreases. The temperature at which this rapid increase in viscosity begins is the "gelatinization onset temperature" referred to in the present invention. The gelatinization onset temperature is measured by the following method. According to the production method of the present invention, by carrying out the slurry preparation step and the stirring step, a high-quality modified resistant starch can be obtained, specifically a modified resistant starch that solves the problems associated with conventional resistant starches and that, when used in foods, does not impair the inherently pleasant, smooth texture of the food. If the product temperature of the starch slurry during stirring is below 50°C or exceeds the gelatinization onset temperature of the starch in the starch slurry, a high-quality modified resistant starch cannot be obtained. From the viewpoint of ensuring the above-mentioned effect, the lower limit of the product temperature of the starch slurry during stirring is preferably 52°C or higher, more preferably 55°C or higher. From the same viewpoint, the upper limit of the product temperature of the starch slurry during stirring is preferably 2 to 7°C, more preferably 5 to 10°C, lower than the gelatinization onset temperature of the starch in the starch slurry.

[0022] <Method for Measuring Gelatinization Onset Temperature> A differential scanning calorimetry (DSC8000, manufactured by Perkin-Elmer) was used as the measuring device. The "starch in the starch slurry" to be measured was obtained by drying the starch slurry. 10 mg of the measurement target (starch) in dry mass and 40 μL of water were placed in a sample pan, the sample pan was sealed, and the temperature of the contents of the sample pan was raised from 30°C to 120°C at a rate of 5°C / min, and the change in calorific value was measured. The extrapolated onset temperature of the obtained endothermic peak (the temperature at the intersection of a straight line extending the low-temperature baseline toward the high-temperature side and a tangent line drawn at the point where the gradient of the curve on the low-temperature side of the endothermic peak is maximum) was taken as the gelatinization onset temperature to be measured.

[0023] From the viewpoint of more reliably achieving the intended object of the present invention, the stirring time of the starch slurry in the stirring step is preferably 1 to 24 hours, more preferably 3 to 24 hours. The start point of the stirring time is the point at which the stirring operation of the starch slurry is started, and the end point is the point at which the stirring operation is stopped. Furthermore, when the stirring operation is performed multiple times in the stirring step, i.e., when a period during which the starch slurry is not stirred is provided between the preceding and succeeding stirring operations, or when an operation other than stirring is performed, the stirring time is the sum of the stirring times of the respective stirring operations.

[0024] The stirring of the starch slurry in the stirring step can be carried out in a conventional manner using a known stirring device such as any of various mixers. The rotation speed of the stirring device varies depending on the stirring time, the amount of starch slurry to be stirred, etc., but is preferably 25 to 800 rpm, more preferably 50 to 600 rpm.

[0025] From the viewpoint of more reliably achieving the intended object of the present invention, the pH of the starch slurry subjected to the stirring step is preferably 5.0 to 7.0, more preferably 5.0 to 6.0. In adjusting the pH of the starch slurry, an acidic agent such as hydrochloric acid and / or an alkaline agent such as sodium hydroxide may be added to the starch slurry as a pH adjuster, if necessary.

[0026] In the first production method, the modified resistant starch obtained through the stirring step may be subjected to post-treatments such as drying and pulverization, as needed. The drying treatment is a treatment for reducing the moisture content of the modified resistant starch, and can be carried out by appropriately using known drying methods such as air drying and hot air drying. The pulverization treatment can be carried out in a conventional manner using known pulverization means such as a pin mill or a roll mill.

[0027] The ratio of the dietary fiber content of the modified resistant starch (in terms of dry mass of starch in the starch slurry after the stirring step) to the dietary fiber content of the starch in terms of dry mass of starch in the starch slurry before the stirring step (hereinafter also referred to as the "dietary fiber content change rate") is preferably 0.90 or more, more preferably 0.92 or more, from the viewpoint of ensuring that foods using the modified resistant starch of the present invention contain sufficient dietary fiber. Furthermore, the upper limit of the dietary fiber content change rate is preferably 0.99 or less, more preferably 0.98 or less, from the viewpoint of preventing a decrease in texture due to an excess of dietary fiber in foods using the modified resistant starch of the present invention. The dietary fiber content change rate can be adjusted by appropriately adjusting the amount of water added relative to the amount of water added to the raw material starch (resistant starch) in the slurry preparation step and the conditions of the stirring step (such as stirring time).

[0028] Next, a second manufacturing method of the present invention will be described. Regarding the second manufacturing method, differences from the first manufacturing method will be described. Regarding the second manufacturing method, the above description of the first manufacturing method applies as appropriate to the configurations not specifically described.

[0029] The second production method includes a first step of preparing phosphate cross-linked starch as the resistant starch, and a second step of modifying the prepared resistant starch. The first step includes steps 1-1, 1-2, and 1-3, which are carried out in this order.

[0030] In step 1-1, 100 parts by mass of raw starch is added to 100 to 300 parts by mass, preferably 120 to 200 parts by mass, and more preferably 130 to 180 parts by mass of water to obtain a starch slurry, and the pH of the starch slurry is adjusted to 10.0 to 12.0, preferably 10.5 to 11.8, and more preferably 11.0 to 11.7 (pH adjustment step). By maintaining the pH of the starch slurry within this range, it becomes possible to promote the phosphate cross-linking reaction in the subsequent step 1-2 while preventing the disadvantage of gelatinization of the starch in the starch slurry. The raw starch used in step 1-1 is a starch that has not been subjected to a phosphate cross-linking treatment, and specific examples include unprocessed starches such as tapioca starch, potato starch, corn starch, waxy corn starch, wheat starch, and rice starch; and processed starches obtained by subjecting the unprocessed starch to a treatment other than phosphate cross-linking (e.g., pregelatinization). These starches can be used alone or in combination of two or more. The pH of the starch slurry can be adjusted by adding an alkaline agent to the starch slurry. The alkaline agent can be any alkaline agent that has been conventionally used in the phosphate cross-linking reaction of starch, and examples thereof include sodium hydroxide, calcium hydroxide, and sodium carbonate. These can be used alone or in combination of two or more.

[0031] In the step 1-2, one or more phosphate crosslinkers selected from sodium trimetaphosphate and phosphorus oxychloride are added to the starch slurry that has been subjected to the step 1-1 and reacted (reaction step). The starch in the starch slurry that has been subjected to the step 1-2 is a phosphate crosslinked starch. In the step 1-2, the amount of the phosphate crosslinker added to the starch slurry is preferably 2.5 to 15 mass%, more preferably 3.5 to 12.5 mass%, and even more preferably 5 to 10 mass%, based on the dry mass of the starch in the starch slurry, from the viewpoint of balancing the promotion of the phosphate crosslinking reaction and the reaction efficiency. The reaction time in the step 1-2 is preferably 3 to 24 hours, more preferably 6 to 24 hours, from the viewpoint of more reliably imparting the desired properties to the starch. The "reaction time" referred to here refers to the period from the time when a phosphate crosslinker is added to a starch slurry whose pH has been adjusted to a range of 10.0 to 12.0 (the time of the first addition if the phosphate crosslinker is added multiple times) to the time when an acidic agent is added to the starch slurry for neutralization. The acidic agent can be any acidic agent conventionally used in phosphate crosslinking reactions of starch, and examples thereof include hydrochloric acid. In neutralizing the starch slurry to complete Step 1-2, the pH of the starch slurry is preferably adjusted to 5 to 7. In Step 1-2, the temperature of the starch slurry is preferably 25 to 45°C, more preferably 30 to 40°C, from the viewpoint of improving the reaction efficiency of the phosphate crosslinking reaction. That is, it is preferable to maintain the temperature of the starch slurry within the above range during the reaction time of Step 1-2. In Step 1-2, it is preferable to stir the starch slurry during the reaction time from the viewpoint of improving the reaction efficiency.

[0032] In the step 1-3, water is added to the starch slurry that has been subjected to the step 1-2 to wash the reactant in the starch slurry, and then, without drying the reactant, the concentration of the reactant in the starch slurry is adjusted to preferably 25 to 50% by mass, more preferably 25 to 45% by mass, and even more preferably 30 to 40% by mass. The concentration of the reactant, i.e., phosphate cross-linked starch (resistant starch), in such a starch slurry is the same as the concentration of the raw material starch (resistant starch) in the starch slurry obtained in the slurry preparation step of the first production method described above.

[0033] The second step includes a stirring step of stirring the starch slurry that has been subjected to the first step. The stirring step of the second step is the same as the stirring step of the first production method described above.

[0034] The modified resistant starch obtained by the production methods of the present invention (production method 1 and production method 2) can be used in various foods, and is particularly useful as an ingredient for reducing the sugar content of dough foods. As used herein, "dough food" refers to a food produced by forming an intermediate product, which is a mixture of powder ingredients such as cereal flour or starch and liquid ingredients such as water, into a predetermined shape, and then heating the resulting product. "Dough" here encompasses clay-like dough (so-called dough) and liquid or paste-like dough (so-called batter). Specific examples of dough foods include bakery foods, noodles, and battered fried foods.

[0035] As used herein, "bakery food" refers to foods obtained by adding liquid ingredients such as water to cereal flour (grain flour, starch) as the main ingredient, and optionally adding auxiliary ingredients such as yeast or leavening agents (e.g., baking powder), salt, and sugar to obtain a fermented or unfermented dough, which is then subjected to heat treatments such as baking, steaming, and deep-frying. Specific examples of bakery foods include breads; pizzas; cakes; Japanese and Western baked goods such as waffles, choux pastries, biscuits, dorayaki, and baked buns; steamed sweets; fried sweets such as donuts and corn dogs; and snacks such as okonomiyaki, takoyaki, chijimi, and negiyaki. Specific examples of cakes include sponge cake, butter cake, roll cake, hotcake, bouche, baumkuchen, pound cake, cheesecake, snack cake, muffin, bar, cookie, crepe, and pancake.

[0036] As used herein, "noodles" refers to foods made by kneading a dough made primarily from cereal flour (cereal flour, starch), to which a liquid ingredient such as water has been added, and optionally with secondary ingredients such as salt, and then 1) rolling or stretching the dough to obtain a noodle sheet dough, which is then stretched, cut, punched, or the like, or 2) extrusion-molded into a predetermined shape such as noodle strands. Specific examples of noodles include soba, udon, hiyamugi, Chinese noodles, spaghetti, macaroni, ravioli, and noodle skins.

[0037] In this specification, "battered fried foods" refers to foods obtained by adding a liquid ingredient such as water to a cereal flour (grain flour, starch) as the main ingredient, and optionally adding auxiliary ingredients such as a leavening agent (baking powder, etc.), salt, sugar, soy sauce, garlic, etc. to obtain a liquid batter, which is then applied to the surface of ingredients and subjected to a heat treatment such as frying or baking. Specific examples of battered fried foods include tempura, fried chicken, tatsuta-age, and fritters.

[0038] The modified resistant starch obtained by the production method of the present invention (hereinafter also simply referred to as "modified resistant starch") can be used in the same manner as various dough ingredients blended into dough foods. For example, in the production of dough foods using batter, such as cakes and fried foods with batter, the modified resistant starch may be blended in at the early stage of dough preparation, or may be blended into the dough after preparing it using other powder ingredients and liquid ingredients. For example, in the production of bread using a straight dough method or dough foods using dough, such as noodles or cookies, the modified resistant starch is preferably blended in at the early stage of dough preparation (for example, before the addition of liquid ingredients) in the same manner as the first dough ingredient, such as wheat flour. For example, in the production of bread using a sponge dough method, the modified resistant starch may be blended as a sponge dough blending ingredient before the sponge dough fermentation, or may be blended into the main kneading ingredients.

[0039] The modified resistant starch may also be blended into a mix for dough foods (hereinafter also simply referred to as a "mix"). The content of the modified resistant starch in the mix is ​​not particularly limited and may be adjusted appropriately depending on the intended use of the mix, but for example, when the dough food to be produced using the mix is ​​the aforementioned bakery food, noodle, or battered fried food, the content is preferably 5 to 40% by mass, and more preferably 10 to 30% by mass, relative to the total mass of the mix, from the viewpoint of balancing the effects of the modified resistant starch (such as reducing the carbohydrate content of the dough food) with the taste and texture of the dough food.

[0040] The mix typically contains one or more types of cereal flour other than the modified resistant starch. In this specification, the term "cereal flour" refers to a cereal-derived powdery substance at room temperature and normal pressure, and encompasses both cereal flour and starch. Unless otherwise specified, "starch" refers to "pure starch" isolated from plants such as wheat, and is distinguished from starch inherent in cereal flour. Examples of cereal flour include wheat flour (strong flour, semi-strong flour, medium-strength flour, weak flour, durum wheat flour, whole wheat flour, etc.), buckwheat flour, rice flour, corn flour, barley flour, rye flour, adlay flour, barnyard millet flour, and foxtail millet flour. Examples of starch include unprocessed starches such as tapioca starch, potato starch, cornstarch, waxy cornstarch, wheat starch, and rice starch; and processed starches obtained by subjecting unprocessed starches to one or more of the following treatments: gelatinization, etherification, esterification, acetylation, cross-linking, and oxidation.

[0041] The total content of cereal flours, including the modified resistant starch, in the mix is ​​not particularly limited and may be adjusted appropriately depending on the intended use of the mix, etc.; for example, when the dough food to be produced using the mix is ​​the aforementioned bakery food, noodle, or battered fried food, the total content of the cereal flours, including the modified resistant starch, is preferably 5 to 90% by mass, and more preferably 10 to 80% by mass, relative to the total mass of the mix.

[0042] In addition to the flour, the mix may contain other ingredients as needed, such as emulsifiers such as glycerin fatty acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, lecithin, organic acid monoglycerides, sodium stearoyl lactylate, and calcium stearoyl lactylate; protein materials such as gluten, gliadin, and glutenin (all wheat proteins), skim milk powder, whey protein (all milk proteins), soy protein, and gelatin; fats and oils such as animal fats and vegetable oils; salt, powdered soy sauce, fermented products such as fruit-derived fermented products, powdered miso paste, amino acids, and other seasonings; dried eggs such as egg powder; sugars, sweeteners; thickening polysaccharides, leavening agents, dairy ingredients, flavorings, enzymes, and colorings. The content of other ingredients in the mix other than the flour may be adjusted appropriately depending on the intended use of the mix.

[0043] The mix can be used as a powder ingredient when producing dough foods. For example, a method for producing bakery foods or noodles using the mix typically includes the steps of adding a liquid ingredient to the mix to prepare a dough (specifically, for example, dough or batter), shaping the dough into a predetermined shape, and then heating the shaped dough (specifically, for example, baking, steaming, frying, or steaming). A method for producing a battered fried food using the mix typically includes the steps of adding a liquid ingredient to the mix to prepare a dough (specifically, for example, batter), adhering the dough to the surface of ingredients, and then placing the ingredients with the batter in heated oil for frying. The liquid ingredient added to the mix can be water, oil, seasoning liquid, egg liquid, milk, or the like, and can be selected appropriately depending on the type of dough food to be produced. The mixing ratio of the mix to the liquid ingredient is not particularly limited, but is generally about 50 to 300 parts by mass per 100 parts by mass of the mix.

[0044] The aspects of the present invention are, for example, as follows: <1> A method for producing a modified resistant starch, comprising: a step of adding 100 to 300 parts by mass of water to 100 parts by mass of a raw starch to obtain a starch slurry; and a stirring step of stirring the starch slurry, wherein the raw starch is a resistant starch, and during the stirring step, the temperature of the starch slurry during stirring is maintained at 50°C or higher and below the gelatinization onset temperature of the starch in the starch slurry. <2> The production method according to <1> above, wherein the resistant starch is a modified starch that has been at least phosphate cross-linked. <3> A method for producing a modified resistant starch, comprising a first step of preparing a resistant starch and a second step of modifying the prepared resistant starch, wherein the first step comprises: a 1-1 step of adding 100 to 300 parts by mass of water to 100 parts by mass of a raw starch to obtain a starch slurry and adjusting the pH of the starch slurry to 10.0 to 12.0; a 1-2 step of adding one or more phosphate crosslinkers selected from sodium trimetaphosphate and phosphorus oxychloride to the starch slurry that has undergone the 1-1 step to react with the starch slurry; and a 1-3 step of adding water to the starch slurry that has undergone the 1-2 step to wash the reactant in the starch slurry, and then adjusting the concentration of the reactant in the starch slurry to 25 to 50% by mass without drying the reactant; and the second step comprises a stirring step of stirring the starch slurry that has undergone the 1st step. A method for producing a modified resistant starch, wherein, in the stirring step, the product temperature of the starch slurry during stirring is maintained at 50°C or higher and at or below the gelatinization onset temperature of the starch in the starch slurry.<4> The method for producing a modified resistant starch according to any one of <1> to <3> above, wherein the stirring time of the starch slurry in the stirring step is 1 to 24 hours.<5> The method for producing a modified resistant starch according to any one of <1> to <4> above, wherein the pH of the starch slurry subjected to the stirring step is 5.0 to 7.0.<6> The method for producing a modified resistant starch according to any one of <1> to <5> above, wherein the ratio of the dietary fiber content, calculated on a dry mass basis, of the modified resistant starch to the dietary fiber content, calculated on a dry mass basis, of the starch in the starch slurry before the stirring step is 0.9 or higher.

[0045] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0046] Examples 1 to 10, Comparative Examples 1 to 4 Modified resistant starches were produced by a method similar to the first production method described above. Specifically, 100 parts by mass of resistant starch and a predetermined amount of water were placed in a container in a thermostatic bath to obtain a starch slurry (slurry preparation step), and the starch slurry was stirred (stirring step) to produce modified resistant starches. The amount of water added in the slurry preparation step, as well as the product temperature, stirring time, and pH of the starch slurry in the stirring step, are shown in Tables 1 and 2 below. In the stirring step, a vertical mixer (manufactured by Hobart Co., Ltd., product name "HL-200") was used as the stirring device to stir the starch slurry, and the rotation speed during stirring was set to 107 rpm. The product temperature of the starch slurry in the stirring step was adjusted by adjusting the temperature in the thermostatic bath. As the resistant starch, phosphate cross-linked starch (manufactured by Matsutani Chemical Industry Co., Ltd., trade name "Pine Starch RT", gelatinization onset temperature 79.5°C, dietary fiber content 95% by mass calculated on starch dry matter basis) was used.

[0047] Examples 11-15, Comparative Examples 5-8 Modified resistant starches were produced by a method similar to the second production method described above. Specifically, a first step was carried out to prepare phosphate-crosslinked starch as the resistant starch, and a second step was carried out to modify the prepared resistant starch. In the first step, unprocessed tapioca starch (manufactured by Siam Modified Starch Co., Ltd., product name "NATIVE TAPIOCA STARCH") was used as the raw starch. First, 100 parts by mass of the raw starch and a predetermined amount of water were placed in a container placed in a thermostatic bath, and the contents of the container were stirred to obtain a starch slurry. An aqueous sodium hydroxide solution was added to the starch slurry to adjust the pH to within a predetermined range (pH adjustment step). The amount of water added in the pH adjustment step and the final pH of the starch slurry are shown in Table 3 below. Next, sodium trimetaphosphate was added as a phosphate crosslinking agent to the starch slurry at a product temperature of 35°C, and the starch slurry was stirred for 10 hours while maintaining the product temperature at 35°C, thereby allowing the phosphate crosslinking reaction of the starch in the starch slurry to proceed (reaction time: 10 hours). Subsequently, a hydrochloric acid aqueous solution was added dropwise to the starch slurry to adjust the pH of the starch slurry to a neutral range, thereby terminating the phosphate crosslinking reaction (reaction step). In the reaction step, the amount of phosphate crosslinking agent added to the starch slurry was 10% by mass relative to the dry mass of starch in the starch slurry. The product temperature of the starch slurry in the first step was adjusted by adjusting the temperature in the thermostatic bath. Next, the starch slurry was centrifuged at 3,000 rpm for 5 minutes, after which the supernatant was removed, and a predetermined amount of water was added to the residue and stirred. This series of washing operations was repeated three times to wash the reaction product in the starch slurry. The precipitate (reactant) in the starch slurry after the third washing operation was the desired phosphate-crosslinked starch. The gelatinization onset temperature of the produced phosphate-crosslinked starch was measured by the above-mentioned method. The measured values ​​are shown in Table 3 below. Without drying the reactant (phosphate-crosslinked starch) in the starch slurry after the third washing operation, the concentration of the reactant in the starch slurry was adjusted to 35 mass % and subjected to the next step, the second step. In the second step, the starch slurry that had been subjected to the first step was subjected to the stirring step under the same conditions as in Example 1, etc., to produce the desired modified resistant starch.

[0048] [Test Example] 33.5% by mass of the prepared modified resistant starch, 33.5% by mass of soft flour, 30% by mass of sugar, and 3% by mass of baking powder were mixed to prepare a hotcake mix. 25 g of whole egg liquid and 75 g of milk were added to 100 g of the hotcake mix as liquid ingredients, and the mixture was hand-mixed using a whisk at 120 rpm for 1 minute to prepare a batter. After allowing the batter to stand for 5 minutes at room temperature and normal pressure, the entire batter was poured onto a griddle and baked at 150°C for 3 minutes. The batter was then inverted and baked again at 150°C for another 3 minutes to obtain a hotcake. A control hotcake was also prepared in the same manner as above, except that the resistant starch used as the raw material for the modified resistant starch was used instead of the modified resistant starch. The resulting hotcakes were tasted by 10 expert panelists, who evaluated the texture (lessness of roughness) according to the following criteria. The results are shown in Tables 1 and 2 below as the average scores of the 10 panelists.

[0049] <Evaluation criteria for texture> 5 points: The texture is much less rough than the control. 4 points: The texture is much less rough than the control. 3 points: The texture is roughly the same as the control. 2 points: The texture is much rougher than the control. 1 point: The texture is much rougher than the control.

[0050]

[0051] As shown in Table 1, in each Example, the amount of water added in the slurry preparation step was 100 to 300 parts by mass per 100 parts by mass of raw starch (resistant starch), and therefore the hotcakes produced had a better texture than those produced in Comparative Examples 1 and 2, which did not meet this requirement. Furthermore, in each Example, the product temperature of the starch slurry during stirring in the stirring step was 50°C or higher and below the gelatinization onset temperature of the starch in the starch slurry, and therefore the hotcakes produced had a better texture than those produced in Comparative Examples 3 and 4, which did not meet this requirement.

[0052]

[0053]

[0054] As shown in Table 3, in each Example, the amount of water added in the pH adjustment step (first step) was 100 to 300 parts by mass relative to 100 parts by mass of raw starch (unmodified starch), and therefore the pancakes produced had a better texture than Comparative Examples 5 and 6, which did not meet this requirement. Furthermore, in each Example, the pH of the starch slurry after adjustment in the pH adjustment step (first step) was 10.0 to 12.0, and therefore the pancakes produced had a better texture than Comparative Examples 7 and 8, which did not meet this requirement.

[0055] According to the present invention, a modified resistant starch is provided which improves the rough texture that is a problem specific to foods containing resistant starch, and which, when used in foods for the purpose of reducing carbohydrate content, does not impair the inherent smooth texture that is pleasant to the tongue of the food.

Claims

1. A method for producing a modified resistant starch, comprising: a step of adding 100 to 300 parts by mass of water to 100 parts by mass of a raw starch to obtain a starch slurry; and a stirring step of stirring the starch slurry, wherein the raw starch is a resistant starch, and in the stirring step, the product temperature of the starch slurry during stirring is maintained at 50°C or higher and below the gelatinization onset temperature of the starch in the starch slurry.

2. The method according to claim 1, wherein the resistant starch is a modified starch that has been subjected to at least a phosphate cross-linking treatment.

3. A method for producing a modified resistant starch, comprising a first step of preparing a resistant starch and a second step of modifying the prepared resistant starch, the first step comprising: a 1-1 step of adding 100 to 300 parts by mass of water to 100 parts by mass of raw starch to obtain a starch slurry and adjusting the pH of the starch slurry to 10.0 to 12.0; a 1-2 step of adding one or more phosphate crosslinkers selected from sodium trimetaphosphate and phosphorus oxychloride to the starch slurry that has been subjected to the 1-1 step to react with the starch slurry; and a 1-3 step of adding water to the starch slurry that has been subjected to the 1-2 step to wash the reactant in the starch slurry, and then adjusting the concentration of the reactant in the starch slurry to 25 to 50% by mass without drying the reactant; and the second step comprising a stirring step of stirring the starch slurry that has been subjected to the 1st step. In the stirring step, the temperature of the starch slurry during stirring is maintained at 50° C. or higher and at or below the gelatinization onset temperature of the starch in the starch slurry.

4. The method according to any one of claims 1 to 3, wherein the starch slurry is stirred for a period of 1 to 24 hours in the stirring step.

5. The method according to any one of claims 1 to 3, wherein the pH of the starch slurry subjected to the stirring step is 5.0 to 7.

0.

6. A manufacturing method described in any one of claims 1 to 3, wherein the ratio of the dietary fiber content of the modified resistant starch, calculated as a dry mass, to the dietary fiber content of the starch in the starch slurry before the stirring step, calculated as a dry mass, is 0.9 or more.

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