JP7763564B2 - Dough composition and bakery food composition - Google Patents

Description

The present invention relates to a dough composition and a bakery food composition containing carboxymethylated cellulose nanofibers.

The manufacturing process for bread, sponge cake, cookies, donuts, rice crackers, soba noodles, and udon noodles involves first preparing a dough composition, molding it into a specific weight and shape, and then obtaining the finished product through a heating process such as roasting, frying, or boiling.

It is known that such dough compositions are made by adding water to starch-containing grain flour, such as wheat flour, which contains gliadin and glutenin, and then kneading the mixture, which produces gluten and gives the dough compositions their characteristic elasticity and extensibility.

In particular, when yeast is added to bread and other breads to undergo a fermentation process, the dough composition expands due to the carbon dioxide produced by fermentation. The dough composition then expands further when heat is applied, and the gluten network hardens due to thermal denaturation even after baking. Therefore, it is known that the dough can maintain its shape after baking.

With regard to dough compositions, attempts have been made to increase the amount of water added (hereinafter referred to as "high hydration") in order to impart softness and moistness to final products such as bread.

However, simply adding water in excess of the water absorption limit of starch-containing grain flour such as wheat flour can sometimes result in the starch not being able to hydrate, resulting in water separation and making it difficult to knead the dough composition. For this reason, when adding a large amount of water to a dough composition, a method is used in which the moisture content of the dough is increased by adding ingredients with high water retention.

For example, a method for producing high-hydration bread (Patent Document 1) has been proposed in which konjac flour, starch, and water are formed into a jelly-like solid by a hydration gel reaction with an alkaline coagulant and the glucomannan in the konjac flour, and the resulting tangible water for high-hydration bread, which has been immersed in an acid solution to adjust the pH to a neutral to acidic range, is used as part of the bread-making water mixture.

Japanese Patent Application Laid-Open No. 2006-320207

However, with the method of Patent Document 1, the water retention capacity of konjac flour is insufficient, and the more water is added, the stickier the dough (dough composition) becomes, resulting in poor workability. Furthermore, as a result of the dough becoming sticky, it becomes difficult to hold together. Furthermore, the bread obtained by baking such dough does not rise sufficiently and is not satisfactory in terms of softness. Furthermore, it is required that the product obtained after baking maintain its softness even after several days have passed (suppression of aging).

The present invention therefore aims to provide a dough composition that, even when a large amount of water is added, can produce a product that is easy to work with, has improved leavening, is soft, and has inhibited staling, as well as a bakery food composition comprising this dough composition.

The present invention provides the following:
(1) A dough composition comprising 100% by weight of starch-containing grain powder, 80 to 150% by weight of water, and 0.05 to 5% by weight of carboxymethylated cellulose nanofibers.
(2) The dough composition according to (1), wherein the carboxymethylated cellulose nanofiber has a degree of carboxymethyl substitution per anhydroglucose unit of the cellulose nanofiber of 0.01 to 0.50 and a degree of crystallinity of cellulose type I of 40% or more.
(3) The dough composition according to (1) or (2), further comprising carboxymethyl cellulose.
(4) The dough composition according to any one of (1) to (3), characterized in that the starch-containing grain powder is a mixture of one or more of wheat flour, starches, rice flour, and buckwheat flour.
(5) A bakery food composition comprising the dough composition according to any one of (1) to (4).

The present invention provides a dough composition that can produce a product with excellent workability, improved rise, softness, and suppressed staling, even when a large amount of water is added, and a bakery food composition comprising this dough composition.

The dough composition of the present invention will be described below. In the present invention, "to" includes the extreme values. In other words, "X to Y" includes the values X and Y at both ends.

The dough composition of the present invention contains 100% by weight of starch-containing grain flour, 80 to 150% by weight of water, and 0.05 to 5% by weight of carboxymethylated cellulose nanofibers.

(Starch-containing grain powder)
In the present invention, any wheat flour typically used in bread making can be used as the starch-containing grain flour (main ingredient). Examples of such wheat flour include strong flour, semi-strong flour, medium-strength flour, weak flour, and durum wheat flour. Of these, strong flour, semi-strong flour, and durum wheat flour are preferred. Furthermore, grain flours other than wheat flour include rye flour, rye wheat flour, corn flour, starches, rice flour, buckwheat flour, various starches, and mixtures thereof, which can be appropriately selected and used depending on the type of dough composition of the desired bread or the like.

These can be used alone or in combination.

(Fermented ingredients)
The fermented ingredients are not particularly limited as long as they are those typically used in dough compositions, and examples of the fermented ingredients include various fermented starters such as sourdough and levain, and yeast (fresh yeast, dry yeast, etc.).

The fermented component is preferably contained in an amount of 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, and even more preferably 1 to 5% by weight, based on 100% by weight of the starch-containing grain powder.

(Water component)
The water component refers to the total amount of water contained in water, eggs, etc. It is important that the water component is contained in the range of 80 to 150% by weight, preferably 80 to 120% by weight, and more preferably 80 to 100% by weight, relative to 100% by weight of the starch-containing grain powder. When the water component is 80% by weight or more, the product obtained by heating such a dough composition is soft and has suppressed aging. Furthermore, when the water component is 150% by weight or less, excessive stickiness is suppressed, and workability can be ensured.

(Carboxymethylated cellulose nanofiber)
Carboxymethylated cellulose nanofibers are nanofibers obtained by converting carboxymethylated cellulose into nanofibers with a nanoscale fiber diameter. Carboxymethylated cellulose has a structure in which some of the hydroxyl groups in the glucose residues that constitute cellulose are ether-bonded to carboxymethyl groups. Carboxymethylated cellulose may take the form of a salt, for example, a metal salt such as sodium carboxymethylated cellulose, and the carboxymethylated cellulose nanofibers may also take the form of a salt.

(Carboxymethyl Substitution Degree)
The carboxymethylated cellulose nanofibers used in the present invention preferably have a degree of carboxymethyl substitution per anhydroglucose unit of cellulose of 0.50 or less. A degree of carboxymethyl substitution exceeding 0.50 is thought to dissolve in water and make it impossible to maintain the fiber shape. Furthermore, the degree of carboxymethyl substitution per anhydroglucose unit of cellulose is preferably 0.01 or more. A degree of carboxymethyl substitution less than 0.01 is thought to require a great deal of energy to defibrate into carboxymethylated cellulose nanofibers. From the viewpoint of operability, the degree of substitution is more preferably 0.02 to 0.50, even more preferably 0.05 to 0.50, and even more preferably 0.10 to 0.40. Introducing carboxymethyl groups into cellulose causes electrical repulsion between cellulose molecules, enabling defibration into nanofibers. The degree of carboxymethyl substitution can be adjusted by controlling the amount of carboxymethylating agent added to the reaction, the amount of mercerizing agent, the composition ratio of water to organic solvent, and the like.

In the present invention, anhydroglucose units refer to the individual anhydroglucose (glucose residues) that make up cellulose. Furthermore, the degree of carboxymethyl substitution (also referred to as the degree of etherification) refers to the proportion of hydroxyl groups in the glucose residues that make up cellulose that have been substituted with carboxymethyl ether groups (the number of carboxymethyl ether groups per glucose residue). The degree of carboxymethyl substitution is sometimes abbreviated as DS.

The carboxymethylated cellulose nanofibers used in the present invention maintain at least a portion of their fibrous shape even when dispersed in water. In other words, when an aqueous dispersion of carboxymethylated cellulose nanofibers is observed under an electron microscope, a fibrous substance can be observed. Furthermore, when the carboxymethylated cellulose nanofibers are measured by X-ray diffraction, a peak corresponding to cellulose type I crystals can be observed.

(Crystallization degree of cellulose type I)
The crystallinity of cellulose type I in the carboxymethylated cellulose nanofibers used in the present invention is preferably 40% or more, and more preferably 50% or more. When the crystallinity of cellulose type I is as high as 40% or more, a high proportion of cellulose maintains its crystalline structure without dissolving in solvents such as water, resulting in high thixotropy and making it suitable for viscosity-adjusting applications such as thickeners. Furthermore, when added to a dough composition, it provides the advantage of making the dough easier to combine and providing good workability even with high water content. The crystallinity of cellulose can be controlled by the concentration of the mercerizing agent, the treatment temperature, and the degree of carboxymethylation. Because high concentrations of alkali are used in mercerization and carboxymethylation, cellulose type I crystals are likely to be converted to type II. However, the desired crystallinity can be maintained by adjusting the degree of modification, such as by adjusting the amount of alkali (mercerizing agent) used. The upper limit of the crystallinity of cellulose type I is not particularly limited. In practice, the upper limit is thought to be approximately 90%.

The method for measuring the crystallinity of cellulose type I of carboxymethylated cellulose nanofiber is as follows:
The sample is placed in a glass cell and measured using an X-ray diffraction measurement device (LabX XRD-6000, manufactured by Shimadzu Corporation). The degree of crystallinity is calculated using the method of Segal et al., where the diffraction intensity at 2θ = 10° to 30° in the X-ray diffraction pattern is used as a baseline, and the degree of crystallinity is calculated using the diffraction intensity of the 002 plane at 2θ = 22.6° and the diffraction intensity of the amorphous portion at 2θ = 18.5° according to the following formula:

Xc=(I002c−Ia)/I002c×100
Xc = Crystallinity of cellulose type I (%)
I002c: 2θ=22.6°, diffraction intensity of the 002 plane Ia: 2θ=18.5°, diffraction intensity of the amorphous portion

The proportion of type I crystals in carboxymethylated cellulose nanofibers is typically the same as that in the carboxymethyl cellulose before it is made into nanofibers.

(fiber diameter, aspect ratio)
The carboxymethylated cellulose nanofibers used in the present invention have a nanoscale fiber diameter of 3 nm to 500 nm, preferably 3 nm to 150 nm, more preferably 3 nm to 20 nm, even more preferably 5 nm to 19 nm, and even more preferably 5 nm to 15 nm.

The aspect ratio of the carboxymethylated cellulose nanofiber is not particularly limited, but is preferably 350 or less, more preferably 300 or less, even more preferably 200 or less, even more preferably 120 or less, even more preferably 100 or less, and even more preferably 80 or less. The lower limit of the aspect ratio is not particularly limited, but is preferably 25 or more, even more preferably 30 or more. An aspect ratio of 25 or more provides the effect of improved thixotropy due to the fibrous shape. The aspect ratio of the carboxymethylated cellulose nanofiber can be controlled by the mixing ratio of solvent and water during carboxymethylation, the amount of chemicals added, and the degree of carboxymethylation. Furthermore, carboxymethylated cellulose nanofibers having an aspect ratio within the above range can be produced, for example, by the production method described below.

The average fiber diameter and average fiber length of carboxymethylated cellulose nanofibers can be measured by analyzing 200 randomly selected fibers using an atomic force microscope (AFM) if the diameter is 20 nm or less, or a field emission scanning electron microscope (FE-SEM) if the diameter is 20 nm or more, and calculating the average. The aspect ratio can be calculated using the following formula:
Aspect ratio = average fiber length/average fiber diameter.

(Method for producing carboxymethylated cellulose nanofibers)
The carboxymethylated cellulose nanofibers used in the present invention are not particularly limited, but can be produced by defibrating carboxymethylated cellulose produced by the following method.

Carboxymethylated cellulose can generally be produced by treating cellulose with alkali (mercerization) and then reacting the resulting mercerized cellulose (also known as alkali cellulose) with a carboxymethylating agent (also known as an etherifying agent). Carboxymethylated cellulose capable of forming nanofibers having the above-described characteristics of the present invention can be produced by carrying out mercerization (alkali treatment of cellulose) in a solvent primarily containing water, followed by carboxymethylation (also known as etherification) in a mixed solvent of water and an organic solvent.

(cellulose)
In the present invention, cellulose refers to a polysaccharide having a structure in which D-glucopyranose (also simply referred to as "glucose residues" or "anhydroglucose") units are linked together via β-1,4 bonds. Cellulose is generally classified into native cellulose, regenerated cellulose, fine cellulose, microcrystalline cellulose (presumably cellulose without amorphous regions) and the like, based on factors such as its origin and production method. In the present invention, any of these celluloses can be used as a raw material for mercerized cellulose. However, in order to maintain a crystallinity of cellulose type I of preferably 40% or more in the carboxymethylated cellulose nanofibers, it is preferable to use cellulose with a high degree of crystallinity of cellulose type I as the raw material. The crystallinity of cellulose type I of the raw cellulose is preferably 70% or more, and more preferably 80% or more. The method for measuring the crystallinity of cellulose type I is as described above.

Examples of natural cellulose include bleached or unbleached pulp (bleached or unbleached wood pulp); linters, refined linters; and cellulose produced by microorganisms such as acetic acid bacteria. The raw materials for bleached or unbleached pulp are not particularly limited, and examples include wood, cotton, straw, bamboo, hemp, jute, and kenaf. The manufacturing method for bleached or unbleached pulp is also not particularly limited, and may be mechanical, chemical, or a combination of the two. Examples of bleached or unbleached pulp classified by production method include mechanical pulp (thermomechanical pulp (TMP) and groundwood pulp), chemical pulp (sulfite pulp such as softwood unbleached sulfite pulp (NUSP) and softwood bleached sulfite pulp (NBSP), and kraft pulp such as softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), and hardwood bleached kraft pulp (LBKP)). In addition to papermaking pulp, dissolving pulp may also be used. Dissolving pulp is chemically refined pulp that is primarily dissolved in chemicals and is used as the main raw material for artificial fibers, cellophane, and the like.

Examples of regenerated cellulose include cellulose dissolved in a certain solvent such as a cuprammonium solution, a cellulose xanthate solution, or a morpholine derivative, and then spun again.
Examples of fine cellulose include those obtained by depolymerizing cellulosic materials, including the above-mentioned natural cellulose and regenerated cellulose (e.g., acid hydrolysis, alkaline hydrolysis, enzymatic decomposition, crushing treatment, vibrating ball mill treatment, etc.), and those obtained by mechanically treating the above-mentioned cellulosic materials.

(mercerization)
Mercerized cellulose (also called alkali cellulose) is obtained by using the above-mentioned cellulose as a raw material and adding a mercerizing agent (alkali).

A solvent that uses water primarily (a water-based solvent) refers to a solvent that contains more than 50% water by weight. The water content in a water-based solvent is preferably 55% by weight or more, more preferably 60% by weight or more, more preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and even more preferably 95% by weight or more. A particularly preferred water-based solvent is one that is 100% by weight (i.e., water).

Solvents other than water (used in a mixture with water) in a water-based solvent include organic solvents used as solvents in the subsequent carboxymethylation step. Examples include alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, isobutanol, and tertiary butanol; ketones such as acetone, diethyl ketone, and methyl ethyl ketone; and dioxane, diethyl ether, benzene, and dichloromethane. These can be used alone or in combination with two or more of these in an amount of less than 50% by weight to be used as solvents in the mercerization step. The content of the organic solvent in a water-based solvent is preferably 45% by weight or less, more preferably 40% by weight or less, even more preferably 30% by weight or less, even more preferably 20% by weight or less, even more preferably 10% by weight or less, even more preferably 5% by weight or less, and even more preferably 0% by weight.

Examples of mercerizing agents include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, and any one or more of these can be used in combination. While the mercerizing agent is not limited to these, these alkali metal hydroxides can be added to the reactor as an aqueous solution, for example, at a concentration of 1 to 60% by weight, preferably 2 to 45% by weight, and more preferably 3 to 25% by weight.

The amount of mercerizing agent used is not particularly limited, but in one embodiment, it is preferably 0.1 mol or more and 2.5 mol or less, more preferably 0.3 mol or more and 2.0 mol or less, and even more preferably 0.4 mol or more and 1.5 mol or less, per 100 g (bone dry) of cellulose.

The amount of solvent, primarily water, used during mercerization is preferably 1.5 to 20 times by weight, and more preferably 2 to 10 times by weight, relative to the cellulose raw material. Using such an amount makes it easier to stir and mix the raw materials, allowing the reaction to occur uniformly throughout the raw materials.

The mercerization process involves mixing the raw material (cellulose) with a solvent primarily consisting of water, adjusting the temperature of the reactor to 0-70°C, preferably 10-60°C, and more preferably 10-40°C, adding an aqueous solution of the mercerizing agent, and stirring for 15 minutes to 8 hours, preferably 30 minutes to 7 hours, and more preferably 30 minutes to 3 hours. This produces mercerized cellulose (alkali cellulose).

The pH during mercerization is preferably 9 or higher, which allows the mercerization reaction to proceed. The pH is more preferably 11 or higher, even more preferably 12 or higher, and may be 13 or higher. There is no particular upper limit to the pH.

Mercerization can be carried out using a reactor capable of mixing and stirring the above components while controlling the temperature, and various reactors conventionally used for mercerization reactions can be used. For example, a batch-type mixing device with two shafts that mixes the above components is preferred from the standpoints of both uniform mixing and productivity.

(carboxymethylation)
Carboxymethylated cellulose is obtained by adding a carboxymethylating agent (also called an etherifying agent) to mercerized cellulose.

Carboxymethylating agents include monochloroacetic acid, sodium monochloroacetate, methyl monochloroacetate, ethyl monochloroacetate, and isopropyl monochloroacetate. Of these, monochloroacetic acid and sodium monochloroacetate are preferred due to the ease of raw material availability.

The amount of carboxymethylating agent used is not particularly limited, but in one embodiment, it is preferably added in the range of 0.5 to 1.5 moles per anhydroglucose unit of cellulose. The lower limit of this range is more preferably 0.6 moles or more, even more preferably 0.7 moles or more, and the upper limit is more preferably 1.3 moles or less, even more preferably 1.1 moles or less. The carboxymethylating agent can be added to the reactor as an aqueous solution of, for example, 5 to 80% by weight, more preferably 30 to 60% by weight, but is not limited thereto, or it can be added in powder form without dissolving.

When using monochloroacetic acid or sodium monochloroacetate as the carboxymethylating agent, the molar ratio of mercerizing agent to carboxymethylating agent (mercerizing agent/carboxymethylating agent) is generally 0.9 to 2.45. This is because if it is less than 0.9, the carboxymethylation reaction may be insufficient, leaving unreacted monochloroacetic acid or sodium monochloroacetate, which may result in waste; and if it exceeds 2.45, a side reaction between the excess mercerizing agent and monochloroacetic acid or sodium monochloroacetate may proceed, resulting in the production of alkali metal glycolate, which may be uneconomical.

The concentration of the cellulose raw material in the carboxymethylation reaction is not particularly limited, but is preferably 1 to 40% (w/v).

Simultaneously with the addition of the carboxymethylating agent, or before or immediately after the addition of the carboxymethylating agent, an organic solvent or an aqueous solution of an organic solvent is appropriately added to the reactor, or the organic solvent other than water used during the mercerization treatment is appropriately reduced by reducing the pressure, etc., to form a mixed solvent of water and an organic solvent, and the carboxymethylation reaction is allowed to proceed in this mixed solvent of water and an organic solvent. The timing of the addition or reduction of the organic solvent may be any time between the end of the mercerization reaction and immediately after the addition of the carboxymethylating agent, and is not particularly limited; however, it is preferable, for example, to add or reduce the organic solvent within 30 minutes before or after the addition of the carboxymethylating agent.

Examples of organic solvents include alcohols such as methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, and tertiary butanol; ketones such as acetone, diethyl ketone, and methyl ethyl ketone; and dioxane, diethyl ether, benzene, and dichloromethane. These can be added alone or in mixtures of two or more to water and used as solvents for carboxymethylation. Of these, monohydric alcohols with 1 to 4 carbon atoms are preferred due to their excellent compatibility with water, and monohydric alcohols with 1 to 3 carbon atoms are even more preferred.

The proportion of organic solvent in the mixed solvent used for carboxymethylation is preferably 20% by weight or more, more preferably 30% by weight or more, even more preferably 40% by weight or more, even more preferably 45% by weight or more, and particularly preferably 50% by weight or more, based on the total weight of water and organic solvent. There is no upper limit to the proportion of organic solvent, and it may be, for example, 99% by weight or less. Considering the cost of the organic solvent to be added, it is preferably 90% by weight or less, even more preferably 85% by weight or less, even more preferably 80% by weight or less, and even more preferably 70% by weight or less.

The reaction medium for carboxymethylation (a cellulose-free mixed solvent of water, organic solvent, etc.) preferably has a lower water content (in other words, a higher organic solvent content) than the reaction medium for mercerization. By satisfying this range, it becomes easier to increase the degree of carboxymethyl substitution while maintaining the crystallinity of the resulting carboxymethylated cellulose. Furthermore, when the reaction medium for carboxymethylation has a lower water content (a higher organic solvent content) than the reaction medium for mercerization, there is also the advantage that, when transitioning from the mercerization reaction to the carboxymethylation reaction, a mixed solvent for the carboxymethylation reaction can be formed by the simple means of adding the desired amount of organic solvent to the reaction system after the mercerization reaction is completed.

A mixed solvent of water and an organic solvent is formed, and the carboxymethylating agent is added to the mercerized cellulose. The mixture is stirred for 15 minutes to 4 hours, preferably 15 minutes to 1 hour, while maintaining a constant temperature, preferably in the range of 10 to 40°C. Mixing of the mercerized cellulose-containing liquid with the carboxymethylating agent is preferably carried out in multiple batches or by dropwise addition to prevent the reaction mixture from becoming too hot. After adding the carboxymethylating agent and stirring for a certain period of time, the temperature is raised if necessary to 30 to 90°C, preferably 40 to 90°C, and more preferably 60 to 80°C, and the etherification (carboxymethylation) reaction is carried out for 30 minutes to 10 hours, preferably 1 to 4 hours, to obtain carboxymethylated cellulose.

For carboxymethylation, the reactor used for mercerization may be used as is, or a separate reactor capable of mixing and stirring the above components while controlling the temperature may be used.

After the reaction is complete, the remaining alkali metal salts may be neutralized with a mineral acid or organic acid. If necessary, by-products such as inorganic salts and organic acid salts may be removed by washing with aqueous methanol, followed by drying, pulverization, and classification to obtain carboxymethyl cellulose or its salts. When washing to remove by-products, the product may be converted into the acid form beforehand and then returned to the salt form after washing. Examples of equipment used for dry pulverization include impact mills such as hammer mills and pin mills, media mills such as ball mills and tower mills, and jet mills. Examples of equipment used for wet pulverization include homogenizers, mass colloiders, and pearl mills.

(Defibrillation into nanofibers)
By defibrating the carboxymethyl cellulose obtained by the above method, it can be converted into cellulose nanofibers with nanoscale fiber diameters.

For defibration, a dispersion of carboxymethyl cellulose obtained by the method described above is prepared. Water is the preferred dispersion medium for ease of handling. Considering the efficiency of defibration and dispersion, the concentration of carboxymethyl cellulose in the dispersion at the time of defibration is preferably 0.01 to 10% (w/v).

The equipment used to defibrate carboxymethyl cellulose is not particularly limited, but can be a high-speed rotary type, colloid mill type, high-pressure type, roll mill type, ultrasonic type, or other type. It is preferable to apply a strong shear force to the carboxymethyl cellulose dispersion during defibration. For particularly efficient defibration, it is preferable to apply a pressure of 50 MPa or more to the dispersion and to use a wet high-pressure or ultra-high-pressure homogenizer capable of applying a strong shear force. The pressure is more preferably 100 MPa or more, and even more preferably 140 MPa or more. Furthermore, prior to defibration and dispersion treatment using a high-pressure homogenizer, the dispersion may be pre-treated, if necessary, using a known mixing, stirring, emulsifying, or dispersing device such as a high-speed shear mixer.

A high-pressure homogenizer is a device that uses a pump to pressurize (high pressure) a fluid and eject it from extremely fine gaps in the flow path, thereby emulsifying, dispersing, breaking down, pulverizing, and ultra-fine-graining particles through the combined energy of collisions between particles and shear forces caused by pressure differences.

In the present invention, carboxymethylated cellulose nanofibers may be used in the form of a dispersion, or may be used as a powder after drying (removal of the dispersion medium), pulverization, and classification.

When the carboxymethylated cellulose nanofibers used in the present invention are used as a powder, they may contain other components as necessary. For example, when producing the powder, it is preferable to add a water-soluble polymer to the carboxymethylated cellulose nanofiber dispersion before drying, as this improves redispersibility. The reason why the water-soluble polymer improves redispersibility is not clear, but it is thought that this is because the water-soluble polymer covers areas of the carboxymethyl cellulose nanofiber surface with low charge density, suppressing the formation of hydrogen bonds and preventing aggregation of the nanofibers during drying.

(Water-soluble polymer)
When carboxymethylated cellulose nanofibers are used as a powder, examples of water-soluble polymers that can be present during the production of the powder include cellulose derivatives (carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, ethyl cellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginates, pullulan, starch, potato starch, arrowroot flour, modified starch (cationized starch, phosphorylated starch, phosphate cross-linked starch, phosphate monoesterified phosphate cross-linked starch, hydroxypropyl starch, hydroxypropylated phosphate cross-linked starch, acetylated adipate cross-linked starch, acetylated phosphate cross-linked starch, acetylated oxidized starch, sodium octenyl succinate starch, acetate starch, oxidized starch), cocoa, and the like. Examples of suitable cellulose nanofibers include starch, gum arabic, locust bean gum, gellan gum, polydextrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soy protein lysate, peptone, polyvinyl alcohol, polyacrylamide, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl acetate, polyamino acids, polylactic acid, polymalic acid, polyglycerin, latex, rosin-based sizing agents, petroleum resin-based sizing agents, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide-polyamine resin, polyethyleneimine, polyamine, vegetable gum, polyethylene oxide, hydrophilic crosslinked polymers, polyacrylates, starch-polyacrylic acid copolymers, tamarind gum, guar gum, and colloidal silica, as well as mixtures of one or more thereof. Among these, cellulose derivatives are preferred in terms of their affinity with carboxymethylated cellulose nanofibers, and carboxymethyl cellulose and its salts are particularly preferred. It is thought that water-soluble polymers such as carboxymethyl cellulose and its salts penetrate between the carboxymethylated cellulose nanofibers and increase the distance between the nanofibers, thereby improving redispersibility.

When carboxymethyl cellulose or a salt thereof is used as the water-soluble polymer, it is preferable to use a carboxymethyl cellulose with a degree of carboxymethyl group substitution per anhydroglucose unit of 0.55 to 1.6, more preferably 0.55 to 1.1, and even more preferably 0.65 to 1.1. Furthermore, carboxymethyl cellulose with longer molecules (higher viscosity) is preferred because it is more effective at increasing the distance between nanofibers. Furthermore, the Brookfield viscosity of a 1 wt% aqueous solution of carboxymethyl cellulose at 25°C and 60 rpm is preferably 3 mPa·s to 14,000 mPa·s, more preferably 7 mPa·s to 14,000 mPa·s, and even more preferably 1,000 mPa·s to 8,000 mPa·s. Note that the "carboxymethyl cellulose or a salt thereof" referred to here as the water-soluble polymer is completely soluble in water, and is therefore distinct from the carboxymethyl cellulose nanofibers described above, the fiber shape of which can be confirmed in water.

The amount of water-soluble polymer blended is preferably 5% to 300% by weight, more preferably 20% to 300% by weight, even more preferably 25% to 200% by weight, and even more preferably 25% to 60% by weight, based on the carboxymethyl cellulose nanofiber (bone dry solids). Blending 5% or more by weight of water-soluble polymer improves redispersibility. On the other hand, blending more than 300% by weight can cause problems such as reduced viscosity characteristics, such as thixotropy, which is a characteristic of carboxymethyl cellulose nanofiber, and reduced dispersion stability. Blending 25% or more by weight of water-soluble polymer is preferable, as it can achieve particularly excellent redispersibility. Furthermore, taking thixotropy into consideration, a blending amount of 200% by weight or less is preferable, with 60% or less by weight being particularly preferable.

(Drying)
A dispersion of carboxymethylated cellulose nanofibers, or a dispersion of carboxymethylated cellulose nanofibers optionally mixed with a water-soluble polymer, is dried (to remove the dispersion medium) to obtain a dry solid containing carboxymethylated cellulose nanofibers. In this case, it is preferable to adjust the pH of the dispersion to 9 to 11 before drying, as this further improves redispersibility.

Drying methods can be any known method, and are not particularly limited. Examples include spray drying, squeezing, air drying, hot air drying, and vacuum drying. Drying equipment is not particularly limited, and includes continuous tunnel dryers, band dryers, vertical dryers, vertical turbo dryers, multi-stage disk dryers, through-flow dryers, rotary dryers, flash dryers, spray dryers, atomized dryers, cylindrical dryers, drum dryers, belt dryers, screw conveyor dryers, rotary dryers with heating tubes, vibrating transport dryers, batch-type box dryers, through-flow dryers, vacuum box dryers, and agitator dryers, which can be used alone or in combination of two or more.

Among these, the use of an apparatus for drying by forming a thin film is preferred from the standpoint of energy efficiency, as it can supply heat energy directly and uniformly to the material to be dried, allowing for more efficient drying in a shorter time. An apparatus for drying by forming a thin film is also preferred because the dried material can be immediately recovered by simple means such as scraping off the thin film. It has also been found that redispersibility is further improved when a thin film is formed and then dried. Examples of apparatus for drying by forming a thin film include drum dryers and belt dryers, which form a thin film on a drum or belt using a blade or die, and then dry the resulting thin film. The thickness of the thin film when forming and drying a thin film is preferably 50 μm to 1000 μm, and more preferably 100 μm to 300 μm. A thickness of 50 μm or more makes it easy to scrape off the material after drying, and a thickness of 1000 μm or less further improves redispersibility.

The residual moisture content after drying is preferably 2% to 15% by weight of the total dried material.

(Crushing)
The pulverization method is not particularly limited, and known methods can be used, including a dry pulverization method in which the material is treated in a powder state and a wet pulverization method in which the material is treated in a dispersed or dissolved state in a liquid. When wet pulverization is performed, it may be performed before the above-mentioned drying.

Examples of equipment used in dry grinding include, but are not limited to, cutting mills, impact mills, airflow mills, and media mills. These can be used alone or in combination, and even in multiple stages using the same model. Of these, airflow mills are preferred. Examples of cutting mills include mesh mills (manufactured by Horai Co., Ltd.), Atoms (manufactured by Yamamoto Hyakuma Manufacturing Co., Ltd.), knife mills (manufactured by Parman), granulators (manufactured by Herbolt), and rotary cutter mills (manufactured by Nara Machinery Manufacturing Co., Ltd.). Examples of impact mills include Pulperizer (manufactured by Hosokawa Micron Corporation), Fine Impact Mill (manufactured by Hosokawa Micron Corporation), Super Micron Mill (manufactured by Hosokawa Micron Corporation), Sample Mill (manufactured by Seishin Corporation), Bantam Mill (manufactured by Seishin Corporation), Atomizer (manufactured by Seishin Corporation), Tornado Mill (Nikkiso Co., Ltd.), Turbo Mill (Turbo Kogyo Co., Ltd.), and Bevel Impactor (Aikawa Iron Works Co., Ltd.). Examples of airflow mills include CGS-type jet mill (manufactured by Mitsui Mining Co., Ltd.), jet mill (manufactured by Sansho Industry Co., Ltd.), Ebara Jet Micronizer (manufactured by Ebara Corporation), Selenium Miller (manufactured by Masuko Sangyo Co., Ltd.), and supersonic jet mill (manufactured by Nippon Pneumatic Mfg. Co., Ltd.). Examples of media mills include vibration ball mills. Examples of equipment used in wet grinding include a mass colloider (manufactured by Masuko Sangyo Co., Ltd.), a high-pressure homogenizer (manufactured by Sanmaru Kikai Kogyo Co., Ltd.), and a media mill. An example of a media mill is a bead mill (manufactured by Imex Co., Ltd.).

(classification)
After pulverization, the carboxymethylated cellulose nanofibers are classified to adjust the particle size to a specific value. The classification method is not particularly limited, but can be carried out, for example, by passing the nanofibers through a mesh (sieve) with a predetermined mesh size. The mesh used is preferably 20 to 400 mesh, more preferably 40 to 300 mesh, and even more preferably 60 to 200 mesh, and these may be used in a multi-stage manner. The median diameter of the powder finally obtained is 10.0 μm to 150.0 μm, preferably 30.0 μm to 130.0 μm, and even more preferably 50.0 μm to 120.0 μm.

In the present invention, the content of carboxymethylated cellulose nanofibers is 0.05% by weight or more, based on the bone dry weight of the starch-containing grain flour, from the viewpoint of obtaining a sufficient swelling-enhancing effect in the product obtained by heating, even when a large amount of water is added, and is 5% by weight or less, preferably 0.1 to 3% by weight, and more preferably 0.2 to 2% by weight, from the viewpoint of the workability, moldability, and hardness of the dough composition.

(auxiliary raw materials)
The dough composition of the present invention may contain auxiliary ingredients other than the above-mentioned raw ingredients, as necessary. Examples of such auxiliary ingredients include yeast food; sugars such as sugar, glucose, fructose, invert sugar, starch syrup, maltose, lactose, and oligosaccharides; eggs or egg powder; dairy products such as skim milk powder, whole milk powder, cheese powder, yogurt powder, and whey powder; fats and oils such as shortening, butter, margarine, and other animal and vegetable oils; emulsifiers; leavening agents; thickeners; sweeteners; flavorings; coloring agents; ascorbic acid; inorganic salts such as salt; enzymes such as glucosidase, glucose oxidase, amylase, lipase, and hemicellulase; and dietary fiber.

(Embodiment)
The dough composition of the present invention can be used for bakery food compositions such as bread, sponge cake, cookies, donuts, etc.; noodles such as soba, udon, pasta, somen, ramen, etc.; ingredients for Chinese cuisine such as spring roll wrappers, gyoza wrappers, and Xiaolongbao wrappers; rice crackers, etc. Among these, it is preferable to use it as a bakery food composition, in view of the effects of being able to obtain products that are excellent in workability even with a large amount of water added (good dough cohesion) and that are soft and have inhibited aging after baking.

The bakery food composition of the present invention comprises the dough composition of the present invention. More specifically, the bakery food composition is obtained by adding a water component and a dispersion liquid containing carboxymethylated cellulose nanofibers to a mixture containing starch-containing grain powder and secondary ingredients such as sugar, fermentation ingredients, oils and fats, skim milk powder, salt, and oligosaccharides added as needed, and stirring the mixture until homogeneous to form a dough (dough composition), followed by fermentation and baking. Note that the method for producing the bakery food composition is not limited to this and may be modified as appropriate.

The dough composition of the present invention contains 100% by weight of starch-containing grain powder, 80 to 150% by weight of water, and 0.05 to 5% by weight of carboxymethyl cellulose nanofibers. This dough composition is well-formed, and products obtained using it have excellent leavening properties. Furthermore, the increased moisture content makes the product soft and inhibits aging (hardening).

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

(Method for measuring degree of carboxymethyl substitution)
1) Approximately 2.0 g of carboxymethylated cellulose fiber (bone dry) was weighed out and placed in a 300 mL Erlenmeyer flask with a stopper.
2) 100 mL of a solution prepared by adding 100 mL of special-grade concentrated nitric acid to 1000 mL of nitric acid methanol was added, and the mixture was shaken for 3 hours to convert the carboxymethyl cellulose salt (carboxymethyl cellulose) into hydrogen-type carboxymethyl cellulose.
3) 1.5 to 2.0 g of hydrogenated carboxymethyl cellulose (bone dry) was weighed out and placed in a 300 mL Erlenmeyer flask with a stopper.
4) The hydrogenated carboxymethyl cellulose was wetted with 15 mL of 80% methanol, and 100 mL of 0.1 N NaOH was added, followed by shaking at room temperature for 3 hours.
5) Excess NaOH was back _- titrated with 0.1N _H2SO4 using phenolphthalein as an indicator.
6) The degree of carboxymethyl substitution (DS) was calculated by the following formula:
A = [(100 × F' - (0.1 N H ₂ SO ₄ ) (mL) × F) × 0.1] / (bone dry weight (g) of hydrogenated carboxymethyl cellulose)
DS=0.162×A/(1-0.058×A)
A: Amount (mL) of 1 N NaOH required to neutralize 1 g of hydrogenated carboxymethyl cellulose
F': Factor _of 0.1N _H2SO4 F: Factor of 0.1N NaOH

(Method for measuring average fiber diameter and aspect ratio)
The average fiber diameter and average fiber length of cellulose nanofibers were analyzed using an atomic force microscope (AFM) for 200 randomly selected fibers. The aspect ratio was calculated using the following formula:
Aspect ratio = average fiber length/average fiber diameter

(Production Example 1)
(Production of carboxymethylated cellulose nanofibers)
A 5-liter twin-screw kneader with the rotation speed adjusted to 100 rpm was charged with 1,089 parts of isopropanol (IPA) and a solution of 31 parts of sodium hydroxide dissolved in 121 parts of water, and 200 parts of hardwood pulp (LBKP, manufactured by Nippon Paper Industries Co., Ltd.) dried at 100°C for 60 minutes (dry weight). The mixture was stirred and mixed at 30°C for 60 minutes to prepare mercerized cellulose. Further, 117 parts of sodium monochloroacetate was added with stirring, and after stirring at 30°C for 30 minutes, the mixture was heated to 70°C over 30 minutes and allowed to undergo a carboxymethylation reaction at 70°C for 60 minutes. The proportion of water in the reaction medium during the mercerization reaction and the carboxymethylation reaction was 10% by weight. After completion of the reaction, the mixture was neutralized, washed with 65% aqueous methanol, deliquored, dried, and pulverized to obtain a sodium salt of carboxymethylated cellulose with a carboxymethyl substitution degree of 0.27 and a crystallinity of cellulose type I of 64%. The methods for measuring the degree of carboxymethyl substitution and the crystallinity of cellulose type I are as described above.

The resulting sodium salt of carboxymethyl cellulose was dispersed in water to form a 1% (w/v) aqueous dispersion. This was then processed three times in a high-pressure homogenizer at 150 MPa to obtain a dispersion of carboxymethyl cellulose nanofibers. The resulting carboxymethyl cellulose nanofibers had an average fiber diameter of 3.2 nm and an aspect ratio of 40.

(Production of CNF powder 1)
The obtained carboxymethylated cellulose nanofibers were dispersed in water to a solid content of 0.7% by weight, and carboxymethyl cellulose (manufactured by Nippon Paper Industries Co., Ltd., product name: F350HC-4, viscosity (1% by weight, 25°C, 60 rpm) approximately 3000 mPa s, degree of carboxymethyl substitution approximately 0.90) was added in an amount of 40% by weight relative to the carboxymethyl cellulose nanofibers (i.e., so that the solid content of carboxymethyl cellulose was 40 parts by weight when the solid content of the carboxymethyl cellulose nanofibers was 100 parts by weight), and the mixture was stirred for 60 minutes with a TK homomixer (12,000 rpm).

0.5 wt% aqueous sodium hydroxide solution was added to this dispersion to adjust the pH to 9, and then it was applied to the drum surface of a drum dryer D0405 (manufactured by Katsuragi Kogyo Co., Ltd.) and dried at 140°C for 1 minute. The resulting dried product was scraped off and then pulverized using an impact mill at a rate of 10 kg per hour to obtain a dried pulverized product with a moisture content of 5 wt%. The pulverized product was classified using a 30 mesh to obtain a powder containing carboxymethylated cellulose nanofibers and carboxymethyl cellulose (CNF Powder 1).

(Examples 1 to 3, Comparative Examples 1 to 5)
(Bread production)
When the ingredients in Table 1 contained CNF powder 1, a CNF dispersion was prepared by stirring CNF powder 1 and water for 30 minutes at 3,000 rpm using a homodisper. Next, the ingredients in Table 1 other than CNF powder 1 and water were added to a bread maker together with the prepared CNF dispersion (or water). Next, the bread maker was set to the bread course (a total of 4 hours for kneading, resting, fermentation, and baking) to produce bread.
In Comparative Example 5, carboxymethyl cellulose (manufactured by Nippon Paper Industries Co., Ltd., SLD-F1) was used in place of CNF powder 1.
The numerical values of the raw materials in Table 1 represent parts by weight.

(evaluation)
(Workability during bread making)
In the Examples and Comparative Examples, the inside of the bread machine was visually inspected after the kneading step, and the state of the dough was evaluated according to the following criteria.
◯: The dough holds together well when kneaded, is not sticky, does not stick to the container, and is easy to work with.
△: The dough holds together well when kneaded, but is sticky and sticks to the container, but this does not cause any problems in use.
×: The dough was not sufficiently united when kneaded, was sticky, and adhered to the container, making it difficult to work with.

(Bread evaluation)
The bread obtained in the Examples and Comparative Examples was allowed to cool at room temperature for 2 hours after production, and then cut into test pieces 20 mm thick from the center with a bread knife to prepare test pieces, which were then subjected to the following measurements.

(height)
The test pieces were measured from the bottom to the top of the pan using a ruler, and the results are shown in Table 1. A higher height indicates improved rise.

(Moisture percentage)
The inner phase of the test specimens, which had been left at room temperature (25°C/50%), was cut into 1 cm squares and their weights, WA, were measured. The 1 cm square test specimens were then dried in a 105°C dryer for 3 hours, and their post-drying weights, WB, were measured. The moisture content was calculated as (WA - WB) / WA x 100. The results are shown in Table 1. The moisture content of the test specimens on the day of firing is shown in the "Moisture Content (Day 0)" column, and the moisture content of the test specimens stored in a zippered vinyl bag in a constant temperature room at 25°C for 3 days after production is shown in the "Moisture Content (Day 3)" column. The change in moisture content between the moisture content after 3 days and the moisture content on the day of firing was calculated and shown in the "ΔMoisture Content" column. In the present invention, the closer the ΔMoisture Content is to 0, the more drying is suppressed.

(Hardness)
The hardness of the test pieces was measured using a rheometer (Food Rheology Tester FRTS-50N, manufactured by Imada). Specifically, a plunger with a diameter of 2.0 cm was used, and the value was recorded when the plunger was pushed 1 cm at a plunge rate of 1 mm/sec. Five or more points were measured, and the average value was calculated. The results are shown in Table 1. The hardness of the test pieces on the day of baking is shown in the "Hardness (0 days)" column, and the hardness of the test pieces stored in a zippered vinyl bag in a constant temperature room at 25°C for three days after production is shown in the "Hardness (3 days)" column. The smaller the value, the softer the bread of the test piece. Furthermore, the change in hardness after three days and the hardness on the day of baking was determined, and this is shown in the "ΔHardness" column. The smaller the value, the more suppressed aging. In the present invention, a ΔHardness of less than 5 can be said to suppress aging.

As is clear from the results in Table 1, the dough compositions of Examples 1 to 3, which contain 80 to 150% by weight of water and 0.05 to 5% by weight of carboxymethylated cellulose nanofibers relative to 100% by weight of starch-containing grain powder, have good dough cohesion and workability even when the amount of water added is increased, and the bread obtained using this dough composition has improved rise, and although it contains a high amount of water, the Δ moisture content is close to 0, preventing drying, and the Δ hardness is less than 5, indicating that it is soft and aging is inhibited.

Claims (3)

The dough contains 100% by weight of one or more wheat flours selected from strong flour, semi-strong flour, medium flour, weak flour, and durum wheat flour, 80 to 150% by weight of a water component, and 0.05 to 5% by weight of carboxymethylated cellulose nanofibers,
The dough composition further contains 25 to 60% by weight of carboxymethyl cellulose or a salt thereof relative to the carboxymethylated cellulose nanofibers,
The carboxymethyl cellulose or salt thereof has a degree of carboxymethyl substitution per anhydroglucose unit in the range of 0.55 to 1.6,
The dough composition is characterized in that the Brookfield viscosity of a 1 wt % aqueous solution of the carboxymethyl cellulose or a salt thereof at 25°C and 60 rpm is in the range of 1,000 to 8,000 mPa·s. The dough composition according to claim 1, characterized in that the carboxymethylated cellulose nanofibers have a degree of carboxymethyl substitution per anhydroglucose unit of 0.01 to 0.50 and a degree of cellulose type I crystallinity of 40% or more. A bakery food composition comprising the dough composition according to claim 1 or 2 .