Method for manufacturing a sheet material and the sheet material

Abstract

To provide a production method of sheet material that nearly maintains the ingredients of foods, without adding conventional raw material for forming, and the sheet material produced thereby.SOLUTION: In a method for producing a sheet material, the sheet material is obtained by mixing a food containing water-insoluble dietary fiber and carboxylic acid. The sheet material contains 50 mass% or more and 100 mass% or less of cellulose-containing foods, and the cellulose has a cellulose II type crystal structure.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a sheet material and the sheet material.

Background Art

[0002] Conventionally, various sheet materials such as pharmaceutical sheets like wet compresses and band-aids, daily necessities sheets like paper and non-woven fabrics, cosmetic sheets like face packs, and edible food sheets have been manufactured. For example, as food sheets, there are crepes, thin fried eggs, oblat, gelatin sheets, dumpling and spring roll wrappers, nori seaweed, etc. These food sheets have good appearance and texture, are favored by consumers, and contribute to various food cultures by wrapping ingredients such as dumplings and nori rolls.

[0003] For example, crepes and thin fried eggs are made into sheet form by utilizing the fact that the protein of the raw egg is denatured and solidified by heat. Oblat is made by adding water to starch and drying, gelatin sheets are made by adding hot water to gelatin and cooling, and dumpling and spring roll wrappers are made into sheet form by adding water to wheat flour etc. and kneading to form starch and gluten. Nori seaweed is made into a sheet where the fibers are intertwined by drying from a state containing moisture. In this way, sheet formation using denaturation of egg protein, formation of sheets using starch and gelatin which are water-soluble polymers, and formation of sheets using entanglement of fibers have been carried out.

[0004] Patent Document 1 discloses a sheet-shaped food containing rice starch, egg white, and non-fat milk solids, and Patent Document 2 discloses a sheet-shaped food containing ingredients such as vegetables and konjac, and binders such as pectin. The main component of konjac is glucomannan which is a water-soluble polymer (water-soluble dietary fiber), and pectin is also a water-soluble dietary fiber. However, when adding raw materials for molding such as eggs and water-soluble polymers, the flavor and texture etc. change. Therefore, there is a demand for a sheet material that can maintain the flavor etc. of the original food almost as it is.

[0005] Thus, while water-soluble dietary fiber has been conventionally used for forming sheets, forming sheets using water-insoluble dietary fiber in food has not been done. Most of the water-insoluble dietary fiber is cellulose, but as the name "water-insoluble" implies, it does not dissolve in water. Normally, compounds with hydroxyl groups are easily soluble in water. However, although cellulose has many hydroxyl groups, it is hardly soluble in water because of hydrogen bonding within and between molecules, making it difficult to hydrate. Furthermore, it is hardly soluble in more common organic solvents and the like. Therefore, it has not been used for making sheets so far.

[0006] As shown in Non-Patent Document 1, the inventor has heretofore dissolved wood powder in carboxylic acid to develop film-like and sheet-like materials. Applying this technique, the inventor has devised a method for manufacturing this sheet material and the sheet material itself.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0008]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The object of the present invention is to provide a method for manufacturing a sheet material that substantially maintains the components of food without adding raw materials for molding as in the prior art, and to provide such a sheet material.

Means for Solving the Problems

[0010] The method for manufacturing a sheet material according to the present invention is characterized in that it is obtained by mixing a food containing water-insoluble dietary fiber and a carboxylic acid. Here, examples of the water-insoluble dietary fiber include cellulose, hemicellulose, chitin, chitosan, etc. Examples of foods containing these include leafy vegetables, root vegetables, seaweeds, grains, tea leaves, beans, seeds, mushrooms, crustaceans, etc.

[0011] In the present invention, after mixing the food containing the water-insoluble dietary fiber and the carboxylic acid, it is preferable to remove the carboxylic acid and form it into a sheet shape. The removal of the carboxylic acid refers to, for example, the removal of carboxylic acid that has not formed an ester or acetal with the hydroxyl group of cellulose. Examples of the removal method include natural drying, vacuum drying, heat drying, washing, filtration, etc.

[0012] In the present invention, the cellulose in the water-insoluble dietary fiber and the carboxylic acid may be reacted, and it is preferable to react the hydroxyl group in the cellulose and the carboxylic acid to form an ester and / or an acetal. In such a reaction, it is considered that the hydroxyl group is modified and the hydrogen bond between the hydroxyl groups is weakened, so that dissolution proceeds and a sheet is easily formed.

[0013] In the present invention, it is presumed that the crystal structure of the cellulose in the water-insoluble dietary fiber has changed. Conventionally, it has been widely known that natural cellulose exists as a crystal. Also, many celluloses that have been once dissolved in a solvent and regenerated or swollen have a crystal structure, but the structure is a cellulose II type crystal structure different from the natural cellulose I type crystal structure. Type I has a parallel-chain molecular packing pattern, Type II has an antiparallel-chain pattern, and within Type I there are further different types. Additionally, Type III and Type IV are also known. In the present invention, since it is considered that the water-insoluble dietary fiber is dissolved or swollen in the carboxylic acid, it is presumed that its crystal structure has changed to a state different from that of the original food, that is, a cellulose type II crystal structure.

[0014] In the present invention, it is preferable that the carboxylic acid is at least one selected from the group consisting of formic acid, glyoxylic acid, pyruvic acid, acetic acid, lactic acid, citric acid, succinic acid, malic acid, tartaric acid, fumaric acid, and gluconic acid. Moreover, the food containing the water-insoluble dietary fiber may be in a powdery form with a diameter of 3 mm or less (90% or more in the particle size distribution having a diameter of 3 mm or less).

[0015] The sheet material according to the present invention contains 50% by mass or more and less than 100% by mass of a food containing cellulose, and is characterized in that the cellulose mainly has a cellulose type II crystal structure. As described above, the cellulose type II crystal structure is a modified form of the cellulose in the original food (for example, cellulose type I crystal structure). Here, the expression of containing less than 100% by mass of the food containing cellulose is because after the crystal structure of cellulose changes and is formed into the sheet material, it is preferable to remove the mixed carboxylic acid as much as possible and be closer to the food itself. The crystal structure can be analyzed by known methods, such as X-ray diffraction, infrared spectroscopy, solid NMR (nuclear magnetic resonance), etc. Note that the sheet material in the present invention allows for a small amount of the original food components to be lost during drying, washing, etc., and for the carboxylic acid of the solvent to remain.

Advantages of the Invention

[0016] The sheet material produced by the present invention can appeal to consumers with a sheet-like appearance while substantially maintaining the components and aroma of the food. In addition, since various foods can be made into sheet form, it can have a diverse impact on food culture. The manufacturing method according to the present invention is not limited to edible sheets, and can manufacture various sheet materials such as sheets that can be used as health foods and pharmaceuticals, scent sheets as daily necessities, and cosmetic sheets such as face packs.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0018] Examples of the water-insoluble dietary fiber in the present invention include cellulose, hemicellulose, chitin, chitosan, and the like. Examples of foods containing water-insoluble dietary fiber include leafy vegetables, root vegetables, seaweeds, grains, tea leaves, beans, seeds, mushrooms, crustaceans, etc. Examples of foods with a high content of water-insoluble dietary fiber include, for example, referring to the Japanese Food Standard Composition Table, sencha, gyokuro, matcha, black tea, soybeans, azuki beans, almonds, cocoa, okara, kinako, anko, sesame, dried shiitake mushrooms, dried daikon radish, burdock, etc. Preferably, it is matcha, black tea powder, cocoa, kinako, sweetened red bean paste, shiitake mushroom powder, vegetable powder, etc. in powder form with a diameter of 3 mm or less. In the case of foods that are not in powder form, it is desirable to grind them with a mill or the like after drying to a powder form with a diameter of 3 mm or less and then mix them with carboxylic acid. In the present invention, foods with a water-insoluble dietary fiber content of 3% or more are more preferable. Foods containing water-insoluble dietary fiber can be used alone or mixed with two or more kinds, and it is desirable to mix them in an amount equal to ~1 / 1000 of the amount of carboxylic acid for ease of handling.

[0019] Examples of the carboxylic acid in the present invention include formic acid, glyoxylic acid, pyruvic acid, acetic acid, lactic acid, citric acid, succinic acid, malic acid, tartaric acid, fumaric acid, gluconic acid, etc. These may be used alone or in combination of two or more. Cellulose has many hydroxyl groups and forms hydrogen bonds within and between molecules, so it is difficult to dissolve in water. However, it is considered that when a carboxylic acid forms an ester or acetal with the hydroxyl group of cellulose, the hydrogen bond between the hydroxyl groups is weakened, and by dissolving part or all of the cellulose, it becomes easier to form a sheet. Therefore, the carboxylic acid may be an aqueous solution, but since it is easier to dissolve at a higher concentration, it is desirable to use carboxylic acids that are liquid at room temperature, such as formic acid, acetic acid, and pyruvic acid, without adding water. In addition, it is desirable to use a carboxylic acid that is solid at room temperature as an aqueous solution dissolved at the maximum concentration that can be dissolved in water, or in a molten state at a temperature above the melting point. Note that the above carboxylic acid can form an ester, and in the case of a carboxylic acid having a carbonyl group or a formyl group, it can form an acetal.

[0020] The method of mixing the food containing water-insoluble dietary fiber and the carboxylic acid may be mechanical mixing using a stirrer, agitator, kneader, mixer, blender, etc., or manual mixing using a spatula, whisk, etc.

[0021] Examples of the method for removing the carboxylic acid include natural drying, vacuum drying, reduced-pressure drying, drying by heating, washing with a good solvent such as water, removal by dialysis using a semipermeable membrane, filtration using an ultrafiltration membrane, etc. For example, in the case of a carboxylic acid with a low boiling point such as formic acid, natural drying or reduced-pressure drying is preferred, and for a carboxylic acid with a high boiling point such as glyoxylic acid, vacuum drying, reduced-pressure drying, or drying by heating is preferred.

[0022] The produced sheet material is cellulose mainly having a cellulose II-type crystal structure different from the cellulose in the original food, and it is preferable to contain 50% by mass or more and less than 100% by mass of the food containing this cellulose. The sheet material obtained in the present invention tends to have translucency. Here, translucency means that when the sheet material is placed on paper with a line printed thereon, the line can be seen through the sheet material. This is presumably because the water-insoluble dietary fiber is dissolved or swollen in the carboxylic acid, resulting in a change in the original structure. The thickness of the sheet material is not particularly limited, but since it may be weak in strength such as being easily torn when it is less than 20 μm, it is preferably 20 μm or more.

[0023] In the method for producing the sheet material according to the present invention, other foods, seasonings, coloring agents, flavors, etc. can be added as necessary, and they may be added together when mixing the carboxylic acid. When producing pharmaceutical sheets, daily necessities sheets, or cosmetic sheets, for example, medicinal ingredients, moisturizers, oils, extracts, preservatives, etc. can also be added. [Examples]

[0024] The sheet material and the method for producing the same according to the present invention will be specifically described based on the following examples, but the present invention is not limited thereto. In the present invention, room temperature means 10°C to 30°C, preferably 15°C to 25°C. [Production Method]

[0025] In Examples 1 to 6, matcha (Uji Matcha of Ito En Co., Ltd. (registered trademark)) and / or kinako (Kinako made from 100% Hokkaido soybeans of Japan Consumers' Co-operative Union) were selected as foods, and formic acid and / or acetic acid were selected as carboxylic acids. On the other hand, Comparative Examples 1 and 2 are examples in which the above matcha or kinako was selected as a food and purified water was used instead of the carboxylic acid. Examples 1 to 6 and Comparative Examples 1 and 2 were mixed (stirred using a magnetic stirrer) under the ratio, temperature, and time conditions shown in Table 1. As a drying container, a petri dish with several protrusions on the lid and having air permeability was selected. After laying a polyethylene terephthalate (Tetoron (registered trademark)) film, which is a base material, on the inside, the mixed solution obtained above was poured in. After natural drying at room temperature for about 3 days, drying under reduced pressure (reducing the pressure to about 10 - 20 hPa using a vacuum pump) was performed at room temperature for 0.5 to 1 hour, and Examples 1 to 6 and Comparative Examples 1 and 2 were obtained. The reason for using a container with a lid is that if the drying rate is too fast, there is a high possibility that cracks will occur in the sheet, and the drying rate is appropriately slowed down. In addition, the base material was used to make it easy to peel off after sheet formation, and drying under reduced pressure was additionally performed as an extra precaution.

Table 1

[0026] 1. Sheet formation For the obtained Examples 1 to 6 and Comparative Examples 1 and 2, the presence or absence of sheet formation was evaluated. When a sheet was formed visually and the thickness could be measured after peeling from the base film, it was marked as ○, and otherwise as ×.

[0027] 2. Sheet translucency It was evaluated whether the sheets of the obtained Examples 1 to 6 had translucency. When the sheet was placed on a paper with a printed line and the line behind could be confirmed through the sheet, it was marked as ○, and otherwise as ×.

[0028] 3. Sheet thickness The thickness of the sheets of the obtained Examples 1 to 6 was measured using a micrometer (manufactured by Mitutoyo). Note that in Table 2, 5 measurements were taken for each sample, and the average value was described.

[0029] 4. Mass ratio of the sheet to the raw material food Taking the food mass before mixing with the carboxylic acid as 100%, the sheet masses of the obtained Examples 1 to 6 were measured. Here, when the mass ratio is 100%, it is considered that the original food component is maintained. However, when it is 100% or less, the food component is lost during drying, etc., and when it is more than 100%, it is considered that carboxylic acid is chemically bonded and remains (part of it is not removed by drying).

[0030] 5. Sheet composition The sheet compositions (mass %) of Examples 1 to 6 obtained were calculated by the following calculation formula. (Mass % of food) = (Mass of food before mixing) / (Mass of sheet) (Mass % of carboxylic acid) = 100% - (Mass % of food)

[0031] The results are shown in Table 2.

Table 2

[0032] As shown in Table 2, Examples 1 to 6 formed sheets, while in Comparative Examples 1 and 2, the food only returned to its original powdery state and no sheet was formed. All of Examples 1 to 6 that formed sheets had translucency. Since the thickness of the sheet is affected by the viscosity of the mixed solution, etc., Examples 1 to 6 had various thicknesses, but all were 20 μm or more. In Example 2, traces of bubbles were observed on the sheet, and in Examples 3 and 5, undissolved particles were observed on the sheet. This means that even if the mixed solution contains bubbles or the powdery food is not completely dissolved, a sheet can be formed. From the results of measuring the mass of the obtained sheet, it is considered that formic acid and acetic acid remained due to chemical bonding, etc. When calculating the composition of the prepared sheet, the food (matcha and / or kinako) in the sheet was 53 mass % to 88 mass %.

[0033] Photographic images of Examples 1 and 3, which are sheet materials, are shown in FIGS. 1 and 2. In order to clearly show the translucency, Figs. 1 and 2 were taken by placing the sheet material on paper with lines printed on it. As shown in the figures, the sheet materials of Examples 1 and 3 had a translucent feeling and the background could be seen through. The sheet materials of Examples 1 to 6 could be bent softly and each had the smell of matcha or kinako. Note that the translucency and softness differed depending on the sheet material, and it is considered that the components in the food affected the physical properties.

Claims

1. A method for manufacturing a sheet material, comprising dissolving a food containing water-insoluble dietary fiber in a carboxylic acid to obtain a mixture without a gelling agent, and then removing the carboxylic acid from the mixture to form it into a sheet.

2. The method for manufacturing a sheet material according to Claim 1, wherein the food containing the water-insoluble dietary fiber is in powder form and is mixed in an amount of not less than one-thousandth to equal amount with respect to the carboxylic acid.

3. The method for manufacturing a sheet material according to Claim 1 or 2, wherein the type I crystal structure of cellulose contained in the food is mainly changed to a type II crystal structure of cellulose.

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