Starch retrogradation inhibitor for starch-containing foods, method for inhibiting starch retrogradation of starch-containing foods, and starch-containing foods

Abstract

To provide a starch aging inhibitor for a starch-containing food product excellent in aging inhibitory effect of starch in the starch-containing food product, a method of inhibiting starch aging of the starch-containing food product, and the starch-containing food product.SOLUTION: A starch aging inhibitor for a starch-containing food product includes water-soluble hemicellulose, wherein a weight average molecular weight (Mw) of the water-soluble hemicellulose is 10,000 or more and 500,000 or less, and formulae (1) and (2) are satisfied when a ratio (M2 / M1) of a mass (M2) of the water-soluble hemicellulose, having a molecular weight of the water-soluble hemicellulose of 1,000 or more, with respect to a mass (M1) of the water-soluble hemicellulose is x (mass%), and the weight average molecular weight (Mw) of the water-soluble hemicellulose is y. 0<y≤7417.4x-278369...(1) 50≤x≤100...(2)SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an inhibitor for suppressing starch retrogradation in starch-containing foods, a method for suppressing starch retrogradation in starch-containing foods, and starch-containing foods.

Background Art

[0002] Foods containing starch such as cooked rice, bread, noodles, etc. are widely distributed. Starch has the property of becoming hard due to retrogradation over time, and the hardening progresses significantly at low temperatures. Therefore, starch-containing foods may lead to deterioration of texture and loss of palatability due to the passage of time or low-temperature storage. For this reason, various studies have been conducted on methods for preventing deterioration of the texture during storage of starch-containing foods.

[0003] For example, as methods for improving the texture of stored cooked rice, a method of cooking raw rice in the presence of α,α - trehalose (see Patent Document 1), a method of adding a yeast-treated product and a thickening stabilizer to the rice before cooking (see Patent Document 2), a method of adding a water-soluble hemicellulose and an organic acid or its salt (see Patent Document 3), and a method of using 0.1 to 30% by weight of trehalose and 0.1 to 30% by weight of water-soluble hemicellulose in combination with rice (see Patent Document 4) have been proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, it is desirable to further suppress the retrogradation of starch in starch-containing foods in order to improve the texture.

[0006] This invention has been made in view of the above circumstances, and aims to provide a starch retrogradation inhibitor for starch-containing foods, a method for inhibiting starch retrogradation in starch-containing foods, and a starch-containing food, which are excellent in inhibiting starch retrogradation in starch-containing foods. [Means for solving the problem]

[0007] The present inventors have discovered that the above problems can be solved by a starch retrogradation inhibitor that contains water-soluble hemicellulose, wherein the weight-average molecular weight (Mw) of the water-soluble hemicellulose is 10,000 or more and 500,000 or less, and where x (mass%) is the ratio (M2 / M1) of the mass of water-soluble hemicellulose containing a molecular weight of 1,000 or more to the mass of the water-soluble hemicellulose, and y is the weight-average molecular weight (Mw) of the water-soluble hemicellulose, and satisfies the following formulas (1) and (2), thereby completing the present invention. More specifically, the present invention provides the following.

[0008] (1) Contains water-soluble hemicellulose, The weight-average molecular weight (Mw) of the aforementioned water-soluble hemicellulose is between 10,000 and 500,000. A starch retrogradation inhibitor for starch-containing foods that satisfies the following formulas (1) and (2), where x (mass%) is the ratio (M2 / M1) of the mass of water-soluble hemicellulose containing a molecular weight of 1000 or more to the mass (M1) of the water-soluble hemicellulose, and y is the weight-average molecular weight (Mw) of the water-soluble hemicellulose. 0 <y≦7417.4x-278369···(1) 50 ≤ x ≤ 100 ···(2)

[0009] (2) A method for inhibiting starch retrogradation of a starch-containing food, comprising the step of incorporating the starch retrogradation inhibitor described in (1) into the starch-containing food.

[0010] (3) A starch-containing food containing water-soluble hemicellulose, The weight-average molecular weight (Mw) of the aforementioned water-soluble hemicellulose is between 10,000 and 500,000. A starch-containing food that satisfies the following equations (1) and (2), where x (mass%) is the ratio (M2 / M1) of the mass of water-soluble hemicellulose containing a molecular weight of 1000 or more to the mass (M1) of the water-soluble hemicellulose, and y is the weight-average molecular weight (Mw) of the water-soluble hemicellulose. y ≤ 7417.4x - 278369 ···(1) 50 ≤ x ≤ 100 ···(2) [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a starch retrogradation inhibitor for starch-containing foods that is excellent in inhibiting starch retrogradation in starch-containing foods, a method for inhibiting starch retrogradation in starch-containing foods, and a starch-containing food. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows the relationship between the ratio (M2 / M1):x (mass%) of the mass of water-soluble hemicellulose containing a molecular weight of 1000 or more relative to the total mass of water-soluble hemicellulose (M1), and the weight-average molecular weight (Mw):y of the water-soluble hemicellulose. [Modes for carrying out the invention]

[0013] The following describes specific embodiments of the present invention in detail. However, the present invention is not limited in any way to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, explanations may be omitted where necessary to avoid repetition, but this does not limit the gist of the invention.

[0014] <Inhibitor of starch retrogradation in starch-containing foods> The starch retrogradation inhibitor for starch-containing foods of the present invention (hereinafter, also referred to as "the starch retrogradation inhibitor of the present invention") contains water-soluble hemicellulose, and the weight-average molecular weight (Mw) of the water-soluble hemicellulose is 10,000 or more and 500,000 or less. When the ratio (M2 / M1) of the mass (M2) of the water-soluble hemicellulose having a molecular weight of ˃1,000 to the mass (M1) of the water-soluble hemicellulose is x (mass%), and the weight-average molecular weight (Mw) of the water-soluble hemicellulose is y, the following formulas (1) and (2) are satisfied. 0 < y ≦ 7417.4x - 278369 ··· (1) 50 ≦ x ≦ 100 ··· (2)

[0015] (Starch-containing foods) The starch-containing foods in which the starch retrogradation inhibitor of the present invention suppresses starch retrogradation are not particularly limited, but include polished rice, brown rice, cooked rice obtained by cooking rice such as glutinous rice, red rice, okowa, cooked rice, pilaf, dry curry, sushi rice, etc., and molded cooked rice processed from these starch-containing foods such as onigiri and sushi rice, or frozen cooked rice obtained by freezing these, breads, noodles such as udon and pasta, sponge cakes, mochi, water manju, etc. confectioneries, frozen foods obtained by freezing these starch-containing foods and chilled foods distributed chilled, etc.

[0016] (Water-soluble hemicellulose) The water-soluble hemicellulose contained in the starch retrogradation inhibitor of the present invention has a weight-average molecular weight (Mw) of 10,000 or more and 500,000 or less. Further, when the ratio (M2 / M1) of the mass (M2) of the water-soluble hemicellulose having a molecular weight of ˃1,000 to the mass (content) (M1) of the water-soluble hemicellulose is x (mass%), and the weight-average molecular weight (Mw) of the water-soluble hemicellulose is y, the above formulas (1) and (2) are satisfied. The weight-average molecular weight (Mw) of the water-soluble hemicellulose is the weight-average molecular weight in terms of pullulan and can be measured by gel permeation chromatography (GPC) equipped with a RI detector.

[0017] Thus, the starch anti - retrogradation agent of the present invention containing water - soluble hemicellulose with a weight - average molecular weight (Mw) of 10,000 or more and 500,000 or less and satisfying formulas (1) and (2) can significantly suppress the hardening of starch in starch - containing foods, as shown in the examples described below, and is excellent in the effect of suppressing the hardening of starch in starch - containing foods.

[0018] The starch contained in rice, wheat flour, etc. has a hard crystal structure due to hydrogen bonds. When cooking rice, the hydrogen bonds of starch are broken and water molecules are incorporated, making it soft. This is called the gelatinization of starch. When cooked rice is left standing or stored at low temperature, the water molecules separate from the starch, gradually becoming hard. This is called the retrogradation of starch. When starch ages (hardens) and the starch - containing food hardens, the texture of the starch - containing food is significantly impaired.

[0019] Water - soluble hemicellulose is a polymer material having constituent sugars such as xylose, arabinose, mannose, galactose, etc. Since it has a high affinity for water, it is considered to have a water - retaining ability. Therefore, it is presumed that water - soluble hemicellulose can suppress the separation of water from gelatinized starch and can suppress the retrogradation (hardening) of starch by containing water - soluble hemicellulose.

[0020] However, even when water - soluble hemicellulose is blended into starch - containing foods, the effect of suppressing the retrogradation (hardening) of starch is insufficient, and there are also cases where the retrogradation of starch cannot be suppressed. In contrast, the present inventors found that the molecular weight of water - soluble hemicellulose greatly contributes to the retrogradation of starch. As a result of further studies, it was found that water - soluble hemicellulose with a weight - average molecular weight (Mw) of 10,000 or more and 500,000 or less and satisfying formulas (1) and (2) can significantly suppress the retrogradation (hardening) of starch. Specifically, as shown in the [Examples] below, it was found that by using water-soluble hemicellulose with a weight-average molecular weight (Mw) of 10,000 to 500,000 and satisfying equations (1) and (2) as an anti-aging component, the hardening of starch in starch-containing foods can be significantly suppressed. In Figure 1, the solid line for equation (1) is shown as y = 7417.4x - 278369. The reason why using water-soluble hemicellulose (hereinafter also referred to as "specific water-soluble hemicellulose") having a weight-average molecular weight (Mw) of 10,000 or more and satisfying formulas (1) and (2) is superior in inhibiting starch retrogradation is presumed to be because the water-soluble hemicellulose swells sufficiently in water.

[0021] On the other hand, if the weight-average molecular weight (Mw) is not between 10,000 and 500,000, or if formula (1) or formula (2) is not satisfied, the effect of suppressing the increase in hardness is poor or not suppressed at all. For example, if the weight-average molecular weight is greater than 500,000 or if formula (1) is not satisfied, the viscosity increases, and it is difficult to exert the starch retrogradation inhibitory effect, possibly because it cannot swell sufficiently in water. Also, if formula (2) is not satisfied, it is difficult to exert the starch retrogradation inhibitory effect, possibly because the water retention capacity is low.

[0022] Thus, the starch retrogradation inhibitor of the present invention is excellent in inhibiting starch retrogradation, and is therefore excellent in suppressing hardening of starch-containing foods over time and in suppressing hardening of starch-containing foods due to low-temperature storage. For this reason, a desirable texture (softness) can be maintained even after time has passed since cooking or after low-temperature storage.

[0023] For example, when storing starch-containing foods at room temperature (e.g., 20°C), refrigerated (e.g., 4°C), or frozen (e.g., -25°C), if the hardness of a starch-containing food without the starch retrogradation inhibitor of the present invention and other starch retrogradation inhibitors after storage is set to 1, then the hardness of a starch-containing food with the starch retrogradation inhibitor of the present invention can be suppressed to less than 0.90 under the same conditions. Hardness is an indicator of starch retrogradation, and the hardness of a starch-containing food can be determined by the method shown in the examples.

[0024] Furthermore, conventionally known starch retrogradation inhibitors (for example, starch retrogradation inhibitors containing trehalose or xylose) may impart sweetness or other flavors to the starch-containing foods to which they are added. On the other hand, the specific water-soluble hemicellulose included as a starch retrogradation inhibitor (hardening inhibitor) in the starch retrogradation inhibitor of the present invention has a weak flavor intensity of its own. Therefore, the starch retrogradation inhibitor of the present invention can suppress starch retrogradation in starch-containing foods without imparting or hardly imparting any unnecessary flavors such as sweetness.

[0025] The water-soluble hemicellulose contained in the starch retrogradation inhibitor of the present invention is, as described above, a weight-average molecular weight (Mw) of 10,000 or more and 500,000 or less, and satisfies formulas (1) and (2). The weight-average molecular weight (Mw) may be 30,000 or more, 50,000 or more, or 100,000 or more, or it may be 350,000 or less, 250,000 or less, or 150,000 or less. The ratio (M2 / M1) of the mass of water-soluble hemicellulose containing a molecular weight of 1000 or more (M2) to the mass of water-soluble hemicellulose (M1), i.e., x (mass%), may be 60 or more, 70 or more, or 90 or less, or 80 or less.

[0026] Examples of the raw materials for the specific water-soluble hemicellulose mentioned above include corn fiber and corn germ derived from sorghum, wheat bran, Napier grass (a perennial grass of the Poaceae family), broad-leaved trees, bamboo, coniferous trees, kenaf, rice straw, wheat straw, rice husks, bagasse, and sugarcane residue.

[0027] The specific form of water-soluble hemicellulose described above may be a liquid (such as a syrup) or a powder.

[0028] (Method for producing the above-mentioned specific water-soluble hemicellulose) Water-soluble hemicellulose can be obtained by eluting the hemicellulose fraction from the cell walls of, for example, corn fiber, using alkaline extraction, acid hydrolysis, or hydrothermal treatment, and then removing low-molecular-weight fractions or performing desalting and concentration operations using RO or NF membranes with low salt inhibition rates to obtain water-soluble hemicellulose fractions of various molecular weights. More specifically, for example, starch contained in corn fiber that has been ground to an average particle size of 500 μm or less is treated with amylase to remove starch, and then extracted in an aqueous sodium hydroxide solution (such as 1N) at 80°C for 60 minutes. After neutralization with 1N hydrochloric acid, an enzyme preparation such as hemicellulase is added to perform a low-molecular-weight treatment. After the enzymatic reaction, the supernatant is collected using a centrifuge, and the low-molecular-weight fraction and rough removal of salts are performed by diafiltration using an RO membrane with a salt rejection rate of 96%. The crudely purified liquid obtained here is desalted with an ion exchange resin and concentrated under reduced pressure, and then powdered using a spray dryer or the like to obtain a powder product. The above-mentioned specific water-soluble hemicellulose can be obtained by adjusting the extraction process conditions, the demolecular-weight treatment conditions, or by mixing multiple types of powders obtained under different conditions.

[0029] (Other ingredients) The starch retrogradation inhibitor of the present invention may or may not contain any components, as long as they do not inhibit the effects of the present invention. Such optional ingredients include, for example, water, flavorings, thickeners, sweeteners (sugar, isomerized sugar, glucose, fructose, fructose-glucose syrup, glucose-fructose syrup, honey, starch syrup, powdered starch syrup, maltodextrin, sorbitol, maltitol, reduced starch syrup, maltose, trehalose, brown sugar, etc.), dietary fiber, proteins (milk, soy, beef extract, chicken extract, pork extract, fish extract, gelatin, etc.), acidulants (citric acid, acetic acid, lactic acid, malic acid, tartaric acid, and other organic acids), minerals (calcium, magnesium, iron, potassium, zinc, copper, etc.), amino acids (arginine, valine, leucine, isoleucine, etc.), spices (garlic, ginger, sesame, chili pepper, wasabi, sansho pepper, myoga ginger, etc.), emulsifiers, enzymes, functional ingredients, preservatives, stabilizers, antioxidants, vitamins, etc. The amounts of these ingredients added can be adjusted as appropriate depending on the desired effect.

[0030] Furthermore, the starch retrogradation inhibitor of the present invention may or may not contain conventionally known property modifiers for starch-containing foods. Examples of conventionally known property modifiers include carbohydrates (maltose, maltotriose, thickening polysaccharides, etc.).

[0031] Furthermore, the starch retrogradation inhibitor of the present invention may or may not contain components used in conventional methods for producing cooked rice, bread, etc. Examples of such components include pH adjusters and organic acids.

[0032] <Method for suppressing starch retrogradation in starch-containing foods> The present invention provides a method for suppressing starch retrogradation in starch-containing foods, which includes the step of incorporating the above-described starch retrogradation inhibitor of the present invention into the starch-containing food. By incorporating the starch retrogradation inhibitor into the starch-containing food, retrogradation (hardening) of the starch-containing food can be suppressed, and hardening due to the passage of time or low-temperature storage of the starch-containing food can be suppressed.

[0033] The amount of the starch retrogradation inhibitor of the present invention to be incorporated into starch-containing foods is not particularly limited and can be appropriately selected depending on the type of starch-containing food and the desired hardness. For example, the starch retrogradation inhibitor of the present invention is blended with 100 parts by mass of starch material such as raw rice, rice flour, or wheat flour, such that the total amount of the specific water-soluble hemicellulose is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more. Alternatively, the starch retrogradation inhibitor of the present invention is blended with 100 parts by mass of starch material such as raw rice, rice flour, or wheat flour, such that the total amount of the specific water-soluble hemicellulose is preferably 10 parts by weight or less, more preferably 5 parts by mass or less. If the amount is 0.05 parts by weight or more, it is easier to impart desirable physical properties such as hardness to starch-containing foods, and if it is 10 parts by weight or less, the physical properties such as hardness imparted to starch-containing foods tend to be appropriate.

[0034] The timing for incorporating the starch retrogradation inhibitor of the present invention into starch-containing foods is not particularly limited and can be appropriately selected depending on the type of starch-containing food, etc. For example, the starch retrogradation inhibitor of the present invention may be mixed before or during rice cooking, or it may be mixed after rice cooking.

[0035] <Starch-containing foods> The starch-containing food of the present invention contains water-soluble hemicellulose, wherein the weight-average molecular weight (Mw) of the water-soluble hemicellulose is 10,000 or more and 500,000 or less. When the ratio (M2 / M1) of the mass of water-soluble hemicellulose containing a molecular weight of 1,000 or more to the mass of water-soluble hemicellulose (M1) is x (mass%), and the weight-average molecular weight (Mw) of the water-soluble hemicellulose is y, the above formulas (1) and (2) are satisfied. As described above, because it contains the specific water-soluble hemicellulose, the starch-containing food of the present invention has its starch retrogradation suppressed, and hardening due to the passage of time or low-temperature storage is suppressed. Therefore, the starch-containing food of the present invention can maintain a desirable texture (softness) even after time has passed since cooking or after low-temperature storage. Furthermore, dryness due to storage is also suppressed. In addition, the starch-containing food can have little to no unwanted flavors such as sweetness from starch retrogradation inhibitors (for example, sweetness from trehalose or xylose). The starch-containing food, the specific water-soluble hemicellulose mentioned above, and the amounts used are the same as those described in the <Starch Retrogradation Inhibitor for Starch-Containing Foods> and <Method for Inhibiting Starch Retrogradation for Starch-Containing Foods> above.

[0036] The starch-containing food of the present invention may be sterilized and packaged. The method and order of sterilization and packaging are not particularly limited. When packaging products, suitable containers include plastic products such as polyethylene terephthalate (PET) (retort pouches, plastic bottles, etc.), metal products such as steel and aluminum (cans, etc.), and paper cartons. [Examples]

[0037] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples, and can take various forms as long as it can solve the problems of the present invention. Note that Example 1-1 should be interpreted as a reference example.

[0038] <Production of water-soluble hemicellulose> Water-soluble hemicellulose a-h was produced using the following method. Furthermore, the weight-average molecular weight (Mw) and the ratio (M2 / M1) of the mass of water-soluble hemicellulose containing a molecular weight of 1000 or more to the total mass of water-soluble hemicellulose (M1) were determined for water-soluble hemicellulose a-h using the following method. The Mw and M2 / M1 values ​​for the water-soluble hemicellulose used are shown in the table. The results of determining whether water-soluble hemicellulose a-h satisfies equations (1) and (2) are also shown in the table, with ○ indicating satisfaction and × indicating non-satisfaction.

[0039] [Weight-average molecular weight (Mw) of water-soluble hemicellulose] The weight-average molecular weight (Mw) of water-soluble hemicellulose a to h was determined by HPLC (using a radioisotope detector) with standard pullulan (manufactured by Showa Denko K.K.) as the standard substance. The measurement conditions for the HPLC method are as follows: Guard column: TSKgel PWH (inner diameter 7.5mmφ x length 75mm, 1 piece, manufactured by Tosoh Corporation) Column: TSKgel GMPW (7.5mm inner diameter x 300mm length, 3 columns, manufactured by Tosoh Corporation) Column temperature: 40℃ Flow rate: 1.0 ml / min; Eluent: 0.2 M sodium nitrate aqueous solution

[0040] [The ratio (M2 / M1) of the mass of water-soluble hemicellulose containing a molecular weight of 1000 or more to the total mass of water-soluble hemicellulose (M1)] The M2 / M1 ratio was calculated by dividing the mass of water-soluble hemicellulose with a molecular weight of 1000 or more (M2), which was determined from the integrated molecular weight distribution curve obtained by the HPLC method described above, by the mass of water-soluble hemicellulose (M1).

[0041] [Water-soluble hemicellulose a (weight average molecular weight (Mw): 17359, M2 / M1: 37.6% by mass)] Corn fiber that had been pulverized and starch-removed to 10% by weight was extracted under a 0.2 M sodium hydroxide aqueous solution (80°C, 1 hour), then neutralized with 1 M hydrochloric acid, and 0.3% by weight of hemicellulase (Novozymes) was added for enzymatic treatment at 50°C (50°C, 2 weeks). After enzymatic treatment, the supernatant was collected by centrifugation (3000 G, 10 minutes), and 0.1% by weight of powdered activated carbon was added for activated carbon treatment (60°C, 1 hour). The powdered activated carbon was removed by suction filtration using glass fiber filter paper, and the activated carbon treated solution was collected. The activated carbon treated solution was desalted using ion exchange resins (cation exchange resin DOWEX 88 (Dow Chemical) and anion exchange resin DOWEX 22 (Dow Chemical)) and concentrated under reduced pressure, and then powdered in a freeze dryer to obtain water-soluble hemicellulose a.

[0042] [Water-soluble hemicellulose b (weight average molecular weight (Mw): 207811, M2 / M1: 61.3% by mass)] A slurry was obtained by extracting 10% by weight of pulverized and starch-de-starched corn fiber under a 0.8 M sodium hydroxide aqueous solution (80°C, 5 hours). To this slurry, 40% by weight of a slurry obtained by extracting 10% by weight of pulverized and starch-de-starched corn fiber under distilled water (200°C, 5 minutes) was added and mixed. This mixture was neutralized with 1 M hydrochloric acid, and the supernatant was collected by centrifugation (3000 G, 10 minutes). 0.1% by weight of powdered activated carbon was added and activated carbon treatment was performed (50°C, 1 hour). The powdered activated carbon was removed by suction filtration using glass fiber filter paper, and the activated carbon treated solution was collected. The activated carbon treated solution was desalted using ion exchange resins (cation exchange resin DOWEX 88 (manufactured by Dow Chemical) and anion exchange resin DOWEX 22 (manufactured by Dow Chemical)), concentrated under reduced pressure, and then powdered using a freeze-dryer to obtain water-soluble hemicellulose b.

[0043] [Water-soluble hemicellulose c (weight average molecular weight (Mw): 309055, M2 / M1: 99.1% by mass)] Corn fiber that had been pulverized and starch-removed to 10% by weight was extracted under a 0.8 M sodium hydroxide aqueous solution (80°C, 5 hours), then neutralized with 1 M hydrochloric acid, and the supernatant was collected by centrifugation (3000 G, 10 minutes). 0.1% by weight of powdered activated carbon was added and activated carbon treatment was performed (60°C, 1 hour). The powdered activated carbon was removed by suction filtration using glass fiber filter paper and the activated carbon treated solution was collected. The activated carbon treated solution was desalted using ion exchange resins (cation exchange resin DOWEX 88 (manufactured by Dow Chemical) and anion exchange resin DOWEX 22 (manufactured by Dow Chemical)), concentrated under reduced pressure, and then powdered in a freeze-dryer to obtain water-soluble hemicellulose c.

[0044] [Water-soluble hemicellulose d (weight average molecular weight (Mw): 114575, M2 / M1: 84.6% by mass)] Corn fiber that had been pulverized and starch-removed to 10% by weight was extracted under a 0.2 M sodium hydroxide aqueous solution (80°C, 1 hour), then neutralized with oxalic acid (1 M hydrochloric acid), and enzymatic treatment was carried out with 0.1% by weight of hemicellulase (Novozymes) at 50°C for 3 hours. After enzymatic treatment, the supernatant was collected by centrifugation (3000 G, 10 minutes), and activated carbon powder was added for activated carbon treatment (60°C, 1 hour). The activated carbon powder was removed by suction filtration using glass fiber filter paper, and the activated carbon treated solution was collected. The activated carbon treated solution was desalted using ion exchange resins (cation exchange resin DOWEX 88 (Dow Chemical) and anion exchange resin DOWEX 22 (Dow Chemical)) and concentrated under reduced pressure, and then powdered in a freeze dryer to obtain water-soluble hemicellulose d.

[0045] [Water-soluble hemicellulose e (weight average molecular weight (Mw): 44221, M2 / M1: 68.2% by mass)] Corn fiber that had been pulverized and starch-removed to 10% by weight was extracted under a 0.2 M sodium hydroxide aqueous solution (80°C, 1 hour), then neutralized with oxalic acid (1 M hydrochloric acid), and enzymatic treatment was carried out by adding 0.1% by weight of hemicellulase (Novozymes) (50°C, 22 hours). After enzymatic treatment, the supernatant was collected by centrifugation (3000 G, 10 minutes), and activated carbon powder was added to perform activated carbon treatment (60°C, 1 hour). The activated carbon powder was removed by suction filtration using glass fiber filter paper, and the activated carbon treated solution was collected. The activated carbon treated solution was desalted using ion exchange resins (cation exchange resin DOWEX 88 (Dow Chemical) and anion exchange resin DOWEX 22 (Dow Chemical)), concentrated under reduced pressure, and then powdered in a freeze dryer to obtain water-soluble hemicellulose e.

[0046] [Water-soluble hemicellulose f (weight average molecular weight (Mw): 11367, M2 / M1: 84.8% by mass)] Corn fiber that had been pulverized and starch-removed to 3% by weight was extracted under distilled water (175°C, 20 minutes), and the extract was recovered by suction filtration using glass fiber filter paper. The extract was subjected to ultrafiltration to remove low molecular weight fractions and crude salts using an ultrafiltration membrane with a molecular weight cutoff of 500 Da. 5% by weight of powdered activated carbon was added to the resulting crude purified liquid and subjected to activated carbon treatment (60°C, 1 hour). The powdered activated carbon was removed by suction filtration using glass fiber filter paper, and the activated carbon treated liquid was recovered. The activated carbon treated liquid was desalted using ion exchange resins (cation exchange resin DOWEX88 (manufactured by Dow Chemical) and anion exchange resin DOWEX22 (manufactured by Dow Chemical)), concentrated under reduced pressure, and then powdered in a freeze-dryer to obtain water-soluble hemicellulose f.

[0047] [Water-soluble hemicellulose g (weight average molecular weight (Mw): 213810, M2 / M1: 66.6% by mass)] A slurry was obtained by extracting 10% by weight of pulverized and starch-de-starched corn fiber under a 0.8 M sodium hydroxide aqueous solution (80°C, 5 hours). To this slurry, 35% by weight of a slurry obtained by extracting 10% by weight of pulverized and starch-de-starched corn fiber under distilled water (200°C, 5 minutes) was added and mixed. This mixture was neutralized with 1 M hydrochloric acid, and the supernatant was collected by centrifugation (3000 G, 10 minutes). 0.1% by weight of powdered activated carbon was added and activated carbon treatment was performed (50°C, 1 hour). The powdered activated carbon was removed by suction filtration using glass fiber filter paper, and the activated carbon treated solution was collected. The activated carbon treated solution was desalted using ion exchange resins (cation exchange resin DOWEX 88 (manufactured by Dow Chemical) and anion exchange resin DOWEX 22 (manufactured by Dow Chemical)), concentrated under reduced pressure, and then powdered in a freeze-dryer to obtain water-soluble hemicellulose g.

[0048] [Water-soluble hemicellulose h (weight average molecular weight (Mw): 64820, M2 / M1: 52.6% by mass)] A slurry was prepared by extracting 10% by weight of pulverized and starch-de-starched corn fiber in a 0.2 M sodium hydroxide aqueous solution at 80°C for 1 hour, then neutralizing it with 1 M hydrochloric acid, and finally enzymatically treating it with 0.1% by weight of hemicellulase (Novozymes) at 50°C for 22 hours. A slurry prepared by extracting 10% by weight of pulverized and starch-de-starched corn fiber in distilled water at 200°C for 5 minutes was added at a concentration of 45% by weight and mixed. The supernatant was collected from this slurry by centrifugation (3000 G, 10 minutes), and activated carbon powder was added at a concentration of 0.1% by weight for activated carbon treatment at 60°C for 1 hour. The activated carbon powder was removed by suction filtration using glass fiber filter paper, and the activated carbon treated solution was collected. The activated carbon-treated solution was desalted using ion exchange resins (cation exchange resin DOWEX88 (manufactured by Dow Chemical) and anion exchange resin DOWEX22 (manufactured by Dow Chemical)), concentrated under reduced pressure, and then powdered using a freeze-dryer to obtain water-soluble hemicellulose h.

[0049] <Test 1: Rice> The following materials and water-soluble hemicellulose a-h were used to cook raw rice, and the change in hardness during storage was evaluated. (material) Trehalose (powder): Manufactured by Hayashibara Co., Ltd. Xylose (powder): Manufactured by Kanto Chemical Co., Ltd.

[0050] (Preparation of cooked rice) Cooked rice was prepared using commercially available raw rice (Akita Komachi rice from Akita Prefecture, polished rice) and the following method. (1) 150g of uncooked rice was washed and transferred to a rice cooker, and the amount of water listed in Tables 1-1 and 1-2 was added to make a total of 368g. (2) The amount of water-soluble hemicellulose, trehalose, or xylose listed in Tables 1-1 and 1-2 was added and lightly stirred, and then the rice was cooked in a rice cooker. (3) After the rice is cooked, lightly stir it with a rice paddle and let it steam for 1 hour with the keep-warm function turned off. (4) Wrap each 50g portion in plastic wrap and let it cool at room temperature for 1 hour, then store at room temperature (20°C) or in the refrigerator (4°C) for 24 hours.

[0051] (Hardness measurement) The hardness of cooked rice was measured using the following method immediately after cooling at room temperature for 1 hour (on the same day), after storage at room temperature (24 hours at room temperature), and after refrigeration (24 hours in the refrigerator). The measurement was repeated 10 times, and the average value was calculated. The results are shown in the "Hardness" column of Tables 1-1 and 1-2. For hardness measurement, a rheometer (manufactured by Yamaden Co., Ltd.) was used. Three grains of cooked rice were compressed to 50% of the sample height using a Φ30 mm cylindrical plunger at a compression speed of 1 mm / s. The maximum load was considered to represent the hardness of each grain of rice. The hardness after 24 hours of storage at room temperature (20°C) or refrigerated (4°C) is shown in the "Hardness Change Rate" column, with the hardness of Comparative Example 1-1 set to 1. A lower hardness change rate indicates that hardening is suppressed and that the hardening (aging) suppression effect is high. Materials with a hardness change rate of less than 0.90 were evaluated as having excellent hardening suppression effects.

[0052] [Table 1-1]

[0053] [Table 1-2]

[0054] As shown in Tables 1-1 and 1-2, in Comparative Example 1-1, which did not contain trehalose, xylose, or water-soluble hemicellulose, the hardness of the cooked rice increased with storage. However, in the examples in which water-soluble hemicellulose c-h, which have a weight-average molecular weight of 10,000 to 500,000 and satisfy formulas (1) and (2), were added, the rate of hardness change was low, and the hardness was significantly lower compared to Comparative Example 1-1, confirming excellent hardness suppression effect (starch retrogradation suppression effect). On the other hand, it can be seen that the comparative examples in which trehalose or xylose were added, or in which water-soluble hemicellulose a-b that did not satisfy formulas (1) and (2), had a poor or no effect in suppressing hardness increase. Figure 1 shows the relationship between the ratio (M2 / M1)x (mass%) of the mass of water-soluble hemicellulose containing a molecular weight of 1000 or more (M2) to the mass of water-soluble hemicellulose (M1) used in the examples and comparative examples, and the weight-average molecular weight (Mw)y of the water-soluble hemicellulose.

[0055] <Test 2: Starch Gel> Starch gels were prepared using the following materials and water-soluble hemicellulose d, and the change in hardness during storage was evaluated.

[0056] (material) Trehalose (powder): Manufactured by Hayashibara Co., Ltd. Non-glutinous rice starch: Manufactured by Joetsu Starch Co., Ltd.

[0057] (Preparation of starch gel) Starch gel was prepared using the following method. (1) All the materials listed in Table 2 were mixed and stirred at room temperature. (2) After stirring at 60°C for 30 minutes, the mixture was steam-heated in a steam convection oven (tanico) at 95°C for 30 minutes. (3) The sample was filled into a hardness test container, allowed to cool at 25°C for 3 hours, and then stored in a refrigerator (4°C).

[0058] (Hardness measurement) The hardness of the starch gel was measured using the following method immediately after cooling at 25°C for 3 hours (on the same day) and after refrigerated storage (96 hours in the refrigerator). The measurement was repeated twice, and the average value was calculated. The results are shown in the "Hardness" column of Table 2. A rheometer (manufactured by Yamaden Co., Ltd.) was used to measure the hardness of the starch gels, which were measured while still filled in their containers. The hardness of each starch gel was considered to be the maximum load obtained when the sample was compressed to 50% of its height at a compression speed of 1 mm / s using a Φ20 mm cylindrical plunger. The hardness after 96 hours of storage in a refrigerator (4°C) is shown in the "Hardness Change Rate" column, with the hardness of Comparative Example 2-1 set to 1. Products with a hardness change rate of less than 0.90 were evaluated as having excellent hardening suppression effect.

[0059] [Table 2]

[0060] As shown in Table 2, the hardness of the starch gel increases with storage. However, in the example in which water-soluble hemicellulose with a weight-average molecular weight of 10,000 to 500,000 and satisfying formulas (1) and (2) was added, the rate of hardness change was low, and the hardness was significantly lower compared to Comparative Example 2-1, confirming its excellent effect in suppressing hardness increase.

[0061] <Exam 3: Sponge Cake> Sponge cakes were prepared using the following materials and water-soluble hemicellulose d, and the change in hardness during storage was evaluated.

[0062] (material) Trehalose (powder): Manufactured by Hayashibara Co., Ltd. Sugar: Manufactured by Nisshin Sugar Co., Ltd. Whole eggs: Manufactured by Ise Delica Co., Ltd. Cake flour: Manufactured by Nissin Foods Co., Ltd. Baking powder: Manufactured by Aikoku Co., Ltd. Salad oil: Manufactured by J-Oil Mills Co., Ltd.

[0063] (Preparing the sponge cake) The sponge cake was prepared using the following method. (1) After whisking whole eggs with sugar and hemicellulose d or trehalose, add cake flour and baking powder and mix, then add salad oil and mix to prepare the batter. (2) The prepared dough was poured into molds and baked in a steam convection oven (tanico) at 170°C for 12 minutes. (3) After cooling at room temperature for 1 hour, the samples were stored at room temperature (20°C) and frozen (-25°C).

[0064] (Hardness measurement) The hardness of sponge cakes was measured using the following method immediately after baking (on the same day), after storage at room temperature (24 hours), and after frozen storage (240 hours). Frozen samples were used for measurement after thawing at room temperature. The measurement was repeated five times, and the average value was calculated. The results are shown in the "Hardness" column of Table 2. A rheometer (manufactured by Yamaden Co., Ltd.) was used to measure hardness. For sponge cake samples cut into 2cm x 2cm pieces, the load applied when compressed to 30% of the sample height at a compression speed of 1mm / s using a Φ20mm cylindrical plunger was considered the hardness of each sponge cake. The hardness after storage at room temperature (20℃) for 24 hours or frozen (-25℃) for 240 hours is shown in the "Hardness Change Rate" column, with the hardness of Comparative Example 3-1 set to 1. Samples with a hardness change rate of less than 0.90 were evaluated as having excellent hardening suppression effect.

[0065] [Table 3]

[0066] As shown in Table 3, the hardness of sponge cake increases with storage, but in the example in which water-soluble hemicellulose with a weight-average molecular weight of 10,000 to 500,000 and satisfying formulas (1) and (2) was added, the rate of hardness change was low and the hardness was significantly lower compared to Comparative Example 3-1, confirming its excellent effect in suppressing the increase in hardness.

[0067] <Exam 4: Bread> Bread was prepared using the following materials and water-soluble hemicellulose d, and the change in hardness during storage was evaluated.

[0068] (material) Trehalose (powder): Manufactured by Hayashibara Co., Ltd. Strong flour: Manufactured by Nissin Foods Co., Ltd. Sugar: Manufactured by Nisshin Sugar Co., Ltd. Table salt: Manufactured by the Salt Business Center (a foundation). Skim milk powder: Manufactured by Morinaga Milk Industry Co., Ltd. Yeast Food: Manufactured by Nissin Foods Co., Ltd. Shortening: Manufactured by Nissin Foods Co., Ltd.

[0069] (Bread preparation) The bread was prepared using the following method. (1) All ingredients were mixed in the quantities listed in Table 4, and bread was prepared using a home bread maker (Panasonic). (2) Remove immediately after baking, allow to cool at room temperature for 1 hour, then store at room temperature (20°C).

[0070] (Hardness measurement) The hardness of the bread was measured immediately after baking (on the same day) and after storage at room temperature (24 hours) using the following method. The measurement was repeated three times, and the average value was calculated. The results are shown in the "Hardness" column of Table 4. For hardness measurement, a rheometer (manufactured by Yamaden Co., Ltd.) was used. For samples of bread cut into 2cm x 2cm pieces, the load applied when the sample was compressed to 30% of its height using a Φ20mm cylindrical plunger at a compression speed of 1mm / s was considered the hardness of each piece of bread. The hardness after storage at room temperature (20°C) for 24 hours is shown in the "Hardness Change Rate" column, with the hardness of Comparative Example 4-1 set to 1. Products with a hardness change rate of less than 0.90 were evaluated as having excellent hardening suppression effect.

[0071] [Table 4]

[0072] As shown in Table 4, the hardness of the bread increases with storage, but in the example in which water-soluble hemicellulose with a weight-average molecular weight of 10,000 to 500,000 and satisfying formulas (1) and (2) was added, the rate of hardness change was low and the hardness was significantly lower compared to Comparative Example 4-1, confirming its excellent effect in suppressing the increase in hardness.

Claims

1. Contains water-soluble hemicellulose, The weight-average molecular weight (Mw) of the aforementioned water-soluble hemicellulose is 10,000 or more and 500,000 or less. A starch retrogradation inhibitor for starch-containing foods that satisfies the following formulas (1) and (2), where x (mass%) is the ratio (M2 / M1) of the mass of water-soluble hemicellulose containing a molecular weight of 1000 or more to the mass (M1) of the water-soluble hemicellulose, and y is the weight-average molecular weight (Mw) of the water-soluble hemicellulose. 0<y≦7417.4x-278369...(1) 50 ≤ x ≤ 90 ... (2)

2. A method for suppressing starch retrogradation of a starch-containing food, comprising the step of incorporating the starch retrogradation inhibitor described in claim 1 into the starch-containing food.

3. A starch-containing food containing water-soluble hemicellulose, The starch-containing food is cooked rice obtained by cooking polished rice, brown rice, or glutinous rice, molded cooked rice obtained by processing the cooked rice, or frozen cooked rice obtained by freezing the cooked rice. The weight-average molecular weight (Mw) of the aforementioned water-soluble hemicellulose is 10,000 or more and 500,000 or less. A starch-containing food that satisfies the following formulas (1) and (2), where x (mass%) is the ratio (M2 / M1) of the mass of water-soluble hemicellulose containing a molecular weight of 1000 or more to the mass (M1) of the water-soluble hemicellulose, and y is the weight-average molecular weight (Mw) of the water-soluble hemicellulose. y≦7417.4x-278369...(1) 50 ≤ x ≤ 90 ... (2)

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