JP2023047856A - Rice texture deterioration inhibitor, rice softness improver, and rice production method - Google Patents

Abstract

To provide a technique for suppressing deterioration in rice texture accompanying the lapse of time after rice cooking and cryopreservation, and a technique for improving softness of rice.SOLUTION: There are provided a rice texture deterioration inhibitor containing cellulase as active ingredient, and a rice softness improver containing cellulase as active ingredient. The present invention can suppress deterioration in rice texture accompanying the lapse of time after rice cooking and cryopreservation. The present invention can improve rice softness. The present invention can contribute to suppression of deterioration in quality accompanying the lapse of time after production and cryopreservation, extension of an expiration date or reduction in food waste, for processed food such as rice.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD The present invention relates to an agent for suppressing deterioration of the texture of cooked rice, an agent for improving the softness of cooked rice, and a method for producing cooked rice using these, which contain cellulase as an active ingredient.

Processed foods using boiled rice include various forms such as packed rice, retort rice, chilled or room temperature box lunches, rice balls, and frozen foods (grilled rice balls, fried rice, pilaf, etc.). In the processed foods using such cooked rice, there is a problem that the starch contained in the cooked rice deteriorates with the lapse of time after production or storage at low temperature, and the texture of the cooked rice deteriorates. The best-before date is also set for the deterioration of the texture of cooked rice, in addition to quality deterioration (rot) due to the growth of microorganisms.

From this, if the texture of cooked rice can be maintained for a long time immediately after cooking, it can contribute to maintaining the quality of products and extending the expiration date. Therefore, techniques for suppressing the deterioration of the texture of cooked rice have been researched and developed. A technique for producing boiled rice that does not deteriorate in texture and taste for a long time by adding is disclosed.

On the other hand, cellulase is an enzyme that decomposes cellulose, which is the main component of plant cell walls. Patent Document 2 discloses a technique for improving texture by soaking brown rice in an aqueous cellulase solution and then cooking the rice.

Japanese Patent No. 2521771 JP-A-10-94368

However, although the technology described in Patent Document 1 has been confirmed to have the effect of maintaining the texture of cooked rice for up to 72 hours (3 days), it is unclear whether the deterioration of the texture can be suppressed after a longer period of time. is. In addition, the technique described in Patent Document 2 makes cellulase act on the surface of brown rice wrapped in a bran layer containing a large amount of dietary fiber to decompose the indigestible fiber and soften the originally hard texture. (Paragraphs [0002], [0004], [0008]). That is, the cellulase described in Patent Document 2 is only used to improve the texture of brown rice immediately after cooking, and is used to prevent the aging of starch in cooked rice, including not only brown rice, but also split rice and polished rice. It is unknown whether the accompanying deterioration of texture can be suppressed.

As described above, even in view of the prior art, it cannot be said that the technology capable of suppressing the deterioration of the texture of cooked rice due to the passage of time after cooking or storage at low temperature is sufficiently provided. The present invention has been made to solve such problems, and an object of the present invention is to provide a technique for suppressing the deterioration of the texture of cooked rice due to the passage of time after cooking or storage at low temperature. Another object of the present invention is to provide a technique for improving the softness of cooked rice.

As a result of intensive research, the present inventors have found that cellulase can suppress the deterioration of the texture of cooked rice due to the passage of time after cooking and storage at low temperature, and can improve the softness of cooked rice. In addition, the present inventors have found that deterioration of the texture of cooked rice can be remarkably suppressed by using cellulase and a predetermined reduced starch syrup in combination. Based on these findings, the inventors completed the following inventions.

(1) The agent for suppressing deterioration of texture of cooked rice according to the present invention contains cellulase as an active ingredient.

(2) The agent for improving the softness of cooked rice according to the present invention contains cellulase as an active ingredient.

(3) In the present invention, the cooked rice may be cooked rice obtained by cooking portioned rice or polished rice.

(4) The agent for suppressing deterioration of texture of cooked rice or the agent for improving softness of cooked rice according to the present invention may further contain a reduced starch syrup selected from the following (a) to (c) as an active ingredient;
(a) reduced starch syrup having a sugar composition of less than 30% by mass of monosaccharides and less than 50% by mass of pentasaccharides or higher;
(a) reduced starch syrup having a sugar composition of 50% by mass or more of pentasaccharide or higher;
(c) Reduced starch syrup obtained by reducing starch syrup having a dextrose equivalent of 10 or more and 50 or less.

(5) In the present invention, the reduced starch syrup may be used at a solid content concentration of 0.3 parts by weight or more and 7 parts by weight or less per 100 parts by weight of uncooked rice.

(6) In the present invention, the cellulase may be a mixed cellulase composition containing the following (a) to (d);
(a) a cellulase having 90% or more amino acid sequence identity with SEQ ID NO: 1;
(b) a cellulase having 90% or more amino acid sequence identity with SEQ ID NO:2;
(c) a cellulase having 90% or more amino acid sequence identity with SEQ ID NO:3;
(d) a cellulase having greater than 90% amino acid sequence identity with SEQ ID NO:4;

(7) The method for producing cooked rice according to the present invention has a step of adding the agent for suppressing deterioration of texture or the agent for improving softness according to the present invention and cooking the rice.

ADVANTAGE OF THE INVENTION According to this invention, the food texture deterioration of cooked rice accompanying the passage of time after cooking and low-temperature storage can be suppressed. Therefore, according to the present invention, it is possible to contribute to suppression of deterioration in quality of processed foods containing boiled rice due to passage of time after production or storage at low temperatures, extension of best-before dates, or reduction of food loss. Moreover, according to the present invention, it is possible to improve the softness of cooked rice, so that it is possible to impart a preferable texture to the cooked rice.

FIG. 4 is a diagram showing an evaluation sheet used by each panel for scoring in the sensory test. 2 is a bar graph showing the maximum load of the cooked rice of Example 1 (Samples 1 to 5) after storage for 2 hours after cooking. Sample 1 contains cooked rice containing no improver, Sample 2 contains cellulase as a improver, Sample 3 contains low-saccharification reduced starch syrup, Sample 4 contains medium-saccharification reduced starch syrup, and Sample 5 contains low-saccharification reduced starch syrup and cellulase, respectively. It is cooked rice. 4 is a bar graph showing the maximum load of the cooked rice of Example 2 (Samples 1 to 6) after storage at 20° C. for 5 days. Sample 1 is cooked rice containing no modifier, Sample 2 is cellulase as a modifier, Sample 3 is low saccharification reduced starch syrup, Sample 4 is medium saccharification reduced starch syrup, Sample 5 is low saccharification reduced starch syrup and cellulase, Sample 6 is rice containing low-saccharification-reduced starch syrup, medium-saccharification-reduced starch syrup and cellulase, respectively. FIG. 2 is a diagram showing the results of a sensory test after storing the boiled rice of Example 2 (Samples 1 to 6) at 20° C. for 5 days. (I) is a table showing the evaluation score of each evaluation item (average value of the scoring results of each panel), (II) is a bar graph showing the evaluation score of the “overall evaluation”, and (III) is the score of each panel. It is a table showing the results. 4 is a bar graph showing the maximum load after storage at 5° C. for 1 day for the cooked rice of Example 3 (Samples 1 to 6). Sample 1 is cooked rice containing no modifier, Sample 2 is cellulase as a modifier, Sample 3 is low saccharification reduced starch syrup, Sample 4 is medium saccharification reduced starch syrup, Sample 5 is low saccharification reduced starch syrup and cellulase, Sample 6 is rice containing low-saccharification-reduced starch syrup, medium-saccharification-reduced starch syrup and cellulase, respectively. FIG. 10 is a diagram showing the results of a sensory test of the boiled rice of Example 3 (Samples 1 to 6) after storage at 5° C. for 2 days. (I) is a table showing the evaluation score of each evaluation item (average value of the scoring results of each panel), (II) is a bar graph showing the evaluation score of the “overall evaluation”, and (III) is the score of each panel. It is a table showing the results. 4 is a bar graph showing the maximum load of the cooked rice of Example 4 (Samples 1, 2, 3, 5, 6 and 8) after storage at 20° C. for 5 days. Sample 1 is cooked rice containing no improver, and Samples 2, 3, 5, 6 and 8 are obtained by blending low saccharification reduced starch syrup, medium saccharification reduced starch syrup and cellulase as improvers, and varying the amount of reduced starch syrup added. It is rice. FIG. 10 is a diagram showing the results of a sensory test of the boiled rice of Example 4 (Samples 1 to 8) after storage at 20° C. for 5 days. (I) is a table showing the evaluation score of each evaluation item (average value of the scoring results of each panel), (II) is a bar graph showing the evaluation score of the “overall evaluation”, and (III) is the score of each panel. It is a table showing the results. 10 is a bar graph showing the maximum load after storage at 20° C. for 5 days for cooked rice of Example 5 (Samples 2 to 5). Sample 2 is cellulase A, sample 3 is cellulase B, and samples 4 and 5 are cooked rice blended with cellulase A or cellulase B, medium saccharification reduced starch syrup and low saccharification reduced starch syrup. FIG. 10 is a diagram showing the results of a sensory test of the boiled rice of Example 5 (Samples 1 to 5) after storage at 20° C. for 5 days. (I) is a table showing the evaluation score of each evaluation item (average value of the scoring results of each panel), (II) is a bar graph showing the evaluation score of the “overall evaluation”, and (III) is the score of each panel. It is a table showing the results.

The present invention will be described in detail below. The present invention is a "cooked rice texture deterioration inhibitor" and "cooked rice softness improver" (hereinafter, these agents may be collectively referred to as "this agent"). ) and a method for producing cooked rice (hereinafter sometimes referred to as “this method”).

In the present invention, "cooked rice" refers to cooked rice. The boiled rice may be unseasoned, or may be seasoned in some way, such as cooked rice, pilaf, and sushi. The term “cooking rice” refers to the process of cooking rice, that is, the operation of heating rice with water to an edible level. "Rice" refers to uncooked rice that has not been heated to the point where it can be overeaten, unless otherwise specified. In the present invention, the degree of rice polishing is not particularly limited, and it may be brown rice, polished rice (polished rice), or rice that has been polished for 3 minutes, 5 minutes, 7 minutes, or the like.

In the present invention, suppressing the deterioration of the texture of cooked rice means reducing the extent to which the texture of cooked rice deteriorates.

The deterioration of the texture of cooked rice after cooking is generally considered to be due to aging of starch, which is the main component of rice. Starch retrogradation progresses with the passage of time in a temperature environment around 60°C to 0°C. Susumu, Rice Cooking and Aging of Starch, Culinary Science, Vol.3, No.4, pp.225-229, 1970).

That is, the deterioration of the texture of cooked rice generally progresses with the lapse of time after cooking or storage at low temperature under a temperature environment of about 60°C to 0°C. The following (i) to (vi) are given as specific examples of such deterioration in texture.
(i) Hardening: The soft texture is reduced and the food becomes hard.
(ii) Decrease in chewy texture: The chewy and elastic texture is reduced, resulting in a crumbly texture.
(iii) Decrease in feeling of grain: grains of cooked rice become difficult to feel in the mouth.
(iv) Decrease in moist feeling: The moist texture is reduced, and the texture becomes dry or dry.
(v) Decreased plumpness: The plumpness of the texture is reduced, resulting in a firmer texture.
(vi) Decrease in overall deliciousness: Overall texture deteriorates, and deliciousness cannot be felt.

In the present invention, whether or not the deterioration of the texture of cooked rice is suppressed can be determined, for example, by storing cooked rice X using the present agent and cooked rice Y not using the present agent under the same conditions for a certain period of time, and then measuring the physical properties. It can be confirmed by measuring each load with a testing machine and comparing them. As a result, if a comparison result is obtained in which the cooked rice X has a smaller load (that is, is softer) than the cooked rice Y, it can be determined that deterioration of the texture is suppressed by the present agent.

Alternatively, whether or not the deterioration of the texture of the cooked rice was suppressed can be determined, for example, by storing the cooked rice X using the present agent and the cooked rice Y not using the present agent under the same conditions for a certain period of time, and then measuring the above (i ) to (vi) are performed as evaluation items, and the results can be compared. As a result, cooked rice X has (i) a lesser degree of hardening (that is, softer), (ii) a greater crispness, (iii) a greater graininess, and (iv) a greater moistness than cooked rice Y. , (v) great plumpness, or (vi) overall good taste, it can be judged that deterioration of texture is suppressed by this agent.

In the present invention, improving the softness of cooked rice means increasing the softness of the texture (making the texture softer) of cooked rice immediately after cooking for about one day.

In the present invention, whether or not the softness of cooked rice is improved is determined, for example, by cooking rice X using the present agent and rice Y not using the present agent under the same conditions, and then using a physical property tester. It can be confirmed by measuring and comparing the load of If the comparison results show that the load on the cooked rice X is smaller than that of the cooked rice Y (that is, it is softer), it can be determined that the softness is improved by the present agent.

This drug contains cellulase as an active ingredient. Cellulase is an enzyme that hydrolyzes cellulose. .1.91) and glucan 1,4-β-glucosidase (EC 3.2.1.74).

Endoglucanases (EG) (EC 3.2.1.4) are enzymes that hydrolyze cellulose chains in an endo-type mode of action to produce glucose, cellobiose and cellooligosaccharides, endo-1,4-β-glucanases, Also called endocellulase. Cellobiohydrolase (EC 3.2.1.91) and glucan 1,4-β-glucosidase (EC 3.2.1.74) act in an exo-type mode of action, releasing cellobiose or glucose from the ends of cellulose chains. to release. Among them, cellobiohydrolase (CBH) is an enzyme that produces cellobiose from the ends of cellulose chains, and is also called cellulose 1,4-β-cellobiositase, avicelase, exocellulase, and the like. β-Glucosidase (EC 3.2.1.21) acts on short-chain cellooligosaccharides, cellobiose and β-glucoside to liberate glucose from non-reducing ends.

In the present invention, the cellulase may be one type of enzyme, or two or more types may be used in combination. A composition (mixture) containing two or more types of cellulases is sometimes referred to as a "mixed cellulase composition" in the present invention. That is, in the present invention, a "mixed cellulase composition" may be used as the cellulase.

Cellulases are known to be produced by many microorganisms ranging from bacteria to filamentous fungi. Examples of cellulase-producing microorganisms include bacteria such as Butyrivibrio fibrisolvens, Cellulomonas fimi, Cellulomonas uda, Cellvibrio gilvus, Clostridium thermocellum, Pseudomonas fluorescence, and Ruminococcus albus. Actinomycetes include Streptomyces lividans, Thermomonospora curvata, and Thermomonospora fusca. Examples of filamentous fungi include Aspergillus aculeatus, Aspergillis niger, Aspergillus oryzae, Chaetomium cellulolyticum, Humicola insolens, Irpex lacteus, Phanerochaete chrysosporium, Penicillium purpurogenum, Schizophyllum commune, Sporotrichum thermophile, Trichoderma reesei, Trichoderma viride, Trichoderma koninngi, and the like.

Cellulases produced by microorganisms such as those exemplified above are commercially available, and they can be used in the present invention. Commercially available cellulases include, for example, "Sumizyme AC" (Shinnihon Kagaku Kogyo), "Cellulase A 'Amano' 3" (Amano Enzyme), "Cellulosine AC40" (HBI), "Cellulosin T3" (HBI), "Cellulase SS” (Nagase ChemteX), “Onozuka RS” (Yakult Pharmaceutical Industry), “Cellulase from Trichoderma sp. Godo Shusei), “Sucrase C” (Mitsubishi Chemical Foods), “Viscamyl Flow” (DuPont), “Laminex” (DuPont), “Cellulase Y-NC” (Yakult Pharmaceutical Industry), “Cellulosein AL8” (HBI), Examples include "Cellulase XL-531" (Nagase ChemteX), "Cellulase Nagase" (Nagase ChemteX), and "Softagen" (Taisho Technos).

Examples of commercially available Trichoderma reesei-derived cellulase preparations include "Celluclast (registered trademark)" (Novozymes), "GODO-TCL" (Godo Shusei Co., Ltd.), and "Besserex (registered trademark)" (Godo Shusei Co., Ltd.). ), “Onozuka 3S” (Yakult Pharmaceutical Industry), “Biocellulase W” (Kerry I & F Cork/Ireland), “Biobake ZIP”, “Cellulase T ‘Amano’ 4” (Amano Enzyme), “Steam C” (new Nippon Kagaku Kogyo), "BAKEZYME X-CELL" (DSM FOOD Speciakties), and "BAKEZYME WholeGain" (DSM FOOD Speciakties).

Examples of the mixed cellulase composition include those containing the following (a) to (d);
(a) a cellulase having 90% or more amino acid sequence identity with SEQ ID NO: 1;
(b) a cellulase having 90% or more amino acid sequence identity with SEQ ID NO:2;
(c) a cellulase having 90% or more amino acid sequence identity with SEQ ID NO:3;
(d) a cellulase having greater than 90% amino acid sequence identity with SEQ ID NO:4;

Here, SEQ ID NO: 1 (514aa) is the amino acid sequence of cellobiohydrolase I (CBHI, Cel7A) derived from QM6a strain, the type strain of Trichoderma reesei (GenBank: EGR44817.1). .

SEQ ID NO: 2 (471aa) is the amino acid sequence of cellobiohydrolase II (CBHII, Cel6A) from Trichoderma reesei strain QM6a (GenBank: EGR51017.1).

SEQ ID NO: 3 (459aa) is the amino acid sequence of endoglucanase I (EGI, Cel7B) from Trichoderma reesei strain QM6a (GenBank: EGR48251.1).

SEQ ID NO: 4 (418aa) is the amino acid sequence of endoglucanase II (EGII, Cel5A) from Trichoderma reesei strain QM6a (GenBank: EGR51020.1).

That is, enzymes (a) to (d) are identical or highly similar to Trichoderma reesei-derived cellulases (CBHI, CBHII, EGI and EGII) in terms of amino acid sequence and enzymatic activity, respectively. can.

Trichoderma reesei produces and secretes a variety of cellulases, but at the protein level, (a) is 40-60%, (b) is 12-20%, (c) is 5-10%, and (d) is 1. These (a) to (d) can be said to be the main enzyme components (Lisa Rosgaard et. al., Biotechnol. Prog. 2007, 23, 1270-1276) (Vinzant, T. B. et. ., Appl. Biochem. Biotechnol. 2001, 91-93, 99-107).

That is, a mixed cellulase composition containing (a) to (d) can be obtained by culturing Trichoderma reesei. Many strains of Trichoderma reesei are available, and any strain can be used in the present invention as long as it does not lose the ability to produce cellulase. Examples of available strains include T. reesei NBRC 31326, T. reesei NBRC 31327, T. reesei NBRC 31328, T. reesei NBRC 31329, T. reesei ATCC 66589, and T. reesei ATCC 26921. can.

Methods for obtaining cellulase by culturing Trichoderma reesei are also known to those skilled in the art (Studies on the production and application of cellulase from Trichoderma reesei QM-9414 Krishna SH, et al. Bioprocess Engineering 22(5), 467- 470, (2000)) (JP 2018-19622). Also in the present invention, a cellulase or a mixed cellulase composition can be obtained by culturing a Trichoderma reesei strain according to such a known method. For example, the medium may be either a synthetic medium or a natural medium, as long as it contains nutrients such as carbon sources, nitrogen sources, inorganic salts, vitamins, etc. necessary for growth of the strain and cellulase production. Cellulase inducers such as cellulose, sophorose, and cellooligosaccharides (cellobiose, cellotriose, cellotetraose, cellopentaose, cellohexaose, etc.) are added to the medium.

Cultivation is preferably carried out under aerobic conditions such as shaking culture or aeration stirring culture. The culture temperature is preferably 10° C. or higher, more preferably 20° C. or higher, more preferably 25° C. or higher, and preferably 50° C. or lower, more preferably 42° C. or lower, more preferably 35° C. or lower. Also, it is preferably 10 to 50°C, more preferably 20 to 42°C, and more preferably 25 to 35°C. The pH during culture is 3-9, preferably 4-5. The culture time is 10 hours to 10 days, preferably 2 to 7 days.

A more specific culture method is exemplified below. First, a 500 mL flask is charged with 50 mL of preculture medium for preculture. Spores of the Trichoderma reesei strain are inoculated here so as to be 1×10 ⁵ spores/mL, and cultured with shaking at 28° C. and 220 rpm for 2 days. Next, as the main culture, 10% (v/v) of the preculture solution is inoculated into a jar fermenter filled with the preculture medium, and cultured at 28° C. and an aeration rate of 0.5 vvm for 5 days. The pH is adjusted to 4.5 with 5% aqueous ammonia, and the stirring rate is varied so that the dissolved oxygen is 3.0 ppm. The composition of the medium is as follows.
Medium _composition for preculture: 1% glucose, 0.14% ( _NH4 ) _2SO4 , _0.2 % _KH2PO4 , 0.03% _CaCl2.2H2O , 0.03% _{MgSO4.7H 2} O, 0.1% meat peptone, 0.05% yeast extract, 0.1% Tween 80, 50 mM tartrate buffer (pH 4.0).
Medium composition for main culture: 10% crystalline _cellulose , 0.42% ( _NH4 ) _2SO4 , 0.2% _KH2PO4 , 0.03% _CaCl2.2H2O , _0.03 % _MgSO4 • _7H2O , 0.1% meat peptone, 0.05% yeast extract, 0.1% Tween 80, 0.2% antifoam.

After the culture is completed, the culture is collected, and if necessary, the bacterial cells are disrupted by ultrasonic waves or pressurization. After solid-liquid separation by filtration or centrifugation, ultrafiltration, salting out, dialysis, chromatography Cellulases or mixed cellulase compositions can be extracted and purified by appropriate combination of lithography and the like. The degree of purification is not particularly limited. The culture supernatant or its crudely purified product itself can also be used as a cellulase or mixed cellulase composition. In addition, the cellulase-containing solution may be used as it is in liquid form, or may be used as a powdery composition obtained by vacuum drying or freeze drying.

In addition, the QM6a strain, which is the type strain of Trichoderma reesei, has been sequenced (Diego Martinez et. al., Nature Biotechnology, Vol. 26, Num. 5, May 2008). Therefore, cellulase derived from Trichoderma reesei can also be obtained by gene recombination technology. In this method, the cellulases (a), (b), (c) and/or (d) may be expressed in a suitable expression system. That is, after inserting a nucleic acid sequence encoding (a), (b), (c) and/or (d) into a suitable vector to obtain a recombinant vector, the recombinant vector is transferred to a suitable host. to obtain a transformant. Then, by culturing the resulting transformant to express (a), (b), (c) and/or (d), a cellulase or mixed cellulase composition can be obtained from the culture.

In addition, cellulases are chemically synthesized according to chemical synthesis methods such as the Fmoc method (fluorenylmethyloxycarbonyl method) and the tBoc method (t-butyloxycarbonyl method) based on known amino acid sequence information such as SEQ ID NOs: 1 to 4. In addition to being able to be synthesized, it can also be chemically synthesized using various commercially available peptide synthesizers.

The activity of cellulase can be measured by quantifying reducing ends produced by an enzymatic reaction (hydrolysis) using carboxymethylcellulose (CMC) as a substrate using a dinitrosalicylic acid reagent or the Somogyi-Nelson method. For example, the enzyme solution is added to a 1% CMC substrate solution, the enzyme reaction is allowed to proceed for a certain period of time, and then the enzyme reaction is stopped by boiling or the like. Take 0.1 mL of the enzyme reaction solution in a test tube, add 0.3 mL of dinitrosalicylic acid reagent, mix well, cover with a glass bulb and boil for 5 minutes. After cooling with tap water, 2.5 mL of distilled water is added to dilute, and the absorbance at 500 nm is measured to quantify reducing sugars. There is a positive correlation between the magnitude (intensity) of cellulase activity and the amount of reducing sugar produced.

One unit of cellulase activity is defined as the amount of enzyme that liberates 1.0 μmole of glucose from a substrate cellulose (e.g., carboxymethylcellulose) at pH 5.0, 37° C. for 1 hour (incubation for 2 hours). can be done.

The enzyme reaction conditions for cellulase depend on its type and origin. 60 to 65° C., and pH 4 to 6 can be exemplified as the optimum pH.

The identity of amino acid sequences can be confirmed according to conventional methods, for example, FASTA (http://www.genome.JP/tools/fasta/), Basic local alignment search tool (BLAST; http://www. ncbi.nlm.nih.gov.) and Position-Specific Iterated BLAST (PSI-BLAST; http://www.ncbi.nlm.nih.gov.). The term “identity” refers to consistency and is used interchangeably with “identity”.

Reduced starch syrup is a kind of sugar alcohol obtained by reducing starch syrup. Here, starch syrup is a substance obtained by saccharifying starch with acid or enzyme, and is a mixture of monosaccharide (glucose) and polysaccharide (oligosaccharide, dextrin, etc.). Therefore, the reduced starch syrup is also a mixture containing two or more sugar alcohols among monosaccharide sugar alcohols and polysaccharide sugar alcohols (disaccharide, trisaccharide, tetrasaccharide, pentasaccharide or more).

Reduced starch syrup is sometimes classified into high-saccharified reduced starch syrup, medium-saccharified reduced starch syrup and low-saccharified reduced starch syrup according to the degree of saccharification. In the present invention, among these, medium-saccharified and reduced starch syrup and/or low-saccharified and reduced starch syrup are preferably used.

Specifically, the sugar composition of the medium-saccharified reduced starch syrup includes (a) a sugar composition containing less than 30% by mass of monosaccharides and less than 50% by mass of pentasaccharides or higher, or (d) 2 to 10% by mass of monosaccharides. %, 15-55% by weight of disaccharides, 15-65% by weight of trisaccharides, 1-15% by weight of tetrasaccharides and 1-38% by weight of pentasaccharides and higher.

Specifically, the sugar composition of the low-saccharification reduced starch syrup includes (a) a sugar composition containing 50% by mass or more of pentasaccharide or higher, or (e) 1 to 10% by mass of monosaccharides and 6 to 21% of disaccharides. 7-23% by weight of trisaccharides, 5-13% by weight of tetrasaccharides and 50-82% by weight of pentasaccharides and higher.

In the present invention, the sugar composition refers to the ratio of each sugar to the total sugar mass expressed as a percentage. That is, it is the mass percentage of each saccharide when the total mass of saccharides is 100.

Sugar composition can be confirmed using high performance liquid chromatography (HPLC). That is, a chromatogram is obtained by subjecting the reduced starch syrup to HPLC as a sample. In the chromatogram, the sum of the areas of all peaks corresponds to the "total sugar mass", and the area of each peak corresponds to the "mass of each sugar". Therefore, the mass percentage of each sugar in the sample can be calculated as the ratio of the area of each peak to the sum of the areas of all detected peaks. The conditions for HPLC can be appropriately set according to standard methods, and the following conditions can be exemplified.
<<Conditions of HPLC>>
Column; MCI GEL CK04S (10mm ID x 200mm)
Eluent; high pure water flow rate; 0.4 mL/min injection volume; 20 μL
Column temperature; 65°C
Detection; Differential refractive index detector RI-10A (Shimadzu Corporation)

Since the reduced starch syrup is produced by reducing the starch syrup, the degree of saccharification of the reduced starch syrup conforms to the degree of saccharification of the starch syrup. That is, the higher the degree of saccharification of the raw starch syrup, the higher the degree of saccharification of the reduced starch syrup, and the lower the degree of saccharification of the raw starch syrup, the lower the degree of saccharification of the reduced starch syrup. A dextrose equivalent value (DE) is generally used as an index of the degree of saccharification of starch syrup. DE is the ratio (percentage) of the reducing sugar to the total solid content when the reducing sugar in the sample is measured as glucose. The maximum value of DE is 100, which means that all the solid content is glucose, and the smaller the DE, the more oligosaccharides and polysaccharides are.

That is, the DE of the raw material starch syrup for medium-saccharified reduced starch syrup can be exemplified by more than 30, 31 or more, 32 or more, 45 or less, 46 or less, 47 or less, 48 or less, 49 or less, and 50 or less.

Examples of the DE of raw starch syrup for low-saccharification reduced starch syrup include 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, and 30 or less.

In addition, as the DE of the raw material starch syrup for medium-saccharified to low-saccharified reduced starch syrup, (c) 10 or more and 50 or less can be exemplified.

The DE of starch syrup can be measured by the following method.
《How to measure DE》
Accurately weigh 2.5 g of the sample and dissolve it in water to make 200 mL. Measure 10 mL of this solution, add 10 mL of 1/25 mol/L iodine solution (Note 1) and 15 mL of 1/25 mol/L sodium hydroxide solution (Note 2), and leave in a dark place for 20 minutes. Next, after adding 5 mL of 2 mol/L hydrochloric acid (Note 3) and mixing, titrate with 1/25 mol/L sodium thiosulfate solution (Note 4). When the liquid turns slightly yellow near the end point of titration, add 2 drops of starch indicator (Note 5) and continue the titration until the color of the liquid disappears. A blank value is obtained using water, and DE is obtained from the following equation (1).
(Note 1) 1/25 mol/L iodine solution: Put 20.4 g of potassium iodide and 10.2 g of iodine into a 2 L volumetric flask, dissolve with a small amount of water, and add water up to the marked line.
(Note 2) 1/25 mol/L sodium hydroxide solution: Put 3.2 g of sodium hydroxide into a 2 L volumetric flask, dissolve with a small amount of water, and add water up to the marked line.
(Note 3) 2 mol/L hydrochloric acid: Gradually add 150 mL of hydrochloric acid to 750 mL of water while stirring.
(Note 4) 1/25 mol/L sodium thiosulfate solution: Put 20 g of sodium thiosulfate into a 2 L volumetric flask, dissolve with a small amount of water, and add water up to the marked line.
(Note 5) Starch indicator: Dissolve 5 g of soluble starch in 500 mL of water, and dissolve 100 g of sodium chloride therein.

In the present invention, a commercially available reduced starch syrup may be used as it is, or it may be produced and used according to a method known to those skilled in the art. Examples of commercially available medium-saccharified reduced starch syrup include "Sweet OL", "Sweet G3", "SE 57" and "SE 58" (manufactured by Bussan Food Science). , “Sweet NT”, “SE 30” and “SE 100” (manufactured by Bussan Food Science).

A known method for producing reduced starch syrup includes a reduction reaction in which hydrogen is added to starch syrup (raw sugar). In the reduction reaction by hydrogenation, for example, a 40 to 75% by mass raw sugar aqueous solution is charged into a high-pressure reactor together with a reduction catalyst, the hydrogen pressure in the reactor is 4.9 to 19.6 MPa, and the reaction liquid temperature is is adjusted to 70 to 180° C., and the reaction is carried out with stirring until hydrogen absorption is no longer observed. Thereafter, the reduced catalyst is separated, decolorized and desalted by ion-exchange resin treatment and, if necessary, activated carbon treatment, etc., and then concentrated to a predetermined concentration, whereby high-concentration reduced starch syrup can be produced.

Cellulase or cellulase and reduced starch syrup can be blended and used as one material in the process of producing cooked rice, like seasonings such as sugar and other additives. Preferably, it is used by adding to rice or water in which rice is soaked before or during rice cooking. Cellulase and reduced starch syrup may be added at the same time or at different times.

That is, the method for producing cooked rice according to the present invention has a step of adding this agent and cooking rice. The method may include other steps as long as they do not impair the features of the present invention. Such processes include, for example, a food material mixing process, a seasoning process, a molding process, a cooling process, a packaging process, a sterilization process, and the like.

The amount of cellulase to be added (addition amount) can be appropriately set according to the type of rice, the desired texture and taste, the presence/absence/type/amount of auxiliary materials, and the like. As a specific blending amount, 0.07 to 700 units of cellulase can be exemplified per 100 parts by weight of rice.

The blending amount (addition amount) of the reduced starch syrup can also be appropriately set according to the type of rice, the desired texture and taste, the presence/absence/type/amount of auxiliary materials, and the like. As a specific amount, the lower limit of the reduced starch syrup per 100 parts by weight of rice is 0.1 parts by weight or more, 0.15 parts by weight or more, 0.2 parts by weight or more, 0.25 parts by weight or more, 0 .3 parts by weight or more and 0.35 parts by weight or more can be exemplified. In addition, the upper limit of the reduced starch syrup is 10 parts by weight or less, 9.5 parts by weight or less, 9 parts by weight or less, 8.5 parts by weight or less, 8 parts by weight or less, or 7.5 parts by weight with respect to 100 parts by weight of rice. Below, 7 parts by weight or less can be exemplified.

Hereinafter, the present invention will be described based on each embodiment. However, the technical scope of the present invention is not limited to the features shown by these examples.

<Test method>
(1) Improver In this example, cellulase and/or reduced starch syrup were used as improvers.

Cellulases were commercially available products shown in Table 1 unless otherwise specified. The commercial product "Celluclast 1.5L" is a mixed cellulase composition containing (a) to (d) derived from Trichoderma reesei (Lisa Rosgaard et. al., Biotechnol. Prog. 2007, 23, 1270 -1276).

Commercial products shown in Table 2 were used as the reduced starch syrup.

(2) Rice Cooking Rice was cooked according to the following procedures <1> to <7>.
<1> Wash-free rice was soaked in water for 1 hour.
<2> The water used for soaking was discarded, and only the soaked rice (soaked rice) was used.
<3> Fresh water and bacteriostatic agent, salad oil, cellulase and reduced starch syrup were added to the soaked rice. The details of the amount of each substance to be added are shown in the formulation of each example. is 0 to 7% by mass (solid content concentration)). The amount of cellulase was 0.35 U per 100 g of rinse-free rice.
<4> Rice was cooked in a rice cooker to obtain rice.
<5> After the cooked rice was loosened, it was subdivided into portions of about 170 g and placed in containers with lids.
<6> The boiled rice was allowed to cool at room temperature for 15 minutes without covering the container.
<7> The lid of the container was closed and the cooked rice was stored at 20°C or 5°C for 2 hours to 5 days.

(3) Measurement of load About 15 g of cooked rice was placed in a cup and compressed using a creep meter RE2-33005C (Yamaden) circular plunger at a compression rate of 1.0 mm/sec until it was compressed and deformed by 50% by volume. , the load (N) was measured. Eight specimens were performed for each sample, and the average value was calculated for the maximum load.

(4) Sensory test A sensory test was performed by eating cooked rice by an analytical panel consisting of 2 to 7 persons (A to Ko). The evaluation sheet used for the sensory test is shown in FIG. As shown in FIG. 1, the evaluation items were four items of "softness", "sticky feeling", "grainy feeling" and "moist feeling". The above four items were scored by each panel on a five-point scale from 1 to 5 according to the criteria shown below, with Sample 1 (without improver) as the standard of 3 points.
"Softness" 5 points: clearly soft, 4 points: slightly soft, 3 points: equivalent to sample 1, 2 points: slightly hard, 1 point: clearly hard.
“Moist feeling” 5 points: clearly strong sticky feeling, 4 points: slightly strong sticky feeling, 3 points: equivalent to sample 1, 2 points: slightly brittle texture, 1 point: obviously brittle texture .
"Grainy feel" 5 points: Clearly strong grainy feel, 4 points: Slightly strong grainy feel, 3 points: Same as sample 1, 2 points: Slightly weak grainy feel, 1 point: Clearly weak grainy feel.
"Moist feeling" 5 points: obviously strong moist feeling, 4 points: slightly strong moist feeling, 3 points: equivalent to sample 1, 2 points: slightly strong dry feeling, 1 point: clearly strong dry feeling.

The scoring results were obtained by averaging the scores of all panels for each sample and rounding off to the second decimal place to obtain the score. In addition, the average value of the evaluation points of the above four items was calculated, and this was used as the evaluation point of the "comprehensive evaluation".

<Example 1> Effect of improving the softness of cooked rice Cooked rice was produced by cooking rice according to the formulation shown in Table 3, and stored for 2 hours.

The load of the cooked rice stored for 2 hours was measured by test method (3). The results are shown in FIG. As shown in FIG. 2, all of Samples 2 to 5 had a smaller load than Sample 1. In particular, the load of sample 2 was remarkably small. That is, the samples blended with "cellulase", "low saccharification reduced starch syrup", "medium saccharification reduced starch syrup" or "cellulase and low saccharification reduced starch syrup" were softer than the samples not blended. In particular, the sample containing "cellulase" was remarkably soft. From these results, it was clarified that adding "cellulase", "low saccharification reduced starch syrup", "medium saccharification reduced starch syrup" or "cellulase and low saccharification reduced starch syrup" can improve the softness of cooked rice.

<Example 2> Effect of suppressing deterioration of texture during storage at room temperature Cooked rice was produced by cooking with the formulation shown in Table 4, and stored at 20°C for 5 days.

(1) Measurement of load The load of cooked rice stored at 20°C for 5 days was measured according to test method (3). The results are shown in FIG. As shown in FIG. 3, all of Samples 2 to 6 had a smaller load than Sample 1. In particular, the loads of Samples 2 and 6 were remarkably small. In other words, the samples containing "cellulase", "low saccharification reduced starch syrup", "medium saccharification reduced starch syrup", "cellulase and low saccharification reduced starch syrup" or "cellulase, low saccharification reduced starch syrup and medium saccharified reduced starch syrup" were not mixed. It was soft compared to the sample. In particular, the samples containing "cellulase" or "cellulase, low-saccharification-reduced starch syrup and medium-saccharification-reduced starch syrup" were remarkably soft. From these results, when "cellulase", "low saccharification reduced starch syrup", "medium saccharification reduced starch syrup", "cellulase and low saccharification reduced starch syrup" or "cellulase, low saccharification reduced starch syrup and medium saccharified reduced starch syrup" are added, It became clear that the hardening of boiled rice with the passage of time can be suppressed.

(2) Sensory evaluation The cooked rice stored at 20°C for 5 days was subjected to a sensory test by three panelists (A to C) according to test method (4). The results are shown in FIG. As shown in FIG. 4, sample 2 (cellulase) had higher evaluation points for "softness" and "sticky feeling" than sample 1 (no improver), and had higher scores for "grainy feeling" and "moist feeling". were equivalent. In addition, the "comprehensive evaluation" was higher than that of sample 1. From these results, it was clarified that the addition of cellulase can suppress the deterioration of the texture of cooked rice (hardening, decrease in chewy texture) over time after cooking.

Next, sample 3 (low saccharification reduced starch syrup) had a higher evaluation score for "grain feeling" than sample 1 (no improver), but "softness", "sticky feeling" and "moist". The score for “feeling” was low. "Comprehensive evaluation" was equivalent to Sample 1. From these results, it was clarified that low-saccharification-reduced starch syrup alone is not sufficient to suppress the deterioration of the texture of cooked rice (hardening, decrease in stickiness, decrease in moistness) over time after cooking. rice field.

Next, sample 4 (medium saccharified reduced starch syrup) had a lower evaluation score for "grain feeling" than sample 1 (no improver), but had "softness", "sticky feeling" and "moist feeling". The evaluation score for “feeling” was high. The "comprehensive evaluation" was higher than sample 1. From these results, it was clarified that the addition of medium saccharification reduced starch syrup can suppress the deterioration of the texture of cooked rice (hardening, decrease in sticky feeling, decrease in moist feeling) over time after cooking.

Next, sample 5 (low-saccharification-reduced starch syrup and cellulase) was compared to sample 1 (no improver), and all of "softness", "sticky feeling", "grainy feeling" and "moist feeling" It was highly rated. The "overall evaluation" was significantly higher than sample 1. Compared to sample 2 (cellulase) and sample 3 (low-saccharification-reduced starch syrup), sample 5 had the highest "softness", "sticky feeling", "moist feeling" and "overall evaluation". In addition, as for the evaluation points of sample 5, a synergistic effect was observed in comparison with samples 2 and 3 in "softness", "sticky feeling", "moist feeling" and "comprehensive evaluation". From these results, when low-saccharification-reduced starch syrup and cellulase are added together, the deterioration of the texture of cooked rice (hardening, reduction in stickiness, reduction in graininess, and reduction in moistness) over time after cooking is remarkably improved. It turned out that it can be suppressed.

Finally, sample 6 (low-saccharification-reduced starch syrup, medium-saccharification-reduced starch syrup, and cellulase) had "softness", "stickiness", "graininess" and "moistness" compared to sample 1 (no improver). All of the evaluation points for "feeling" were high. The "overall evaluation" was significantly higher than sample 1. Even when compared with sample 2 (cellulase), sample 3 (low saccharified reduced starch syrup) and sample 4 (medium saccharified reduced starch syrup), sample 6 was the highest in terms of "sticky feeling", "moist feeling" and "overall evaluation". rice field. In addition, in sample 6, the amount of low-saccharification reduced starch syrup and medium-saccharification reduced starch syrup added was half that of samples 3 and 4, respectively, and the total amount of reduced starch syrup added was equal. there is In view of this, the evaluation points of sample 6, compared to samples 2, 3, and 4, are "sticky feeling", "grainy feeling", "moist feeling" and "overall evaluation", synergistic effect It was observed. From these results, it was found that when low-saccharification-reduced starch syrup, medium-saccharification-reduced starch syrup, and cellulase were added together, the texture of cooked rice deteriorated over time after cooking (hardening, reduction in stickiness, reduction in graininess, and reduction in moistness). It became clear that the decrease in

<Example 3> Effect of suppressing deterioration of texture during refrigerated storage Cooked rice was produced by cooking rice according to the formulation shown in Table 4 of Example 2, and stored at 5°C for 1 to 2 days.

(1) Measurement of load The load of cooked rice stored at 5°C for 1 day was measured according to test method (3). The results are shown in FIG. As shown in FIG. 5, all of Samples 2 to 6 had a smaller load than Sample 1. In particular, the loads of Samples 2, 3, 4 and 6 were remarkably small. In other words, the samples containing "cellulase", "low saccharification reduced starch syrup", "medium saccharification reduced starch syrup", "cellulase and low saccharification reduced starch syrup" or "cellulase, low saccharification reduced starch syrup and medium saccharified reduced starch syrup" were not mixed. It was soft compared to the sample. In particular, samples blended with "cellulase", "low saccharification reduced starch syrup", "medium saccharification reduced starch syrup" or "cellulase, low saccharification reduced starch syrup and medium saccharified reduced starch syrup" were remarkably soft. Based on these results, adding "cellulase,""low-saccharification-reduced starch syrup,""medium-saccharification-reduced starch syrup,""cellulase and low-saccharification-reduced starch syrup," or "cellulase, low-saccharification-reduced starch syrup, and medium-saccharification-reduced starch syrup" can be stored at low temperatures. It became clear that hardening of the boiled rice which accompanies can be suppressed.

(2) Sensory Evaluation The cooked rice stored at 5° C. for 2 days was subjected to a sensory test by 6 panelists (A, Otsu, Ding-Kung) according to test method (4). The results are shown in FIG. As shown in FIG. 6, sample 2 (cellulase) had a lower evaluation score for "sticky feeling" than sample 1 (no improver), but "softness", "graininess" and " Moist feeling” score was high. In addition, the "comprehensive evaluation" was higher than that of sample 1. From these results, it was clarified that the addition of cellulase can suppress the deterioration of the texture of cooked rice (hardening, deterioration of graininess, deterioration of moistness) due to low-temperature storage.

Next, sample 3 (low saccharification reduced starch syrup) has all the evaluation points of "softness", "sticky feeling", "granular feeling" and "moist feeling" compared to sample 1 (no improver). it was high. In addition, the "comprehensive evaluation" was higher than that of sample 1. From these results, it was clarified that the addition of low-saccharification-reduced starch syrup can suppress the deterioration of the texture of cooked rice (hardening, reduction in chewy texture, reduction in graininess, reduction in moistness) associated with low-temperature storage.

Next, sample 4 (medium saccharified reduced starch syrup) has higher evaluation points for "softness", "sticky feeling" and "grainy feel" than sample 1 (no improver), and "moist feeling". were equivalent. The "comprehensive evaluation" was higher than sample 1. From these results, it was clarified that the addition of medium-saccharified reduced starch syrup can suppress the deterioration of the texture of cooked rice (hardening, reduction in chewy texture, reduction in graininess) that accompanies low-temperature storage.

Next, sample 5 (low-saccharification-reduced starch syrup and cellulase) was compared to sample 1 (no improver), and all of "softness", "sticky feeling", "grainy feeling" and "moist feeling" It was highly rated. The "overall evaluation" was significantly higher than sample 1. Compared to sample 2 (cellulase) and sample 3 (low-saccharification-reduced starch syrup), sample 5 had the highest "softness", "sticky feeling", "moist feeling" and "overall evaluation". In addition, as for the evaluation points of sample 5, a synergistic effect was observed in comparison with samples 2 and 3 in "softness", "sticky feeling", "moist feeling" and "comprehensive evaluation". From these results, it was found that the combined addition of low-saccharification-reduced starch syrup and cellulase can remarkably suppress the deterioration of the texture of cooked rice (hardening, reduction in stickiness, reduction in graininess, and reduction in moistness) associated with low-temperature storage. It was revealed.

Finally, sample 6 (low-saccharification-reduced starch syrup, medium-saccharification-reduced starch syrup, and cellulase) had "softness", "stickiness", "graininess" and "moistness" compared to sample 1 (no improver). All of the evaluation points for "feeling" were high. The "overall evaluation" was significantly higher than sample 1. Even when compared with sample 2 (cellulase), sample 3 (low saccharification reduced starch syrup) and sample 4 (medium saccharification reduced starch syrup), "softness", "sticky feeling", "moist feeling" and "comprehensive evaluation" Sample 6 was the highest. In addition, in sample 6, the amount of low-saccharification reduced starch syrup and medium-saccharification reduced starch syrup added was half that of samples 3 and 4, respectively, and the total amount of reduced starch syrup added was equal. there is In view of this, the evaluation points of sample 6, compared to samples 2, 3, and 4, are synergistic in "softness", "sticky feeling", "moist feeling" and "overall evaluation". It was observed. From these results, it was found that when low-saccharification-reduced starch syrup, medium-saccharification-reduced starch syrup, and cellulase were added together, deterioration in the texture of cooked rice (hardening, reduction in stickiness, reduction in graininess, and reduction in moistness) associated with low-temperature storage was observed. It became clear that it can suppress remarkably.

<Example 4> Examination of the amount of reduced starch syrup to be added Rice was cooked according to the formulation shown in Table 5 to produce boiled rice, which was stored at 20°C for 5 days. Sample 1 is cooked rice containing no improver, and Samples 2 to 8 are cooked rice mixed with cellulase, moderately saccharified reduced starch syrup and low saccharified reduced starch syrup. The amount of cellulase added was 5 ppm (0.35 U per 100 g of uncooked rice) for each of Samples 2 to 8. The amount of reduced starch syrup to be added is between 0.35 and 7% by mass (solid content concentration, outer ratio) of uncooked rice, and varies from sample to sample. The ratio of the medium saccharified reduced starch syrup and the low saccharified reduced starch syrup was 1:1 for all samples 2-8.

(1) Measurement of load Of the cooked rice stored at 20 ° C. for 5 days, sample 1 (no improver, 0%), sample 2 (0.35%), sample 3 (0.7%), sample 5 (2 .1%), Sample 6 (3.5%) and Sample 8 (7%) were measured for load by test method (3). The results are shown in FIG. As shown in FIG. 7, compared with sample 1, sample 2, sample 3, sample 5, sample 6 and sample 8 all had smaller loads. In particular, the loads of samples 2, 3, 5 and 6 were remarkably small. That is, when the concentration of the reduced starch syrup added was 0.35%, 0.7%, 2.1%, 3.5% and 7%, the cooked rice was softer than the sample containing no improver. rice field. From these results, it was clarified that reduced starch syrup can suppress hardening of cooked rice with the lapse of time after cooking, regardless of its concentration.

(2) Sensory evaluation The cooked rice stored at 20°C for 5 days was subjected to a sensory test by two panelists (A and B) according to test method (4). The results are shown in FIG.

As shown in FIG. 8, the evaluation points for “softness” and “moist feeling” were higher than those of sample 1 (0%) for all of sample 2 (0.35%) to sample 8 (7%). it was high. The evaluation score of “sticky feeling” was lower in sample 8 than in sample 1, but was higher in samples 2 to 7 (5.6%) than in sample 1. Sample 3 (0.7%) had the same evaluation score as Sample 1, but Samples 2 and 4 (1.4%) to Sample 8 scored higher than Sample 1. rice field. All of Samples 2 to 8 had a higher “comprehensive evaluation” than Sample 1.

That is, when the concentration of the reduced starch syrup was 0.35%, 0.7%, 1.4%, 2.1%, 3.5%, 5.6% and 7%, the improver was added. Softness, sticky feeling, grainy feeling and/or moist feeling were greater than those of the samples not blended. From these results, reduced starch syrup can suppress the deterioration of the texture of cooked rice (hardening, decrease in chewy texture, decrease in graininess and/or decrease in moist texture) over time after cooking, regardless of the addition concentration. became clear.

<Example 5> Investigation of types of enzymes Rice was cooked according to the formulation shown in Table 6 to produce rice, which was stored at 20°C for 5 days. However, the cellulase is a commercial product shown in Table 1 of test method (1) (referred to as "cellulase A" in this Example 5) and a commercially available cellulase derived from filamentous fungi (referred to as "cellulase B" in this Example 5). was used. Sample 1 is cooked rice containing no improver. As improvers, sample 2 is cellulase A, sample 3 is cellulase B, and samples 4 and 5 are cooked rice blended with cellulase A or cellulase B and moderately saccharified reduced starch syrup or low saccharified reduced starch syrup. Specifications for Cellulase B are shown below.

Cellulase B: 1100 CUN/g (liquid product). Derived from the genus Aspergillus. It has both endo-type and exo-type cellulase activities. Optimal pH; pH 3-5. Optimal temperature: 40-70°C (pH 4.5). Heat resistance; up to 60°C (residual activity of 90% or more, pH 4.5, 60 minutes).
* 1 CUN is the activity that generates a reducing power equivalent to 1 μmole of glucose per minute when 1 mL of the enzyme solution is added to 4 mL of 0.625% CMC-Na (pH 5.5) and allowed to act at 40°C for 30 minutes. and

(1) Measurement of load Load was measured for samples 2 to 5 of the cooked rice stored at 20°C for 5 days according to test method (3). The results are shown in FIG. As shown in FIG. 9, sample 2 (cellulase A) and sample 3 (cellulase B) had equivalent loads. Moreover, sample 4 (cellulase A and reduced starch syrup) and sample 5 (cellulase B and reduced starch syrup) had the same load. That is, the cooked rice containing cellulase B had the same hardness as the cooked rice containing cellulase A. From these results, it was clarified that cellulase can suppress hardening of cooked rice over time after cooking, regardless of the type of cellulase.

(2) Sensory evaluation The cooked rice stored at 20°C for 5 days was subjected to a sensory test by two panelists (A and B) according to test method (4). The results are shown in FIG.

As shown in FIG. 10, first, when sample 2 (cellulase A) and sample 3 (cellulase B) are compared, the evaluation points for "softness", "sticky feeling" and "moist feeling" are the same for sample 2 and Sample 3 had the same value. Sample 3 was lower than Sample 1, and Sample 2 was higher than Sample 1 only for the "graininess". The "comprehensive evaluation" of sample 2 was slightly higher, but almost the same. Next, when sample 4 (cellulase A and reduced starch syrup) and sample 5 (cellulase B and reduced starch syrup) are compared, sample 4 and sample 5 have the same evaluation points for "softness" and "moist feeling". there were. Although Sample 4 scored higher for "sticky feel", "grainy feel" and "comprehensive evaluation", they were almost the same.

That is, the cooked rice containing cellulase B had the same softness, stickiness, graininess and moistness as the cooked rice containing cellulase A. From these results, it is clear that cellulase, regardless of its type, can suppress the deterioration of the texture of cooked rice (hardening, reduction in stickiness, reduction in graininess, and/or reduction in moistness) over time after cooking. Became.

Claims (7)

An agent for suppressing deterioration of cooked rice texture, containing cellulase as an active ingredient. An agent for improving the softness of cooked rice containing cellulase as an active ingredient. 3. The agent according to claim 1 or 2, wherein the cooked rice is cooked rice obtained by cooking portioned rice or polished rice. The agent according to any one of claims 1 to 3, further comprising a reduced starch syrup selected from the following (a) to (c) as an active ingredient;
(a) reduced starch syrup having a sugar composition of less than 30% by mass of monosaccharides and less than 50% by mass of pentasaccharides or higher;
(a) reduced starch syrup having a sugar composition of 50% by mass or more of pentasaccharide or higher;
(c) Reduced starch syrup obtained by reducing starch syrup having a dextrose equivalent of 10 or more and 50 or less. 4. The agent according to claim 3, wherein the reduced starch syrup is used at a solid content concentration of 0.3 parts by weight or more and 7 parts by weight or less per 100 parts by weight of uncooked rice. The agent according to any one of claims 1 to 5, wherein the cellulase is a mixed cellulase composition containing the following (a) to (d);
(a) a cellulase having 90% or more amino acid sequence identity with SEQ ID NO: 1;
(b) a cellulase having 90% or more amino acid sequence identity with SEQ ID NO:2;
(c) a cellulase having 90% or more amino acid sequence identity with SEQ ID NO:3;
(d) a cellulase having greater than 90% amino acid sequence identity with SEQ ID NO:4; A method for producing cooked rice, comprising the step of adding the agent according to any one of claims 1 to 6 and cooking the rice.

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