JP2023092981A - Frozen cooked rice improving agent, frozen cooked rice, cooked rice obtained by naturally thawing frozen cooked rice, and method of producing frozen cooked rice - Google Patents

Abstract

To provide frozen cooked rice from which cooked rice having excellent softness, stickiness, and granular feeling can be obtained even when naturally thawed after freezing, and to provide a frozen cooked rice improving agent used to realize such properties.SOLUTION: Provided is an improver for frozen cooked rice that is naturally thawed for consumption, wherein the raw material rice of the frozen cooked rice is rice satisfying specific conditions for amylose content [X] and moisture content [Y], the whole of the improver contains 0.0014-0.047% by weight (solid content equivalent) of a specific extract of a plant belonging to the Brassicaceae family, and contains 5000-166500 units of α-glycosyltransferase and 150-5000 units of α-amylase with respect to 100 g of the improver, and the α- glycosyltransferase/alpha-amylase (enzyme activity ratio) is 0.5 to 500.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to frozen cooked rice that is naturally thawed after freezing and suitable for eating as it is.

Frozen cooked rice is thawed by heating with a microwave oven, thawing naturally, and cooked rice such as pilaf is thawed by heating and thawing by direct fire. For cooked rice foods that are preferred to be warm, thawing by heating with a microwave oven or an open flame is desirable. There are some foods that should not be thawed, and in recent years, there has been a demand for frozen cooked rice foods that can be easily and deliciously eaten simply by natural thawing without the use of equipment.

However, frozen boiled rice prepared using raw material rice with a low water content or a relatively high amylose content will have a hard and non-sticky texture when thawed naturally. Therefore, when using such a raw material rice, the amount of water is increased compared to normal rice cooking conditions. declines markedly.

Therefore, in Patent Document 1, in order to obtain a cooked rice food that can maintain the quality before freezing even in natural thawing and can be eaten unheated after thawing, sucrose fatty acid esters with an HLB of 8 or more, edible oils and fats, and sugar compounds Disclosed is a modifier composition for frozen cooked rice obtained by spray-drying an oil-in-water emulsion containing However, when the frozen cooked rice using the modifier composition for frozen cooked rice is naturally thawed, it is hard and lacks stickiness, and the emulsifiers and fats used give off-flavours and off-flavours.

JP-A-2001-275590

It is an object of the present invention to provide frozen cooked rice that can give cooked rice with good softness, stickiness and graininess even when it is naturally thawed after freezing, and to provide a frozen cooked rice improver used therefor.

The inventors of the present invention have made intensive studies to solve the above problems, and as a result, a frozen product containing a specific amount of an extract of a plant belonging to the Brassicaceae family, α-glycosyltransferase, and α-amylase in raw rice The inventors have found that cooked rice cooked by adding a rice improver and a specific amount of water has good softness, stickiness, and grainy texture even when it is naturally thawed after freezing, leading to the completion of the present invention. .

That is, the first aspect of the present invention is a frozen cooked rice improver, wherein the raw rice of the frozen cooked rice has an amylose content [X] (% by weight) and a water content [Y] (% by weight) that meet the following conditions (A ) or (B), in the entire frozen cooked rice improver, 0.0014 to 0.047% by weight (in terms of solid content) of the extract of a plant belonging to the Brassicaceae family, and 100 g of the improver In contrast, the extract contains 5,000 to 166,500 units of α-glycosyltransferase and 150 to 5,000 units of α-amylase, and the α-glycosyltransferase/α-amylase (enzyme activity ratio) is 0.5 to 500. is a mixture in which the amount of plants belonging to the Brassicaceae (wet weight) / the total amount of water and ethanol (weight ratio) is 0.05 to 10, is extracted at 5 to 160 ° C. for 0.1 to 36 hours. Later, it relates to an improver for frozen boiled rice to be eaten after natural thawing, which is an extract from which the residue of the extract of a plant belonging to the Brassicaceae family has been removed.
[Condition (A)] 11.5≦X<19 and 11≦Y<7.0+8.5×{1−[(X−19.0)/8.5] ² } ^1/2
[Condition (B)] 19≤X≤25 and 11≤Y≤15.5

It is preferable that the improving agent for frozen cooked rice contains 0.1 to 3.3% by weight of HM pectin based on the whole improving agent for frozen cooked rice.

The second aspect of the present invention is frozen cooked rice prepared by cooking a raw material for rice cooking and then freezing the rice, wherein the raw material for rice cooking includes raw rice, solids contained in an extract of a plant belonging to the Brassicaceae family, water, α -Contains glycosyltransferase and α-amylase, and the solid content contained in the extract of a plant belonging to the Brassicaceae family is 0.000014 to 0.0014 parts by weight and water is 150 to 150 parts by weight per 100 parts by weight of the raw rice 190 parts by weight, and 50 to 5000 units of α-glycosyltransferase and 1.5 to 150 units of α-amylase per 100 g of the raw rice, and the α-glycosyltransferase/α-amylase (enzyme activity ratio ) is 0.5 to 500, and the raw rice is rice that satisfies the conditions (A) or (B) in amylose content [X] (% by weight) and water content [Y] (% by weight). It relates to frozen boiled rice for eating after natural thawing.

In the frozen cooked rice, the raw material for rice cooking preferably contains 0.001 to 0.1 parts by weight of HM pectin with respect to 100 parts by weight of the raw material rice.

In the frozen cooked rice, the raw material for cooking rice preferably contains 1 to 3 parts by weight of the improving agent for frozen cooked rice with respect to 100 parts by weight of the raw rice.

The third aspect of the present invention relates to cooked rice obtained by naturally defrosting the frozen cooked rice.

The fourth aspect of the present invention is a method for producing frozen cooked rice that can be naturally thawed and eaten, wherein the raw material for rice cooking is cooked and then frozen. Solid content contained in the extract of the plant belonging to the family, water, α-glycosyltransferase, and α-amylase, and the solid content contained in the extract of the plant belonging to the Brassicaceae family is 0 per 100 parts by weight of the raw material rice .000014 to 0.0014 parts by weight, 150 to 190 parts by weight of the water, 50 to 5000 units of the α-glycosyltransferase and 1.5 to 150 units of the α-amylase per 100 g of the raw rice. and the α-glycosyltransferase/α-amylase (enzyme activity ratio) is 0.5 to 500, and the raw material rice has an amylose content [X] (weight %) and moisture content [Y] (% by weight) satisfies the condition (A) or (B), and the extract is the amount of plants belonging to the Brassicaceae family (wet weight) / total amount of water and ethanol A mixture having a (weight ratio) of 0.05 to 10 is subjected to an extraction treatment at 5 to 160° C. for 0.1 to 36 hours, and then the extract residue of the plant belonging to the Brassicaceae family is removed. , relates to a method for producing frozen boiled rice for natural thawing and eating.

According to the present invention, it is possible to provide frozen cooked rice that can obtain cooked rice with good softness, stickiness and graininess even if it is naturally thawed after freezing, and a frozen cooked rice improver used therefor.

Condition (A) or (B) regarding amylose content [X] (% by weight) and water content [Y] (% by weight) in raw rice according to one embodiment of the present invention as region (A) or region (B) It is a graph showing. (X, Y), point A (11.5, 11), point B (19, 11) [= point G], point C (25, 11), point D (25, 15.5), and point E(19, 15.5) is shown on the graph. Region (A) is the region surrounded by points A, B and E, and region (B) is the region surrounded by points B, C, D and E. Condition (C) or (D) based on amylose content [X] (% by weight) and water content [Y] (% by weight) in raw rice according to one embodiment of the present invention as region (C) or region (D) It is a graph showing. (X, Y), point F (13, 11), point G (19, 11) [= point B], point H (21, 11), point I (21, 15), and point J (19, 19, 15) is shown on the graph. Region (C) is the region surrounded by points F, G and J, and region (D) is the region surrounded by points G, H, I and J.

The present invention will be described in more detail below. The improver for frozen cooked rice of the present invention is an improver used for frozen cooked rice made from a specific rice as a raw material. Each contains a specific amount of α-amylase.

In the present invention, frozen cooked rice means cooked rice in a state of being frozen after cooking rice ingredients containing a specific raw material rice in a specific amount. By adding a specific amount of the improving agent for frozen cooked rice during cooking, the rice has good softness, stickiness, and graininess even if it is naturally thawed after freezing. In the present invention, "natural thawing" means thawing at 0 to 30°C, and includes refrigerating thawing and microwave thawing performed in a refrigerator or the like. Here, the term "softness" means that each grain of rice has moderate softness and elasticity and moderately brittle texture, unlike sticky and soft rice grains. The term "stickiness" means that the rice grains have an appropriate sticky texture without feeling dry or crumbly. The term "grain texture" means a texture in which rice grains do not stick to each other, that is, do not form lumps, and one can feel each grain of rice when eating.

The raw material rice has an amylose content [X] (% by weight) and a water content [Y] (% by weight) under condition (A): 11.5 ≤ X < 19, 11 ≤ Y < 7.0 + 8.5 × { 1-[(X-19.0)/8.5] ² } ^1/2 , or preferably satisfies condition (B): 19≦X≦25, 11≦Y≦15.5 (see FIG. 1) , condition (C): 13≦X<19, 11≦Y<11.0+4×{1−[(X−19.0)/6] ² } ^1/2 , or condition (D): 19≦X≦ 21, it is more preferable to satisfy 11≤Y≤15 (see FIG. 2). Here, X is the amylose content (% by weight) in the starting rice, and Y is the water content (% by weight) in the starting rice. The effect of the present invention can be easily obtained by using the raw material rice within the range of the condition (A) or the condition (B).

The extract of the plant belonging to the Brassicaceae is a mixture in which the total amount of the plant belonging to the Brassicaceae (wet weight) / the total amount of water and ethanol has a specific weight ratio, is subjected to an extraction treatment at a specific temperature for a specific time, and then extracted. It is an extract from which residues have been removed.

Examples of the plants belonging to the Brassicaceae family include, but are not limited to, Chinese cabbage, Japanese radish, broccoli, bok choy, Japanese mustard, turnip, white mustard, nozawana, Hiroshima greens, mizuna, and mustard. Among these, kaiware radish, which is a sprout of radish, is preferable from the viewpoint of availability.

Water and/or ethanol are preferable as the solvent used for the extraction from the plant belonging to the Brassicaceae family. From the viewpoint of the flavor and texture of cooked rice after natural thawing, only water is more preferable.

Regardless of whether water or ethanol is included as a solvent, the content of the water and the ethanol is the plant belonging to the Brassicaceae family (wet weight) / the total amount of the water and the ethanol. (weight ratio) is preferably from 0.05 to 10, more preferably from 0.1 to 5, and even more preferably from 0.2 to 1. If the weight ratio is less than 0.05, the stickiness and texture of the cooked rice after natural thawing may be poor. On the other hand, if the weight ratio exceeds 10, the extraction efficiency may deteriorate and the manufacturing cost of the frozen cooked rice improver may increase.

The extraction treatment temperature is preferably 5 to 160°C, more preferably 10 to 140°C, even more preferably 20 to 120°C. If the extraction treatment temperature is lower than 5°C, the extraction efficiency may be poor, and the stickiness and graininess of the cooked rice after natural thawing may be poor. Moreover, if the extraction treatment temperature exceeds 160° C., special pressurization equipment is required, which may complicate the extraction method.

The extraction treatment time is preferably 0.1 to 36 hours, more preferably 0.5 to 24 hours, even more preferably 1 to 12 hours. If the extraction treatment time is shorter than 0.1 hour, the extraction efficiency may deteriorate, and the stickiness and graininess of the cooked rice after natural thawing may deteriorate. In addition, if the extraction processing time exceeds 36 hours, the effect on the softness, stickiness, and graininess of the cooked rice after natural thawing reaches a ceiling despite the fact that the extraction takes time, resulting in poor extraction efficiency. may become.

The content of the plant extract belonging to the Cruciferous family in the improver for frozen cooked rice is preferably 0.0014 to 0.047% by weight, and preferably 0.0026 to 0.047% by weight, in terms of solid content, based on the whole improver for frozen cooked rice. 024% by weight is more preferred, and 0.004 to 0.02% by weight is even more preferred. If the content of the extract of a plant belonging to the Brassicaceae family is less than 0.0014% by weight, the stickiness and texture of the cooked rice after natural thawing may be poor. On the other hand, if it is more than 0.047% by weight, the boiled rice after natural thawing may be too soft, or the off-taste of the extract of the cruciferous plant may be imparted.

The α-glycosyltransferase is a transferase that cleaves a portion of 1,4-α-glucan to form a new intramolecular and/or intermolecular α-1,6 bond. The α-glycosyltransferase is not particularly limited as long as it can be used for food applications (grade), can be appropriately selected, and commercially available products can be used as appropriate. Commercially available products include, for example, the product name “Sensea foam” (manufactured by Novozymes Japan).

The α-glycosyltransferase content in the improver for frozen boiled rice is preferably 5000 to 166500 units, more preferably 5800 to 36000 units, even more preferably 6630 to 19680 units, per 100 g of the improver. If the content is less than 5,000 units or more than 166,500 units, the graininess of cooked rice after natural thawing may deteriorate.

The activity of the α-glycosyltransferase is determined by reducing the absorbance of the iodine-amylose complex at 660 nm by 1% per minute under standard conditions (pH 7.2, 60°C). unit. The α-glycosyltransferase activity is measured as follows.

First, amylose type III (Sigma): 10 mg was added to 2 M NaOH: 0.5 ml, then pure water: 1 ml was added, and 2 M HCl: 0.5 ml and phosphate buffer (pH 7.2) were added. ): Add 7.8 ml to prepare the substrate solution. Further, iodine: 0.26 g and potassium iodide: 2.6 g were dissolved in pure water: 10 ml: iodine/iodide stock solution: 100 µl, 2 M hydrochloric acid: 50 µl was added, and pure water: 26 ml was further added to stop. Prepare reagents.

Then, 50 μl of the enzyme solution (α-glycosyltransferase aqueous solution) diluted to an absorbance of 0.15 to 0.3 was mixed with 50 μl of the substrate solution, and the mixture was incubated at 60° C. for 30 minutes. , the stop reagent: 2 ml is added, mixed well, and the absorbance at 660 nm (X1) is measured. Then, absorbance (X0) at 660 nm is measured in the same manner except that the substrate solution is changed to phosphate buffer (pH 7.2).

On the other hand, the absorbance (Y1) at 660 nm is measured in the same manner except that the enzyme solution (α-glycosyltransferase aqueous solution) is changed to pure water in the measurement of the absorbance (X1). Then, in the measurement of the absorbance (Y1), the absorbance (Y0) at 660 nm is measured in the same manner, except that the substrate solution is changed to a phosphate buffer (pH 7.2). The α-glycosyltransferase activity (U/ml) is calculated using the measured values and the following formula.
Activity of α-glycosyltransferase (U/ml) = {(X0-X1)/(Y0-Y1)} x 100 x dilution rate x (1/30) x (1/0.05)

The α-amylase refers to an enzyme having the activity of cleaving the linear structure (amylose) and branched structure (amylopectin) of starch molecules to decompose them into dextrin and maltose. The α-amylase may be a commercially available product, for example, product name “Biozyme A” (manufactured by Amano Enzyme), product name “Novamil 10000BG”, product name “Novamil 3DBG” (both manufactured by Novozymes Japan) ), product name “Sumiteam L”, product name “Sumiteam AS” (both manufactured by Shin Nihon Chemical Industry Co., Ltd.), and the like.

The α-amylase content is preferably 150 to 5000 units, more preferably 430 to 3360 units, even more preferably 750 to 1730 units, per 100 g of the improving agent. If the content is less than 150 units, the stickiness and texture of the cooked rice after natural thawing may decrease. If it is more than 5,000 units, the softness of cooked rice after natural thawing may decrease.

The α-amylase activity is defined as the amount (ml) of 1% soluble starch degraded when reacted for 30 minutes at pH 5.0 and 40° C. using soluble starch as a substrate. The amount of enzyme (amount of α-amylase) that decomposes 1 ml is defined as 1 unit. The α-amylase activity is measured according to the standard analytical method of the National Research Institute of Brewing. Specifically, it is as follows.

Glacial acetic acid: 11.55 ml of A solution made 1000 ml with pure water: 5.9 ml, and sodium acetate: 27.21 g dissolved in pure water to make 1000 ml B solution: 14.1 ml were mixed. If it does not reach exactly 5.0, adjust the pH to 5.0 using solution A or solution B to prepare a 0.2 mM acetate buffer. Soluble starch: Add a small amount of hot water to 1 g, stir well and boil for 1 to 2 minutes, then add 0.01 M acetate buffer (pH 5.0): 20 ml to adjust the pH to 5.0 , Pure water is added to adjust the volume to 100 ml, and a starch solution is prepared. An iodine solution is prepared by adding 0.1 g of potassium iodide and 50 ml of 10% hydrochloric acid to 0.0317 g of iodine and dissolving it in 1000 ml of pure water. Calcium acetate: 0.176 g, sodium acetate: 2.722 g, sodium chloride: 5.844 g are dissolved in pure water to make 1000 ml, and 10% acetic acid: 10 ml is further added to prepare a salt solution. The enzyme (α-amylase) is appropriately diluted with the salt solution to prepare an enzyme solution (α-amylase solution).

The starch solution: 2 ml is taken in a test tube and preheated at 40° C. for 5 minutes. 0.1 ml of the enzyme solution (α-amylase solution) was added to initiate the reaction, and 0.1 ml of the reaction solution was pipetted into a test tube containing 10 ml of the iodine solution. Take, mix well and measure the transmittance (T %) colorimetrically at 670 nm through a 10 mm path length absorption cell while maintaining at 25°C. The transmittance (T%) is measured over time (every 0.5 minutes or 1 minute).

As a control solution for colorimetry, 0.1 ml of an enzyme solution (α-amylase solution) mixed with 2 ml of pure water is sampled and 10 ml of the iodine solution is added. A reaction time (t minutes) corresponding to 66% is found from among these series of T% values.

The α-amylase activity (U/ml) is calculated using the reaction time and the following formula.
Activity of α-amylase (U/ml) = 2 x (1/0.1) x (30/t) x dilution rate

In the improver for frozen boiled rice, the α-glycosyltransferase/α-amylase (enzyme activity ratio) is preferably 0.5-500, more preferably 1-100, even more preferably 5-50. If the enzyme activity ratio is less than 0.5, the texture of cooked rice after natural thawing may be reduced. If it is more than 500, the stickiness of cooked rice after natural thawing may decrease.

From the viewpoint of the softness and stickiness of the frozen cooked rice after natural thawing, it is preferable to further add HM pectin to the improver for frozen cooked rice. The content of the HM pectin is preferably 0.1 to 3.3% by weight, more preferably 0.17 to 1.05% by weight, and 0.23 to 0.56% by weight in the entire frozen cooked rice improver. % is more preferred. If the content of the HM pectin is out of the above range, the expected effect of improving the softness and stickiness of cooked rice after natural thawing may not be obtained.

Here, the HM pectin is a polysaccharide composed mainly of methylated galacturonic acid and/or galacturonic acid, and refers to pectin in which methylated galacturonic acid accounts for 50% by weight or more of all galacturonic acids. The HM pectin may be a commercial product, for example, product name "GENU YM115-LJ", product name "GENU JM-150-J" (all manufactured by CP Kelco), product name "SM-478", Product name "SM-666" (both manufactured by San-Ei Gen FFI Co., Ltd.), product name "AYD5110SB" (manufactured by Unitech Foods Co., Ltd.), and the like.

The form of the improving agent for frozen cooked rice of the present invention is not particularly limited, and may be liquid, paste, powder, solid, etc., preferably liquid. When formulating a frozen rice improver, excipients include, for example, monosaccharides such as glucose and fructose; oligosaccharides such as sucrose, lactose and maltose; dextrin, starch hydrolysates such as powdered starch syrup; malto-oligosaccharides such as , maltotetraose, maltopentaose and maltohexaose; sugar alcohols such as sorbitol, mannitol, maltitol and powdered reduced starch syrup; and whey protein.

Further, the improving agent for frozen boiled rice can contain arbitrary components within a range that does not impair the object of the present invention. Examples of such optional ingredients include gelatin; polysaccharides such as xanthan gum and pullulan; food emulsifiers such as glycerin fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters and lecithin; Starches made from grains such as corn (waxy corn), potatoes, glutinous potatoes, tapioca, rice, and glutinous rice; Modified starch; Organic acids such as acetic acid, lactic acid, and citric acid; Grain vinegar made from grains such as rice, wheat, and corn; Fruit vinegar made from fruit juices such as apples and grapes; Synthesis using alcohol and acetic acid as raw materials Vinegar; processed vinegar obtained by adding flavorings and other concomitant ingredients to these vinegars; ume vinegar produced as a by-product in the production of umeboshi; and desalted or concentrated ume vinegar.

The frozen cooked rice of the present invention is obtained by cooking a raw material for rice cooking containing a specific amount of a specific raw material rice, and then freezing it. ), a specific amount of solids contained in the extract of a plant belonging to the Brassicaceae family, and specific amounts of α-glycosyltransferase and α-amylase.

The raw material for rice cooking has an amylose content [X] (% by weight) and a water content [Y] (% by weight) under conditions (A): 11.5 ≤ X < 19, 11 ≤ Y < 7.0 + 8.5 × {1−[(X−19.0)/8.5] ² } ^1/2 , or it preferably contains raw material rice that satisfies the condition (B): 19≦X≦25, 11≦Y≦15.5 , condition (C): 13≦X<19, 11≦Y<11.0+4×{1−[(X−19.0)/6] ² } ^1/2 , or condition (D): 19≦X≦ 21, it is more preferable to include raw rice that satisfies 11 ≤ Y ≤ 15. Here, X is the amylose content (% by weight) in the starting rice, and Y is the water content (% by weight) in the starting rice. The effect of the present invention can be easily obtained by setting the range of the condition (A) or the condition (B).

In the raw material for rice cooking, the content of raw rice within the condition (A) or condition (B) is preferably 70 to 100% by weight, more preferably 80 to 100% by weight, more preferably 90 to 100% by weight, based on the whole raw material for rice cooking. 100% by weight is more preferred. If it is less than 70% by weight, it may not be possible to enjoy the good softness, stickiness and graininess of cooked rice after natural thawing, which are the effects of the present invention.

In the raw material for rice cooking, the content of water is preferably 150 to 190 parts by weight, more preferably 160 to 185 parts by weight, and more preferably 170 to 180 parts by weight with respect to 100 parts by weight of raw rice in the raw material for cooking rice. More preferred. If the water content is less than 150 parts by weight, the cooked rice after natural thawing may lack softness and stickiness. If it is more than 190 parts by weight, the cooked rice after natural thawing may be too soft or lack graininess. The content of water also includes the amount of water absorbed during washing of the raw material rice.

The content of the extract of a plant belonging to the Brassicaceae family is preferably 0.000014 to 0.0014 parts by weight, preferably 0.00005 to 0.00005 parts by weight, in terms of solid content, with respect to 100 parts by weight of raw rice in the raw material for cooking rice. 0.0007 parts by weight is more preferred, and 0.0001 to 0.0004 parts by weight is even more preferred. If the content is less than 0.000014 parts by weight, the stickiness and texture of cooked rice after natural thawing may be poor. On the other hand, if it is more than 0.0014 parts by weight, the cooked rice after natural thawing may be too soft, or the off-taste of the extract of the plant belonging to the family Brassicaceae may be imparted. The extract of a plant belonging to the Brassicaceae family contained in the raw material for cooking rice is the same as the extract of a plant belonging to the Brassicaceae family contained in the improving agent for frozen cooked rice.

The content of the α-glycosyltransferase is preferably 50 to 5,000 units, more preferably 75 to 1,000 units, and even more preferably 100 to 500 units per 100 g of raw rice in the raw material for rice cooking. If the content is less than 50 units or more than 5000 units, the graininess of the cooked rice after natural thawing may deteriorate. The α-glycosyltransferase contained in the raw material for cooking rice is the same as the α-glycosyltransferase contained in the improving agent for frozen cooked rice.

The α-amylase content is preferably 1.5 to 150 units, more preferably 10 to 100 units, and even more preferably 20 to 50 units per 100 g of raw rice in the raw material for rice cooking. If the content is less than 1.5 units, the stickiness and texture of cooked rice after natural thawing may be reduced. If it is more than 150 units, the cooked rice after natural thawing may be less soft and grainy. The α-amylase contained in the raw material for cooking rice is the same as the α-amylase contained in the improving agent for frozen cooked rice.

In the raw material for cooking rice, the α-glycosyltransferase/α-amylase (enzyme activity ratio) is preferably 0.5-500, more preferably 1-100, and even more preferably 5-50. If the enzyme activity ratio is less than 0.5, the graininess of cooked rice after natural thawing may deteriorate. If it is more than 500, the stickiness of cooked rice after natural thawing may decrease.

From the viewpoint of the softness and stickiness of the cooked rice after natural thawing, it is preferable to further contain HM pectin in the raw material for cooking rice. The content of the HM pectin is preferably 0.001 to 0.1 parts by weight, more preferably 0.003 to 0.03 parts by weight, more preferably 0.003 to 0.03 parts by weight, based on 100 parts by weight of raw rice in the raw material for rice cooking. 005 to 0.015 parts by weight is more preferred. If the content is outside the above range, the expected effect of improving the softness and stickiness of cooked rice after natural thawing may not be obtained. The HM pectin contained in the raw material for cooking rice is the same as the HM pectin contained in the improver for frozen cooked rice.

The solid content, water, the α-glycosyltransferase, the α-amylase, and the HM pectin contained in the extract of the plant belonging to the Brassicaceae contained in the raw material for cooking rice can be added separately. Alternatively, a blend of these may be added, and the necessary amount can be easily added by adding it as the improving agent for frozen boiled rice.

When frozen cooked rice is produced using the frozen cooked rice improving agent, the raw material for cooking rice may contain the improving agent for frozen cooked rice, and the content thereof is based on 100 parts by weight of raw rice in the raw material for cooking rice. On the other hand, 1 to 3 parts by weight is preferable, 2 to 2.9 parts by weight is more preferable, and 2.5 to 2.8 parts by weight is even more preferable. If the content is less than 1 part by weight or more than 3 parts by weight, the softness, stickiness and graininess of the cooked rice after natural thawing may deteriorate.

An embodiment of the method for producing frozen boiled rice of the present invention is illustrated below.
With respect to 100 parts by weight of raw rice, 0.000014 to 0.0014 parts by weight of solid content contained in the extract of the plant belonging to the Brassicaceae family, and 150 to 190 parts by weight of water including water absorption during washing, 50 to 5000 units of α-glycosyltransferase and 1.5 to 150 units of α-amylase per 100 g of raw rice in the raw material for rice cooking, and the α-glycosyltransferase/α-amylase (enzyme activity ratio) Rice is cooked with the raw materials for rice cooking obtained by mixing so that the ratio is 0.5 to 500.

There are no particular restrictions on the method of cooking rice. The cooked rice is directly frozen, or after being packaged in a subdivided packaging container such as a tray, a retort pack, or another film pack, it is quickly frozen by a conventional method. When used as rice for sushi, seasonings such as vinegar are added in a conventional manner immediately after the rice is cooked to prepare sushi rice, and the rice is molded into the shape of sushi rice for nigiri sushi, or used as sushi material. It can also be flash-frozen after combining.

The frozen cooked rice improver and frozen cooked rice of the present invention are suitable for cooked rice such as sushi rice and rice balls that are naturally thawed after freezing and eaten as they are. It can also be used for cooked rice such as pilaf, fried rice, dry curry, brown rice, white rice, red rice, steamed rice, and mixed rice.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. In addition, "parts" and "%" in the examples are based on weight.

Raw materials used in Examples and Comparative Examples are as follows.
1) Akitakomachi (rinse-free rice, amylose content [X]: 16.4% by weight, water content [Y]: 12.0% by weight)
2) Novozymes Japan Co., Ltd. "Sensea foam" (25000 units (U))
3) Shin Nihon Kagaku Kogyo Co., Ltd. "Sumiteam AS (1500 units (U))
4) "Novamyl 10000BG" manufactured by Novozymes Japan Co., Ltd.
5) "GENU pectin type JM-150-J" manufactured by CP Kelco
6) "Echogel K-OB" manufactured by CP Kelco
7) "Emulgy MS" manufactured by Riken Vitamin Co., Ltd.
8) "Poem K30" manufactured by Riken Vitamin Co., Ltd.
9) Mitsubishi Chemical Foods Co., Ltd. "Ryoto Sugar Ester S-1170"
10) "Sorbitol Ueno" manufactured by Ueno Pharmaceutical Co., Ltd.
11) Koshihikari (rinse-free rice, amylose content [X]: 16.5% by weight, water content [Y]: 14.5% by weight)
12) Kiyonishiki (amylose content [X]: 18.0% by weight, water content [Y]: 12.5% by weight)
13) Nipponbare (amylose content [X]: 21.5% by weight, water content [Y]: 15.0% by weight)
14) Hoshiyutaka (amylose content [X]: 25.5% by weight, water content [Y]: 13.6% by weight)

<Evaluation of frozen cooked rice>
Each of the frozen cooked rice obtained in Examples and Comparative Examples was stored at 25°C for 4 hours, and 10 skilled panelists evaluated the naturally thawed cooked rice, and the average value of the evaluation points was taken as the sensory evaluation. bottom. The evaluation criteria at that time were as follows.

(Softness) Akitakomachi is used as the raw material rice, no improving agent for frozen cooked rice is added, and comparison with unfrozen cooked rice (Reference Example 1) that has been cooled to 25 ° C. immediately after preparation 5 points: Reference Example 1 Equivalent to and very preferable softness is felt 4 points: Slightly inferior to Reference Example 1, but moderate softness is felt 3 points: Inferior to Reference Example 1, slightly hard or slightly soft, 2 points: worse than Reference Example 1, hard or too soft 1 point: much worse than Reference Example 1, clearly hard or clearly too soft

(Stickness) Akitakomachi is used as the raw rice, no frozen cooked rice improver is added, and a comparison with unfrozen cooked rice (Reference Example 1) that has been cooled to 25 ° C. immediately after preparation 5 points: with Reference Example 1 Equivalent and very favorable stickiness can be felt 4 points: Slightly inferior to Reference Example 1, but moderate stickiness can be felt 3 points: Inferior to Reference Example 1, slightly less sticky, but there is no problem in terms of product quality Level 2 points: Worse than Reference Example 1, less sticky, slightly dry feeling 1 point: Much worse than Reference Example 1, clearly no stickiness, dry feeling

(Graininess) Akitakomachi is used as the raw material rice, no improver for frozen cooked rice is added, and comparison with unfrozen cooked rice (Reference Example 1) that has been cooled to 25 ° C. immediately after preparation 5 points: Reference Example 1 Equivalent to, 4 points where the graininess is felt firmly: Slightly inferior to Reference Example 1, but moderate graininess is felt 3 points: Inferior to Reference Example 1, the graininess is slightly less, but in terms of product quality 2 points: Worse than Reference Example 1, less graininess, binding between rice grains can be felt 1 point: Much worse than Reference Example 1, clearly no graininess, rice grains is tied to

(comprehensive evaluation)
A comprehensive evaluation was made based on the evaluation results of softness, stickiness, and graininess. The evaluation criteria in that case are as follows.
A: Evaluations of softness, stickiness, and graininess all satisfy 4.0 to 5.0 points B: Evaluations of softness, stickiness, and graininess are all 3.5 to 5.0 points and having at least one score of 3.5 or more and less than 4.0 C: Evaluation of softness, stickiness, and graininess are all 3.0 or more and 5.0 or less, and Those with at least one score of 3.0 or more and less than 3.5 points D: Evaluation of softness, stickiness, and graininess are all 2.0 points or more and 5.0 points or less, and 2.0 points or more and 3 At least one score of less than 0 E: At least one score of less than 2.0 in the evaluation of softness, stickiness, and graininess

(Production Example 1) Production of an extract of a plant belonging to the Brassicaceae family 770 g (wet weight) of commercially available radish sprouts (manufactured by Murakami Noen) was added to 2.5 L of distilled water and extracted at 100°C for 1 hour. After filtration using filter paper (manufactured by Advantech), the recovered filtrate was concentrated under reduced pressure using an ultrafiltration concentrator (manufactured by Advantech, product number: UHP-150) to obtain about 200 mL of a concentrated liquid. This was centrifuged at 10,000×g for 10 minutes to recover a supernatant having a solid concentration of 0.7 mg/ml. This supernatant was used as an extract of a plant belonging to the family Brassicaceae (Radiant radish extract).

(Example 1) Preparation of frozen cooked rice According to Table 1, 0.14 weight of the extract of a plant belonging to the Brassicaceae family (Production Example 1) is added to 100 parts by weight of raw rice: rinse-free rice "Akitakomachi" as a raw material for cooking rice. 0.008 parts by weight of α-glycosyltransferase, 0.027 parts by weight of α-amylase and 178 parts by weight of water were added, and after standing for 1 hour, rice was cooked using an IH jar rice cooker. The cooked rice was shaped into 60 g each and held in a -30° C. rapid freezer for 30 minutes to obtain frozen cooked rice. The obtained frozen cooked rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation. Table 1 shows the unit amount of each enzyme, the activity ratio, and the solid content of the extract in each example and reference example.

(Examples 2 to 6) Preparation of Frozen Cooked Rice According to the composition shown in Table 1, 0.002 parts by weight of α-glycosyltransferase and 0.027 parts by weight of α-amylase of Example 1 were added to 0.002 parts by weight and 0.027 parts by weight of α-amylase, respectively. 0067 parts by weight (Example 2), 0.03 parts by weight and 0.10 parts by weight (Example 3), 0.003 parts by weight and 0.10 parts by weight (Example 4), 0.2 parts by weight and 0 067 parts by weight (Example 5), or 0.03 parts by weight and 0.001 parts by weight (Example 6). and obtained frozen rice. The obtained frozen boiled rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation.

(Reference Example 1) Preparation of cooked rice In Example 1, the extract of a plant belonging to the Brassicaceae family, α-glycosyltransferase, and α-amylase were not added, and 178 parts by weight of water was changed to 150 parts by weight. Rice was cooked in the same manner as in Example 1, and the cooked rice was cooled to 25°C.

As is clear from Table 1, the extract of a plant belonging to the Brassicaceae family contains 50 to 5000 units of α-glycosyltransferase and 1.5 to 150 units of α-amylase per 100 g of raw rice, and α-glycosyltransferase/ The raw material for rice cooking with α-amylase (enzyme activity ratio) in the range of 0.5 to 500 was cooked and then frozen (Examples 1 to 6). , stickiness, and graininess were evaluated as good.

(Comparative Examples 1 to 6) Production of Frozen Cooked Rice According to the composition shown in Table 2, 0.002 parts by weight of α-glycosyltransferase and 0.027 parts by weight of α-amylase of Example 1 were added to 0.002 parts by weight and 0.027 parts by weight of α-amylase, respectively. 0067 parts by weight (Comparative Example 1), 0.21 parts by weight and 0.067 parts by weight (Comparative Example 2), 0.002 parts by weight and 0.0005 parts by weight (Comparative Example 3), 0.03 parts by weight and 0 .11 parts by weight (Comparative Example 4), 0.003 parts by weight and 0.1 parts by weight (Comparative Example 5), or 0.032 parts by weight and 0.001 parts by weight (Comparative Example 6) After cooking the rice in the same manner as in Example 1, the cooked rice was shaped and frozen to obtain frozen cooked rice. The obtained frozen boiled rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation. Table 2 shows the unit amount of each enzyme, the activity ratio, and the solid content of the extract in each comparative example.

As is clear from Table 2, the frozen cooked rice (Comparative Example 1) using a raw material for cooking rice with a low α-glycosyltransferase content of 38 units per 100 g of the raw rice was poorly evaluated for the texture of the cooked rice after natural thawing. , the overall evaluation was D. Frozen cooked rice (Comparative Example 2), which uses a raw material for cooking rice with a large amount of α-glycosyltransferase of 5250 units per 100 g of raw rice, has a poor evaluation of the softness and graininess of the cooked rice after natural thawing, and the overall evaluation is D. there were. Frozen cooked rice (Comparative Example 3) using a raw material for cooking rice with a low α-amylase content of 0.75 units per 100 g of raw rice was poorly evaluated for the stickiness and graininess of the cooked rice after natural thawing, and the overall evaluation was D. Met. Frozen cooked rice (Comparative Example 4) using a raw material for cooking rice with a large amount of α-amylase of 165 units per 100 g of raw rice was poorly evaluated for softness and graininess after natural thawing, and the overall evaluation was D. rice field. The frozen cooked rice (Comparative Example 5) using a raw material for cooking rice with a low α-glycosyltransferase/α-amylase (enzyme activity ratio) of 0.42 in the raw rice had a poor evaluation of the graininess of the cooked rice after natural thawing. Comprehensive evaluation was D. Frozen cooked rice (Comparative Example 6) using a raw material for cooking rice with a large α-glycosyltransferase/α-amylase (enzyme activity ratio) of 533 in the raw rice has a poor evaluation of the stickiness of the cooked rice after natural thawing, and the overall evaluation is was D.

(Comparative Example 7) Preparation of frozen cooked rice According to the formulation in Table 2, 0.008 parts by weight of α-glycosyltransferase in Example 1 was changed to 0.3 parts by weight, and 0.027 parts by weight of α-amylase and cruciferous After cooking rice in the same manner as in Example 1, except that 0.14 parts by weight of the plant extract (Production Example 1) was not added, the cooked rice was shaped and frozen to obtain frozen cooked rice. The obtained frozen boiled rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation.

As is clear from Table 2, frozen cooked rice ( In Comparative Example 7), the evaluation of grainy texture of cooked rice after natural thawing was poor, and the overall evaluation was D.

(Comparative Example 8) Preparation of frozen cooked rice According to the composition of Table 2, 0.027 parts by weight of α-amylase of Example 1 was not added, and 0.004 parts by weight of β-amylase was added instead. After cooking the rice in the same manner as in 1, the cooked rice was shaped and frozen to obtain frozen cooked rice. The obtained frozen boiled rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation.

As is clear from Table 2, the frozen cooked rice (Comparative Example 8) using the raw material for cooking rice to which β-amylase was added instead of adding α-amylase was evaluated for the texture of the cooked rice after natural thawing. It was bad, and the comprehensive evaluation was D.

(Examples 7 to 8 and Comparative Examples 9 to 10) Preparation of frozen cooked rice According to the composition of Table 3, 0.14 parts by weight of the extract of a plant belonging to the Brassicaceae family of Example 1 (Production Example 1) was added to 0.02 parts by weight. Example 1 except that parts by weight (Example 7), 2.0 parts by weight (Example 8), 0.014 parts by weight (Comparative Example 9), or 4.4 parts by weight (Comparative Example 10) were changed. After cooking the rice in the same manner as in , the cooked rice was shaped and frozen to obtain frozen cooked rice. The obtained frozen cooked rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation. Table 3 shows the unit amount of each enzyme, the activity ratio, and the solid content of the extract in each example and comparative example.

As is clear from Table 3, the raw material for cooking rice was used in which the content of solids contained in the extract of a plant belonging to the Brassicaceae relative to 100 parts by weight of raw rice was in the range of 0.000014 to 0.0014 parts by weight. All of the frozen boiled rice (Examples 1, 7 to 8) were evaluated to be good in terms of softness, stickiness and graininess after natural thawing. On the other hand, frozen cooked rice (Comparative Example 9) using a raw material for cooking rice with a low content of 0.000010 parts by weight of the extract from which the residue of the extract of the plant belonging to the Brassicaceae was removed with respect to 100 parts by weight of the raw material rice (Comparative Example 9) The stickiness and texture of the cooked rice after thawing were poor, and the overall evaluation was D. In addition, frozen boiled rice (Comparative Example 10) using a raw material for cooking rice with a high solid content of 0.0031 parts by weight contained in the extract of a plant belonging to the Brassicaceae relative to 100 parts by weight of the raw material rice (Comparative Example 10) The evaluation of the softness of the cooked rice was poor, and the overall evaluation was D.

(Comparative Example 11) Production of frozen cooked rice Extraction of a plant belonging to the Brassicaceae family without adding 0.008 parts by weight of α-glycosyltransferase and 0.027 parts by weight of α-amylase of Example 1 according to the formulation in Table 3 Product (Production Example 1) After cooking rice in the same manner as in Example 1, except that 0.14 parts by weight was changed to 10 parts by weight, the cooked rice was shaped and frozen to obtain frozen cooked rice. The obtained frozen cooked rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation.

As is clear from Table 3, the content of solids contained in the extract of a plant belonging to the Brassicaceae family relative to 100 parts by weight of raw rice without adding α-glycosyltransferase and α-amylase was 0.007 parts by weight. The frozen cooked rice (Comparative Example 11) using a large amount of raw materials for rice cooking was poorly evaluated for the texture of the cooked rice after natural thawing, and the overall evaluation was D.

(Example 12) Preparation of frozen cooked rice According to the composition shown in Table 4, after cooking rice in the same manner as in Example 1, except that 0.007 parts by weight of HM pectin was added, the cooked rice was shaped and frozen. I got frozen rice. The obtained frozen boiled rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation. Table 4 shows the unit amount of each enzyme, the activity ratio, and the solid content of the extract in each example and comparative example.

As is clear from Table 4, the frozen cooked rice (Example 12) using the raw material for rice cooking in which the content of HM pectin was in the range of 0.001 to 0.1 parts by weight with respect to 100 parts by weight of the raw material rice was naturally thawed. The softness, stickiness and texture of the cooked rice were evaluated as good. In particular, compared with the frozen cooked rice (Example 1) to which HM pectin was not added, the softness and stickiness of the cooked rice after natural thawing were excellent.

(Comparative Example 12) Preparation of frozen cooked rice According to the composition of Table 4, the extract of the plant belonging to the Brassicaceae family of Example 1 (Production Example 1), 0.008 parts by weight of α-glycosyltransferase, and α-amylase were added. First, the rice was cooked in the same manner as in Example 1, except that the added water was changed from 178 parts by weight to 190 parts by weight, and 0.67 parts by weight of HM pectin was added. got The obtained frozen boiled rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation.

As is clear from Table 4, the extract of a plant belonging to the family Brassicaceae (Production Example 1), α-glycosyltransferase and α-amylase were not added, and the content of HM pectin relative to 100 parts by weight of raw rice was 0.00. Frozen cooked rice (Comparative Example 12) using a large amount of raw materials for rice cooking, 67 parts by weight, was evaluated poorly for the stickiness and graininess of the cooked rice after natural thawing, and the overall evaluation was E.

(Examples 13-14 and Comparative Examples 13-14) Production of frozen cooked rice ), 145 parts by weight (Comparative Example 13), or 200 parts by weight (Comparative Example 14), after cooking, the cooked rice was shaped and frozen to obtain frozen cooked rice. rice field. The obtained frozen boiled rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation.

As is clear from Table 4, the frozen cooked rice (Examples 1, 12 to 14) using the raw material for rice cooking in which the content of added water was in the range of 150 to 190 parts by weight with respect to 100 parts by weight of the raw material rice was naturally thawed. The softness, stickiness and texture of the cooked rice were evaluated as good. On the other hand, the frozen cooked rice (Comparative Example 13) using a raw material for cooking rice in which the content of added water was as small as 145 parts by weight with respect to 100 parts by weight of raw rice was poor in the softness and stickiness of the cooked rice after natural thawing. was D. In addition, frozen cooked rice (Comparative Example 14) using a raw material for cooking rice with a large content of added water of 200 parts by weight with respect to 100 parts by weight of raw rice was poorly evaluated for the softness and graininess of the cooked rice after natural thawing. The evaluation was D.

(Example 15) Production of improving agent for frozen boiled rice According to Table 5, 93.2 parts by weight of a sorbitol solution heated to 40°C was stirred using a chemist stirrer (manufactured by Tokyo Rikagaku Kiki Co., Ltd., product number: ZZ-1020). While stirring at 41.7S ^-1 , α-glycosyltransferase: 0.3 parts by weight, α-amylase: 1.0 parts by weight, a plant extract belonging to the family Brassicaceae (Production Example 1): 5 0 parts by weight, HM pectin: 0.25 parts by weight, and xanthan gum: 0.25 parts by weight were added and dissolved to obtain a frozen boiled rice improver. The solid content of the plant extract belonging to the Brassicaceae family, the α-glycosyltransferase content, the α-amylase content, and the α-glycosyltransferase/α-amylase (enzyme activity ratio) in the obtained frozen cooked rice improver were determined. Table 5 shows. Table 5 shows the unit amount of each enzyme, the activity ratio, and the solid content of the extract in each example.

(Example 16) Preparation of improver for frozen boiled rice According to the composition of Table 5, 0.3 parts by weight of α-glycosyltransferase was changed to 6.6 parts by weight, and 1.0 part by weight of α-amylase was changed to 0.22 parts by weight. , 5.0 parts by weight of the extract of a plant belonging to the Brassicaceae family (Production Example 1) to 13.6 parts by weight, 0.25 parts by weight of HM pectin to 0.5 parts by weight, and 93.2 parts by weight of sorbitol A modifier for frozen boiled rice was obtained in the same manner as in Example 15, except that the content was changed to 78.8 parts by weight. The solid content of the plant extract belonging to the Brassicaceae family, the α-glycosyltransferase content, the α-amylase content, and the α-glycosyltransferase/α-amylase (enzyme activity ratio) in the obtained frozen cooked rice improver were determined. Table 5 shows.

(Example 17) Preparation of improver for frozen boiled rice According to the composition of Table 5, 0.3 parts by weight of α-glycosyltransferase was changed to 0.1 part by weight, and 1.0 part by weight of α-amylase was changed to 3.33 parts by weight. , and 93.2 parts by weight of sorbitol were changed to 91.07 parts by weight to obtain a frozen boiled rice improver in the same manner as in Example 15. The solid content of the plant extract belonging to the Brassicaceae family, the α-glycosyltransferase content, the α-amylase content, and the α-glycosyltransferase/α-amylase (enzyme activity ratio) in the obtained frozen cooked rice improver were determined. Table 5 shows.

(Example 18) Preparation of improving agent for frozen cooked rice According to the formulation in Table 5, add water: 28.73 parts by weight to 50 parts by weight of sorbitol solution heated to 40 ° C. (product number: ZZ-1020)), while stirring at 41.7 S ^-1 , α-glycosyltransferase: 0.66 parts by weight, α-amylase: 0.11 parts by weight, belonging to the cruciferous family Plant extract (Production Example 1): 5.0 parts by weight, HM pectin: 0.25 parts by weight, and xanthan gum: 0.25 parts by weight were added and dissolved. After adding 2.5 parts by weight of sucrose fatty acid ester to this, the temperature was raised to 80° C. while stirring, and 10.0 parts by weight of glycerin fatty acid ester and 2.5 parts by weight of citric acid monoglyceride were added and dissolved. bottom. The resulting solution was homogenized with a high-speed emulsifying and dispersing machine (“Product number: Homomixer MARK II” manufactured by Primix Co., Ltd.) while being cooled to 55°C. got The solid content of the plant extract belonging to the Brassicaceae family, the α-glycosyltransferase content, the α-amylase content, and the α-glycosyltransferase/α-amylase (enzyme activity ratio) in the obtained frozen cooked rice improver were determined. Table 5 shows.

(Example 19) Preparation of frozen cooked rice According to Table 6, as a raw material for cooking rice, raw rice: 2.8 parts by weight of the improving agent for frozen cooked rice of Example 15, 178 parts by weight of water for 100 parts by weight of rinse-free rice "Akitakomachi" Weight parts were added, and after standing for 1 hour, rice was cooked using an IH jar rice cooker. The cooked rice was shaped into 60 g each and held in a -30° C. rapid freezer for 30 minutes to obtain frozen cooked rice. The obtained frozen boiled rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation. Table 6 shows the unit amount of each enzyme, the activity ratio, the solid content of the extract, and the amount of HM pectin in each example.

(Examples 20 to 22) Preparation of frozen cooked rice According to Table 6, 2.8 parts by weight of the frozen cooked rice improver of Example 19 (Example 15) was added to 1.0 part by weight of the frozen cooked rice improver of Example 16. (Example 20), 2.0 parts by weight of the frozen cooked rice improver of Example 17 (Example 21), or 2.8 parts by weight of the frozen cooked rice improver of Example 18 (Example 22) After cooking the rice in the same manner as in Example 19, except that the rice was cooked, the cooked rice was shaped and frozen to obtain frozen cooked rice. The obtained frozen boiled rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation.

As is clear from Table 6, with respect to 100 parts by weight of raw rice, the solid content contained in the extract of a plant belonging to the Brassicaceae family is in the range of 0.000014 to 0.0014 parts by weight, and A raw material for cooking rice containing 50 to 5000 units of α-glycosyltransferase and 1.5 to 150 units of α-amylase, and having an α-glycosyltransferase/α-amylase (enzyme activity ratio) in the range of 0.5 to 500. All of the frozen cooked rice used (Examples 19 to 22) were evaluated to be good in terms of softness, stickiness and graininess after natural thawing.

(Example 23) Preparation of frozen cooked rice According to Table 7, rice was cooked in the same manner as in Example 19, except that the raw rice: rinse-free rice "Akitakomachi" was changed to rinse-free rice "Koshihikari". Each was molded and held in a rapid freezer at -30°C for 30 minutes to obtain frozen boiled rice. The obtained frozen cooked rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation. Table 7 shows the unit amount of each enzyme, the activity ratio, the solid content of the extract, and the amount of HM pectin in each example, comparative example, and reference example.

(Reference Example 2) Preparation of cooked rice The same procedure as in Example 23 was performed except that 2.8 parts by weight of the frozen cooked rice improver of Example 15 was not added and 178 parts by weight of water was changed to 150 parts by weight. Rice was cooked in the same manner, and the cooked rice was cooled to 25°C.

(Example 24) Preparation of frozen boiled rice According to Table 7, raw rice: non-washed rice ``Akitakomachi'' was changed to ``Kyonishiki'', which was washed with running water three times, and then water was added to make the amount of added water 178 parts by weight. The rice was cooked in the same manner as in Example 19 except that the rice was cooked, and the cooked rice was shaped into 60 g each and held in a -30°C rapid freezer for 30 minutes to obtain frozen cooked rice. The obtained frozen cooked rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation.

(Reference Example 3) Production of boiled rice In Example 24, except that 2.8 parts by weight of the frozen boiled rice improver of Example 15 was not added and 178 parts by weight of water was changed to 150 parts by weight, the same procedure as in Example 24 was performed. Rice was cooked in the same manner, and the cooked rice was cooled to 25°C.

(Example 25) Preparation of frozen boiled rice According to Table 7, raw rice: rinse-free rice ``Akitakomachi'' was changed to ``Nipponbare'', which was washed with running water three times, and then water was added to make the amount of added water 178 parts by weight. The rice was cooked in the same manner as in Example 19 except that the rice was cooked, and the cooked rice was shaped into 60 g each and held in a -30°C rapid freezer for 30 minutes to obtain frozen cooked rice. The obtained frozen cooked rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation.

(Reference Example 4) Production of boiled rice In Example 25, except that 2.8 parts by weight of the frozen boiled rice improver of Example 15 was not added, and 178 parts by weight of water was changed to 150 parts by weight, the same procedure as in Example 25 was performed. Rice was cooked in the same manner, and the cooked rice was cooled to 25°C.

(Comparative Example 15) Preparation of frozen boiled rice According to Table 7, raw rice: rinse-free rice ``Akitakomachi'' was changed to ``Hoshiyutaka'', and after washing this with running water three times, water was added to make the amount of added water 178 parts by weight. The rice was cooked in the same manner as in Example 19 except that the rice was cooked, and the cooked rice was shaped into 60 g each and held in a -30°C rapid freezer for 30 minutes to obtain frozen cooked rice. The obtained frozen cooked rice was stored at −20° C. for 7 days and then naturally thawed (at 25° C. for 4 hours) for evaluation.

(Reference Example 5) Preparation of cooked rice In Comparative Example 15, except that 2.8 parts by weight of the frozen cooked rice improver of Example 15 was not added and 178 parts by weight of water was changed to 150 parts by weight, the same procedure as in Comparative Example 15 was performed. Rice was cooked in the same manner, and the cooked rice was cooled to 25°C.

As is clear from Table 7, the frozen cooked rice (Examples 19, 23 to 25) using raw rice that satisfies the conditions (A) and (B) in terms of amylose content [X] and water content [Y] is natural. The softness, stickiness and texture of the thawed cooked rice were evaluated as good. On the other hand, the frozen cooked rice (Comparative Example 15) using a raw material for cooking rice with a high amylose content [X] of 25.5% by weight in the raw rice was poorly evaluated for the stickiness and graininess of the cooked rice after natural thawing. The evaluation was D.

Claims (7)

A frozen cooked rice improver,
The raw material rice of the frozen cooked rice is rice that has an amylose content [X] (% by weight) and a water content [Y] (% by weight) that satisfies the following condition (A) or (B),
0.0014 to 0.047% by weight (in terms of solid content) of the extract of a plant belonging to the Brassicaceae family in the whole of the improver for frozen cooked rice, and 5000 to 166500 units of α-glycosyltransferase per 100 g of the improver , containing 150-5000 units of α-amylase,
The α-glycosyltransferase/α-amylase (enzyme activity ratio) is 0.5 to 500,
The extract is a mixture in which the amount of plants belonging to the family Brassicaceae (wet weight) / the total amount of water and ethanol (weight ratio) is 0.05 to 10. The mixture is extracted at 5 to 160 ° C. for 0.1 to 36 hours. A food improver for frozen boiled rice to be naturally thawed and eaten, which is an extract obtained by removing the residue of the extract of a plant belonging to the Brassicaceae family after processing.
[Condition (A)] 11.5≦X<19 and 11≦Y<7.0+8.5×{1−[(X−19.0)/8.5] ² } ^1/2
[Condition (B)] 19≤X≤25 and 11≤Y≤15.5 2. The improving agent for frozen cooked rice to be eaten after natural thawing according to claim 1, which contains 0.1 to 3.3% by weight of HM pectin in the whole improving agent for frozen cooked rice. Frozen cooked rice obtained by cooking raw materials for rice cooking and then freezing,
The raw material for rice cooking contains raw rice, solids contained in the extract of a plant belonging to the Brassicaceae family, water, α-glycosyltransferase, and α-amylase,
0.000014 to 0.0014 parts by weight of solids contained in the extract of a plant belonging to the Brassicaceae family and 150 to 190 parts by weight of water with respect to 100 parts by weight of the raw material rice;
and 50 to 5000 units of α-glycosyltransferase and 1.5 to 150 units of α-amylase per 100 g of the raw rice,
The α-glycosyltransferase/α-amylase (enzyme activity ratio) is 0.5 to 500,
The raw rice is frozen boiled rice for eating after natural thawing, wherein the amylose content [X] (% by weight) and the water content [Y] (% by weight) satisfy the following conditions (A) or (B): .
[Condition (A)] 11.5≦X<19 and 11≦Y<7.0+8.5×{1−[(X−19.0)/8.5] ² } ^1/2
[Condition (B)] 19≤X≤25 and 11≤Y≤15.5 4. The frozen cooked rice according to claim 3, wherein said raw material for cooking rice contains 0.001 to 0.1 parts by weight of HM pectin with respect to 100 parts by weight of said raw material rice. The raw material for cooking rice contains 1 to 3 parts by weight of the frozen cooked rice improver according to claim 1 or 2 with respect to 100 parts by weight of the raw rice, and the natural thawed product according to claim 3 or 4. Frozen rice for eating. Cooked rice obtained by naturally defrosting the frozen cooked rice according to any one of claims 3 to 5. A method for producing frozen cooked rice to be naturally thawed and eaten, comprising:
Rice cooking raw materials are cooked and then frozen,
The raw material for rice cooking includes raw rice, solids contained in the extract of a plant belonging to the Brassicaceae family, water, α-glycosyltransferase, and α-amylase,
With respect to 100 parts by weight of the raw material rice, the solid content contained in the extract of the plant belonging to the Brassicaceae is 0.000014 to 0.0014 parts by weight, and the water is 150 to 190 parts by weight,
The α-glycosyltransferase is 50 to 5000 units and the α-amylase is 1.5 to 150 units per 100 g of the raw rice, and the α-glycosyltransferase/α-amylase (enzyme activity ratio) ) is mixed so that it is 0.5 to 500,
The raw material rice is rice that has an amylose content [X] (% by weight) and a water content [Y] (% by weight) that satisfies the following condition (A) or (B),
The extract is a mixture in which the amount of plants belonging to the family Brassicaceae (wet weight) / the total amount of water and ethanol (weight ratio) is 0.05 to 10. The mixture is extracted at 5 to 160 ° C. for 0.1 to 36 hours. A method for producing frozen boiled rice to be eaten after natural thawing, which is an extract from which the residue of the extract of a plant belonging to the Brassicaceae family has been removed after being treated.
[Condition (A)] 11.5≦X<19 and 11≦Y<7.0+8.5×{1−[(X−19.0)/8.5] ² } ^1/2
[Condition (B)] 19≤X≤25 and 11≤Y≤15.5

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