JP7305466B2 - Liquid quality improver for cooked rice and method for producing cooked rice - Google Patents

Description

The present invention relates to a liquid quality improver for cooked rice. The present invention also relates to a method for producing cooked rice using the liquid quality improver.

Cooked rice is sold in various forms in supermarkets, convenience stores, and the like. For example, it is sold in the form of being packed in a container as a staple food for commercially available lunch boxes, or in the form of being packed in a transparent plastic container for consumption on the day itself. Most of these types of cooked rice are eaten as they are after being heated in a microwave oven as needed, but since they can be easily applied to other rice dishes such as fried rice, omelet rice, and rice porridge, in recent years the sales volume has increased to household use.・Both commercial use is on the rise.

By the way, these cooked rices are generally mass-produced by machines in supermarket backyards, prepared food factories, and the like. Therefore, the production suitability of cooked rice is important, and it is necessary to add a large amount of oil to cooked rice. In addition, from the viewpoint of cost, the amount of water added during cooking is increased in order to improve the yield, so there is a risk that the texture may be impaired. In addition, cooked rice is sold or distributed at stores in a chilled temperature range or at room temperature. There is concern about the occurrence of problems.

In order to solve the above problems, the rice raw material is added with an oxidoreductase such as glucose oxidase and a metal-containing substance such as iron-containing yeast and iron salt, and then the rice is cooked to increase the stickiness of the cooked rice. It has been proposed to do so (see Patent Literature 1). Further, it has been proposed to improve the quality of cooked rice by adding a specific amount of a branching enzyme to the cooked rice material and then cooking the rice (see Patent Document 2).

WO2015/105112 JP 2018-117553 A

However, the techniques described in Patent Literatures 1 and 2 both involve the addition of powdered formulations and enzymes, and are complicated to handle. In addition, these techniques do not have a shelf life function that can suppress the growth of microorganisms in cooked rice.

Moreover, even if an attempt was made to prepare a liquid quality improver for boiled rice by simply adding a powdered enzyme to a liquid, it was difficult to distribute the agent while maintaining its activity sufficiently. Furthermore, this tendency was particularly remarkable when a large amount of acetic acid was added to the improver in order to suppress the growth of microorganisms in cooked rice.

Therefore, there is a demand for a cooked rice quality improver that can suppress the growth of microorganisms added to the cooked rice while sufficiently maintaining the enzyme activity that improves the quality of the cooked rice while being in an easy-to-handle liquid form.

As a result of a sincere study on the above problems, the present inventors unexpectedly found that a liquid for cooked rice that contains vinegar, has an acetic acid content exceeding a specific amount, and is added so that the pH of cooked rice is below a certain level The quality improver contains an enzyme and an organic acid salt, α-amylase and glucose oxidase are used as enzymes, and the above problems can be solved by adjusting the Brix value of the liquid quality improver within a specific range. . The present inventors have completed the present invention based on such findings.

That is, according to one aspect of the present invention,
Contains vinegar,
The acetic acid content is more than 3.0% by mass,
It is added so that the pH of the rice after cooking is 6.20 or less when measured by the following measurement method.
In the liquid quality improver for cooked rice,
containing enzymes and organic acid salts,
the enzyme comprises α-amylase and glucose oxidase;
characterized by a Brix value of 45.0% or more and 75.0% or less,
A liquid quality improver for cooked rice is provided.
<Method for measuring pH of cooked rice>
Add 2 parts by mass of ion-exchanged water to 1 part by mass of boiled rice, pulverize with a mixer or the like so that the whole is uniform, and measure with a pH measuring instrument at 1 atmospheric pressure and 20°C product temperature.

In the aspect of this invention, it is preferable that the said liquid quality improver contains 2 mass % or more of salt.

In the aspect of this invention, it is preferable that the acetic acid content of the said liquid quality improver is 7.0 mass % or less.

In the aspect of the present invention, it is preferable that the liquid quality improver is added so that the acetic acid content of the cooked rice becomes 0.03% by mass or more.

In the aspect of this invention, it is preferable that the acetic acid content of the said vinegar is 10 mass % or more and 20 mass % or less.

In an aspect of the present invention, the organic acid salt is at least one selected from the group consisting of acetate, citrate, lactate, fumarate, tartrate, malate, and gluconate. is preferred.

In the aspect of the present invention, it is preferable that two or more of the above organic acid salts are included.

In the aspect of this invention, it is preferable that the said organic acid salt contains an acetate and a citrate.

Also, according to another aspect of the present invention,
A method for producing cooked rice,
Including the step of adding the liquid quality improver to the cooked rice raw material,
characterized by having a pH of 6.20 or less when measured by the following measuring method,
A method for producing cooked rice is provided.
<Method for measuring pH of cooked rice>
Add 2 parts by mass of ion-exchanged water to 1 part by mass of boiled rice, pulverize with a mixer or the like so that the whole is uniform, and measure with a pH measuring instrument at 1 atmospheric pressure and 20°C product temperature.

According to the present invention, it is possible to provide a cooked rice quality improving agent that can suppress the growth of microorganisms in the cooked rice added at the same time while sufficiently maintaining the enzyme activity that improves the quality of cooked rice, even though it is in a liquid state. Moreover, according to this invention, the manufacturing method of the cooked rice using the said quality improving agent for cooked rice can also be provided.

<Liquid improver for cooked rice>
The liquid quality improver of the present invention contains at least a specific enzyme, vinegar, and an organic acid salt, and is added at the same time while sufficiently maintaining the enzyme activity that improves the quality of cooked rice while being in a liquid state. Microbial growth in cooked rice can also be suppressed. In the present invention, the quality of cooked rice refers to texture, flavor, shelf life, etc. of cooked rice, and at least any one of these should be improved.

(rice)
In the present invention, cooked rice means not only cooked rice obtained by cooking white rice or brown rice, but also barley rice obtained by cooking white rice and barley together, steamed rice obtained by cooking or steaming polished glutinous rice, and the like. included. Cooked rice also includes cooked and processed rice such as various types of cooked rice, brown rice, vinegared rice, red rice, and rice containing ingredients such as chestnuts or beans.

(pH of cooked rice)
In the present invention, the pH of cooked rice is defined by adding 2 parts by mass of ion-exchanged water to 1 part by mass of cooked rice, pulverizing the mixture with a mixer or the like so that the whole is uniform, and adjusting the pressure to 1 atm and the product temperature to 20 ° C. It is a value measured using a pH measuring device (desktop pH meter F-72 manufactured by Horiba, Ltd.).
The cooked rice in the present invention has a pH of 6.20 or less as measured by the above method. A lower limit of 5.40 or more is preferred in terms of flavor.

(Liquid quality improver and acetic acid content of cooked rice)
The acetic acid content of the liquid quality improver for cooked rice is more than 3.0% by mass, the upper limit is, for example, 7.0% by mass or less, and the lower limit is preferably 3.2% by mass or more. It is preferably 3.5% by mass or more, and the upper limit is preferably 6.8% by mass or less, more preferably 6.7% by mass or less. The acetic acid content of the liquid quality improver can be adjusted by adding vinegar or acetic acid as described below. If the acetic acid content of the liquid quality improver is within the above numerical range, the pH of the cooked rice can be easily adjusted within the desired range, and microbial growth in the cooked rice can be suppressed. If the content of acetic acid in the liquid quality improver is below the above range, a large amount of acetic acid must be added to suppress microbial growth in cooked rice, which is undesirable in terms of cost.
The acetic acid content of the liquid quality improver and cooked rice can be calculated by the following method (neutralization titration method: quantitative formula). The acetic acid content of cooked rice is calculated by adding 2 parts by mass of ion-exchanged water to 1 part by mass of cooked rice, pulverizing the whole with a mixer or the like so that the whole is uniform, and multiplying the value calculated by the following method by 3. Just do it.
First, a liquid quality improver or pulverized cooked rice was accurately collected, diluted 10 times with deionized water, and 2 drops of 3.1% phenolphthalein solution was added as an indicator to the diluted solution (100 g) to determine the titer. Neutralization titration is performed with a known 0.1 mol/L sodium hydroxide solution, and the acetic acid content of the liquid quality improver is determined by the following formula.
Acetic acid content of liquid quality improver (% by mass) = {(60.05 x 0.1 x F x V) x 100}/{sample collection amount (10 g) x 1000}
60.05: Molecular weight of acetic acid 0.1: Molar concentration (mol/L) of sodium hydroxide solution
F: titer of 0.1 mol / L sodium hydroxide solution V: titration volume (mL) of 0.1 mol / L sodium hydroxide solution

(Brix value of liquid quality improver)
The Brix value of the liquid quality improver is 45.0% or more and 75.0% or less, and the lower limit is preferably 48.0% or more, more preferably 50.0% or more, and still more preferably 55%. % or more, and the upper limit is preferably 73.0% or less, more preferably 70.0% or less, and still more preferably 67.0% or less. If the Brix value of the liquid quality improver is below the above range, the enzymatic activity cannot be sufficiently maintained. If the Brix value of the liquid quality improver exceeds the above range, the viscosity of the liquid quality improver becomes extremely high, making it difficult to mix with the cooked rice material. The Brix value in the liquid quality improver can be prepared by blending those commonly used in foods, and the use of saccharides such as maltose is preferable from the standpoint of flavor.
The Brix value of the liquid quality improver is a value measured at 20°C using a refractometer and corresponds to the mass percentage of the sucrose aqueous solution at 20°C.

(enzyme)
In the present invention, at least α-amylase and glucose oxidase are used as enzymes. By using α-amylase and glucose oxidase together as additive enzymes for cooked rice, both the stickiness and graininess of the surface of the cooked rice can be improved, and the texture is smooth and has moderate hardness, which is very preferable. It becomes quality rice. The use of α-amylase alone can improve the stickiness of the surface of the cooked rice, but the cooked rice loses graininess. On the other hand, if only glucose oxidase is used, the texture of the cooked rice can be improved, but the cooked rice as a whole will be rough and have a bad texture.

α-Amylase is an enzyme that randomly cleaves α-1,4-bonds of starch to decompose it into polysaccharides, maltose and oligosaccharides. By adding α-amylase to cooked rice, the stickiness of the surface of cooked rice can be improved by decomposing amylose, which is starch. The α-amylase used in the present invention may be a commercial product, and those with an enzymatic activity of, for example, 500,000 to 1,000,000 U/g can be used.

The content of α-amylase in the liquid quality improver is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.05% by mass or more and 2% by mass, based on the total liquid quality improver. or less, more preferably 0.1% by mass or more and 1% by mass or less. If the α-amylase content is within the above numerical range, the enzymatic activity that improves the quality of cooked rice can be sufficiently maintained.

Glucose oxidase is an enzyme that has the activity of catalyzing a reaction that produces gluconic acid and hydrogen peroxide using glucose, oxygen, and water as substrates. It is presumed that the hydrogen peroxide produced by this reaction oxidizes the SH groups in the protein, thereby promoting the formation of SS bonds (disulfide bonds) and forming a crosslinked structure in the protein. Glucose oxidase is known to have various origins such as those derived from microorganisms and plants, but the origin of glucose oxidase used in the present invention is not particularly limited as long as it has the above-mentioned activity, Even glucose oxidase can be used, and recombinant enzymes can also be used. Addition of glucose oxidase to cooked rice can improve graininess of the cooked rice. The glucose oxidase used in the present invention may be a commercial product, and one having an enzymatic activity of, for example, 500 to 5000 U/g can be used.

The content of glucose oxidase in the liquid quality improver is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.003% by mass or more and 0.5% by mass, relative to the entire liquid quality improver. % or less, more preferably 0.005 mass % or more and 0.1 mass % or less. If the content of glucose oxidase is within the above numerical range, the enzymatic activity that improves the quality of cooked rice can be sufficiently maintained.

(vinegar)
The liquid quality improver of the present invention contains vinegar. By using food-derived vinegar as a raw material containing acetic acid, the growth of microorganisms can be suppressed without impairing the original flavor of cooked rice. Vinegar is obtained by acetic acid fermentation of grains such as rice, malt and sake lees, fruits such as grapes and apples, vegetables such as onions, carrots and tomatoes, other agricultural products, and alcohol. Examples of such vinegar include rice vinegar, black vinegar, five grain vinegar, wine vinegar, apple vinegar, and tomato vinegar. These vinegars may be used individually by 1 type, and may use 2 or more types together.

The acetic acid content of the vinegar is not particularly limited, but is, for example, 10% by mass or more and 20% by mass or less, the lower limit is preferably 13% by mass or more, more preferably 15% by mass or more, and the upper limit is is preferably 19% by mass or less, more preferably 18% by mass or less. Incidentally, the vinegar used in the present invention may be a commercially available product. The acetic acid content of vinegar can be measured in the same manner as the method for measuring the acetic acid content of the liquid quality improver described above.

The content of vinegar in the liquid quality improver is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 45% by mass or less, and still more preferably, based on the total liquid quality improver. is 15% by mass or more and 40% by mass or less. If the content of the vinegar is within the above numerical range, it is possible to sufficiently maintain the enzyme activity that improves the quality of the cooked rice, and at the same time suppress the growth of microorganisms in the cooked rice added.

(Organic acid salt)
The liquid quality improver of the present invention contains an organic acid salt. Organic acid salts include salts of organic acids such as acetic acid, citric acid, lactic acid, fumaric acid, tartaric acid, malic acid, and gluconate (eg, sodium, potassium, calcium, etc.). Among these, it is preferable to use sodium acetate, sodium citrate, sodium lactate, sodium fumarate, sodium tartrate, sodium malate, sodium gluconate and the like. point is preferable. These organic acid salts may be used individually by 1 type, and may use 2 or more types together.

The content of the organic acid salt in the liquid quality improver is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, relative to the entire liquid quality improver, More preferably, it is 5% by mass or more and 12% by mass or less. If the content of the organic acid salt is within the above numerical range, the growth of microorganisms in the cooked rice added at the same time can be suppressed while sufficiently maintaining the enzyme activity that improves the quality of the cooked rice.

(Other raw materials)
In addition to the raw materials described above, the liquid quality improver can be blended by appropriately selecting various raw materials commonly used for liquid quality improvers within a range that does not impair the effects of the present invention. Other raw materials include, for example, acetic acid, amino acids, salt, sweeteners, thickeners, and the like. Among these, the liquid quality improver is preferably 2% by mass or more, more preferably 3% by mass or more and 10% by mass or less, more preferably 4% by mass or more and 8% by mass, based on the total mass of the liquid quality improver. It is preferable to include the following salts. If the salt content is within the above numerical range, the enzymatic activity that improves the quality of cooked rice can be sufficiently maintained.

(Method for preparing liquid quality improver)
A method for preparing the liquid quality improver is not particularly limited, and a conventionally known method can be used. For example, fresh water, enzymes, vinegar, organic acid salts, and other raw materials such as salt and sweeteners are put into a stirring tank and uniformly mixed using a mixer to prepare a liquid quality improver. can be done.

(Manufacturing equipment)
For the preparation of the liquid quality improver of the present invention, equipment commonly used for food production can be used. Examples of such devices include general stirrers, stick mixers, stand mixers, homomixers, homodispers, and the like. Examples of the shape of the stirring blades of the stirrer include propeller blades, turbine blades, paddle blades, anchor blades, and the like.

<Method for producing cooked rice>
The method for producing cooked rice of the present invention includes the step of adding the liquid quality improver to the cooked rice raw material. The amount of the liquid quality improver to be added may be appropriately adjusted so that the obtained cooked rice has a pH of 6.20 or less as measured by the above method. Moreover, the liquid quality improver is preferably added so that the acetic acid content of the cooked rice is 0.03% by mass or more.

Subsequently, the cooked rice can be obtained by performing a step of cooking the cooked rice raw material to which the liquid quality improving agent is added. A method of cooking rice is not particularly limited, and a conventionally known method can be used. Furthermore, a step of accommodating or packaging the obtained cooked rice in a container or packaging material may be performed.

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention should not be construed as being limited to the contents of the following examples.

<Preparation of liquid quality improver for cooked rice>
A liquid quality improver for cooked rice was prepared according to the blending ratios shown in Tables 1 and 2. Specifically, in a stirring tank, maltose, vinegar (acetic acid content: 15% by mass), common salt, sodium citrate and/or sodium acetate and/or sodium malate and/or sodium lactate as an organic acid salt, α as an enzyme Amylase (500,000 to 5,000,000 U/g) and/or glucose oxidase (1000 to 2000 U/g), 50% acetic acid, and pure water were charged and uniformly mixed using a mixer to prepare a liquid quality improver. For each of the obtained liquid quality improvers for cooked rice, the pH was measured using a pH measuring device (desktop pH meter F-72 manufactured by Horiba, Ltd.) at 1 atm and a product temperature of 20 ° C. were all 3.5 to 5.5.
Tables 1 and 2 show the enzymatic activities of α-amylase and glucose oxidase for each liquid quality improver.

(Measurement of acetic acid content)
The acetic acid content of the liquid quality improver was calculated by the following method (neutralization titration method: quantitative formula). First, a liquid quality improver was accurately taken and diluted 10-fold with deionized water. Neutralization titration was carried out with a 1 mol/L sodium hydroxide solution, and the acetic acid content of the liquid quality improver was determined according to the following formula. The results are shown in Tables 1 and 2.
Acetic acid content of liquid quality improver (% by mass) = {(60.05 x 0.1 x F x V) x 100}/{sample collection amount (10 g) x 1000}
60.05: Molecular weight of acetic acid 0.1: Molar concentration (mol/L) of sodium hydroxide solution
F: titer of 0.1 mol / L sodium hydroxide solution V: titration volume (mL) of 0.1 mol / L sodium hydroxide solution

(Brix value measurement)
The Brix value of the liquid quality improver was measured by adjusting the temperature to 20° C. using a digital refractometer (Atago Digital Refractometer RX-7000i). The results are shown in Tables 1 and 2.

<Production of cooked rice>
After washing and draining the commercially available uncooked rice, 1.5 times the mass of the uncooked rice was added with fresh water and immersed at room temperature for 1 hour. After that, the liquid quality improver prepared above and stored at 4°C for 21 days was added in a proportion of 2.0% by mass with respect to the mass of uncooked rice, and mixed well so that the whole was uniform. bottom. Subsequently, rice was cooked by a rice cooker in accordance with a conventional method.

Rice was cooked in the same manner, except that the liquid quality improver of Example 1 was separately added in a proportion of 5.0% by mass with respect to the mass of uncooked rice (Example 1-2).
Rice was cooked in the same manner, except that the liquid quality improver of Example 5 was added separately at a rate of 1.0% by mass and 1.3% by mass with respect to the mass of uncooked rice ( Examples 5-2, 5-3).

<Measurement of pH and acetic acid content of cooked rice>
Add 2 parts by mass of ion-exchanged water to 1 part by mass of cooked rice, grind it with a mixer or the like so that the whole is uniform, and set it to 1 atmospheric pressure and a product temperature of 20 ° C. pH was measured using a desktop pH meter F-72). The results are shown in Tables 3 and 4.
Moreover, the acetic acid content of the cooked rice was 0.03% by mass or more, except for Comparative Example 1.

<Sensory evaluation of cooked rice>
The texture of the cooked rice cooked above was sensory evaluated by a trained panel according to the following criteria. Evaluation results are shown in Tables 3 and 4. In the following evaluation, if the evaluation is 3 points or more, it can be said that the result is good. The control section refers to rice cooked in the same manner as above without adding the liquid quality improver.
[Evaluation criteria for texture of cooked rice]
4: Compared to the control group, both the stickiness of the surface of the cooked rice and the graininess of the cooked rice were remarkably improved, and the texture was very favorable.
3: Compared to the control group, both the stickiness of the surface of the cooked rice and the texture of the cooked rice were improved, and the texture was favorable.
2: Compared to the control group, either the stickiness of the surface of the cooked rice or the grainy texture of the cooked rice was not improved, and the improvement of the texture was not sufficient.
1: Compared to the control group, neither the stickiness of the surface of the cooked rice nor the graininess of the cooked rice was improved, and the texture was equivalent.

<Evaluation of longevity of cooked rice>
After adding a diluted culture solution so that the amount of added bacteria (Bacillus subtilis) is about 10 / g with respect to the mass of the cooked rice, it is heated at 25 ° C. for 48 hours. cultured. After that, it was inoculated onto a standard agar medium and cultured at 35° C. for 48 hours, and then the number of colonies was measured. Evaluation results are shown in Tables 3 and 4.
○: The number of bacteria after the bacteria addition test was 10 ⁵ cfu or less.
×: The number of bacteria after the bacteria addition test was over 10 ⁵ cfu.

<Enzyme activity residual rate evaluation>
[α-amylase]
(Reagents and reagents used)
1) 0.2 mol/L acetate buffer:
13.6 g of sodium acetate (trihydrate) was dissolved in water to make 500 mL, and the pH was adjusted to 5.7 using a 0.2 mol/L acetic acid solution.
2) Iodine test solution:
5 mL of 0.05 M iodine solution and 0.4 mL of 25% potassium iodide solution were added to water to make 20 mL. 5.8 mL of 6N hydrochloric acid was added to 5 mL of this iodine/potassium iodide solution, and the volume was adjusted to 250 mL with water.
3) 1.0% soluble starch solution:
2 g of soluble starch (manufactured by Merck & Co., special reagent for analysis) was weighed precisely, heated at 105° C. for 4 hours, and the loss on drying was measured in advance. Soluble starch corresponding to 2 g of dry matter was accurately weighed and suspended in about 20 mL of water. This suspension was slowly added to about 100 mL of boiling water and dissolved, followed by gentle boiling for 30 seconds. After standing to cool, 40 mL of the 0.5 mol/L acetate buffer (pH 6.0) prepared above was added, and the volume was made up to 200 mL with water.
4) Substrate solution:
Add 1 mL of water to 10 mL of the 1.0% soluble starch solution prepared above and mix, take 0.1 mL of the solution, put it in 10 mL of the iodine test solution prepared above, and immediately mix to obtain a blank solution. was measured at a wavelength of 620 nm, and a 1.0% soluble starch solution exhibiting an absorbance of 0.9 to 1.0 was selected and used as a substrate solution.

(Activity measurement method)
Exactly 10 mL of the substrate liquid was taken and shaken for 10 minutes in a constant temperature shaking bath at 40°C, and then 1 mL of the liquid quality improver diluted with ion-exchanged water (20 times by weight) was accurately added and immediately shaken. After that, it was shaken at 40°C. A 0.1 mL aliquot was taken every 1 minute from the start of the reaction, placed in 10 mL of an iodine test solution prepared in advance, and immediately mixed to obtain a test solution. The absorbance At when the blue color of the test solution disappeared and changed to red was measured at a wavelength of 620 nm. As a blank test solution, 1 mL of water was used instead of the sample solution, and the absorbance Ab was measured in the same manner as the test solution. Using Ab and At, the enzymatic activity was determined from the following formula. As a unit, 1 U/g was defined as the enzymatic activity of 1 g of the enzyme that reduces the blue color caused by iodine in the substrate solution (soluble starch) by 10% per minute.
Enzyme activity (U/g) = (Ab-At)/Ab x 100/10 x 1/t x 1/w
t: reaction time (minutes)
w: Amount (g) of enzyme in 1 mL of 20-fold diluted liquid quality improver

[glucose oxidase]
Using glucose as a substrate, glucose oxidase is allowed to act in the presence of oxygen to produce hydrogen peroxide, and the produced hydrogen peroxide is allowed to act with peroxidase in the presence of aminoantipyrine and phenol to produce a color tone exhibited by a quinoneimine dye. , measured and quantified at a wavelength of 500 nm. The amount of enzyme required to oxidize 1 µmol of glucose per minute was defined as 1 U (unit). The enzyme activity (U/g) was obtained by dividing this by the amount (g) of the enzyme.

Immediately after preparation of the liquid quality improver and after storage (4°C, 21 days), the enzymatic activities of α-amylase and glucose oxidase were calculated using the above method, and the enzymatic activities of the enzymes immediately after adjustment after storage were calculated. The value divided by the activity was defined as the residual enzyme activity rate, which was evaluated according to the following criteria. Evaluation results are shown in Tables 3 and 4.

[Evaluation Criteria for Residual Enzyme Activity]
◯: Both enzyme activity residual rates of α-amylase and glucose oxidase were 80% or more and 100% or less.
Δ: Both of α-amylase and glucose oxidase had a residual enzyme activity rate of 50% or more, and either or both of them had a residual enzyme activity rate of less than 80%.
x: The residual rate of either α-amylase or glucose oxidase was less than 50%.

All of the liquid quality improvers for cooked rice of Examples 1 to 16 had an evaluation standard of 4 points for the texture of the cooked rice after cooking, and good results were obtained for the evaluation of the shelf life of the cooked rice and the evaluation of the residual rate of enzyme activity. .
The liquid quality improver for cooked rice of Comparative Example 1 had an acetic acid content of 3.0% by mass, and the pH of the cooked rice after cooking was higher than 6.2. .
The liquid quality improver for cooked rice of Comparative Example 2 had an α-amylase enzymatic activity residual rate of 80% or more and 100% or less, but since it did not contain glucose oxidase at all, the cooked rice after cooking was compared with the control group. As a result, the stickiness of the surface was improved, but the graininess was impaired, which was not preferable.
In the liquid quality improver for cooked rice of Comparative Example 3, the enzyme activity residual rate of glucose oxidase was 80% or more and 100% or less, but since α-amylase was not blended at all, the cooked rice after cooking was compared with the control group. As a result, the graininess was improved, but the texture as a whole was rough and unfavorable.
Since the liquid quality improver for cooked rice of Comparative Example 4 had a Brix value of less than 45%, the enzymatic activities of α-amylase and glucose oxidase could not be sufficiently maintained.

Claims (9)

Contains vinegar,
The acetic acid content is more than 3.0% by mass,
It is added so that the pH of the rice after cooking is 6.20 or less when measured by the following measurement method.
In the liquid quality improver for cooked rice,
containing enzymes and organic acid salts,
the enzyme comprises α-amylase and glucose oxidase;
characterized by a Brix value of 45.0% or more and 75.0% or less,
Liquid quality improver for cooked rice.
<Method for measuring pH of cooked rice>
Add 2 parts by mass of ion-exchanged water to 1 part by mass of boiled rice, pulverize with a mixer or the like so that the whole is uniform, and measure with a pH measuring instrument at 1 atmospheric pressure and 20°C product temperature. characterized in that the liquid quality improver contains 2% by mass or more of salt,
The liquid quality improver according to claim 1. The acetic acid content of the liquid quality improver is 7.0% by mass or less,
The liquid quality improver according to claim 1 or 2. The liquid quality improver is added so that the acetic acid content of the cooked rice is 0.03% by mass or more,
The liquid quality improver according to any one of claims 1-3. The acetic acid content of the vinegar is 10% by mass or more and 20% by mass or less,
The liquid quality improver according to any one of claims 1-4. The organic acid salt is at least one selected from the group consisting of acetate, citrate, lactate, fumarate, tartrate, malate, and gluconate,
The liquid quality improver according to any one of claims 1-5. characterized by containing two or more of the organic acid salts,
The liquid quality improver according to any one of claims 1-6. characterized in that the organic acid salts include acetates and citrates,
The liquid quality improver according to any one of claims 1-7. A method for producing cooked rice,
A step of adding the liquid quality improver according to any one of claims 1 to 8 to the cooked rice raw material,
characterized by having a pH of 6.20 or less when measured by the following measuring method,
A method for producing rice.
<Method for measuring pH of cooked rice>
Add 2 parts by mass of ion-exchanged water to 1 part by mass of boiled rice, pulverize with a mixer or the like so that the whole is uniform, and measure with a pH measuring instrument at 1 atmospheric pressure and 20°C product temperature.