JP7842542B2 - Rice cooking method and the flavor-enhancing and preservative agent used for cooked rice. - Google Patents

Description

This invention relates to a method for producing cooked rice, and to a rice flavor enhancer and preservative agent, in which a rice flavor enhancer and preservative agent is added to raw rice before cooking, resulting in cooked rice with good flavor, high moisture retention, good shelf life, and a flavor comparable to freshly cooked rice when reheated in a microwave after refrigeration.

Many additives are used in bento boxes and rice balls sold at supermarkets and convenience stores to improve shelf life and texture. In particular, recent demands for rice include the ability to extend shelf life without affecting taste, resistance to aging at low temperatures, good moisture retention for economical use, maintaining a taste close to freshly cooked rice for a long time after microwave reheating, and not interfering with the original flavor of the recipe.

In this context, prior art has described methods for producing cooked rice that imparts a flavor equivalent to conventional cooked rice products seasoned after cooking, while suppressing the development of a hard core (Patent Document 1), and cooking rice in which flavor and/or its persistence are significantly improved by adding a mixture obtained by mixing low-decomposition starch with a specific molecular weight and dextrin with a specific DE value in a specific mass ratio to cooked rice (Patent Document 2). It also describes a blended vinegar mainly composed of vinegar, sugars, salt, and high-intensity sweeteners that is lower in calories and costs than conventional vinegars, and does not impair the flavor or texture when mixed with cooked rice to make sushi rice (Patent Document 3). While these descriptions in prior art are all for sushi rice, the rice in this application is intended for plain white rice or colored rice that does not have a noticeable sour taste or vinegar odor. Preparations for sushi rice result in cooked rice with a strong sour taste and sweetness, which is too strong for other types of cooked rice.

Patent No. 6842075 Japanese Patent Publication No. 2017-077223 Japanese Patent Publication No. 2010-29175

The object of this invention is to provide a method for producing cooked rice in which a flavor-improving and spoilage-preventing agent is added during cooking, resulting in cooked rice with a good flavor, no acetic acid odor or sourness, high moisture retention (even when using more cooking water than the standard amount, the rice remains non-sticky and has a good texture), good shelf life, and a flavor that is virtually indistinguishable from freshly cooked rice when reheated in a microwave after refrigeration. The invention also provides a rice flavor-improving and spoilage-preventing agent.

As a result of diligent research, the inventors have discovered that when cooking rice, by adding or containing 1 to 3.5% by weight of a rice flavor-improving and preservative agent, which contains 1.0 to 18.2% by weight of acetic acid, 3.3 to 45.0% by weight of reduced starch hydrolysate, and 3.3 to 45.0% by weight of reducing sugar, and optionally salt, to 130 to 185% by weight of water relative to the raw rice, it is possible to obtain cooked rice that is free from acetic acid odor and sourness, has good flavor, high shelf life, high yield, is less susceptible to aging during storage, and exhibits excellent texture reproduction after microwave heating. The present invention was completed based on this finding.
In other words, the present invention is
1. A method for producing cooked rice, in which, during cooking, 1.0 to 3.5% by weight of a rice flavor enhancer and preservative, comprising 1.0 to 18.2% by weight of acetic acid, 3.3 to 45.0% by weight of reduced starch hydrolysate, 3.3 to 45.0% by weight of reducing sugar, and 0 to 17.0% by weight of salt, is added to 130 to 185% by weight of water relative to the raw rice, and the rice is then cooked.
2. The method for producing cooked rice according to claim 1, wherein the flavor-improving and spoilage-preventing agent for cooked rice contains 1.4 to 15.6% by weight of acetic acid, 6.6 to 40.0% by weight of hydrolyzed reduced starch, 6.6 to 40.0% by weight of reducing sugar, and 5 to 14% by weight of salt.
3. A flavor-improving and spoilage-preventing agent for cooked rice, comprising 1.0 to 18.2% by weight of acetic acid, 3.3 to 45.0% by weight of hydrolyzed reduced starch, 3.3 to 45.0% by weight of reducing sugar, and 0 to 17% by weight of salt.
4. The flavor-improving and spoilage-preventing agent for cooked rice according to claim 3, comprising 1.4 to 15.6% by weight of acetic acid, 6.6 to 40.0% by weight of reduced starch hydrolysate, 6.6 to 40.0% by weight of reducing sugar, and 5 to 14% by weight of salt.
That is the case.

The acetic acid used in this invention can be any edible vinegar, and can be either brewed vinegar or synthetic vinegar. Examples of brewed vinegars include black vinegar, rice vinegar, grain vinegar, apple vinegar, grape vinegar, fruit vinegar, and other brewed vinegars. Among these, synthetic vinegars and brewed vinegars (brewed vinegars that are neither grain vinegar nor fruit vinegar) are preferred due to their less sweetness and less distinctive flavor, while natural brewed vinegars (brewed vinegars that are neither grain vinegar nor fruit vinegar) are even more preferred. Furthermore, it can be used in either liquid or powder form. In this invention, powdered vinegar prepared by dissolving reduced starch hydrolysate in water with brewed vinegar and then adjusting the acidity to the desired level by spray drying can also be used.

The proportion of acetic acid (acetic acid equivalent acidity) in the rice flavor-improving and preservative agent (sometimes referred to as the formulation) used in this invention is 1.0 to 18.2% by weight, preferably 1.4 to 15.6% by weight, relative to the total amount of formulation components. The range of acetic acid added to raw rice during cooking is 0.036 to 0.182% by weight, preferably 0.044 to 0.156% by weight.

The reduced starch hydrolysates used in this invention are classified into high-saccharification reduced starch syrup, medium-saccharification reduced starch syrup, and low-saccharification reduced starch syrup depending on their degree of saccharification. While any of these can be used, rice should ideally have a lower sweetness. Therefore, medium-saccharification reduced starch syrup and low-saccharification reduced starch syrup are preferred, with low-saccharification reduced starch syrup being more preferred.

In the present invention, the proportion of reduced starch hydrolysate in the total formulation is 3.3 to 45.0% by weight, preferably 6.6 to 40.0% by weight, and more preferably 11.0 to 33.3% by weight, for liquid formulations. The proportion of reduced starch hydrolysate relative to raw rice during cooking is 0.033 to 1.575% by weight, preferably 0.066 to 1.400% by weight, and more preferably 0.11 to 1.166% by weight.

In this invention, the sweetness levels of reduced starch hydrolysates, with sugar set to 1, are 0.6-0.7 for high-saccharification reduced starch syrup, 0.4-0.5 for medium-saccharification reduced starch syrup, and 0.1-0.3 for low-saccharification reduced starch syrup. However, the sweetness level of "H-Pinex" manufactured by Matsutani Chemical Industry Co., Ltd., used in the examples, is 0.17.

The reducing sugars used in this invention are specifically palatinite, erythritol, lactitol, sorbitol, maltitol, etc., but palatinite and erythritol are preferred, and palatinite is more preferred.

In the present invention, the proportion of reducing sugar in the formulation is 3.3 to 45.0% by weight, preferably 6.6 to 40.0% by weight, and more preferably 11.0 to 33.3% by weight, relative to the total formulation in the case of a liquid formulation. Furthermore, the proportion of reducing sugar relative to raw rice is 0.033 to 1.575% by weight, preferably 0.066 to 1.400% by weight, and more preferably 0.11 to 1.166% by weight.

In this invention, the sweetness levels of reducing sugars, with sugar set to 1, are as follows: palatinite 0.45, erythritol 0.85, lactitol 0.35, sorbitol 0.54, and maltitol 0.95.

In this invention, the total amount of reduced starch hydrolysate and reducing sugars (total amount of sweetening components) is 33.0 to 50.0% by weight, preferably 33.0 to 40.0% by weight, relative to the total amount of the formulation.

In the rice flavor-improving and preservative agent of the present invention, the ratio of reduced starch hydrolysate to reducing sugar is 5:45 to 45:5 by weight, preferably 1:4 to 4:1, and more preferably 1:2 to 2:1.

In this invention, to incorporate the rice flavor-improving and preservative agent into cooked rice, the preparation is added to raw rice before cooking with water (added water) or a seasoning liquid containing it, and then cooked, allowing the preparation to fully penetrate the rice.
The rice cooking method in this invention can be carried out using conventionally known general methods and is not particularly limited. As a pretreatment before cooking, it is sufficient to wash the raw rice and soak it in water; in the case of pre-washed rice, washing is not necessary.
In the embodiments of the present invention, a rice cooker (JAI-H) manufactured by Tiger Corporation was used as the rice cooker pot, but the invention is not particularly limited to this.
In normal rice cooking, the amount of water added is typically 120-160% by weight (standard amount) of water relative to the weight of the raw rice (including the weight of water absorbed during washing) after quickly washing and draining the raw rice before cooking. However, when cooking rice with the formulation of the present invention, 130-185% by weight, preferably 140-180% by weight, of the raw rice is used as the amount of water added. Since people have preferences regarding the texture of rice (hardness, softness, etc.), in this test, an amount of water added of 150% by weight relative to the weight of the raw rice was used as the main standard amount.

In this invention, the amount (X) of the rice flavor-improving and deterioration-preventing agent added is 1.0 to 3.5% by weight (0.6 to 2.1% by weight in the case of a powder formulation) relative to the raw rice, preferably 1.2 to 3.0% by weight (0.7 to 1.8% by weight in the case of a powder formulation), and more preferably 1.5 to 3.0% by weight (0.9 to 1.8% by weight in the case of a powder formulation).

In this invention, the amount of water added (Y) by weight during rice cooking is the standard amount added, and is 3 to 42% by weight relative to the raw rice.
More specifically, regarding the amount of flavor-improving and preservative-free additive for cooked rice, when (X) is 1 to 3.5% by weight, the amount of added water during rice cooking (Y) is within the range of (X) × 3 to (X) × 12 (water addition coefficient of 3 to 12). Preferably, when (X) is 1.5 to 3.0% by weight, the same formula applies, and (Y) is within the range of (X) × 3 to (X) × 12% by weight.
In the case of powder formulations, since there is no water in the formulation, the amount of formulation to be added will be about 60% of that for liquid formulations. Therefore, the amount of water to be added should be the same as the amount used for liquid formulations.
In the present invention, the sweet components of the rice flavor enhancer and spoilage inhibitor are reduced starch hydrolysate and reducing sugars contained in the formulation. The sweetness level of the formulation is an index representing the sweetness of these components, and is expressed as a relative value with the sweetness intensity of 1% by mass of sucrose (at 20°C) set to 1.
The flavor-improving and spoilage-preventing agent for cooked rice of the present invention has a sweetness level of 6 to 29, preferably 10 to 20, and more preferably 11 to 19.

The salt used in this invention may include natural salts such as premium salt, regular salt, white salt, roasted salt, refined salt, rock salt, and seaweed salt, as well as synthetic salts. Any salt, whether synthetic or natural, is acceptable as long as it is suitable for consumption. The proportion of salt used in this invention is 0 to 17% by weight, preferably 5 to 14% by weight, relative to the total weight of the formulation.

The rice flavor enhancer and preservative used in this invention may be in powder or paste form, but a liquid form is easier to use in the rice manufacturing process.
The method for preparing the liquid formulation used in this invention is not particularly limited, and it can be prepared by dissolving each weighed raw material in water. In actual production, it is preferable to manufacture it in a tank equipped with a stirrer. However, the raw materials may be difficult to dissolve individually. It is thought that some components may agglomerate upon water absorption, forming poorly soluble solids, which cannot be easily dissolved once formed. In such cases, this can be greatly improved by weighing the required amount of raw materials in advance, sieving or crushing them as necessary, and mixing them uniformly to form the formulation.
The water used in the manufacture of the present invention is not particularly restricted as long as it is purified water, but purified water with low mineral content is preferable. There are also no particular restrictions on the temperature of the purified water, but warm water is preferable because the raw materials dissolve more easily. Furthermore, the present invention can be prepared as a stable liquid formulation by preparing a concentrated solution that does not recrystallize at 0°C. It can also be diluted to adjust to the required concentration.

The effect of the rice flavor-improving and preservative agent of the present invention is further enhanced by adding organic acids or their salts.
Examples of organic and inorganic acids and their salts that can be used include fumaric acid, monosodium fumarate, citric acid, trisodium citrate, sodium acetate, malic acid, sodium malate, tartaric acid, potassium bitartrate, sodium tartrate, succinic acid, monosodium succinate, disodium succinate, ferulic acid, phytic acid, adipic acid, lactic acid, sodium lactate, ascorbic acid, sodium ascorbate, gluconic acid (including glucono delta-lactone), sodium gluconate, sodium carbonate, sodium bicarbonate, and the like.

The present invention's flavor-improving and preservative agent for cooked rice and the food containing it may also contain various additives depending on the purpose, such as amino acids like glycine, DL-alanine, and monosodium glutamate; seasonings like potassium chloride and salt; pH adjusters like sodium acetate; sweeteners; sugars; sugarcane extract; thickeners; acidulants; oils and fats; spices and their extracts; antibacterial agents like ethanol, polylysine, protamine, nisin, hop extract, and lysozyme; preservatives; various vitamins; orthophosphates; metaphosphates; polyphosphates; pyrophosphates; nutritional fortifiers; antioxidants; and enzymes (α-amylase, β-amylase, glucoamylase, α-glucosidase, etc.). These additives may be added to the formulation or used in combination with the formulation.

The rice flavor enhancer and spoilage inhibitor of the present invention can be used in various processed rice products, such as plain cooked rice, foods seasoned during cooking (such as mixed rice dishes), foods seasoned after cooking (such as fried rice), and molded rice such as rice balls.
Rice cooked using this method has a good flavor upon cooking, enhances its shelf life (bacteriostatic properties) at room temperature to refrigerated temperatures after cooking, and improves moisture retention. As a result, it maintains the fluffy texture of freshly cooked rice for a long period, minimizes and prevents deterioration of the rice during storage, and can be reheated in a microwave to reproduce the excellent texture, shelf life, and moisture retention that are close to that of freshly cooked rice.

The present invention will be specifically described below with reference to examples.

As the flavor-improving and preservative agent for cooked rice (which may be referred to as "formulation" in this specification), the components listed in Table 1 were mixed and dissolved to prepare formulations (a) through (n).

Rice Cooking Method 1. Rice was cooked using a standard electric rice cooker without adding any cooking agents (conventional method).
150g of uncooked rice was weighed and immediately rinsed with water. The amount of water added, including the water absorbed during rinsing, was adjusted to 225g (150% of the weight of the uncooked rice). After soaking for 20 minutes, the rice was cooked, and then steamed for another 20 minutes.
2. The preparation (f) from Table 1 was added, and the rice was cooked using an electric rice cooker.
The additional weight percentage of water added to raw rice was estimated based on the following formula.
(X): Amount of formulation added (weight %)
(Y): Amount of water added when cooking rice (by weight %)
Formula: (Y) = (X) × 3 to (X) × 12
However, the upper limit for (Y) was set at 35% by weight.
150g of uncooked rice was weighed and immediately rinsed with water. Water was added to the uncooked rice so that the amount of water added, including the water absorbed during rinsing, was [standard amount + (Y)]% of the weight of the uncooked rice. Rice flavor enhancer and spoilage inhibitor (f) was added to the added water and stirred well. After soaking in water for 20 minutes, the rice was cooked in an electric rice cooker and then steamed for another 20 minutes.
White rice was cooked using the method described above, and the cooked rice was weighed. The results are shown in Table 2.

*The weight of cooked rice is the weight (g) after steaming for 20 minutes after cooking, and the yield is the weight percentage when the weight of additive-free cooked rice (150% of the standard amount) is set to 100%.

3. Observation of the texture of cooked rice and its aging state during storage. Ten experienced panelists conducted sensory evaluations of freshly cooked rice and rice stored at 10°C for 24 and 48 hours, before and after microwave heating. The results are shown in Table 3.

*The 10°C storage test was discontinued for samples that were too soft, as they could not be deemed to have any commercial value.

Criteria for evaluating the state of aging
A: Close to freshly cooked, good.
B: Shows almost no signs of aging, in good condition.
C: Slight aging, good condition
D: Somewhat aged
E: Aging is progressing
F: Extremely advanced aging

Based on the rice cooking method of Example 2, the yield of cooked rice was measured for rice cooked with formulations (a) and (j) listed in Table 1 of Example 1, and for rice cooked without any additives or with only acetic acid added. The results are shown in Table 4.

The results of the sensory evaluation by 10 experienced panelists are shown in Table 5.

*The 10°C storage test was discontinued for samples that were too soft, as they could not be deemed to have any commercial value.

Storage Test Method: Cooked rice, after steaming and cooling to room temperature (15°C), was aseptically divided into 10g portions, inoculated with 0.1ml of Bacillus cereus solution (300 CFU/ml), and stored at 15°C.
Table 6 shows the elapsed time and total bacterial count.

Following the cooking method of Example 2, white rice was cooked using the formulation shown in Table 1, and the yield (Table 7), the state of the cooked rice, and the state of aging after storage (Table 8) were compared by sensory testing.

Results of sensory evaluation (by 10 experienced panelists)

*The 10°C storage test was discontinued for samples that were too soft, as they could not be deemed to have any commercial value.

Assessment of aging
A: Close to the state after cooking, good.
B: Shows almost no signs of aging, in good condition.
C: Slight aging, good condition
D: Somewhat aged
E: Aging is progressing
F: Extremely advanced aging

Following the cooking method of Example 2, white rice was cooked using the formulations shown in Table 1, and the yield (Table 9), the state of the cooked rice, and the state of aging after storage (Table 10) were compared by sensory testing.

Sensory evaluation (by 10 experienced panelists)

Assessment of the state of aging
A: Close to the state after cooking, good.
B: Shows almost no signs of aging, in good condition.
C: Slight aging, good condition
D: Somewhat aged
E: Aging is progressing
F: Extremely advanced aging

Storage Test Method: Cooked rice, after steaming and cooling to room temperature, was aseptically divided into 10g portions. Each portion was inoculated with 0.1ml of Bacillus cereus solution (300 CFU/ml) and stored at 25°C. The relationship between storage time and total viable cell count is shown in Table 11.

Following the cooking method of Example 2, white rice was cooked using the formulation shown in Table 1, and the yield (Table 12), the state of the cooked rice, and the state of aging after storage (Table 13) were compared by sensory testing.

Formulation (n) could not be formulated because the solute was insoluble, but each component was added to the added water separately for sweetness comparison and testing was conducted.

Sensory evaluation (by 10 experienced panelists) results

Assessment of the state of aging
A: Close to the state after cooking, good.
B: Shows almost no signs of aging, in good condition.
C: Slight aging, good condition
D: Somewhat aged
E: Aging is progressing
F: Extremely advanced aging

Storage Test Method: Cooked rice, after steaming and cooling to room temperature, was aseptically divided into 10g portions. 0.1ml of Bacillus cereus solution (300 CFU/ml) was inoculated into each portion, and the total number of viable bacteria was measured after keeping the rice at 10°C for 24 to 96 hours. The results are shown in Table 14.

Following the rice cooking method of Example 2, an α-amylase preparation (Spitase R, manufactured by Nagase ChemteX Corporation) was added at a concentration of 0.1% of the raw rice in the pre-cooking step. White rice was then cooked using preparation (f) shown in Table 1, and the yield (Table 15), the state of the cooked rice, and the state of aging after storage (Table 16) were compared by sensory testing. In this experiment, the standard amount of cooking water was set at 130% by weight of the raw rice.

*All samples except 7-2 were treated with 0.1% Spitase R. Sensory evaluation (by 10 experienced panelists)

Assessment of the state of aging
A: Close to the state after cooking, good.
B: Shows almost no signs of aging, in good condition.
C: Slight aging, good condition
D: Somewhat aged
E: Aging is progressing
F: Extremely advanced aging

The cooked rice obtained by the method of the present invention is substantially free of acetic acid odor and sourness, has a high yield, good flavor, and excellent shelf life at room temperature. Moreover, the flavor and texture when reheated in a microwave or steamer after being stored at room temperature or low temperature is comparable to that of freshly cooked rice. Therefore, this method can be implemented in supermarkets, convenience stores, restaurants, and eateries that manufacture and sell rice-based foods, such as packaged white rice, red bean rice, mixed rice, and rice balls.

Claims (4)

A method for producing cooked rice, comprising adding 1.0 to 3.5% by weight of a rice flavor enhancer and preservative to 130 to 185% by weight of cooking water relative to the raw rice, and cooking the rice. The additive contains 1.0 to 18.2% by weight of acetic acid, 6.6 to 40.0% by weight of reduced starch hydrolysate with a sweetness of 0.1 to 0.3, 6.6 to 40.0% by weight of palatinite (registered trademark) , and 0 to 17.0% by weight of salt, with a weight ratio of 4/1 to 1/4 for the reduced starch hydrolysate and palatinite (registered trademark), and a total weight of 33.0 to 50.0% by weight of the combined additive. A method for producing cooked rice according to claim 1, wherein the flavor-improving and preservative agent for cooked rice contains 1.4 to 15.6% by weight of acetic acid, 6.6 to 40.0% by weight of reduced starch hydrolysate with a sweetness of 0.1 to 0.3, 6.6 to 40.0% by weight of palatinite (registered trademark) , and 5 to 14.0% by weight of salt, the weight ratio of the reduced starch hydrolysate to palatinite (registered trademark) is 4/1 to 1/4, and the total weight of both is 33.0 to 50.0% by weight . A flavor-improving and spoilage-preventing agent for cooked rice, containing 1.0 to 18.2% by weight of acetic acid, 6.6 to 40.0% by weight of reduced starch hydrolysate with a sweetness of 0.1 to 0.3, 6.6 to 40.0% by weight of palatinite (registered trademark) , and 0 to 17% by weight of salt, wherein the weight ratio of the reduced starch hydrolysate to palatinite (registered trademark) is 4/1 to 1/4, and the total weight of both is 33.0 to 50.0% by weight . A flavor-improving and spoilage-preventing agent for cooked rice according to claim 3, comprising 1.4 to 15.6% by weight of acetic acid, 6.6 to 40.0% by weight of reduced starch hydrolysate with a sweetness of 0.1 to 0.3, 6.6 to 40.0% by weight of palatinite (registered trademark ) , and 5 to 14% by weight of salt, wherein the weight ratio of the reduced starch hydrolysate to palatinite (registered trademark) is 4/1 to 1/4 , and the total weight of both is 33.0 to 50.0% by weight .