JPH10262580A - Production of boiled rice - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a boiled rice by using a low quality rice, having taste same as the boiled rice obtained by using a high quality rice, and hardly lowering the taste as the time passage by boiling the rice with an acidic water formed by electrolysis of water. SOLUTION: The objective boiled polished rice having good taste same as that of the boiled polished rice obtained by boiling a high quality rice with a neutral water is obtained by boiling a low quality rice with an acidic water formed by electrolysis of water. A good sushi rice is obtained by blending the boiled rice with blended vinegar because the texture-reduction thereof according to the time passage is low and discoloring degree thereof is also small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing cooked rice such as white rice and sushi rice.

[0002]

2. Description of the Related Art Generally, clean neutral water such as tap water is used for cooking rice, and delicious rice can be cooked by taking into consideration the degree of water used and heat. With the advancement of cooking utensils, rice cookers now automatically control rice cooking conditions, so that cooked rice with a substantially constant taste can be cooked with little consideration for the amount of water used and the amount of heat.

[0003] However, there are two types of rice, good-tasting rice (high-quality rice) and low-tasting rice (low-quality rice), depending on the quality of the rice. It is unavoidable that the taste is superior even if the rice is cooked using the same rice cooker.

[0004] For this reason, it is desired to develop a rice cooking method in which low-quality rice is used to cook rice having substantially the same delicious taste as high-quality rice. An example of the rice cooking method is disclosed in Japanese Patent Laid-Open No. 7-289.
No. 178 is proposed.

In the rice cooking method, rice is cooked using electrolyzed water generated by electrolyzing water. Rice is immersed in acidic water, which is one of the electrolyzed waters, and then the rice is acidified. The rice soaked in the above is cooked with alkaline water which is the other of the electrolyzed water.

[0006]

By the way, the present inventors have conducted intensive studies on the rice cooking method. As a result, when low-quality rice is cooked using alkaline water, neutral water such as tap water is removed. Although the taste of white rice immediately after cooking is improved compared to the case of using and cooking rice, the taste decreases over time and is inferior to the taste of white rice cooked with neutral water after a predetermined time has elapsed , And that once the taste was reduced, it was not possible to recover the taste of cooked rice cooked with neutral water even by subsequent heat treatment with a microwave oven.

[0007] Accordingly, an object of the present invention is to address such a problem. Cooked rice using low-quality rice has the same taste as cooked rice using high-quality rice, and there is little deterioration in taste over time. Is to manufacture.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for producing cooked rice. The method comprises producing rice by cooking rice using acidic water produced by electrolyzing water. The present invention is characterized in that the obtained cooked rice is prepared into sushi rice.

[0009] Thus, in the present invention, cooked rice obtained by cooking rice is hereinafter referred to as white rice, and cooked rice prepared by combining white rice with vinegar is referred to as sushi rice.

[0010]

[Effects and Effects of the Invention] When low-quality rice is cooked using electrolyzed water generated by electrolysis of water, the rice is cooked regardless of whether the electrolyzed water is acidic or alkaline. The degree of gelatinization of the white rice immediately after is higher than that of white rice cooked using neutral water such as tap water, and is close to white rice obtained by cooking high-quality rice with neutral water.

[0011] When comparing white rice using acidic water with white rice using alkaline water, the degree of gelatinization is higher for white rice using acidic water than white rice using alkaline water.
In addition, it was found that the degree of gelatinization did not decrease over time and the degree of coloring over time was small.

Therefore, when low-quality rice is cooked using acidic water, high-quality rice can be obtained with the same good taste as white rice cooked using neutral water. Also,
The white rice is particularly good as a sushi rice which is required to maintain a good taste for several hours after preparation with combined vinegar, since the deterioration of the good taste over time and the degree of coloring are small.

[0013]

【Example】

(1) Rice for cooking and water for cooking As rice for cooking, white rice (high-quality rice) from Koshihikari from Shimane Prefecture and rice from Hiroshima Prefecture, which were polished after storage for 10 months in brown rice produced in 1995 and were polished. Thousands of white rice (low quality rice)
And high-quality rice as common tap water (pH 6.95), and low-quality rice as the same tap water, acid water and alkaline water generated by electrolyzing water. Each type was adopted.

However, for electrolysis of water, a diaphragm electrolyzer HOX-40A (trade name) manufactured by Hoshizaki Electric Co., Ltd.
Is used to electrolyze general tap water (pH 6.95) as raw water to produce acidic water (pH 3.95) generated in the anode chamber.
75) with alkaline water (pH
9.25) was collected, and the acidic water and the alkaline water were supplied to rice cooking water.

(2) Cooking Conditions One sample of 145 g of high-quality rice and three samples of 145 g of low-quality rice are collected, and each sample rice is stirred twice with 200 cc of tap water 20 times, and then washed three times. Drain for 30 minutes. Next, 200 cc of the above-mentioned rice cooking water was added to the drained rice washes, and the rice was cooked using a commercially available electric rice cooker. In cooking rice, heating and steaming together 3
It cooked for 0 minutes and obtained four kinds of white rice.

(3) Preparation of sushi rice To 20 cc of rice vinegar, 3 g of salt and 6 g of white sugar are added and dissolved with stirring to prepare four samples of combined vinegar, each of which is combined with various types of freshly cooked white rice collected on a plate. Vinegar was added and uniformly mixed for 1 minute while blowing to prepare four types of sushi rice.

(4) Measurement of various characteristics (4a) Taste analysis of rice for cooking: 200 μm for each rice for cooking
The crushed powder was used to measure the amount of amylose, protein, water and fatty acid using a taste meter manufactured by Satake Seisakusho, TBIC (trade name), and the taste was calculated from these values. Table 1 shows the obtained results.

(4b) Characteristics of rice washing waste liquid: For high-quality rice and low-quality rice, the amounts of protein and starch eluted in the rice washing waste liquid when the rice was washed with the water for cooking rice were measured. pH: Measured with a Horiba pH meter D-12 (trade name). Eluted amount of protein: Measured by a dye binding method using Kit-I (trade name), a protein assembly manufactured by Bio-Rad. Amount of starch eluted: The amount of free reducing sugar in 1 cc of washing rice waste liquid was determined by the Somogyi and Nelson method. 1 cc of washing rice waste liquid is treated with trifluoroacetic acid (final concentration 2N) for 100
After hydrolyzing at 4 ° C for 4 hours, this was diluted 10-fold, and the total reducing sugar was quantified in the same manner as above. The difference between the total reducing sugar and the free reducing sugar was multiplied by 0.90 to obtain the starch elution amount. Table 2 shows the obtained results.

(4c) Degree of gelatinization of cooked rice: each white rice immediately after cooking,
10 hours from each sushi rice after 1 hour and 6 hours storage
g were collected, crushed in cold ethanol, suction-filtered and dehydrated to obtain a powder sample. 8 cc of water was added to 80 mg of each powder sample and homogenized, and 2 cc of
Was collected and adjusted to 25 cc with a 0.8 M acetate buffer to prepare a suspension sample, and sodium hydroxide solution was added to the other 2 cc for alkali gelatinization, followed by neutralization with acetic acid. This was adjusted to 25 cc with a 0.8 M acetate buffer to prepare a suspension sample. Based on the method of Kainuma et al., The degradability of β-amylase and pullulanase in 2 cc of each sample was measured, and the gelatinization degree was calculated from the ratio. The results obtained are shown in Table 3 for white rice and Table 4 for sushi rice.
Shown in

(4d) Measurement of cooked rice texture: Various white rice was measured by GTX-2 (trade name), a texturometer manufactured by General Food Co. based on the method of Okave.
The hardness and stickiness of each white rice were measured by the granulation method, and the stickiness / hardness was calculated. However, the measurement conditions are as follows. That is, the sample: three rice grains (product temperature about 20
Degrees Celsius), plunger ... Lusart cylinder (diameter 18m)
m), clearance: 0.2 mm, mastication speed: 6 times /
Min, voltage: 1 V, recording speed: 750 mm / min. The obtained results are shown in Table 3 for white rice and in Table 5 for sushi rice.

(4e) Coloring degree of sushi rice: 1 for each sushi rice
The degree of coloring after storage for 6 hours was determined according to JISZ8722.
Based on a, L ^* a ^* b ^* values belonging to the CIE system were measured using a Minolta colorimeter CR-300 (trade name). Table 6 shows the obtained results.

(4f) pH of outer layer and inner layer of sushi rice:
Regarding the pH of the outer layer, 10 g of sushi rice was deaerated water (pH
7) After shaking for 1 minute in 20 cc, the filtrate was suction-filtered with a glass filter to obtain a filtrate, which was measured with a pH meter. Regarding the pH of the inner layer, 40 cc of degassed water (pH 7) was added to the rice grains remaining on the glass filter, and a homogenizer manufactured by Sakuma Seisakusho, 500AC-2 was used.
(Trade name) for 2 minutes to obtain the pH of the obtained liquid,
It was measured with a pH meter. Table 7 shows the obtained results.

(4g) Sensory test: Using sushi rice using tap water as water for cooking rice as a reference (3 points) using a consumer panel of 10 people, and evaluating color, gloss, acidity, hardness, stickiness, and comprehensive evaluation The 6 properties were evaluated on a 1-5 scale scale. The obtained results are shown in Table 8 and FIG. However, the solid line graph in FIG. 1 shows sushi rice using tap water, the one-chain line graph shows sushi rice using acidic water,
The broken line graph is a sensory evaluation of sushi rice using alkaline water.

(5) Consideration (about white rice) The factors that affect the taste characteristics of cooked rice include amylose content and protein content contained in rice. These contents are shown in Table 1 for high-quality rice and low-quality rice. When compared on the basis of, protein content is almost the same in both rice, but low quality rice is higher in amylose content,
It can be seen that low quality rice has a lower taste value than high quality rice.

A comparison of the degree of gelatinization and texture of white rice obtained by cooking high-quality rice and low-quality rice based on Table 3 shows that when both rices were cooked using tap water, low rice was obtained. Quality rice has a lower gelatinization degree than high quality rice,
It is hard and less sticky, and there is a clear significant difference in the stickiness index (stickiness / hardness). This is shown in Table 1.
This is in good agreement with the taste value shown in FIG.

On the other hand, as for white rice obtained by cooking low-quality rice using acidic water and alkaline water, both of the white rice have increased gelatinization degree, decreased hardness and increased stickiness. In addition, the (stickiness / hardness) is improved to a value close to the characteristics of high-quality rice white rice. However, when the acidic water is used as the cooking water, the gelatinization degree and all the textures are superior to the case where the alkaline water is used, and it can be seen that the rice is more delicious.

In order to clarify the mechanism of improving the quality of cooked rice (white rice) of low-quality rice by electrolytically generated water (acidic water or alkaline water), the characteristics of the rice washing waste liquid in Table 2 are referred to.
When the water for washing rice is tap water, the amount of protein and the amount of starch eluted in the waste rice washing liquid are higher in high quality rice than in low quality rice.

The starch granules are fixed in the endosperm cells by salt-soluble proteins such as albumin and globulin. The stickiness of the cooked rice is determined by the fact that the starch granules on the surface of the rice grains flow out of the rice grains during the cooking process, and gelatinize and swell. This is caused by forming a film on the surface of cooked rice. For this reason, it is considered that low-quality rice, in which the amount of protein and starch eluted is small, has less stickiness than high-quality rice. Therefore, it is considered that, by solubilizing the salt-soluble protein in the rice washing process, the outflow of starch is promoted, and stickiness is expressed in cooked rice.

When alkaline water is used as cooking water, the amount of protein and starch eluted from low-quality rice is higher than when tap water is used. This is presumed to be due to the solubilization of the protein present on the rice grain surface due to the surfactant activity caused by the hydroxyl ions contained in the alkaline water, thereby increasing the stickiness of the white rice.

On the other hand, when acidic water is used as the rice-cooking water, the amounts of protein and starch eluted from low-quality rice do not increase as much as when alkaline water is used as the rice-cooking water. Thus, the mechanism by which the acidic water increases the stickiness of the white rice is not clear, but it is presumed that low-quality rice is subjected to acid hydrolysis due to the low pH effect of starch during the heating process.

As described above, the texture of white rice is the same as that of high-quality rice using tap water as the water for cooking when electrolytically generated water such as acidic water or alkaline water is used as the water for cooking low-quality rice. It turns out that it improves to almost the same. In addition, it can be seen that among the electrolyzed waters, acidic water has an effect of further improving the texture as compared with alkaline water.

(6) Consideration (About sushi rice) Sushi rice is generally used from about 1 hour after preparation and is generally used up after about 6 hours. The gelatinization degree, texture, texture, 1 hour and 6 hours after preparation, etc. And the degree of coloring.

Regarding the gelatinization degree of sushi rice of low-quality rice, referring to Table 4, when using acidic water as the water for cooking rice, it is the highest when using alkaline water and tap water. It can be seen that aging of the starch is suppressed. In addition, when alkaline water is used, the degree of gelatinization is lower than when tap water is used, and it can be seen that the aging of starch is further promoted as compared with other cases.

For the texture of the sushi rice of low quality rice one hour after the preparation, see Table 5, and when using electrolytically produced water (acidic water or alkaline water) as the water for cooking rice, use tap water. It can be seen that the hardness is lower and the stickiness is increased as compared with that of sushi rice of high quality rice, which is almost equal to that of high quality rice. This tendency is maintained even after the lapse of 6 hours, and it can be seen that good texture is maintained even during storage of sushi rice. From this, it can be seen that sushi rice in the case of using acidic water has excellent storage stability.

With respect to the degree of coloration of sushi rice of low quality rice, it can be seen from Table 6 that the L ^* value when acid water is used as the cooking water and the b ^* value when alkaline water is used have specificities. Can be Sushi rice using acid water is L
^It can be seen that the sushi rice using alkaline water has a high b ^* value and exhibits a yellow color when the ^* value is high and the whiteness is increasing. The color difference (ΔE) between the case where the electrolytic water is used and the case where the tap water is used exceeds the value of 2.5, which is the discrimination range by the human naked eye.

The phenomenon that the whiteness of sushi rice increases when acidic water is used as the cooking water has the effect of enhancing the ingredients placed on the sushi rice, and improves the inherent characteristics of the sushi rice.

(7) Sensory Evaluation Referring to Table 8 and FIG. 1 for the sensory test of sushi rice by a consumer panel of 10 people, when acid water was used as the water for cooking rice, the color, gloss, sourness, Consumer panels rate high scores and high palatability in all aspects of hardness, stickiness, and overall rating. In particular, sushi rice using acidic water has been evaluated as having a strong sourness, and sushi rice using alkaline water has been evaluated as having a weak sourness.

It is presumed that white rice cooked with acidic water has a good permeation of combined vinegar and thus has a strong sour taste, and that of white rice cooked with alkaline water allows the mixed vinegar to penetrate into the white rice. It is presumed that the permeation of acidity is blocked.

Table 7 shows the results of measuring the pH of the outer layer and the inner layer of low quality rice sushi rice. The pH of the sushi rice in the case of using acidic water was the lowest in both the inner and outer layers until 2 hours after the preparation of the sushi rice. . This indicates that the permeation of combined vinegar in white rice when using acidic water is good.

On the other hand, in white rice using alkaline water,
A large amount of metal ions in alkaline water have migrated, and in the process of combining vinegar into the white rice, acetate ions in the combined vinegar combine with the metal ions in the white rice to form salts and block acidity. It is presumed that the acidity was evaluated as weak.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

[0045]

[Table 5]

[0046]

[Table 6]

[0047]

[Table 7]

[0048]

[Table 8]

[Brief description of the drawings]

FIG. 1 is an evaluation graph showing the results of a sensory test of sushi rice.

Claims (2)

[Claims] 1. A method for producing cooked rice, wherein rice is cooked by using acidic water generated by electrolyzing water to obtain cooked rice. 2. A method for producing cooked rice, wherein rice is cooked using acidic water generated by electrolyzing water, and the obtained cooked rice is prepared as vinegared rice.