JP2000139374A - Method of cooking rice - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of cooking rice comprising using water produced by diaphragmed electrolysis as the water for washing and immersing rice and for addition to rice so as to improve the properties of cooked rice through degree-of-gelatinization increase, hardness reduction and glutinousness increase. SOLUTION: This method of cooking rice involving rice washing process, rice immersing process and water addition process comprises using water produced by diaphragmed electrolysis (pref. acidic water produced in an anode chamber or alkaline water produced in a cathode chamber) as the water for washing and immersing rice and for addition to rice.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rice cooking method having steps of washing, dipping, and adding water.

[0002]

2. Description of the Related Art Generally, a method of cooking rice includes washing, dipping, and adding water (cooking), and efforts have been made to cook rice in a delicious manner. On a daily basis,
Consideration is given to the degree of rice washing, immersion and water addition, the degree of heating (temperature during cooking, time), and the like.

[0003] As a completely different method of improving rice cooking, as disclosed in JP-A-7-289178 and Japanese Utility Model Registration No. 3008083,
There has been proposed a method in which rice is washed with ordinary water such as tap water, and the washed rice is immersed in electrolytically generated water generated by diaphragm electrolysis, and then water is added to cook rice. In the rice cooking method, acidic water is used as water for immersion, and alkaline water is used as water for rice cooking.

[0004]

In the rice cooking improvement method described above, the superiority or inferiority is determined based on sensory evaluation data, and the superiority or inferiority is always determined based on scientific grounds. Not something. Therefore, an object of the present invention is to provide a rice cooking method in which the superiority and inferiority based on sensory evaluation data and the superiority and inferiority based on scientific grounds are consistent, and a rice cooker having more excellent taste can be cooked. It is in.

[0005]

SUMMARY OF THE INVENTION The present invention provides a method for washing rice, dipping,
The present invention relates to a rice cooking method having a water addition step, wherein the rice cooking method is characterized by using electrolyzed water generated by diaphragm electrolysis for all water for washing, dipping and water addition.

[0006] In the rice cooking method according to the present invention, acidic water generated in an anode chamber can be used as the electrolyzed water.
Is preferably in the range of 3.0 to 6.0.

[0007] In the rice cooking method according to the present invention,
As the electrolyzed water, alkaline water generated in a cathode chamber can be used, and when alkaline water is used, the pH of the alkaline water is in the range of 8.5 to 10.0. preferable.

[0008]

[Effects and Effects of the Invention] In the rice cooking of old rice, when acid water or alkaline water is adopted as water used in all processes, the gelatinization degree is increased as compared with the case where tap water is used, It was found that the hardness decreased, the stickiness increased, and the characteristics of cooked rice improved. In this case, it is most effective to improve the characteristics of cooked rice by using the same water in a series of steps of washing, dipping, and adding water by using only acidic water and alkaline water.

It is recognized that the improvement of cooked rice characteristics by acidic water is caused by solubilization of globulin fraction, activation of amylolytic enzyme by low pH, and acid hydrolysis of starch. In addition, it is recognized that the improvement of the cooked rice characteristics by the alkaline water is caused by remarkable solubilization of the globulin fraction, activation of the amylolytic enzyme by high pH, and chemical gelatinization of the starch by the alkali.

[0010]

[Example] (Cooking rice): In this example, Nihon Haruko rice (storage period: 1 year) was used as test rice, and tap water (pH 6.95), acidic water (pH 3.75), alkaline water was used as test water. (PH 9.25), and a rice cooking experiment was performed by the method shown in FIG.

However, the test rice was old Nihonbare rice from Shimane Prefecture, and the tap water was produced by Matsue City tap water, and the electrolyzed water was produced by an electrolyzed water generator (HOX-40A type) manufactured by Hoshizaki Electric Co., Ltd. Acid water and alkaline water. In addition, pH 3.75 set with acidic water is the pH which has confirmed that the effect of improving the characteristics of cooked rice with alkaline water is the highest.
This is the pH value of acidic water generated on the anode chamber side when alkaline water of 9.25 is generated.

As shown in FIG. 1, the method of cooking the test rice is as follows.
It comprises a rice washing step of washing the test rice, a soaking step of immersing the washed rice after the washing, a step of adding water to the dipped rice after the washing, a heating step, a steaming step, and a cooling step. In the rice cooking method, the test rice is washed twice with test water and drained, and freshly washed water is added to the washed rice at 25 ° C.
Immersed in water for 30 minutes, drained the water, added 1.5 times the weight of fresh water to the immersed rice after draining, heated in an electric rice cooker for 18 minutes, and then steamed for 12 minutes, 25 ° C
For 1.5 hours. Table 1 shows how the pH of the test water changes in each step of the rice cooking.

[0013]

[Table 1] Referring to Table 1, among the test waters in each step of rice cooking, in the case of acidic water and alkaline water, which are electrolytically generated water, in the washing and dipping step, the pH changes to near neutrality due to elution of components from the rice. However, it can be seen that the water addition step is on the more acidic side and the more alkaline side than the tap water. This means
When cooking rice, if the test water is acidic or alkaline water,
It means that it is heated at a lower or higher pH than tap water.

(Sensory Evaluation): Each rice cooked by the method shown in FIG. 1 was subjected to a sensory evaluation by a consumer panel of 20 persons. Evaluation is the color, gloss, hardness, stickiness, taste,
The six characteristics of the comprehensive evaluation were performed on a scale of +3 to -3, using rice as the test water as tap water as a reference (0). The results are shown in the graph of FIG.

Referring to the graph of FIG. 2, cooked rice using acidic water or alkaline water as test water is glossy and softer than cooked rice using tap water as test water.
It turns out that it is sticky, tastes good, and has high suture evaluation.
Also, it can be seen that cooked rice using acidic water as test water is white rice having a particularly high color evaluation as compared with cooked rice using alkaline water or tap water as test water.

From these results, when old rice is cooked using acidic water or alkaline water as test water, the characteristics of cooked rice are improved as compared with the case where tap water is used as test water. This was sensually confirmed.

(Rice cooked rice texture): In order to test the characteristics of each cooked rice, the cooked rice texture was measured by a three grain method and the gelatinization degree of the cooked rice was measured by a BAP method. Table 2 shows the obtained results.

[0018]

[Table 2] Referring to Table 2, cooked rice using acid water or alkaline water as test water has lower hardness, increased stickiness, and starch paste as compared with cooked rice using tap water as test water. Formation and swelling are promoted. From these results, when rice is cooked using acidic water or alkaline water as test water, compared with the case where tap water is used as test water, rice rice texture is improved. Understand.

Next, in order to compare cooked rice tissues, cooked rice immediately after cooking was freeze-dried, and its cross section was observed by SEM. This observation confirmed that cooked rice using tap water as a test water had many large holes dispersed throughout. These holes are presumed to be traces formed by dehydration of the aggregates of starch and water that is not sufficiently hydrated by freeze-drying. On the other hand, in cooked rice using alkaline water as test water, this hole shows a considerably small state, and in cooked rice using acidic water as test water, compared with cooked rice using alkaline water as test water. It has a very small state.

From these results, it can be seen that, in cooked rice using acidic water or alkaline water as test water, the hydration state of starch is improved as compared with cooked rice using tap water as test water.
It is presumed that the tendency is remarkable in cooked rice using acidic water as test water.

(Modification mechanism of cooked rice characteristics of test water) From the above examination results, cooked rice using acidic water or alkaline water as test water is compared with cooked rice using tap water as test water. It was found that gelatinization and swelling were promoted. Therefore, in order to elucidate the mechanism of modifying the characteristics of cooked rice by the acidic water or alkaline water as the test water, using a model system,
Influences on gelatinization and swelling of starch (1) solubilization of protein, (2) activity of amylolytic enzyme, (3) hydrolysis of starch by acid and disintegration of starch by alkali, (4) electrolysis water The synergistic effects were examined.

(1) Protein solubilization: The test rice was prepared as rice flour having a particle diameter of 300 μm or less, and the rice flour was added with 10 times (by weight) of test water (acidic water, alkaline water, tap water) and added to the rice flour. After shaking at 2 ° C. for 2 hours, the amount of the eluted protein was measured using a protein assay kit. Table 3 shows the obtained results.

[0023]

[Table 3] Referring to Table 3, it can be seen that the elution amount of protein is higher in acidic water or alkaline water than in tap water, and particularly high in alkaline water. From these results, compared to tap water, acidic water and alkaline water dissolve more of the rice protein that is hard to dissolve in old rice, making it easier for water to penetrate into rice grains during the heating process of rice cooking. It is presumed that gelatinization and swelling of starch are promoted.

Further, when the composition of the protein eluted by SDS-PAGE was examined, the protein eluted by any of the test waters most frequently eluted in the band near 14 kDalton, which is estimated to be the globulin fraction. Elution in other bands was slight. Further, since no specific band was detected in each test water, in acidic water and alkaline water, the solubilized protein was mainly globulin, and the solubility was improved more than the pH of the test water. It is presumed to be due to a surfactant activity.

(2) Activity of starch-degrading enzyme:
It contains endogenous starch-degrading enzymes, which are known to act in the heating process of rice cooking. Therefore, in order to examine the effect of electrolyzed water on starch-degrading enzymes, total sugars extracted from rice flour as reaction products were measured by the phenol-sulfuric acid method and reducing sugars were measured by the somogi-Nelson method. Table 4 shows the obtained results.

[0026]

[Table 4] Referring to Table 4, the elution amount of both the total sugar and the reducing sugar is higher in acidic water or alkaline water than in tap water,
In particular, it can be seen that this tendency is high in acidic water. From these results, it can be seen that starch decomposes more easily in the heating process of rice cooking in tap water than in acidic water and alkaline water.

Further, in order to examine the composition of the sugar eluted from the rice flour, the amounts of various sugars were measured by HPLC. The obtained result (elution amount) is shown in the graph of FIG. Referring to the graph, there is no significant difference in the elution amount between fructose and sucrose in any of the test waters.However, the elution amount of glucose is higher in acidic water than in tap water, and maltose is higher. Was found to have a low elution amount. It was found that the amount of glucose and maltose dissolved in alkaline water was higher than that in tap water.

From these results, the high amount of sugar eluted in acidic water and alkaline water is due to the release of glucose and maltose from starch during the heating process of cooking rice due to the action of endogenous starch-degrading enzymes. It is supposed to be.

Maruyama et al. Report that there are two types of α-amylase in rice and that the optimum pH is in the range of 5-6. In rice cooking using acidic water as test water, the pH of water during the heating process of rice cooking is determined by the optimal pH of these α-amylases.
Since it is close to H, it is presumed that the enzyme activity due to the pH effect is improved. Also, in acidic water, since the amount of glucose eluted is high and the amount of maltose eluted is low,
It is also presumed that α-glucosidase is activated and the enzyme activity is improved by the activity of α-glucosidase.

On the other hand, in alkaline water, the amount of reaction products is increased, although the pH is far from the optimum pH of α-amylase. According to Maruyama et al., These α-amylases are calcium ions, magnesium ions,
It has been confirmed that it is activated by sodium ions or the like. Therefore, in rice cooking using alkaline water as test water, α increases due to an increase in cations transferred from the anode to the cathode.
-It is presumed that the activity of amylase is improved.

As described above, in rice cooking using acidic water or alkaline water as test water, gelatinization and swelling of starch are promoted by increasing the activity of starch-degrading enzymes due to pH and / or ionic effects. It turned out to be.

(3) Hydrolysis of starch by acid and degradation of starch by alkali: When starch is heated on the acidic side, acid hydrolysis occurs, and when it is heated on the alkaline side, chemical gelatinization occurs. Therefore, the effect of heating starch on the low pH side or high pH side of electrolytically produced water on the starch was examined. Using the test rice, a starch fraction was prepared by a dilute alkali method, 10 times (by weight) of test water was added, and the mixture was steamed and heated to 10 wt. % Starch gelatinization liquid, and then 70 wt. The reducing sugar dissolved in the% ethanol fraction was measured by the Somogi-Nelson method. Table 5 shows the obtained results.

[0033]

[Table 5] Referring to Table 5, when starch is heated in acidic water or alkaline water, the reducing sugar contained in the gelatinized solution is higher than when heated in tap water. From these results,
In rice cooking using acidic water and alkaline water as test waters, it is recognized that acid hydrolysis by acidic water and alkali gelatinization by alkaline water occur during the heating process of rice, and these influence starch gelatinization and swelling. It is presumed that it is exerting.

From the above examination results, it can be seen that acidic water and alkaline water improve the characteristics of cooked rice by different mechanisms.

(4) Synergistic effect of electrolyzed water: In order to establish a more effective method of cooking rice using electrolyzed water as test water, the existence of a synergistic effect of acidic water and alkaline water was examined. In the rice washing step, the immersion step, and the water addition step of rice cooking, rice was cooked by setting four types of combinations using the same water in two consecutive steps. Table 6 shows the texture of the obtained cooked rice.

[0036]

[Table 6] Referring to Table 6, it is recognized that the hardness of the cooked rice is significantly reduced when the electrolytically generated water is used in combination as compared with the case where tap water is used as the test water. No significant difference was observed in the case of using tap water as test water. Therefore, a synergistic effect on the cooking of acidic water and alkaline water cannot be expected.

Therefore, in rice cooking, it is most effective to improve the characteristics of cooked rice by using the same water in each of the steps of washing, immersing, and adding water by using acidic water and alkaline water alone. found.

[Brief description of the drawings]

FIG. 1 is a process chart showing a rice cooking method to which the present invention is applied.

FIG. 2 is a graph showing a sensory evaluation of cooked rice.

FIG. 3 is a graph showing the amount of eluted substances from rice flour.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenji Kobayashi F-term (reference) in Hoshizaki Electric Co., Ltd. 3rd-16 Sakaemachi South Building, Toyoake City, Aichi Prefecture 4B023 LE11 LK01 LP03 LP11

Claims (3)

[Claims] 1. A rice cooking method having rice washing, immersion and water addition steps, wherein the water produced by the electrolysis with diaphragm is used for all of the water for washing, immersion and water addition. 2. The rice cooking method according to claim 1, wherein acidic water generated in an anode chamber is used as the electrolyzed water. 3. The rice cooking method according to claim 1, wherein alkaline water generated in a cathode chamber is used as the electrolytically generated water.