JP2002065181A - Method for cooking rice - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cooking rice by which the distribution of water content in the cooked rice is unified even when the cooking of the rice is carried out in a single container, and a high-quality cooked rice excellent in flavor and texture, such as palatability, glutinousness and elasticity can be provided. SOLUTION: A soaked rice and water for cooking are charged into a heat- resistant container 11 for cooking the rice in the single container, and the resultant container 11 containing the rice and water is subjected to a microwave heating and a stream heating in order. The heat-resistant container has at least a part of an opening part of the container, covered with a film 13 having steam-permeability. The microwave heating is carried out by heating the contents at 1-50 deg.C/min heating rate to 70-100 deg.C while cooling the covering part of the film. The steam heating is carried out after carrying out the microwave heating in a state of the soaked rice and the water for cooking being charged in the heat resistant container having the opening part, and covering the microwave-heated product with the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rice cooking method,
Specifically, the present invention relates to a rice cooking method capable of obtaining high-quality cooked rice.

[0002]

2. Description of the Related Art Cooking rice has long been performed by heating using wood burning as a heat source in a kiln and a pot. Today, for home use, propane gas combustion, rice cooking by electric heaters, heating using electromagnetic waves, etc. are performed, and industrially, similarly, gas combustion, electric heaters, steam heating, microwave heating, etc. Rice is being cooked. Containers (pots) used for rice cooking have also been improved from iron pots to materials having a high heat transfer coefficient and high corrosion resistance, such as stainless steel and aluminum alloys. As described above, the improvement of the heat source and the container in the rice cooking is constantly being promoted.

[0003] Japanese Patent Application Laid-Open No. 11-20865 discloses a method in which rice (immersed rice) and water (rice for cooking) are filled in a molded container made of a heat-resistant synthetic resin or the like and cooked by heating. This method is a so-called single-meal container cooking method in which one meal is cooked by steam heating. In the case of mass production, a continuous steam heating device is used. For example, it is difficult to sufficiently generate convection of water at the time of boiling, which is preferable during rice cooking, because heat conduction and transmission to the entire environment are performed. Therefore, compared to a rice cooking method using gas or electricity whose maximum temperature exceeds 100 ° C., the stickiness and elasticity of rice grains are low in quality, and the taste tends to be slightly less.

Further, cooked rice cooked in a single-meal container tends to have a non-uniform water distribution.
Since the water content was slightly higher, the food tended to be softer than the cooked rice at the top of the container. The tendency of the water distribution to be non-uniform is slightly observed even when rice is cooked with an electric rice cooker.

Therefore, the present invention makes it possible to make the water distribution in cooked rice uniform even when cooking rice in a single-meal container.
It is an object of the present invention to provide a rice cooking method capable of obtaining high-quality cooked rice excellent in taste and texture such as stickiness and elasticity.

[0006]

Means for Solving the Problems To achieve the above object, a rice cooking method according to the present invention is characterized in that rice water is added to immersed rice in which raw rice has been washed and soaked, microwave heating is performed, and then steam heating is performed. It is characterized by:

[0007] Further, the method is characterized in that the immersion rice and the cooking water are filled in a heat-resistant container, particularly a heat-resistant container for cooking individual meals, and then heating is performed. It is characterized in that at least a part of the film is covered with a vapor-permeable film, and the microwave heating is performed while cooling a covered portion of the film.

Further, microwave heating is performed in a state where the dipped rice obtained by washing and soaking the raw rice and rice cooking water are filled in a heat-resistant container having an opening, and then the opening of the heat-resistant container is It is characterized in that steam heating is performed after coating with a film having a vapor permeable portion in part.

The microwave heating is performed at 1 to 50 ° C.
It is characterized in that the product temperature is raised from 70 to 100 ° C. at a heating rate of / min.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, raw rice in the present invention is:
In addition to polished rice, brown rice may be used. The polished rice is white rice, rice divided into seven parts, rice divided into five parts, and the like. The water content of the immersed rice may be 25 to 40% by weight,
It is 65 to 85 g, preferably 70 to 80 g per g.

In the present invention, the raw rice is washed by a conventional method,
Microwave heating is first performed in a state where a predetermined amount of cooked water is added to immersed rice immersed in water for a predetermined time, and then steam heating is performed. That is, the former stage of the rice cooking process is performed by microwave heating, and the latter stage of the rice cooking process is performed by steam heating. Thereby, high-quality cooked rice can be obtained as compared with the case of cooking by microwave heating alone or steam heating alone.

In the conventional rice cooking method using only microwave heating, since microwave heating is heating with high selectivity to water molecules, convection is remarkably generated in the rice cooker, and cooked rice is cooked. It has the advantage that the quality such as stickiness, elasticity, and taste is improved. However, if microwave heating is performed until the end of rice cooking, there is a disadvantage that the surface of cooked rice is dried and becomes hard texture. In addition, there is a problem that energy (electricity) cost is high.

On the other hand, the rice cooking method using only steam heating has the advantage of low energy cost, but the convection is weakened because the whole rice cooking container is heated, and the cooked rice has low stickiness and elasticity. It has a drawback that it has little flavor.

In a general rice cooking process, in the initial stage, particularly for 5 to 20 minutes, the immersed rice is heated while absorbing the cooking water. The initial heating conditions affect the quality of the cooked rice. At this time, by selectively heating the water molecules by microwaves, the immersion rice can absorb a necessary and sufficient amount of cooked water.

The conditions for heating by microwaves vary somewhat depending on conditions such as the properties of the raw rice, the ratio of the cooked water, the initial temperature of the cooked water, the shape of the rice cooker, and the like. It can be selected in the range of 50 ° C / min, preferably 1.5 to 25 ° C / min, more preferably 5 to 15 ° C / min. When the heating rate is less than 1 ° C./min, it is difficult to obtain a remarkable quality improvement as compared with steam-only rice cooking, and the rice cooking time is too long. On the other hand, if the heating rate exceeds 50 ° C./min, the heating time is too short, and the rice cannot absorb water sufficiently, and the texture of the cooked rice cooked after steam cooking may be softened.

The ultimate temperature in this microwave heating (the maximum temperature during microwave heating) is in the range of 70 to 100 ° C., preferably 80 to 100 ° C., and more preferably 9 to 100 ° C.
It is in the range of 0-100 ° C. If the ultimate temperature is lower than 70 ° C., the water absorption of rice may be insufficient, and
If the temperature exceeds 00 ° C., the taste and texture of the cooked rice may be impaired.

[0017] The microwave heating rice cooking time depends on the heating rate and the temperature reached, but is suitably in the range of 1 to 70 minutes, preferably 2 to 40 minutes, more preferably 5 to 20 minutes. . If it is less than 1 minute, water absorption of rice is not sufficient, and if it exceeds 70 minutes, rice cooking time becomes too long.

As the microwave, an oscillator having a frequency of 2450 MHz generally used in a home microwave oven or the like may be used, and the output is 50 to 1000 W, preferably 100 to 500 W per 200 g of cooked cooked rice. . When the microwave output is less than 50 W, the time required for heating becomes extremely long, and when the output exceeds 1000 W, the heating is performed in a very short time. The taste may be impaired. The microwave output may be the same throughout the microwave heating time, or may be changed midway. For example, heating at 200 W for 12.75 minutes, heating at 200 W for 10.5 minutes, and then heating at 100 W for 4.75 minutes.
You may make it heat for 5 minutes.

The form and structure of the microwave heating device for performing microwave heating are arbitrary, and may be either a batch type or a continuous type. In addition, when using moderately preheated hot water as the rice cooking water, good rice can be cooked even if the microwave heating time is shortened as compared with the case where the normal temperature rice cooking water is used.

The steam heating performed after the microwave heating can be performed in the same manner as ordinary steam heating, and may be either a batch type such as a steamer or a continuous type using a belt conveyor. The steam temperature in this steam heating is
80 to 100 ° C, preferably 90 to 100 ° C, more preferably 95 to 100 ° C.
60 minutes, preferably 15 to 40 minutes, more preferably 20 minutes
~ 30 minutes. When the steam temperature is less than 80 ° C. or the heating time is less than 5 minutes, it is difficult to sufficiently heat, and the cooked rice has low stickiness, elasticity, and umami.

The rice cooker used for cooking rice can be made of various materials as long as it has heat resistance and is suitable for food hygiene. However, when microwave heating is performed, microwaves are reflected. A material other than a metal container, for example, a synthetic resin, glass, ceramic, paper, or the like is used. Among them, rice cookers made of synthetic resin are optimal because they can be used continuously from microwave heating to steam heating, and are lightweight, have sufficient strength, and are not easily damaged.

As the synthetic resin, in consideration of heat resistance, moldability, strength and the like, a polypropylene resin is preferable, and an ethylene-vinyl acetate copolymer having low oxygen permeability is sandwiched between the polypropylene resin layers. The best one is a laminated sheet.

Further, by using a synthetic resin rice cooker, the container can be used continuously from microwave heating to steam heating. However, after microwave heating is performed in the synthetic resin rice cooker, You may make it transfer to a metal rice cooker and perform steam heating. In addition, in the case of microwave heating, a container-shaped thing for holding cooked water is indispensable, but when the cooked water is completely absorbed by rice by microwave heating, there is no free water Alternatively, rice heated by microwave can be transferred from a container to a belt conveyor and steam-heated.

The rice cooker can be of any size and shape from small to large according to the purpose of the cooked rice. For example, in the case of an individual meal rice cooker, the cooked rice amount is equivalent to one serving. The size should be large enough to accommodate about 200 g.

For example, when cooking rice for one meal, the raw rice is washed by a usual method, immersed in immersion water for a predetermined time, and then a predetermined amount of immersed rice and rice cooked water are mixed in a predetermined size and shape. Heat-resistant container, for example, filling the laminated sheet into a synthetic resin heat-resistant container molded into a tray shape, put this into a microwave heating device such as a microwave oven and perform a predetermined microwave heating, and then What is necessary is just to put in a steam heating device such as a steamer and perform predetermined steam heating. This makes it possible to obtain cooked rice with improved taste and texture compared to cooked rice cooked only by microwave heating or cooked rice cooked only by steam heating.

Alternatively, microwave heating and steam heating may be performed after at least a part of the opening of the container filled with a predetermined amount of immersed rice and cooking water is covered with a film having vapor permeability. Further, microwave heating may be performed with the container opening being opened, and thereafter, at least a part of the opening may be covered with a vapor-permeable film, and then steam heating may be performed.

[0027] By covering the container opening with a film having vapor permeability, excess steam generated from the rice cooker during heating can be radiated to the outside, and foreign substances can be prevented from entering the inside. it can.

At this time, the entire surface of the opening of the container may be covered with a vapor-permeable film, and the joint between the vapor-permeable film and the vapor-impermeable film, or a part of the vapor-permeable film is processed. To make it impervious to steam,
A film obtained by laminating a vapor-impermeable film on a part of a vapor-permeable film, a material obtained by processing a part of a vapor-impermeable film to make it vapor-permeable, and the like can be used.

As the vapor permeable film, various materials can be used as long as they have vapor permeability and heat resistance and are compatible with food hygiene. For example, a film obtained by processing 100% high-density polyethylene fibers into a sheet, a mixed paper made of paper pulp and polyethylene fibers, or the like can be used. The vapor-impermeable film may be any film having a predetermined heat resistance, and may be polyethylene or a laminated film of polyethylene and polyester, which is generally used for packaging food.

When joining a vapor-permeable film and a vapor-impermeable film, heat bonding (heat sealing),
It can be performed by bonding or the like. In the case where a part of the vapor-permeable film is processed to be non-vapor-permeable, it can be performed by applying a predetermined temperature and pressure to the vapor-permeable film. Furthermore, when laminating a vapor-permeable film and a vapor-impermeable film, it can be carried out by ordinary lamination or adhesion depending on the material of the film. Also, when processing a part of the vapor-impermeable film to make it vapor-permeable, for example, a small hole is made to penetrate the film with a needle-like material, or a gap such as a slit having a length of several mm is provided. This makes it possible to transmit the vapor when the vapor pressure is applied to the film. By appropriately forming such small holes and slits in the vapor-permeable film, the vapor permeability can be adjusted.

When the vapor permeability is low, the container or the film may expand significantly during microwave heating. In such a case, the covering of the film is cooled by blowing air with a fan or the like. In addition, the expansion of the container or the film can be reduced.

Further, microwave heating and heating are performed in a state where the opening of the heat-resistant container filled with the immersed rice and the rice cooking water is covered with a film having a microbial barrier property and at least a part of which has vapor permeability. After steam heating, after cooking rice, cover the vapor permeable part or the whole container with a gas barrier film with low oxygen permeability, etc. It keeps sterile condition, resists oxidation, does not allow water vapor to enter and exit, can be stored for a long time, and has aseptic-filled packed rice with excellent taste and texture.

As the film having microbial barrier properties and vapor permeability, various films can be used unless there is a problem in food hygiene. For example, a heat-resistant laminated film of polyethylene or polyester and a high-density polyethylene fiber film can be used. Can be used.

As described above, by combining the two heating methods, the quality such as stickiness, elasticity (waist) and umami that could not be obtained by each of the individual rice cookers is improved, the surface is not dried, and the hardness is just good. Is obtained. In addition, energy costs can be reduced as compared with rice cooked by microwave heating alone. Further, the energy cost can be further reduced by slightly increasing the temperature of the cooked water to shorten the microwave heating time.

[0035]

Example 1 An experiment of cooking rice in an individual food container was conducted. As shown in FIG. 1, 115 g of immersed rice obtained by washing and immersing polished rice and 85 g of cooking water are filled in a heat-resistant container 11 made of polypropylene having an inner volume of 300 mL, and the opening of the container is made of polyethylene and polyester. A laminated vapor impermeable film 12,
A vapor-permeable film 13 made of a high-density polyethylene fiber film (manufactured by DuPont: Typek 1073B) was covered with a butt-bonded film. The area of the vapor permeable film 13 was about 20% of the area of the container opening. The product temperature before heating was 25 ° C. in all cases. In Experimental Example 10, the opening was opened without coating the film.

Then, rice was cooked under the conditions shown in Table 1. Microwave heating was performed twice at a time in a microwave batch-type oven with a frequency of 2450 MHz, and the output of the oscillator was adjusted to set the heating rate, heating time, and ultimate temperature. The steam heating was performed by a continuous steam heating device, the steam temperature was 100 ° C., and the heating time was 20 minutes. Experimental Examples 1 and 2 are comparative examples, in which steam-cooked rice alone and microwave-cooked rice were cooked under the conditions of steam-cooked rice and microwave-cooked rice.

[0037]

[Table 1]

The quality of the cooked cooked rice was subjected to an eating test (sensory test) based on Experimental Examples 1 and 2, and the softness, uniformity of moisture, stickiness, elasticity, and taste were comprehensively evaluated. In addition, the physical properties (texture) of the cooked rice were measured using a physical property measurement device (Texture Analyzer TA-XT2) manufactured by Stable Micro Systems. The measurement items were hardness (Hardness, [g]) and adhesiveness (Adhesivenes).
s, [gs]), elasticity (Springiness, [-]), and cohesiveness (Cohesiveness, [-]). Hardness is an index indicating the crushing strength of rice grains. The softer the value, the harder the value. Adhesiveness is an index of stickiness of rice grains. A smaller value indicates less stickiness, and a larger value indicates more stickiness. Elasticity is an index indicating the elasticity (strength of the waist) of rice grains. The lower the numerical value, the lower the elasticity, and the higher the numerical value, the higher the elasticity. The cohesiveness is a property related to the strength (fragility) of the internal bonding of the rice grains. The smaller the numerical value, the weaker the cohesiveness, and the larger the numerical value, the greater the cohesiveness. The texture was measured for each grain of cooked rice, and the average value for 20 grains was determined. The relationship between the texture value and the sensory test for eating rice is close but not simple. Table 2 shows the results of the eating test and the measurement results of the texture.

[0039]

[Table 2] ◎ A very remarkable quality improvement is observed as compared with the reference cooked rice (Experimental Examples 1 and 2). ○ Significant quality improvement compared to standard cooked rice. △ Quality improvement compared to standard cooked rice.

In the steam-heated single-cooked rice of Experimental Example 1, the stickiness of cooked rice is insufficient, and in the microwave-heated single-cooked rice of Experimental Example 2, although the stickiness and elasticity are improved, the surface becomes too hard and the surface is dried. Was. In comparison, the rice cooked in each of the examples showed an improvement in quality in all of the eating tests, and in many cases, the quality improvement was particularly remarkable and showed excellent results. Also, differences were observed in the texture measurement results, and it is presumed that these integrated results appeared in the eating test results.

Example 2 The heating rate in microwave heating was changed as shown in Table 3. The container opening was similarly covered with the same film as in Example 1. The conditions other than microwave heating, such as steam heating, were the same as in Example 1. Table 3 shows the results of eating tests on the cooked rice. In addition, in the eating test, the same conditions as those of Experimental Example 7 with the highest evaluation in Example 1 were used as a reference. In addition, even those having a low evaluation (cross marks in Table 3) had better quality than cooked rice cooked by steam alone or cooked by microwave heating alone.

[0042]

[Table 3] 品質 The quality is as good as the reference cooked rice (Experimental example 15). ○ The quality is almost the same as the standard cooked rice. × The quality is slightly inferior to the standard cooked rice.

Example 3 The ultimate temperature (end temperature) in microwave cooking rice was changed as shown in Table 4. The container opening was similarly covered with the same film as in Example 1. The conditions other than microwave heating, such as steam heating, were the same as in Example 1. Table 4 shows the results of eating tests on the cooked rice. In addition, in the eating test, the same conditions as those of Experimental Example 7 with the highest evaluation in Example 1 were used as a reference.
In addition, even those having a low evaluation (cross marks in Table 3) had better quality than cooked rice cooked by steam alone or cooked by microwave heating alone.

[0044]

[Table 4] 品質 Good quality comparable to standard cooked rice (Experimental example 24). ○ The quality is almost the same as the standard cooked rice. × The quality is slightly inferior to the standard cooked rice.

[0045]

As described above, according to the rice cooking method of the present invention, it is possible to obtain cooked rice with excellent taste and texture compared to the rice cooking method of simply steam cooking or microwave heating. Can be. In particular, it is suitable for cooking rice in individual containers, and furthermore, the total cooking time can be shortened, and the production efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a heat-resistant container used in Examples.

[Explanation of symbols]

11: heat-resistant container, 12: vapor-impermeable film, 13
... Vapor permeable film

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Osamu Yoshida, Inventor F-term in Nippon Sanso Corporation 1-16-7 Nishi-Shimbashi, Minato-ku, Tokyo (Reference) 4B023 LE11 LE15 LP10 LP13 LP19 4B055 AA03 BA22 BA62

Claims (6)

[Claims] 1. A rice cooking method comprising adding rice cooking water to immersed rice in which raw rice is washed and immersed, microwave heating, and then steam heating. 2. The rice cooking method according to claim 1, wherein heating is performed after filling the dipped rice and rice cooking water in a heat-resistant container. 3. The rice cooking method according to claim 2, wherein at least a part of the opening of the heat-resistant container is covered with a film having vapor permeability. 4. The rice cooking method according to claim 3, wherein the microwave heating is performed while cooling a coating portion of the film. 5. The microwave heating is performed in a state where the dipped rice obtained by washing and soaking the raw rice and rice cooking water are filled in a heat-resistant container having an opening, and then the opening of the heat-resistant container is A rice cooking method comprising performing steam heating after coating with a film having a steam permeable portion in part. 6. The rice cooking method according to claim 1, wherein the microwave heating increases the product temperature to 70 to 100 ° C. at a rate of 1 to 50 ° C./min.