JP6784165B2 - How to make instant rice - Google Patents

Description

The present invention relates to instant rice that is restored with hot water or the like and eaten, and in particular, relates to a method for producing instant rice that can be eaten in a shorter time than before without cooking in a microwave oven or the like.

Conventionally, in the method of producing instant rice in which raw rice is steamed under pressure to form an alpha (α) layer on the surface of rice grains, and then the rice is cooked and dried, the formation of the pregelatinized layer makes the rice relatively cooked. While the simmering of rice is prevented and the yield of the product is improved, the swelling of the rice grains does not proceed because the pregelatinized layer hinders the absorption of water into the rice grains during rice cooking, and therefore, in the drying process after rice cooking. It is swelled and dried at a high temperature (see Patent Document 1). As a result, the water absorption during rice cooking is increased, and the rice is fluffy and swells to improve the appearance.

However, since Patent Document 1 is swelled and dried at a high temperature, it has a so-called "puffed-grain" texture, lacks graininess, and has a slightly baked color. In addition, due to insufficient water absorption during rice cooking due to the pregelatinized layer on the surface of rice grains and slow water permeation rate during restoration, it took about 8 minutes to return to hot water.

JP 2013-51889

In view of the above problems, an object of the present invention is to provide a method for producing instant rice that can be restored faster than before by promoting water absorption and permeation of water into rice grains during rice cooking and the like.

In order to achieve the above object, the invention of claim 1 is
In a method for producing instant rice, which comprises heat-treating raw rice under pressure to form an pregelatinized layer on the surface layer of rice grains, then cooking the rice, and then drying the rice.
The pressurized heat treatment is a pressure steaming treatment using saturated steam, and includes a step of rapidly reducing the pressure after holding the pressurized state for a certain period of time to generate minute cracks on the entire surface of rice grains, and further, after cooking the rice. It is characterized by providing a swelling dipping step of dipping and swelling the cooked rice.

In the pressure heat treatment, it is preferable to pressurize the pressure to 0.10 to 0.30 МPa, hold it for 30 to 120 seconds, and then reduce the pressure to atmospheric pressure within 5 to 30 seconds.

Further, the water content of the rice grains immediately after cooking the rice may be 60 to 70%, and the water content of the rice grains after the swollen soaking may be 75 to 80%.

According to the method for producing instant rice of the present invention, in the pressure heat treatment in the pre-process of rice cooking, an pregelatinized layer is formed on the surface layer of the rice grain, and the rapid depressurization causes minute cracks on the entire surface of the rice grain. Moreover, since the pregelatinized layer is formed in a dense glassy substance, when the cooked rice is immersed in the next step, water is absorbed evenly and promptly into the cooked rice from the minute cracks of the whole cooked rice. Further, sufficient swelling is achieved without destroying the rice grains by the microcracks. Therefore, a sufficient porous structure is formed inside the rice grains by the drying treatment immediately after the swelling, and the permeation of water at the time of restoration proceeds more quickly, and the hot water can be reconstituted faster than before. Further, since the surface layer portion of the rice grains is formed into a dense glassy substance, the rice grains do not boil or elute during rice cooking and swelling soaking, and the yield is improved as compared with the conventional case.

Further , according to the present invention, after maintaining a high pressure state for 30 to 120 seconds, the pressure is reduced to atmospheric pressure at once within 5 to 30 seconds, so that the pregelatinized layer formed on the surface layer of rice grains is densely vitreous. It is possible to effectively reproduce the formation and uniform formation of microcracks of appropriate size on the entire surface of rice grains.

According to the invention described in claim 2 , by adjusting the cooking water so that the water content of the cooked rice immediately after cooking is 60 to 70% (weight) , the swelling of the cooked rice in the next dipping step can be smoothly performed. It can progress and reach the target water content of 75-80% (weight) for swollen immersion in a short time.

It is a manufacturing flow diagram in the manufacturing method of the instant rice by embodiment of this invention. It is explanatory drawing of pressurization and rapid decompression in the pressurization heat treatment by this embodiment. It is an enlarged cross-sectional photograph of a rice grain when the pressure was reduced for 10 seconds after pressure-steaming at 0.3 MPa. It is also an enlarged cross-sectional photograph of rice grains when the pressure is reduced for 30 seconds. Similarly, it is an enlarged cross-sectional photograph of a rice grain when the pressure is reduced for 60 seconds.

Hereinafter, embodiments of the present invention will be described with reference to the manufacturing flow chart of FIG.
The raw material rice in the present invention is generally commercially available polished rice, and the water content may be 16% or less, and there are no particular restrictions on the variety. The raw material rice may be raw rice that has not been washed or soaked, or so-called non-washed rice.

Step S1: Pressurized steaming step This pressurized steaming step uses saturated steam to form a thin pregelatinized layer on the surface layer of rice grains without pregelatinizing the raw rice to the center prior to the subsequent rice cooking step. Perform pressure heat treatment. A conventionally known steam cooker may be used as the device for performing this processing. For example, a net conveyor for carrying rice grains is horizontally installed in a closed pressurized heating tank, and above the transport start end side of the net conveyor. Faces the raw material supply pipe and the discharged raw material discharge pipe below the end side of the conveyor, and the raw material supply pipe and the raw material discharge pipe are rotary valves for keeping the inside of the pressurized heating tank airtight. Etc. are provided. Further, a supply pipe and a discharge pipe for pressurized heated steam (saturated steam) are connected to the pressurized heating tank.

In the pressure steaming step of step S1, the pressure in the tank is gradually increased by supplying saturated steam in the pressure-heated state into the pressure-heating tank, and 0.1 to 0 in about 120 seconds. The pressure is raised to 3 MPa, preferably 0.3 MPa, and the state is held for 30 to 120 seconds, preferably 60 seconds, and then the discharge pipe is opened to reach atmospheric pressure at once in 5 to 30 seconds, preferably 10 seconds. Rapid depressurization (see FIG. 2).
An pregelatinized layer is formed on the surface layer of rice grains by the pressure steaming step. Comparing the case of 0.1 MPa and the case of 0.3 MPa, the treatment temperature of 0.3 MPa is higher (140 ° C. or higher). , The pregelatinized layer tends to be formed relatively thick, while in the case of 0.1 MPa, the pregelatinized layer is relatively thin, so that the textures of the two are slightly different. Therefore, it is possible to make instant rice with different textures by changing the pressure.
It should be noted that the supply of the saturated steam is not limited to the supply of the saturated steam alone, but the pressurization efficiency can be improved and the generation of condensed water can be prevented by heating the saturated steam in combination with compressed air. it can.

In the pressure steaming step S1, an pregelatinized layer having a surface layer portion of rice grains of about 0.1 to 0.5 mm is formed, and the rapid depressurization causes microcracks substantially evenly over the entire surface of the rice grains. These microcracks are formed to a length of about 100 μm when rapidly depressurized from 0.3 MPa to atmospheric pressure in 10 seconds (see FIG. 3), and are punctate holes when depressurized for 30 seconds at the same pressure (see FIG. 3). (See FIG. 4), almost no change is seen after 60 seconds of depressurization (see FIG. 5). On the other hand, in the case of rapid decompression for a short time of less than 5 seconds, problems such as rice grains being blown off violently and cracks becoming uneven occur.
Further, by the rapid depressurization treatment, the pregelatinized layer of the rice grain surface layer portion is formed into a dense glassy substance.

Step S2: Rice-cooking step In the rice-cooking step S2, the pressure-steaming treatment is performed to form a dense pregelatinized layer on the surface layer, and rice grains having substantially uniform microcracks over the entire surface are completely pregelatinized. It is a process to make it. As the rice cooking device, a known rice cooking device such as steam rice cooking or kettle rice cooking can be appropriately selected. At this time, the cooked rice water is adjusted so that the water content of the cooked rice immediately after cooking is 60 to 70%, which is higher than the usual 60 to 62%. For example, in the case of cooking rice in a kettle, it is preferable to add water about twice the weight of rice grains as rice cooking water to the rice cooking kettle so that the soaking time in the kettle is 15 minutes, the cooking time is 20 minutes, and the steaming time is 50 minutes.

In the rice cooking step S2, the rice grains are hard to boil due to the dense and glassy pregelatinized layer formed on the surface layer portion thereof, whereby the grain feeling of the rice grains at the time of restoration can be obtained, but on the other hand, the inside of the rice grains Microcracks are evenly generated over the entire surface of the rice grain, which is a factor that hinders smooth water absorption, water absorption from the microcracks into the rice grain is uniformly promoted, and complete pregelatinization is performed up to the center of the rice grain. ..

Step S3: Swelling and Immersion Step In the swelling and soaking step S3, the cooked rice cooked in the rice cooking step S2 is immersed in warm water at a temperature of 50 to 90 ° C., preferably 70 ° C. for 40 to 60 minutes. In this swelling and dipping step S3, water is absorbed so that the water content of the rice grains is 75 to 80% to swell. At this time, the dense pregelatinized layer on the surface layer of the rice grains does not cause the rice grains to swell and lose their shape, while the permeation of water from the microcracks becomes active. Further, even if the rice grains swell, for example, the volume becomes about 1.5 times, the rice grains do not split significantly in the longitudinal direction due to the presence of the microcracks, and the surface of the rice grains can be stretched and sufficiently swelled. It will be possible.

In the swelling and dipping step S3, there is also an action of swelling the rice grains and removing the stickiness of the surface of the cooked rice to promote single graining. Further, when the temperature of the immersion water is 70 ° C. or higher, it has an effect of suppressing the growth of bacteria. However, if the temperature exceeds 90 ° C., elution of the rice grain surface starts and the yield decreases, which is not preferable.

Step S4: Drying step In the drying step S3, the swollen rice grains placed on the net conveyor or the like are ventilated with hot air at 100 to 130 ° C. for 25 to 60 minutes, and the water content of the rice grains is dried to 5 to 10%. .. At this time, a porous structure is formed in the traces of the swelled rice grains from which water has been removed (porous), whereby water absorption into the rice grains at the time of restoration proceeds more quickly.

〔Example〕
2015 Koshihikari polished rice produced in Hiroshima Prefecture (90% yield, 14% water content) was prepared, pressed to 0.3 MPa in 120 seconds with saturated steam at 144 ° C without washing and soaking, and held for 60 seconds. Immediately after that, the pressure was rapidly reduced to normal pressure in 10 seconds. As a result, an pregelatinized layer was formed on the surface layer of the rice grain, and minute cracks were formed substantially uniformly on the entire surface of the rice grain. The water content of the rice grains at this time was 18%. Next, using a normal rice cooker for home use, the cooked rice was adjusted and cooked for 45 minutes to obtain cooked rice having a water content of 66%.

Next, the cooked rice was taken out from the rice cooker and immersed in warm water at 60 ° C. for 40 minutes of swelling and immersion treatment. The water content of the rice grains after swelling was 75 to 80%. Then, hot air at 130 ° C. was blown through the rice grains at a wind speed of 7.5 m / sec for 30 minutes, and dried so that the water content was 8%.

Table 1 shows the results of the restoration test for comparing the instant rice obtained in the above example with the instant rice not subjected to rapid depressurization in the pressure steaming step. Each of the samples weighed 50 g, and 90 ml of water and boiling water were added to each of the stand pack containers to restore and eat.
As a result, in this example, the case of adding hot water was restored in 5 minutes, and the case of water was restored in 25 minutes, and the taste was excellent with an appropriate graininess. In addition, the yield for raw rice was 81.35%, which exceeded the yield of 70% by the conventional manufacturing method.

According to the present invention, it is possible to mass-produce instant rice having excellent resilience and a high yield as compared with the conventional one, which is extremely useful.

S1 Pressurized steaming process
S2 rice cooking process
S3 swelling immersion step
S4 drying process

Claims (2)

In a method for producing instant rice, which comprises heat-treating raw rice under pressure to form an pregelatinized layer on the surface layer of rice grains, then cooking the rice, and drying the cooked rice grains.
The pressure heat treatment is a pressure steaming treatment with saturated steam, and the pressure is 0.1.
After pressurizing to 0 to 0.30 MPa and holding for 30 to 120 seconds, the process includes a step of rapidly depressurizing to atmospheric pressure within 5 to 30 seconds to generate minute cracks on the entire surface of the rice grain, and further, after cooking the rice. A method for producing instant rice, which comprises a swelling step of immersing cooked rice in hot water at 50 to 90 ° C. to swell it. The method for producing instant rice according to claim 1, wherein the water content of the cooked rice immediately after cooking is 60 to 70% (weight), and the water content of the rice grains after the swollen soaking is 75 to 80% (weight) .