JPS61209558A - Production of instant rice - Google Patents

Abstract

PURPOSE:To obtain an instant rice which can be reconstituted extremely quickly simply by the addition of hot water to give a reconstituted rice having the taste and flavor of ordinary cooked rice, by immersing cooked rice in water until the amount of the absorbed water reaches a specific range, aging the swollen rice, freezing slowly and drying the product. CONSTITUTION:Rice is washed with water, immersed in water, drained and steamed, or is cooked as it is to effect the complete gelatinization of the starch in rice grain. The gelatinized rice is immersed in water until the water-content of the rice reaches about 70-80%, and drained. The rice grain is swollen, and the gelatinized startch on the surface of the rice grain is dissolved in water to separate the grians from each other. The gelatinized starch of the swollen and separated rice is converted to the nongelatinized state by keeping the grain in an aging atmosphere for a necessary period. The treated rice is subjected to the slow freezing to effect the partial destruction of the cell structure by the ice crystal formed in the rice grain. The permeability of hot water in reconstitution process can be improved by this procedure. The rice grain is thawed, and then dried to obtain the objective instant rice.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention restores the rice extremely quickly just by pouring hot water, and its taste and texture are almost comparable to those of ordinary cooked rice. This invention relates to a method for producing instant rice that enables easy preparation of cooked rice.

[Technical background of the invention]

This kind of instant rice has already been provided on the market in various forms such as pregelatinized rice, freeze-dried rice, and puffed rice.

However, in Japan, where cooked rice is the staple food, the requirements for flavor are extremely high, so in the case of instant rice like the one mentioned above, it is difficult to feel satisfied with the flavor after restoration, and this also makes it difficult to cook, which is important as an instant food. The current situation is that it is quite difficult to achieve something that satisfies both parties when it comes to providing the convenience of both. For example, the above-mentioned gelatinized rice obtained by drying cooked rice with hot air or the like may have a good taste, but it still requires about 5 minutes of boiling for restoration, and there are some difficulties in making it ready-to-eat.

On the other hand, even with freeze-dried rice that uses vacuum freeze-drying to make the rice grain structure more porous without impairing its flavor, recovery is not that far off when actually exposed to boiling water; It takes longer than the gelatinized rice mentioned above, and even if it is restored, it lacks the so-called viscoelasticity characteristic of boiled rice, so it is still insufficient for instant rice. Furthermore, the so-called puffed rice obtained by puffing cooked rice has a much more porous form than the above-mentioned freeze-dried rice, so it can be quickly restored by boiling water, but on the other hand, the rice grain structure itself may be destroyed. The reality is that the flavor is far from that of cooked rice because it is so advanced.

[Purpose of the invention]

This invention was made with the above-mentioned in mind, and its purpose is to restore the food very quickly just by pouring boiling water over it, and to have a food that is inferior to regular cooked rice in terms of taste and texture. An object of the present invention is to provide a method for producing instant rice that exhibits no flavor.

[Summary of the invention]

In order to achieve the above object, in this invention, raw rice is first washed and soaked in water, then drained and steamed, or cooked as it is to completely gelatinize the rice grain starch. Rice is soaked in water to absorb about 70-80% of the water, then drained. This soaking treatment swells the rice grains and dissolves the gelatinized starch on the surface of the rice grains in water to form single grains. Next, the swollen, single-grained cooked rice starch is beta-ized, that is, kept in an aging atmosphere for a required period of time, thereby aging the swollen cooked rice starch.
It not only fixes the shape structure itself but also prevents the rice grains from sticking together. The above treatment imparts permeability to hot water over time. Thereafter, the cooked rice is either thawed or passed through a roller to form single grains, and then dried. For this drying process, any method such as ventilation drying with hot air or vacuum drying may be used, but in order to further reduce the drying cost, drying process using a fluidized bed dryer may be performed. Dry until it becomes less than 5%. The raw material rice may be either polished rice or brown rice, but in the case of the latter, it can be gelatinized in the same way as polished rice by using a pressure cooker or partially gelatinizing it and then steaming it. .

To further explain the embodiment of the present invention, the washed raw rice is soaked in water for at least one hour to reduce the water content to about 30%, and then steamed or cooked to reduce the water content to 50-60%. % of rice. Next, this cooked rice is immersed in about 4 times the amount of water and swelled with water to bring the water content to about 70 to 80%.

This amount of absorbed water is essential for swelling the rice grain structure and for the desired growth of ice crystals during slow freezing treatment, and if the water content is less than 70%, not only will the swelling of the rice grain structure be insufficient; In the next slow freezing process, the growth of rice grain-like ice crystals becomes underdeveloped, impairing the water absorption and restoring properties of the final product. In addition, if the moisture content exceeds 80%, broken rice will often occur during drying in the final treatment process, and the excess moisture, combined with the heat of the drying wind, will re-gelatinize the aged starch on the surface of the rice grains and cause them to bind together. This results in so-called baby rice, which significantly impedes drying, and especially when this drying is fluidized bed drying, the fluidity of the rice grain group is hindered, resulting in a significant reduction in drying efficiency. By the immersion treatment in water, the gelatinized starch on the surface of each rice grain is dissolved to some extent, preventing the rice grains from sticking together and making them into single grains. Therefore, it is desirable that this dipping treatment be carried out with appropriate stirring, agitation, etc. as necessary. The above-described soaking treatment for swelling and making rice grains into single grains can achieve its effects in about one hour.

Next, the soaked cooked rice is drained to remove excess water, and then placed on a tray or the like at 0 to 10°C.

Preferably, it is maintained at 0 to 4°C for several hours to age the gelatinized starch of the cooked rice. Due to the aging of the starch, the rice grain structure is solidified and retained in the water-absorbing and swollen state caused by the above-mentioned soaking treatment. In addition, during the above treatment, 0 to 4°C is the temperature range in which the aging of gelatinized starch, that is, its β conversion, occurs fastest, and in this case, the desired aging state can usually be reached in about 6 to 7 hours. Similar effects can be obtained in other temperature ranges by appropriately adjusting the aging time.

The cooked rice after the aging process is subsequently subjected to a slow freezing process, but this freezing process destroys part of the cell walls and cell membranes with ice crystals that form outside the cells of the rice grains. This is to facilitate penetration into the country. Note that the above effect cannot be obtained by rapid freezing, in which ice crystals are generated within the cell before the formation of extracellular ice crystals, and therefore this process is effective at reducing the maximum ice crystal formation zone between -3 and -5°C by approximately 1.
It is necessary to slowly freeze the material over a period of time, and for this purpose, it is usually possible to process the material by means such as leaving it in a frozen temperature range of -10°C. The frozen rice is subjected to a drying process to become a final product. This drying may be done by any method such as through-air drying or vacuum freeze-drying, but since the amount of water removed accounts for 70% or more of the processed amount, it is preferable to use through-air drying, which has a lower drying cost, and in this case, a fluidized bed dryer. Alternatively, a band-type aerated dryer or the like can be used. In either case, the moisture content must be kept at 5% or less in order to provide good preservability.

In the cooked rice obtained through the above steps, the relationship between the moisture content during swelling in the soaking process and the properties of the cooked rice during its restoration is as follows.

[Embodiments of the invention]

This invention will be described below with reference to specific embodiments.

After washing 1.6 kg of standard rice as raw rice with water, the water temperature was 25°C.
The moisture content of rice grains is reduced to 30% by soaking in water at ℃ and draining.
And so. This soaked rice was placed in a steamer and steamed for 30 minutes under normal pressure to obtain steamed rice with a moisture content of 55%. Next, this was immersed in 7:2 water and kept for 1 hour with occasional stirring to swell and make the water content of cooked rice 75%. Further, this cooked rice is placed on a colander and drained by natural dehydration, then placed on a tray and left in a refrigerator at 1°C for 6 hours to age the starch. Next, the cooked rice was transferred to a freezer at -10°C and held there, thereby performing a slow freezing process corresponding to the time required to pass through the maximum ice crystal formation zone at -3 to -5°C for 3 hours. After crushing and loosening the frozen cooked rice with a roller, it was put into a fluidized bed dryer with an air temperature of 90°C and dried to obtain 1.3 kg of instant rice.

After adding about 3 times the amount of boiling water to the above instant rice and keeping it for 1 minute,
When drained, the taste and texture were almost the same as regular cooked rice.

〔Effect of the invention〕

As described above, this invention aims to prevent the cooked rice from sticking to each other by soaking the cooked rice in water to swell the cooked rice grains due to water absorption and to dissolve and remove surface gelatinized starch, and then to age the swollen cooked rice. The starch is aged once, thereby fixing the structure of the cooked rice grains while retaining the absorbed moisture, thereby preventing the rice grains from binding to each other and deforming, that is, making the cooked rice grains into single grains, and making it easier to prepare for the next slow freezing process. Moisture necessary for ice crystal formation is retained within the rice grains.

During the slow freezing process, this water is generated as ice crystals outside the cells within the rice grain structure when it passes through the maximum ice crystal formation zone, thereby destroying part of the cell wall and facilitating the penetration of hot water during restoration. .

By subjecting this cooked rice to a drying process and drying it to a moisture content of 5%, the above-mentioned state is maintained as it is, and the instant rice obtained as a final product is compared to the conventional instant rice, which is restored within about 1 minute by passing boiling water. It has extremely excellent characteristics in terms of ease of cooking, and also has a taste and texture that is almost comparable to ordinary cooked rice. Therefore, it can be provided to the market as an instant food that can fully meet the general demand for this kind of cooked rice, and its practical value can be expected to be great.

Claims (1)

[Claims] 1. Washed rice is soaked in water, then drained and steamed, or cooked as it is, and the resulting cooked rice is soaked in water to reduce the moisture content to about 70 to 80%. A method for producing instant rice, which comprises aging cooked rice swollen by absorption, followed by slow freezing and drying. 2. The method for producing instant rice according to claim 1, wherein the aging treatment is carried out while maintaining the cooked rice at a temperature of 0 to 10°C. 3. The method for producing instant rice according to claim 1, wherein the slow freezing treatment is such that the frozen cooked rice passes through the maximum ice crystal formation zone for about 1 hour or more.