JP5683420B2 - Processed rice and its manufacturing method - Google Patents

Description

  The present invention relates to processed rice that can be easily cooked in a short time and a method for producing the same.

  In recent years, there has been a growing need for foods that can be easily eaten without the need for cooking. Research and development of such foods is ongoing and many products are on the market. As for cooked rice, products are being developed that save time for eating. Cooking rice at home takes about 1 hour, most of which is time required for water absorption of raw rice. If the rice is in the same level of water absorption as the cooked rice in advance, the time required for cooked rice, that is, gelatinization of rice starch is short.

  Therefore, processed rice called quick-cooked rice with reduced water absorption time has been developed. Conventional quick-cooked rice has fine cracks and pores in the rice grain. However, such rice has a problem that a shell crack occurs when water is absorbed. Furthermore, even in the dry state, the rice grains themselves are brittle and there is a problem that broken rice is generated. In addition, there is a problem that the grain of rice is easily crushed during eating and chewing, and the grain texture that greatly contributes to the texture of the cooked rice is impaired.

  In Patent Document 1, rice that has been soaked and sufficiently absorbed is steamed for 5 to 20 minutes, and only the surface part of the rice grain is pregelatinized, the central part is kept in a β-starch state, and further dried at 50 to 70 ° C. Quick-cooked rice with a content of about 13-15% is disclosed. The quick-cooked rice described in Patent Document 1 does not contain moisture necessary for cooking. For this reason, it is necessary to add water when cooking rice. However, since the water absorption rate is slow, the added water is not absorbed quickly. Therefore, when heated using a microwave oven, there is a problem in that water in the container boils and overflows from the container and is not cooked sufficiently.

  Patent Document 2 discloses a method for producing fast-cooked rice in which brown rice and polished rice are immersed in water or hot water, frozen, and dried under reduced pressure. In this production method, there is a problem that rice grains are crushed and the texture is impaired. Moreover, when water is added and it heats with a microwave oven, a water | moisture content will boil previously and it will not be cooked enough. For this reason, in Patent Document 2, as shown in Example 2, when heating using a microwave oven, it is necessary to use a heat-resistant synthetic resin bag having small holes for deaeration.

  Patent Document 3 is characterized in that the raw rice is irradiated with microwaves to cause fine cracks on the surface of the raw rice, and the microwave-processed rice having such cracks is dipped for several hours and then dried. The manufacturing method of the quick cooking rice for microwave oven rice cooking is disclosed. Quick-cooked rice produced by this method has fine cracks, so that the rice grains are easily broken when immersed. Moreover, since there is a heating history by microwaves, there is a problem that the flavor is affected.

  Patent Document 4 discloses a method for producing processed rice that can be cooked in a microwave oven by steaming raw material rice that has been subjected to freezing treatment, absorbing the steamed rice, and then freeze-drying it. Furthermore, it is disclosed that low amylose rice is used as raw rice. In this method, the graininess of rice during mastication is slightly changed due to fine cracks caused by freeze-drying. In addition, because of the use of special low amylose rice, there is a difference in texture with sticky rice.

  As described above, conventional quick-cooked rice has a problem that the flavor and texture are inferior to freshly cooked rice, and the quality of the rice is poor because the rice grains are crushed. Therefore, development of processed rice excellent in flavor, texture and quality is required.

Japanese Patent Publication No.42-27281 Japanese Patent Publication No. 60-10695 JP 2003-164263 A JP 2008-131887 A

  Therefore, an object of this invention is to provide the processed rice excellent in flavor, texture, and quality, and its manufacturing method.

  From one aspect of the present invention, a raw rice selected from non-washed rice and polished rice is immersed in hot water for 1 to 5 minutes to obtain a heat-treated rice, a step of rapidly cooling the heat-treated rice, and cooling There is provided a method for producing processed rice, comprising a step of absorbing the heat-treated rice at a temperature of less than 65 ° C. to obtain swollen rice and a step of freeze-drying the swollen rice.

From another aspect of the present invention, a processed rice produced by the above method is provided. The processed rice has pores, has a gelatinized layer on the surface, has an ungelatinized portion at least in the center, and has a volume 1.8 to 2.4 times that of the raw rice.

  ADVANTAGE OF THE INVENTION According to this invention, the processed rice excellent in flavor, texture, and quality and its manufacturing method are provided. The processed rice obtained by the method of the present invention can be cooked in a short time even with a normal rice cooker or pan, and even with a microwave oven, it can be cooked easily in a short time. is there.

  The method for producing processed rice according to the present invention includes a step of immersing raw rice selected from non-washed rice and polished rice in hot water for 1 to 5 minutes to obtain heat-treated rice, a step of rapidly cooling the heat-treated rice, and cooling A step of absorbing the heat treated rice at a temperature of less than 65 ° C. to obtain swollen rice, and a step of freeze-drying the swollen rice.

  As raw materials for processed rice, sticky rice, low amylose rice, and the like can be used. Those varieties are not particularly limited. Sticky rice and low amylose rice are made into a state of non-washed rice or polished rice and used as raw rice. It is preferable to use non-washed rice as raw rice.

  Wash-free rice is rice obtained by removing rice bran from brown rice to obtain polished rice, and further removing skin wrinkles from this rice. The following four methods are generally known as methods for producing washing-free rice: 1. BG milled rice production method (a method of peeling the skin using the adhesive strength of the skin); 2. NTWP processing method (method of removing skin wrinkles with a small amount of water and attaching to granular tapioca); 3. Washing and drying method / wet method (method of washing skin dry with water and drying); Semi-washless rice production method (method of removing skin folds by rubbing rice with a polishing machine): (See the homepage of the National Washless Rice Association “http://www.musenmai.com/musenmai.html”). Although the manufacturing method of the non-washing rice used as raw material rice is not specifically limited, From the viewpoint of quality, cost, and the amount of distribution, it is more preferable to use non-washing rice obtained by the BG polished rice manufacturing method.

  In the method of the present invention, first, raw rice is immersed in hot water for 1 to 5 minutes. The raw material rice is used without being washed in advance and impregnated with water. By this treatment, heat-treated rice having a starch gelatinized layer formed on the surface of the rice grain is obtained. The surface gelatinized layer acts as a protective layer for the rice grains. This protective layer prevents the rice grains from cracking after drying. The inside of the rice grain is kept in an ungelatinized state because water necessary for gelatinization is insufficient and the penetration of hot water is insufficient.

  As hot water, hot water having a temperature higher than the gelatinization temperature of rice starch is used. Preferably, hot water having a temperature of 90 ° C. or higher is used. When hot water of less than 90 ° C. is used, the gelatinization speed of the surface is slow, and hot water penetrates into the inside before the surface is gelatinized, so that the ungelatinized state of the center cannot be maintained.

  When the time for immersing the raw rice in hot water exceeds 5 minutes, the hot water penetrates into the rice grains and the gelatinized layer becomes thick. When this gelatinized layer is dried, it becomes a dry amorphous layer of starch gel, which prevents water absorption. Therefore, the water absorption of the processed rice finally obtained falls. If the time of immersion in hot water is less than 1 minute, the gelatinized layer formed on the surface of the rice grain is too thin. Therefore, the function as a protective layer becomes insufficient, and it is difficult to prevent cracking of the rice grains after drying.

  It is desirable to appropriately adjust the time of immersion in hot water according to the variety of rice. Moreover, it is preferable to stir raw rice during heating and to heat it uniformly.

  Next, the heat-treated rice is rapidly cooled. The heat-treated rice that has been immersed in hot water and has passed a predetermined time is immediately separated from the hot water. And the separated heat-treated rice is cooled immediately. Although cooling can be performed using cold water, it is not limited to this. Moreover, what is necessary is just to cool to the temperature below normal temperature, for example, cools to 30 degrees C or less.

  The rapid cooling here is intended to mean that the heat-treated rice separated from the hot water is cooled to a temperature below room temperature within 3 minutes, preferably within 1 minute.

  By rapidly cooling the heat-treated rice, residual heat is prevented from being transmitted to the inside of the rice grain. Thereby, it can prevent that the non-gelatinized layer inside a rice grain reduces. Moreover, it can prevent that the water absorption of the processed rice finally obtained by the gelatinization layer on the surface of rice grain becoming thick falls.

  Next, the cooled heat-treated rice is immersed in warm water to absorb water. This water absorption treatment is performed at a temperature of less than 65 ° C. In addition, the temperature here is not the temperature of warm water, but the temperature of the immersed heat-treated rice. The temperature of the heat-treated rice can be measured by inserting a thermometer such as a temperature sensor into the heat-treated rice.

  The gelatinization temperature of rice starch is generally said to be 65 to 70 ° C. Therefore, by absorbing water at a temperature of less than 65 ° C., the heat-treated rice can be absorbed without gelatinization. Moreover, it is preferable to implement a water absorption process at the temperature of 25 degreeC or more. Water absorption can be promoted by absorbing water at a temperature of 25 ° C. or higher. More preferably, the water absorption treatment is performed at 30 ° C. or higher and 60 ° C. or lower. In addition, said temperature range points out the value in the initial stage of a water absorption process, and the temperature does not need to be maintained through a water absorption process.

  Swelled rice can be obtained by the above water absorption treatment. This swollen rice has a mass approximately 1.8 to 2.2 times that of the raw rice, and has a mass and volume equivalent to cooked rice obtained by cooking ordinary rice by a general method.

  In addition, the swollen rice has a water content of about 52 to 60% by mass. The water content of ordinary cooked rice is about 60% by mass. Therefore, the swollen rice obtained here has a moisture content almost the same as that of ordinary cooked rice.

  Generally, when normal polished rice is immersed in water at room temperature, the saturated moisture is said to be 25 to 35% by mass. In the method of the present invention, water is forcibly absorbed by the heat treatment and the water absorption treatment with warm water as described above, thereby achieving a high water content of about 52 to 60% by mass. The water content can be measured by drying at 135 ° C. for 2 hours under normal pressure.

  Moreover, by achieving such a high water content, swollen rice having a mass and volume approximately 1.8 to 2.2 times that of the raw rice can be obtained. When the swollen rice has the mass and volume in the above ranges, when the cooked processed rice is finally obtained, water absorption at the time of rice cooking is quick, and water content is close to that of the rice cooking rice. it can.

  When the moisture content is low and the swelling is insufficient, the cooked rice obtained by cooking the finally obtained processed rice is ungelatinized or hardened. In addition, a torso crack occurs and the flower blooms. On the other hand, if the water content is too high and the swelling is excessive, the rice grains of the cooked rice are crushed. As a result, the texture and quality deteriorate.

  The water absorption treatment can be carried out by various industrial methods such as a method using a kneader with a heating jacket and a hot water shower, or a method of putting heat-treated rice and hot water into a container or the like.

  After the water absorption swelling is completed, the swollen rice is separated from the warm water and further drained. Draining removes excess water between rice grains. Draining can be carried out by various methods such as natural dehydration using a colander or dehydration using a centrifugal dehydrator.

  After draining, an additive may optionally be added and applied or absorbed into the swollen rice. Examples of additives include antioxidants such as vitamin E, sugars such as trehalose and sorbit, salt, sucrose fatty acid esters for preventing starch aging, and seasonings such as soy sauce and dashi.

  Then, the final processed rice is obtained by freeze-drying the swollen swollen rice. By freezing, the water in the swollen rice becomes fine ice crystals. Fine pores are formed by sublimating the ice crystals by drying. As a result, porous processed rice is obtained. Such processed rice can absorb water in a short time.

  The longer the time required for freezing, the larger the ice crystals that are produced. As a result, the rice grains are easily broken. Therefore, prior to freeze-drying treatment, it is preferable to pre-freeze and rapidly freeze the swollen rice.

  Freeze drying can be performed using a commonly used freeze dryer. For example, the swollen swollen rice can be placed on a tray for a freeze dryer and freeze dried. The drying process can be performed, for example, under a high vacuum of 40 to 65 Pa.

  Such processed rice after freeze-drying preferably has a water content of 7% or less.

By the above method, processed rice having pores, having a gelatinized layer on the surface, and having an ungelatinized portion at least in the center can be produced. Furthermore, this processed rice has about 1.8 to 2.4 times the volume of the raw rice because the swollen rice that has sufficiently absorbed water is subjected to freeze-drying treatment. This is a volume equivalent to cooked rice obtained by cooking ordinary rice using a general method. Here, the volume is measured by filling a 200 ml graduated cylinder with 50 g of a specimen (raw rice, processed rice, etc.).

  Such processed rice can be cooked by adding water and heating. For example, processed rice is put into a cooking utensil or a container, a predetermined amount of water necessary for cooking rice is added to absorb water, and heated for a short time. Cooking rice is completed by gelatinizing rice starch by heating.

  The processed rice of the present invention has a gelatinized layer on the surface of the rice grain, and therefore has high resistance to cracking and high strength after drying. Therefore, it is possible to maintain excellent quality during storage and distribution. Moreover, since the rice grains are not broken during or after cooking, it is possible to provide an excellent texture. In addition, since the gelatinized layer is thin and uniform, there is an advantage that water absorption is not hindered. Furthermore, since the gelatinization layer is thin and the inside of the rice grain is in the state of raw starch, it has an excellent flavor close to that of ordinary cooked rice.

Moreover, since the processed rice of this invention is swollen, it has a volume close | similar to normal cooked rice. Therefore, the water absorption at the time of cooking rice is quick, and the water content close to that of cooked rice can be contained. Moreover, since the expansion | swelling of the rice grain by water absorption is small, the body crack of a rice grain and broken rice are prevented.

  Moreover, since the processed rice of this invention has a pore, more rapid water absorption is possible. Therefore, the time required for water absorption during cooking is remarkably shortened.

  The method for cooking the processed rice is not particularly limited, and any of a pot, a rice cooker, and a microwave oven may be used. The cooked rice produced by the method of the present invention can be cooked in a short time regardless of which method is used, and has a texture and flavor comparable to that of ordinary cooked rice.

  The processed rice of the present invention does not require a special container, unlike conventional quick-cooked rice, even when cooking using a microwave oven. For example, it is also possible to cook rice for one meal using tableware such as a tea bowl. Since the water absorption rate is fast, the added water is absorbed quickly. Therefore, when heating using a microwave oven, water in the container does not boil and overflow from the container. In addition, even if rice is cooked using a microwave oven, it is possible to provide a state closer to ordinary cooked rice, such as a unique rice odor that occurs when rice is cooked using a conventional rice cooker. It has excellent characteristics.

  As described above, according to the present invention, there are provided processed rice and a method for producing the same, which can easily obtain cooked rice and rice cake excellent in flavor, texture and quality in a short time. Further, in the method of the present invention, it is not necessary to use special varieties of rice, so that processed rice can be more easily produced.

[Example 1]
250 g of Koshihikari refined rice was put into a colander, poured into boiling water, and immersed for 2 minutes with occasional stirring to obtain heat-treated rice. The heat-treated rice was immediately exposed to running tap water and cooled to room temperature (26 ° C.). Next, the cooled heat-treated rice was immersed in 3 liters of hot water at about 50 ° C. for 90 minutes to obtain swollen rice. The swollen rice was drained for the colander. The mass of the swollen rice after draining was 510 g. 2 g of vitamin E emulsion was added to the swollen rice and mixed uniformly.

  The swollen rice was then transferred to a freeze-drying tray and frozen in a −40 ° C. freezer. Subsequently, it put in the chamber of the freeze dryer, and was dried on conditions with a vacuum degree of 40-60 Pa and shelf temperature of 60 degreeC. Thereby, 200 g of the intended processed rice was obtained.

  50 g of the obtained processed rice was put in a household tea bowl, and 100 g of water was added thereto. The added water was absorbed by the rice grains almost instantaneously. Next, it was heated for 3 minutes and 40 seconds using a household microwave oven with an output of 500 watts. During heating, there was no foaming or spilling of water, and the rice could be cooked well. The obtained cooked rice was 132 g, which was cooked rice having a freshly prepared texture and flavor equivalent to that of ordinary cooked rice, without breaking the cooked rice.

[Example 2]
100 g of the processed rice obtained in Example 1 was put in a small pan, and 210 g of water was further added and left for 1 minute to absorb water. The pan was then capped, heated on a medium burner on a gas stove for about 8 minutes, turned off and steamed for 2 minutes. As a result, cooked rice equivalent to ordinary cooked rice was obtained without breaking the rice grains.

Claims (4)

A step of immersing raw rice selected from non-washed rice and polished rice in hot water for 1 to 5 minutes to obtain heat-treated rice;
Rapid cooling of the heat treated rice;
A step of absorbing the cooled heat-treated rice at a temperature of less than 65 ° C. to obtain swollen rice having a mass of 1.8 to 2.2 times that of the raw rice and a moisture content of 52 to 60 mass%. When,
Freeze-drying the swollen rice;
Comprising a volume measured by filling a sample of 50g graduated cylinder 200ml is a 1.8 to 2.4 times the volume measured by filling the raw rice 50g graduated cylinder 200ml machining Rice manufacturing method.   The said processed rice is a manufacturing method of Claim 1 which has a moisture content of 7 mass% or less.   The said processed rice is a manufacturing method of Claim 1 or 2 which has a pore and has a gelatinization layer on the surface. A 200 ml graduated cylinder with pores, a gelatinized layer on the surface, an ungelatinized part at least in the center, and a volume measured by filling a 200 ml graduated cylinder with 50 g sample Processed rice that is 1.8 to 2.4 times the volume measured by filling 50 g of raw rice in the container.