JP6045132B2 - Cooking method of mochi rice - Google Patents

Description

  The present invention relates to a method for cooking cooked rice having excellent aroma and flavor and having healthy components.

  Rice is roughly divided into Uruchi rice and Mochi rice. Since glutinous rice is deficient in the function of starch granule-bound starch synthase I, it does not contain any amylose and contains only amylopectin. Amylose and amylopectin are both polymers in which glucose, which is a kind of reducing sugar, is polymerized by a glucoside bond, but the starch structure is different. As a result, Uruchi rice and mochi rice have various physical properties and processing characteristics.

Uruchi rice is widely used all over the world, including Japan, and it can be cooked, boiled, steamed, fried, or a combination of these (cooking methods that leave the shape of rice grains), rice flour noodles, and rice flour bread. In addition, methods for producing various processed products such as confectionery such as dumplings and rice crackers, and beverages such as Japanese sake and amazake have been developed. Among these, the cooking method for eating as a staple food on a daily basis is common in Japan. The cooking and drying method is a cooking method that cooks rice grains by adjusting the amount of water and heat, then steams them to make cooked rice with an excellent texture. An automatic rice cooker has been developed (see Patent Document 1). However, the taste of cooked and dried rice is generally light, and there are no major characteristics in fragrance and flavor, which is considered to be one of the major causes of the decline in rice consumption in Japan.
On the other hand, most of the sticky rice is used for processed foods such as rice cakes, red rice, and confectionery, and is often consumed only on special days such as a halle day. That is, as in the case of Uruchi rice, it is rarely eaten on a daily basis without seasoning, etc., and the cooking method for that is not established in Japan.

JP 2001-46224 A JP 2010-63572 A JP 2008-18096 A Special table 2007-532712 gazette

Kazuhiko Takamiya et al. “Science of food viewed from color”, Science Forum Inc., February 13, 2004 Chemistry and Biology 9, pp.85-96, Japan Society for Agricultural Chemistry, 1971 Yasuko Kakinuma, Kyoko Fukuda, “Effects of improving the quality of cooked rice with bamboo charcoal” Journal of the Japan Society for Cooking Science 35: 139-147 Kenji Kobayashi, Noriaki Tosa, Yasuo Hara, Shuji Horie, “Examination of Cooking Characteristics with Electrolyzed Water” Journal of Japanese Society for Food Science and Technology 43: 930-938, 1996 Ministry of Agriculture, Forestry and Fisheries, Consumer Affairs and Safety Bureau, Consumer Room Communication December Issue: 8-9, 2010 Awazuhara et al, Distribution and characterization of enzymes causing starch degradation in rice (Oryza sativa cv.koshihikari)., J Agric. Food Chem. 48, pp.245-52, 2000

  The problem to be solved by the present invention is to provide a method for cooking cooked rice that can be eaten deliciously without seasoning rice (particularly mochi rice).

  As a result of extensive research, the present inventor has optimized the rice milling method, water immersion method, and heating method to control the quality and amount of sweetness and adjust pH and water activity. It was found that cooked rice having excellent fragrance and flavor and antioxidant melanoidin can be produced by promoting the reaction.

The present invention has been completed based on such findings, and specifically,
A method of cooking rice cakes by immersing rice grains of rice cakes in water, draining and heating,
While adjusting the pH of the water in which the rice grains are immersed to 6.5 to 10.0,
The first heating process in which the time required for the rice grain temperature to reach from 55 ° C to 65 ° C is 20 minutes or longer by adjusting the heating state so that the moisture content of the cooked rice is 39% to 49 %. And steam heating the rice grains by a second heating step that raises the temperature so as to draw a convex curve from 60 ° C. to 90 ° C. in at least 40 minutes and a third heating step that heats at 100 ° C. for at least 60 minutes. It is characterized by doing.

  A sufficiently delicious cooked rice can be provided if the pH of the water in which the rice grains are immersed is 6.5 or more and 10.0 or less, but a more delicious cooked rice can be provided if the pH is 6.8 or more, preferably 7.1 or more. The pH of the water in which the rice grains are immersed can be adjusted by using a pH adjuster or selecting appropriate rice grains.

Moreover, the moisture content of cooked rice after cooking can be adjusted by the amount of immersion water before heating, or by the amount of steam and the amount of hammering water during steam heating.
Furthermore, since 60 ° C is the optimum temperature for saccharifying enzyme (amyloglucosidase) contained in rice grains, it is possible to increase the reducing sugar contained in the rice grains after cooking by increasing the time around 60 ° C. it can.

In the heat cooking method of mochi rice of the present invention, at the time of immersion in water , glucose is added so that the weight ratio of glucose to rice grains is 0.1% to 10.0%, or at least one of valine, glycine and threonine. It is preferable to add two amino acids. Glucose and amino acids may be added alone, or both may be added.
Glucose is one of the substrates of the Maillard reaction and is produced from the main component (starch) of rice grains. Valine, glycine and threonine are also Maillard reaction substrates and are amino acids contained in rice grains. Therefore, the Maillard reaction can be promoted by adding any of these during water immersion .

Moreover, in the heating cooking method of the glutinous rice of this invention, it is preferable to carry out steam heating, and, thereby, the moisture content after cooking can be suppressed low .

Also, brown rice of mochi rice stored at a temperature lower than 25 ° C is refined at a rate of 0-20%, and within 40 months of rice, preferably within 2 weeks, within 2 months It is preferable to heat cook after immersing in water adjusted to a temperature range of 25 ° C to 40 ° C.

In the cooking method of mochi rice according to the present invention, the conditions for promoting the Maillard reaction, that is, the type and amount of the substrate, the heating temperature and time, the pH, and the water activity are controlled so that the cooked rice has an excellent aroma and flavor. Can be provided. Moreover, since many melanoidins which have an antioxidant effect can be produced by Maillard reaction, health maintenance promotion can be aimed at.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the result of Example 1 of this invention, (a) is a figure which shows the change of the free sugar content rate in the rice grain by the difference in a variety and a cultivation year, and a milling rate, (b) is by the difference in a milling rate The figure which shows the change of the saccharifying enzyme activity in a rice grain. It is a figure which shows the result of Example 2 of this invention, and is a figure which shows that the ratio of the free saccharide | sugar by the difference in water immersion temperature and water immersion time changes with varieties, rice milling, and storage methods. It is a figure which shows the result of Example 3 of this invention, (a) is a figure which shows how the temperature change of cooked rice which influences glucose content changes with the difference in a heating method, (b) is 75w. The reference figure which shows the relationship between the heating time when it heats with glucose, and glucose content rate. (A) is a figure which shows the result of Examples 4-6 of this invention, The figure which shows that the change of the content rate of free sugar by the difference in the quantity of immersion water and a heating method changes with milled rice and the storage method, (B) is a figure which shows the result of Example 7 of this invention, and is a figure which shows the difference of the browning of cooked rice by the cooking method (the progress degree of the Maillard reaction). (A) is a figure which shows the result of Example 9 of this invention, The photograph for showing the influence which baking soda addition amount has on the yellowing and browning of cooked rice, (b) is the result of Example 10 of this invention The photograph for showing the influence which glucose addition amount has on the yellowing and browning of cooked rice under weak alkaline conditions. It is a figure which shows the result of Examples 11-12 of this invention, and is the figure of the GC-MS analysis which shows the aromatic component produced | generated by sodium bicarbonate, glucose, glycine, and valine addition.

  The rice cooking method of the present invention includes a cooking method in which melanoidin is produced in cooked rice obtained after heating the rice. Melanoidin is a brown product and is a final product produced through a complex reaction (amino-carbonyl reaction) of an amino compound such as amino acid / protein and a carbonyl compound such as reducing sugar. This production reaction was discovered by L.C. Maillard in 1912 and is called the Maillard reaction. Melanoidins are contained in fermented foods such as soy sauce and miso that have been aged for a long time, or foods that have been heated and roasted at high temperatures such as bread and coffee, and are known to have various physiological functions including antioxidant properties. . Although the chemical structure of melanoidin has not been clarified, it is considered to be an aggregate of many colored substances, and its content is known to be highly correlated with the absorbance at a wavelength of 400 nm (see Non-Patent Document 1).

  In the process of the Maillard reaction, it has been clarified by a simplified model experiment system that sweet scents such as caramel and chocolate and scented scents such as popcorn are produced depending on the types of amino acids and reducing sugars and the heating temperature ( Non-patent document 2). There have been few examples that have focused on the Maillard reaction in the cooking process of cooked rice so far, and it suppresses unpleasant yellowing and oxidation that occurs when a rice cooker (see Patent Document 2) that locally produces rice cake and keep warm for a long time after cooking rice The rice cooker (refer patent document 3) to develop is only developed. However, in various foods such as the above-mentioned soy sauce, miso, bread, coffee, and roasted meat, the Maillard reaction gives a unique and excellent aroma and flavor. The idea of the present invention was also conceived.

  There are many unexplained parts in the Maillard reaction, and it is not easy to control the reaction in a heterogeneous system composed of complex components such as foods. However, it has been shown that the Maillard reaction is affected by pH, water activity, presence of oxygen and metal, heating temperature and heating time, the reaction is inhibited by sulfur dioxide and the like (see Patent Document 4), If these conditions are adjusted well, it is presumed that the amount and quality of melanoidin and aroma components produced by the Maillard reaction can be changed.

  Knowledge regarding pH and minerals that affect pH in rice cooking is limited. Bamboo charcoal soaking solution (pH 8.6 to 9.6, see non-patent document 3) and drinking alkaline electrolyzed water (pH 9 to 10, see non-patent document 4) as water with a pH higher than the Japanese tap water standard pH 5.8 to 8.6 As a result, it was clarified that the cooked rice became softer and the amount of eluate increased. In addition, calcium and magnesium contained in a large amount of hard water yellow the cooked rice, and calcium hardens the cooked rice (see Non-Patent Document 5). However, the effect on flavor and flavor was unknown.

On the other hand, the present inventor, as will be described later, by using an appropriate amount of baking soda recognized as a food additive, the pH of rice grain immersion water is increased to weak alkalinity, and the Maillard reaction can be remarkably accelerated depending on the concentration. I found it. In addition, it is known that fat contained in rice grains is decomposed during storage to produce fatty acids, but the present inventor, as will be described later, the pH of rice grain soaking water decreases with storage time after milling at 25 ° C or higher. Admitted to do.
Therefore, when the Maillard reaction is promoted by adjusting the pH, sodium bicarbonate and other alkaline agents (including one or more of potassium carbonate, sodium carbonate, sodium bicarbonate and potassium phosphate or sodium salts), the above-mentioned It is effective to use weak alkaline water and pay attention to the storage history of rice grains.

  Moreover, when considering cooking and eating on a daily basis, it is desirable to promote the Maillard reaction by a method as simple as possible. The present inventor has found that when the water activity (water content) and the heating temperature / time are set to appropriate values, browning, which is an effective index of melanoidin content in cooked rice, is promoted. In order to adjust the water activity, it is better to cook with a steamer, and when the moisture content of mochi rice obtained by cooking with a steamer was actually examined, it was about 39.0%.

  The water content of typical cooked rice processed foods is as follows: rice: 65.0%, red rice: 58.0%, rice cake: 44.5% (Fourth Japan Food Standard Composition Table, Science and Technology Agency Resource Research Committee, 1982) 1))), it can be seen that the moisture content of mochi rice obtained by cooking using a steamer is kept low. This can be achieved, for example, by sufficiently removing water before the heating after sufficiently immersing in water, heating with a low steam generation amount, and refraining the hammering water normally applied during heating. In addition, when water is appropriately added during heating, the water content after heating reaches, for example, about 49.0%, and browning is suppressed at that time.

  As a precondition for advancing the Maillard reaction, a sufficient amount of reducing sugar and amino compounds such as amino acids and proteins must be contained in the rice grain. Increasing amino compounds such as amino acids and proteins can be realized by devising rice cultivation techniques such as techniques known in the field of crop cultivation, such as increasing the amount of nitrogen fertilization during the ripening period. On the other hand, it is also possible to use mutants whose metabolism / accumulation amount is changed. In order to increase the reducing sugar content, it is important to utilize the action of saccharifying enzymes in rice. The activity of saccharifying enzymes is also affected by differences in the cultivation environment and varieties. Therefore, selection of rice varieties and cultivation history used for cooking is important.

  In addition, the protein content decreases as the fineness ratio is increased. Furthermore, as will be described later, increasing the milling ratio can reduce the content of sucrose, which is abundant at the time of harvest, and it varies depending on the variety and cultivation conditions, but about 40% at the milling ratio 4% and about 8% 80% is 20% and about 90% is excluded. Therefore, it is better to polish rice at a low milling rate of about 4% if you prefer a strong sweetness such as sucrose, and 8% to 20% if you prefer an elegant sweetness such as glucose.

  On the other hand, the present inventor has found that α-amylase activity and amyloglucosidase activity tend to decrease with the lapse of time after sperm as described later. Moreover, the tendency for pH to fall by high storage temperature was found (refer Table 2 mentioned later). For this reason, it is desirable to always store at a low temperature, and to cook and process within one month after pouring, more preferably within two weeks.

The saccharification reaction also proceeds while the rice is immersed in water. The higher the water immersion temperature in the range up to about 60 ° C. and the longer the immersion time, the more the reducing sugar increases, but a part of the generated reducing sugar is eluted in the immersion water. Therefore, it is important to adjust the amount of immersion water. Specifically, approximately 30% of water is absorbed in water at maximum, and the loss due to elution of reducing sugar can be suppressed by immersing in at least 30% of water. It is thought that. However, in order to prevent uneven water absorption, it is preferable to immerse in about 40% of water.
Sucrose exhibiting strong sweetness does not increase during water immersion or heating, and part of it is decomposed during water immersion / heating. However, when only elegant sweetness is desired, it is preferable to elute sucrose by immersing in more water depending on the degree of requirement. In addition, since rot progresses by the activity of the microorganisms mixed in immersion water when immersion temperature is high, when raising immersion temperature, a sterilization process is required.

  One of the most influential factors in reducing sugar content in the cooking process of rice is the heating method. As described in Patent Document 1 and as shown in Non-Patent Document 6, it is considered effective to utilize the activities of α-amylase and amyloglucosidase at 40 ° C. and 60 ° C. as optimum temperatures, respectively. ing.

  As a result of investigating various heating patterns at a moisture content of 39.0% using mochi rice, which is known to be susceptible to the effects of saccharifying enzymes, the present inventor has found that the cooking rice temperature is about 60 ° C. for 4 hours. Until then, it was found that reducing sugar increased slowly until 8 hours (from 8 hours until 12 hours). However, more reducing sugar was produced when heated at about 60 ° C. for 1 hour and then heated to about 90 ° C. for 1 hour than when heated at about 60 ° C. for 2 hours. From this, it can be seen that the reducing sugar content does not depend only on the optimum temperature of amyloglucosidase.

  In addition, it was found that when heating was continued at a relatively low temperature of about 60 ° C. with a steamer with a small amount of steam generation, drying progressed with some rice grains on the surface layer, resulting in a decrease in texture and unevenness. In addition, excessive heating may generate harmful substances such as peroxides and acrylamide. On the other hand, when heating is insufficient, starch gelatinization (alpha-ization) is insufficient, and digestibility and texture are remarkably deteriorated. For this reason, it is necessary to determine the optimum heating temperature and heating time and the optimum moisture content of the cooked rice.

In consideration of the above points, the present inventor has cooked uruchi rice and glutinous rice using a steamer that can maintain the temperature and moisture content of the cooked rice for a relatively long time without causing significant changes in texture. Clarified how to do. In developing the cooking method according to the present invention, the heating conditions particularly considered are the following two points.
(1) Heating conditions with low sweetness but good texture Maintain the cooked rice temperature at about 60 ° C for 20 minutes, then increase the temperature to draw a convex curve up to about 90 ° C in 40 minutes. After that, it is heated at 100 ° C. for 1 to 3 hours.
(2) Heating conditions that the texture is firm and slightly inferior, but the elegant sweetness is relatively strong
Raise the temperature to draw a convex curve up to about 60 ° C in 1 hour. Raise the temperature to draw a convex curve up to about 90 ° C in the next hour. After that, heating is performed at 100 ° C. for 1 to 3 hours, and during that time, heating is performed with the lowest possible steam generation amount.
Hereinafter, some examples performed in order to confirm the effect | action of the said heat cooking conditions are demonstrated. However, the present invention is not limited to these.

The difference in free sugar content and saccharifying enzyme activity by the rice milling method was investigated.
The brown rice of 2008 Koshihikari and 2009 Asahi was milled using a household rice mill (MR-D510, manufactured by TWINBIRD), respectively, and made into fine powder with a grinder. Koshihikari refined at a rate of 0%, 8%, and 20%, and Aso purple refined at a rate of 0% and 4%. After freezing, free sugars were extracted with 10 volumes of 80% ethanol and concentrated, and the glucose and sucrose concentrations in the extract were quantified using HPLC. The result is shown in FIG.

  As shown in FIG. 1 (a), the glucose content was as low as 0.04% or less for all varieties and milling ratios, whereas the sucrose content was as high as 0.68 to 0.80% for brown rice (milling ratio 0%). , Markedly decreased as the precision ratio increased. From this, it was clarified that the sucrose content of brown rice varies greatly depending on the variety and harvest year, but varies greatly depending on the milling rate.

  Next, coconoemochi produced in 2009 was milled and ground at a rate of 0%, 8%, and 32% using a rice mill similar to the above. After fertilization, Megazyme's α-amylase activity measurement kit and International F-kit were used, and the National Tax Agency prescribed analysis method (Heisei 19 National Tax Agency Instruction No. 6, http://www.nta.go.jp/shiraberu/zeiho- α amylase activity and amyloglucosidase activity were measured according to kaishaku / tsutatsu / kobetsu / sonota / 070622 / 01.htm). As a result, the α-amylase activity rapidly decreased and the amyloglucosidase activity gradually decreased as the fineness ratio increased (FIG. 1 (b)).

Changes in free sugar content during water immersion were investigated.
Store brown rice at a low temperature (4 ° C) and store it at room temperature for 1 month or 2 months after milling. It was immersed in 15 g of water at 4 ° C., 25 ° C., 37 ° C. for 12 hours, or at 25 ° C. for 1 hour. Thereafter, water in which the rice was soaked was collected in a centrifuge tube and centrifuged for 10 minutes at 4 ° C. and 14,000 rpm in a high-speed microcentrifuge manufactured by Eppendorf. Then, the glucose and sucrose concentrations contained in the supernatant were quantified using HPLC.

As a result, both Himenomochi and Shiga Hadakaji, which were stored at room temperature for 1 month after milling, increased the amount of glucose eluted in the immersion water as the water immersion temperature was higher and the water immersion time was longer (see FIG. 2). .
On the other hand, the amount of glucose that was stored at room temperature for 2 months after milling was slightly less than that of one that was stored at room temperature for 1 month, and the amount of glucose eluted in the immersion water was maximum when the water immersion temperature was 25 ° C.

From the above results, the saccharifying enzyme activity was high until 1 month after rice polishing, and the enzyme reaction responded well to the water immersion temperature and water immersion time. It was suggested that the response to temperature became dull.
On the other hand, the amount of sucrose gradually decreased as the water immersion temperature increased in both the sample stored at room temperature for 1 month after milling and the sample stored at room temperature for 2 months. From this, it was considered that the amount of sucrose is not affected by saccharifying enzyme but slightly affected by degrading enzyme.
In addition, the amount of sucrose in the immersion water was high even when immersed in water at 25 ° C for 1 hour, and in general, it showed a tendency to increase in 2009 Shigaha double cocoons compared to 2008 Hymenomochi. From these facts, it was found that the amount of glucose and sucrose eluted in the immersion water differs depending on the variety, harvest year, rice milling / storage method and water immersion method.

Changes in glucose content due to differences in heating conditions were examined.
After 90 hours of milling, 90 g of 2008 Hakutomochi stored at room temperature was immersed in 90 g of water and allowed to absorb water overnight at room temperature, then transferred to a stainless steel colander with a diameter of 18 cm, and excess water was removed over 15 minutes. Subsequently, a colander was placed on the upper stage of a two-stage steaming pot containing 600 ml of water, and heated using the Panasonic IH cooker KZ-PH30P under the following conditions (1) to (6). However, for some conditions, 1.5 liters of water or 600 ml of warm water heated to 70 ° C. by preheating was used.
(1) 150w · 2 hours / 700w · 20 minutes (2) 150w · 2 hours (1.5 liters of water) / 700w · 20 minutes (3) 75w · 2 hours (70 ℃ hot water) / 700w · 20 minutes (4) 75w・ 1 hour (70 ℃ hot water) / 150w ・ 1 hour / 700w ・ 20 minutes (5) 700w ・ 5 minutes / 15 minutes standing / 150w ・ 40 minutes / 260w ・ 60 minutes (Hereafter, the condition of (5) is Also called SRT.)
(6) 700w · 20 minutes

  The heating condition (6) is a condition of a short-time heating method usually used for heating cooked rice. FIG. 3A shows the temperature change of cooked rice when heated under the conditions (1) to (6) (in the legend of (1) to (4) shown in FIG. 3A, “700w · 20 "Minute" was omitted.)

  After heating, it was immediately stored frozen at -20 ° C and dried overnight with an 80 ° C ventilator. And after making dried rice fine powder with a grinder, free sugar was extracted with 10 times volume 80% ethanol, and the glucose concentration in an extract was quantified with F-kit by an international company. As a result, the sample heated under the condition (6) had a glucose content of 0.02%, whereas it was 0.10% under the condition (1) and 0.14% under the conditions (2) and (5). . Further, it was 0.16% under the condition (3) and 0.19% under the condition (4).

Thus, the glucose content significantly changed due to the difference in heating conditions. This is considered due to the temperature change pattern. That is, as shown in FIG. 3 (a), in the heating condition with the lowest glucose content (6), the temperature immediately increased to nearly 100 ° C. from the start of heating, whereas (1) to (5) Under these conditions, the temperature gradually increases. That is, it took a long time to pass through the temperature zone around 60 ° C. or a long time from 60 ° C. to 90 ° C.
On the other hand, the texture of the cooked rice was better as the overall heating time was shorter or as the ratio of elapse at high temperature was larger.

In addition, FIG.3 (b) is a reference figure which shows the relationship between the heating time when using 600 ml of warm water preheated at 70 degreeC, and continuing a heating at 75 w, and the glucose content rate in cooked rice. From Fig. 3 (b), when heated at a low output and maintained at a temperature of 60 ° C, the glucose content increases with time, but the rate of increase in glucose content decreases from about 400 minutes. I understand.
From the above, it is necessary to set the heating output and the heating time so that the temperature change pattern during heating becomes appropriate.

The effects of rice milling / storage methods, water immersion conditions, and heating conditions on free sugar content were comprehensively investigated.
90g, 45g or 90g of Y company's 2008 Hymenomochi which was stored at room temperature for 1 year after milling, and H's 2008 Hymenomochi of H company which stored brown rice at low temperature (4 ℃) and passed 1 week after milling. It was immersed in water and allowed to absorb water overnight at room temperature. Subsequently, using the standard equipment and procedure of Example 3, it was heated at 700 w for 20 minutes.

After heating, it was immediately stored frozen at −20 ° C. and dried overnight at 80 ° C. with a draft dryer. The dried cooked rice was pulverized with a grinder, and free sugar was extracted with 10 volumes of 80% ethanol and concentrated. The glucose and sucrose concentrations in the extract were quantified using HPLC. As a result, in the case of 45 g where the amount of immersion water was half that of rice, the glucose content and the sucrose content were both about 0.1% regardless of the length of the post-milling days or the difference in the rice milling method. On the other hand, when the amount of immersion water was the same as that of rice, the glucose content was only about 0.03% even though the number of days elapsed after polishing was short, and sucrose was not detected (see FIG. 4 (a)).
From the above results, it was suggested that the saccharification enzyme tends to be inactivated by the short-time heating method by strong fire, and therefore, the elapsed days after milling and the difference in the milling method do not affect the free sugar content after heating. Moreover, when the amount of immersion water increased, it turned out that especially sucrose content rate falls among free sugar content rates.

  Using the same apparatus and procedure as in Example 4, the rice cake was cooked under the condition (5) shown in Example 3. As a result, compared with the case of the short-time heating method by strong fire in Example 4, the glucose content rate increased remarkably in any case (refer Fig.4 (a)). In particular, in the case of a sample with a short elapsed time after milling considered to have a high saccharifying enzyme activity, it was as high as about 0.31%, so the importance of having a short elapsed time after milling was pointed out. As for the sucrose content, the same results as in Example 4 were obtained, and the amount of elution and loss increased as the amount of immersion water increased.

Brown rice was stored at a low temperature (4 ° C.), and 90 g of H. hinoki mochi produced in 2008 of company H, one week after milling, was immersed in 90 g of water and allowed to absorb water at room temperature overnight. Then, using the same apparatus and procedure as in Example 4, heating was performed at 75 w for 20 minutes or 75 w for 2 hours, and analysis was performed in the same manner as in Example 4. As a result, the glucose content did not reach the result of Example 5 under the heating condition of 75 w · 20 minutes, but increased to 0.39% under the heating condition of 75 w · 2 hours. On the other hand, the sucrose content was low as in Example 4 and Example 5 under any heating condition (see FIG. 4A).
From the above, the rice milling / storage method, water immersion conditions, and heating conditions all affected the free sugar content, but the amount of glucose produced differed greatly depending on the heating conditions.

The effects of heating conditions on melanoidin production and aroma and flavor were investigated.
Brown rice was stored at a low temperature (4 ° C.), and 90 g of 2008 H. nomenocchi from Company H, which had passed 4 months after milling, was soaked in 90 g of water and allowed to absorb water overnight at room temperature. Then, using the same apparatus and procedure as Example 4, after heating at 700w for 20 minutes, it heated at 260w to 3 hours. Alternatively, heating was performed according to the heating condition (5) described above, but the 260w heating time was extended to 3 hours. A portion of the cooked rice was stored frozen at −20 ° C. at the start of heating at 260 w (0 h) and 1 to 3 hours (1 to 3 h) after the start, and dried overnight in an 80 ° C. ventilator. After breaking up the rice grains, the browning degree was measured using Konica Minolta's spectrophotometer CM-5 (measuring conditions: D65 light source, 10 ° field of view, diameter 30 mm Petri dish, specular reflection removal) . Moreover, while cooking the cooked rice during or after heating, the scents produced were compared by a sensory test.

  The result is shown in FIG. In the case of heating at 700w for 20 minutes, the longer the 260w heating time, the chromaticity a * in the red direction increases slightly to 4.08 after 3 hours, while the lightness L * does not change and the chromaticity in the yellow direction b * tended to increase slightly. In the case of SRT heating (heating of (5)), the longer the 260w heating time, the faster the chromaticity a * in the red direction increases to 8.36 after 3 hours, while the lightness L * decreases and the color in the yellow direction Degree b * became higher. In this way, browning markedly progressed with SRT heating, and melanoidin production was promoted. On the other hand, in the case of heating at 700 w for 20 minutes, sweetness and a preferred aroma / flavor were not observed, whereas in SRT heating, an elegant sweetness and a favorable aroma / flavor were observed as the heating increased by 260 w.

Table 1 below compares the moisture content of the cooked rice obtained in the above example with the moisture content of the polished rice of Uruchi rice and cooked processed rice cake. As shown in this table, it can be seen that the mochi rice (SRT) obtained in the above examples has a lower water content than the others. Moreover, since water content rate rises by spraying water during a heating, it turns out that a water content rate can be adjusted with the amount of water spraying during heating.

The effect of storage conditions of polished rice on the pH of immersion water was investigated.
Brown rice was stored at a low temperature (4 ° C), and Shiga-Ha double cocoons produced by company P, less than a month after milling, were stored at 4 ° C, 25 ° C and 35 ° C for 1 year. On the way, some samples were collected at 1, 3, 5, and 7 months and stored at 4 ° C. Two volumes of a pH indicator (methyl red / bromothymol blue) were added and mixed. The color of the supernatant was observed, and the pH of the supernatant was measured with a pH meter (manufactured by HORIBA). As a result, as shown in Table 2 below, it was confirmed that the higher the storage temperature, the lower the pH with time, and the color tone of the supernatant changed from blue-green to red-yellow.

The effects of baking soda addition on the pH and Maillard reaction of rice grain immersion water were investigated.
18 g of water and 0.58 g of glucose were added to 45 g of Shiga feather double rice bran produced in 2009, which was stored at a low temperature (4 ° C.) for less than one year after milling, and allowed to absorb water overnight at room temperature. At that time, 0, 50, 150, 350 mg of sodium bicarbonate was added. The same equipment and procedure as in Example 4 were used, and heating was performed under the condition (5) shown in Example 3. FIG. 5A shows a photograph of rice grains before and after heating and a comparison of color tones. It was inferred that yellowing or browning progressed as the amount of sodium bicarbonate added increased, and the Maillard reaction was promoted.

  In addition, after the milling of rice, it was stored at a low temperature (4 ° C) for about a year and a half. As a result of being immersed in 18 g of water at room temperature overnight, the pH of the immersion water was 6.7, 7.1, 8.6, and 8.9, respectively, and the pH of the immersion water increased according to the amount of sodium bicarbonate added. Moreover, when the pH of the cooked rice was measured using the same equipment and procedure as in Example 4 under the conditions of (6) shown in Example 3, it was 8.3, 9.0, 9.4, and 10.0, respectively. It was confirmed that the pH increased further.

The effect of glucose addition on Maillard reaction under weak alkaline conditions was investigated.
18 g of water and 350 mg of baking soda were added to 45 g of Shiga-Ha double cocoon produced in 2009, which was stored at a low temperature (4 ° C.) for less than one year after milling, and allowed to absorb water overnight at room temperature. At that time, 0 g, 0.2 g, 0.58 g of glucose or 0.58 g of sucrose (sucrose) was added. The same apparatus and procedure as in Example 4 were used, and after heating for 700 w · 20 minutes, the mixture was further heated under conditions of 260 w · 60 minutes. FIG. 5 (b) shows a photograph of rice grains before and after heating and a comparison of color tones. Even though sucrose was added, the color tone was not changed, but it was inferred that yellowing or browning progressed and the Maillard reaction was promoted as the amount of reducing sugar added increased.

The effect of different amino acid types on the formation of aroma components in the Maillard reaction during cooked cooked rice was investigated.
Brown rice was stored at a low temperature (4 ° C.), and 18 g of water was added to 45 g of Shiga-Ha double cocoon produced in 2010 by R Company less than a month after milling and allowed to absorb water overnight at room temperature. At that time, additives were added under the conditions (2) to (5) shown below.
(1) No additives (2) Sodium bicarbonate 0.25g
(3) Sodium bicarbonate 0.25g and glucose 0.5g
(4) Sodium bicarbonate 0.25g and glycine 0.5g
(5) Sodium bicarbonate 0.25g, glucose 0.5g and glycine 0.5g
Using the same equipment and procedure as in Example 4, heating was performed under conditions of 700 w · 20 minutes / 260 w · 40 minutes. Immediately after heating, it is transferred to a cylindrical glass bottle with a diameter of 9 cm and a height of 9 cm, and the aroma components in the headspace are adsorbed to SPME fiber (75um Carboxen / PDMS) at 50 ° C for 1 hour, and GCMS-QP2010plus (column, manufactured by Shimadzu Corporation) (DB-WAX) and analyzed according to the usual method. The results are shown in (1) to (5) of FIG. When baking soda was added, a fragrant aroma like carbonated rice cracker was produced, but as a result of analysis, a lot of acetol was produced. When glycine was added, a sweet dairy-like aroma was produced, but as a result of analysis, a large amount of dimethylpyrazine was produced. According to the 4th Japanese Food Standard Composition Table (1982), 0.14g of glycine is contained per 45g of polished rice.

Brown rice was stored at a low temperature (4 ° C.), and 18 g of water was added to 45 g of Shiga-Ha double cocoon produced in 2010 by R Company less than a month after milling and allowed to absorb water overnight at room temperature. At that time, additives were added under the conditions (6) to (10) shown below. Thereafter, all were heated at 700 w · 20 minutes, and then some were heated at 260 w. The heating time at 260w is shown in parentheses below.
(6) Glucose 0.5g and Valine 0.5g (260w, 40 minutes)
(7) Sodium bicarbonate 0.25g, glucose 0.5g and valine 0.5g (260w · 0 min)
(8) Sodium bicarbonate 0.25g, glucose 0.5g and valine 0.5g (260w, 20 minutes)
(9) Sodium bicarbonate 0.25g, glucose 0.5g and valine 0.5g (260w · 40 minutes)
(10) Sodium bicarbonate 0.25g, glucose 0.5g and threonine 0.5g (260w, 40 minutes)
After heating, analysis was performed according to Example 11. The results are shown in (6) to (9) of FIG. When valine was added, a sweet fried egg-like fragrance was produced, but as a result of analysis, a large amount of isobutanal was produced, and it was found that the amount produced increased with heating time. On the other hand, when threonine was added, a preferable aroma like maple syrup was recognized. According to the 4th edition Japanese food standard ingredient table (1982), 0.19 g of valine and 0.11 g of threonine are contained per 45 g of polished rice.

Brown rice was stored at a low temperature (4 ° C) and less than a month after milling, it was absorbed overnight at room temperature by adding 18 g of water, 0.25 g of baking soda, and 0.5 g of glucose to 45 g of Shigaha double rice cake produced in 2010 by R Company. . At that time, 0.5 amino acid or tripeptide of any one of glutamine, glutamic acid, aspartic acid, phenylalanine, leucine, alanine, arginine, methionine, tryptophan, proline, histidine, tyrosine, lysine, cysteine, serine, isoleucine, glutathione. g was added. According to Example 11, it heated for 700w * 20min / 260w * 40min, and the fragrance produced was compared. As a result, although each produced a characteristic fragrance, no particularly favorable fragrance was observed, and it was considered that optimization of cooking conditions was necessary to produce an excellent fragrance.

Claims (1)

After immersing rice grains of glutinous rice in water, draining and heating to heat cooked rice of glutinous rice,
While adjusting the pH of the water in which the rice grains are immersed to 6.5 to 10.0,
The first heating process in which the time required for the rice grain temperature to reach from 55 ° C to 65 ° C is 20 minutes or longer by adjusting the heating state so that the moisture content of the cooked rice is 39% to 49 %. And steam heating the rice grains by a second heating step that raises the temperature so as to draw a convex curve from 60 ° C. to 90 ° C. in at least 40 minutes and a third heating step that heats at 100 ° C. for at least 60 minutes. A method of cooking rice cakes characterized by