JP2005287394A - Method for producing unpolished rice and germinated unpolished rice by microwave aeration and drying - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing unpolished rice, capable of enhancing retentivity of components (a nutrient component, a fragrance component, and a deliciousness component) inherent in the unpolished rice, especially, retentivity of proteins, by preserving characteristics of the unpolished rice so as not to be lost, while the characteristics are lost during a period in which unhulled rice is dried or stored in conventional means of drying the rice, capable of preventing a surface of the rice from becoming rigid due to migration of the components to a surface layer area, and capable of giving soft and delicious rice (boiled rice), even when the rice is boiled at normal pressure. <P>SOLUTION: This method for producing the unpolished rice which has a high retentive ratio of the proteins, is rich in amino acids, and is soft comprises keeping an inside temperature of the unhulled rice high within such a temperature range as not to damage characteristics of the unhulled rice, by microwave heating, and keeping, on the other hand, a surface temperature of the unhulled rice lower, by aerating the unhulled rice, so as to dry the unhulled rice, wherein water is transferred from the inside of the rice to the surface in a vapor state due to a partial water vapor pressure difference which is brought about by a difference of temperatures between the inside and the surface of the unhulled rice, and the components other than the water are left in the inside of the unhulled rice, by transferring only the water, and further formation of a rigid membrane is prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing brown rice having good component retention by adjusting the movement of moisture in dried rice, especially rice that has been cooked at normal pressure with good component retention by microwave drying of rice. (Cooked rice) relates to a method for producing soft brown rice and germinated brown rice.

  In recent years, the Japanese diet has changed greatly, but the staple food is still rice. Brown rice is understood to be a healthy food because it is rich in starch, protein, especially phosphorus, iron, potassium, vitamin B1 · E, γ-aminobutyric acid (GABA) and the like, and has a high nutritional value. However, compared to polished rice, brown rice is difficult to cook, and because the epidermis is very hard and not delicious in terms of palatability, such as texture, it is rare to eat. However, as the functionality hidden in brown rice becomes clear, efforts have been made to research and develop it so that it can be eaten deliciously with improved longevity and health orientation.

It is considered that the rice (cooked rice) cooked with brown rice is hard because the outer skin is hard and the water absorption is poor, so it cannot cook well.
Except for some sun-dried rice, most are now dried with hot or cold air. In these drying methods, the heat transfer is directed from the surface of the glutinous rice to the inside, and the drying proceeds from the surface of the glutinous rice while leaving moisture inside. In the liquid state, the drying proceeds while the capillary moves to the surface of the rice. As the moisture moves, the solute component also moves from the inside toward the surface of the rice.
Since only the moisture vaporizes and evaporates on the surface of the glutinous rice, the various solute components that have migrated are left behind and deposited on the surface, and the components come into contact with the air and oxidize to form a hard film. Furthermore, with this drying, the lipid component also accumulates on the outermost skin, is oxidized by contact with air, changes to glue or rubber, and hardens the hard film. As the oxidation progresses, the hard film of brown rice is strengthened, and even after cooking, it is difficult to cut with teeth, it remains in the mouth forever, and the mouth feels uncomfortable.

This is the cause of the poor texture of brown rice, worsening the reconstitution and delaying the pre-gelatinization of starch, and also leaving no stickiness or plumpness. Therefore, even if it is immersed in water for a long time to absorb water sufficiently before cooking rice, and using a pressure kettle, the texture and flavor will be lost by soaking for a long time, and it will not be like rice from polished rice.
In addition, the oxidative odor produced by the oxidation of lipids causes an unpleasant odor, which is one of the causes of appetite loss, sacrificing the original taste, and being avoided by consumers. Therefore, in order to prevent oxidation and maintain quality, a vacuum pack or an oxygen scavenger is used.

Germinated brown rice is one way to eat brown rice. The germinated brown rice obtained by shaving the hard and indigestible peel and seed coat on the top surface of brown rice and immersing it in warm water for a specified time can be cooked soft enough with normal pressure rice, and it can be a rich nutritional food A number of manufacturing techniques have been proposed. Among them, after bringing the glutinous rice into contact with water and absorbing water to the saturated moisture content, germinating the glutinous rice until just before the glutinous rice opens while circulating the glutinous rice, taking out the germinated glutinous rice, drying and storing, There is a method for obtaining brown rice by performing rice hulling as necessary (see, for example, Patent Document 1).
In addition, the applicant has proposed the production of an antioxidant dry food that can withstand long-term storage by employing microwave heating to dry the food (see, for example, Patent Document 2).

JP 2002-253148 A Japanese Patent Laid-Open No. 2002-262841

  In the present invention, the retention of the components (nutrients, aroma components, umami components) of brown rice, in particular protein, so as not to lose the characteristics of brown rice that are lost during drying or storage by conventional rice drying means A method for producing brown rice or germinated brown rice that enhances the retention of (amino acids), prevents the hardening of the surface due to the movement of ingredients to the surface layer, and provides a soft and delicious rice (cooked rice) even by cooking at normal pressure The purpose is to provide.

As a result of diligent research, the inventor found that the moisture in the glutinous rice was moved to the surface by performing microwave heating and ventilation to dry the glutinous rice, and the components of the rice could remain inside, and based on this, the present invention It came to make.
That is, the present invention
(1) Moisture generated by the temperature difference between the inside and the surface of the polished rice while keeping the internal temperature high by microwave heating in a temperature range that does not impair the characteristics of the dried rice, while the surface is dried while ventilating at a lower temperature. Due to the difference in vapor partial pressure, the internal moisture is moved to the surface in the state of vapor, and other components remain inside by only the movement of moisture, preventing the formation of a hard film. Rich and soft brown rice production method,
(2) The method for producing soft brown rice having a high protein retention rate as described in the item (1), wherein the temperature of ventilation on the surface is 10 to 25 ° C., and (3) (1) or (2) Provided is a method for producing germinated brown rice, characterized in that brown rice produced by the method described in the paragraph is immersed in water or humidity-treated to germinate 0.5 to 1 mm, washed and then dried by microwave ventilation again To do.
Soft brown rice means brown rice from which rice is cooked at normal pressure and soft and soft rice is obtained (similar to and similar to polished rice).

According to the present invention, the obtained brown rice has a protein retention rate that is extremely high compared to the method for producing brown rice by other drying means, not only immediately after drying, but also after 30 days of storage, Many. And microwave ventilation dry brown rice is closer to polished rice in appearance than hot air dry brown rice, and the polishing powder of each layer is high in brightness, so the cooked rice is whiter.
And the brown rice according to the present invention can be obtained even if it is cooked at normal pressure (cooked rice), the rice cooked is less puffy, the skin of the brown rice is not hard and plump, and it is more refined rice It is close to rice. Of course, the nutritional value is superior to polished rice. Therefore, when brown rice according to the present invention is germinated and cooked in a home germination brown rice maker, it becomes softer and richer in functional components (GABA and the like).

A preferred embodiment of the method for producing soft brown rice or germinated rice of the present invention will be described in detail.
The following drying apparatus is suitable for the microwave heating used in the present invention. The belt conveyor type microwave ventilation drying device is equipped with a radio wave leakage prevention device at the belt entrance / exit in the cavity. The microwave power supply device divides into two in the middle through the waveguide and supplies the microwave from two places on the cavity ceiling. To do. A glass fiber belt conveyor with a mesh-like Teflon finish is mounted on the frame on which the glutinous rice with an insect net on the frame is mounted, and this is circulated inside and outside the cavity. In addition, a ventilating device that blows air with adjusted temperature and humidity along the ventilation guide, ventilates the frame, dehumidifies outside the system, adjusts the temperature, and recirculates is provided. The effective microwave output is 0, 0.125, 0.178, 0.25, 0.5 kW. In order to obtain a high quality product, it is preferable that the drying time is long but the microwave execution output is low.

When microwaves are irradiated, the inside of the rice can be directly heated, and heat transfer and component transfer are reversed from conventional drying means.
When irradiating microwaves on the glutinous rice spread on the gantry, the inside of the glutinous rice is heated, and when the surface of the culm is exposed to a low temperature wind, the moisture inside moves to the surface in the form of steam. The microwave used is an electromagnetic wave of 2400 MHz to 2500 MHz and has a wavelength of about 12 cm. This microwave energy rotates and vibrates the dipole molecules in the rice and is converted into kinetic energy of the molecules. This intense rotation / vibration state of the molecule is equivalent to the thermal motion of the heated molecule.
As a result, the internal temperature rises, and only moisture moves to the low temperature side of the glutinous rice in the vapor state, and the internal protein and solute components remain in place.

The temperature of the air in contact with the surface of the glutinous rice is preferably 10 to 25 ° C., more preferably 18 to 23 ° C., and the air is passed at a wind speed of 0.5 to 2.0 m / sec. The temperature of the surface of rice is measured with an infrared thermometer from the hole in the center of the cavity ceiling.
A portion of the moisture that has moved to the surface does not evaporate, but is eroded by the cold air and condensed and liquefied, so that the moisture concentration on the surface becomes higher than the inside. That is, moisture reduction (drying) proceeds from the inside. A part of the water liquefied on the surface due to the generated water concentration difference moves into the capillary again, and at this time, solute components existing in the surface layer are drawn into the inside, and the water moved inside is heated, and again Vaporizes and re-transfers to a cold surface. While this phenomenon is repeated and drying progresses, surface layer components are taken into the interior over time, and lipid components also move from the pericarp along with moisture and solute components. A surface layer of several microns from which various components and the like have been removed wraps rice in a capsule shape that protects against oxidation by air, so that lipids are difficult to oxidize and impart antioxidant properties.
Conventionally, when lipids are oxidized, the resulting peroxide reacts with the protein in which the peroxide coexists, destroying amino acids and lowering nutrients. As the oxidation of the lipid further proceeds, a carbonyl compound is generated, and an amino-carbonyl reaction occurs with the amino compound, generating an odorous substance and denaturing the amino acid. On the other hand, the method of the present invention imparts antioxidant properties to brown rice as described above, and lipids are difficult to oxidize, so it is possible to produce brown rice containing a large amount of amino acids while suppressing alteration of amino acids. The storage property of brown rice can be improved.

Furthermore, since there is no component transfer / deposition to the surface layer or lipid oxidation, there is no formation of a hard film, which is seen in hot air drying, etc., excellent water absorption, and a brown rice rice with a soft texture when cooked.
The fruit skin acts as a capsule that protects the rice from oxidation until just before cooking rice, and when washed with water before cooking, it can be immersed in water after sharpening the rice to destroy the fruit skin and further improving the water absorption. In this way, there is no hard film, the skin and seed coat can be easily broken, the water absorption can be further improved, and even a regular rice cooker can obtain a brown rice rice with a feeling of being more plump and sticky Can do.

Brown rice obtained by microwave ventilation drying may be germinated with a domestic germinator, cooked and eaten, germinated by humidification or immersion in water, washed and dried by microwave ventilation again to produce dry type germinated brown rice It is possible to produce softer brown rice with higher functionality. In particular, it is preferable to perform humidity conditioning treatment under conditions of a temperature of 17 ° C., a humidity of 70 to 90%, and 6 to 24 hours.
Although the sticky rice used by this invention is not specifically limited, What was made without an agrochemical is preferable.

  Next, the method for producing soft brown rice having a high protein preservation ratio according to the present invention will be described in more detail based on Examples together with Comparative Examples, but the present invention is not limited thereto.

Example 1
As a sample, glutinous rice (Koshihikari, new rice produced in 2003) provided by Agricultural Experiment Station in Kumagaya City, Saitama Prefecture was used. 100 g of the above-described rice was spread on a gantry (200 mm × 300 mm), and 10 sets of 2 stacked layers (total 2.0 kg) were fed into a belt conveyor type microwave ventilation dryer (3000 mm × 1200 mm × H1300 mm). The sample was dried by setting the ventilation temperature to 20 ° C., the wind speed to 1.3 m / second, the belt conveyor speed to 0.2 m / minute, and the microwave effective output to 250 W. Each time it passes through the device, the sample mass is measured, put in the device again, and the moisture content is measured with a heat drying moisture meter (trade name: A & D MX-50, manufactured by A & D Co., Ltd.). Drying was repeated to 14% (corresponding to the moisture content of commercially available rice bran). The drying time was 460 minutes and the average product temperature was 29 ° C. After drying, the rice was packed as it was, and the air was removed and stored at room temperature (20 to 25 ° C.). Brown rice was obtained by mashing the stored rice.

Comparative Example 1
The sample used in Example 1 was placed in the apparatus used in Example 1, and the blast temperature was set to 40 ° C. without drying with microwaves, and the sample was dried. The mass of the sample was measured every 30 minutes, put into the apparatus again, and drying was repeated until the water content was 14%. The drying time was 150 minutes and the average product temperature was 39 ° C. After drying, the rice was packed as it was, and the air was removed and stored at room temperature (20 to 25 ° C.). Brown rice was obtained by mashing the stored rice.

Comparative Example 2
The sample used in Example 1 was dried to a water content of about 14% in the sun (average temperature 23 ° C.) for 4 days. The drying time was 5940 minutes and the average product temperature was 19 ° C. After drying, the rice was packed as it was, and the air was removed and stored at room temperature (20 to 25 ° C.). Brown rice was obtained by mashing the stored rice.

(Evaluation)
The brown rice obtained in Example 1 and Comparative Examples 1 and 2 was pulverized, 1 g of each was weighed, and the protein amount was determined by the Kjeldahl method.

(1) Measurement of component distribution The brown rice obtained in Example 1 and Comparative Example 1 was polished with a rice mill for a sake rice test. The polishing rate was calculated from the amount collected, and the amount of crude protein in each polishing powder was measured. The obtained results are shown in FIG. FIG. 1 is a graph showing the distribution of the amount of crude protein with respect to the polishing rate. In FIG. 1, the vertical axis represents the amount of crude protein (%), and the horizontal axis represents the polishing rate (%).
As is clear from the results in FIG. 1, it was found that the brown rice dried in hot air of Comparative Example 1 had less crude protein in the brown rice compared to the brown rice dried in microwave ventilation of Example 1. From this, it was found that the brown rice of Example 1 had better protein retention than the brown rice of Comparative Example 1.

(2) Measurement of lightness and chromaticity When brown rice after storage was observed with the naked eye, the brown-air dried brown rice of Example 1 was whiter and closer to the polished rice than the hot-air dried brown rice of Comparative Example 1 . Further, the brightness and chromaticity of each polishing powder of (1) above were measured using a colorimetric color difference meter (trade name: Color Meter NE2000, manufactured by Nippon Denshoku Industries Co., Ltd.). As a result, it was found that the brown rice of Example 1 had higher brightness in all layers than the brown rice of Comparative Example 1, and was bright overall.

(3) Change in amount of crude protein by storage The brown rice obtained in Example 1 and Comparative Examples 1 and 2 was stored at 5 ° C. and relative humidity 59% for 5 weeks and 9 weeks, respectively. The amount of crude protein in each sample after storage was measured. The obtained results are shown in FIG. FIG. 2 is a graph showing the relationship between the storage days and the amount of crude protein. In FIG. 2, the vertical axis represents the amount of crude protein (%), and the horizontal axis represents the number of storage days (days).

As is clear from the results in FIG. 2, the amount of crude protein immediately after drying (day 0) was 10% for the hot air dried brown rice of Comparative Example 1 and 12% for the sun dried brown rice of Comparative Example 2. On the other hand, the crude protein content of the brown rice dried by microwave ventilation in Example 1 was as high as 15%. From this result, it was found that the quality (crude protein amount) is affected when the average product temperature is too high or the drying takes too much time.
Next, as to storage stability, as is clear from FIG. 2, brown rice obtained by any drying method showed a high amount of crude protein immediately after drying, but a rapid decrease was observed at the initial stage of storage. After the day, it remained almost constant. Each brown rice had a crude protein amount greater than the crude protein mass of 7.4% of normal brown rice according to the standard table of Japanese food ingredients, but the crude protein amount of the brown rice of Comparative Example 1 was 8. Whereas it was 5%, the crude protein content of the brown rice of Example 1 was as high as 11.4% even after the 30th day. From this, it was found that the brown rice of Example 1 was excellent in storability and the quality (crude protein amount) did not decrease even after long-term storage.
In addition, when it stored on 30 degreeC and the conditions of relative humidity 56%, when the 30th day passed, although the crude protein amount of the brown rice dried by the hot air of the comparative example 1 fell to 7.4%, an Example The crude protein content of 1 brown rice was as high as 10.4%. From this, it was found that even when stored at a high temperature of 30 ° C., the brown rice of Example 1 had a crude protein amount higher than the crude protein mass of normal brown rice according to the Japanese food standard ingredient table.

Example 2
The sticky rice was dried in the same manner as in Example 1. The dried glutinous rice was crushed to obtain brown rice.

Comparative Example 3
The rice was dried in the same manner as in Comparative Example 1 except that the drying time was 160 minutes. The dried glutinous rice was crushed to obtain brown rice.

(Evaluation)
The softness (rheology) of the brown rice obtained in Example 2 and Comparative Example 3 was measured.
First, the brown rice obtained in Example 2 and Comparative Example 3 was placed in a sealed container adjusted to a relative humidity of 75% using a saturated aqueous solution of sodium chloride and stored at 40 ° C. for 6 weeks. 70 g of each stored brown rice was absorbed with water using a constant temperature water bath at 30 ° C. in order to gelatinize the starch uniformly and sufficiently. Then, each brown rice was put into a normal household rice cooker, and a predetermined amount of water was added to cook rice at normal pressure.

  Rheology was measured using 25 grains of cooked brown rice each as a sample, and each was used as a judgment index for the cooking of rice. In order to set the contact area to be cut, the width of each grain is measured and input to the analyzer, and then the sample is placed on the pedestal of the creep meter, and the breaking strength analyzer (high resolution creep meter) using a wedge plunger , Trade name: RE2-30005, manufactured by Yamaden Co., Ltd.).

The breaking strength curve will be described. A model of the breaking strength curve is shown in FIG. In FIG. 3, the vertical axis represents the load (gf) and represents the force pushed back by the sample. The horizontal axis represents the strain rate (%) and represents a value calculated by (deformation distance / original thickness of sample) × 100. Specifically, when the strain rate is 0%, it corresponds to a state where the sample starts to bite with teeth, and when the strain rate is 100%, it corresponds to the state where the upper and lower teeth collide and bite the sample.
When a load is applied by applying a plunger to the sample placed on the pedestal, the sample is distorted, and at some point the sample breaks. This load is called the breaking load. A large breaking load indicates that the sample is hard, and a small breaking load indicates that the sample is soft. As the load is further applied, the fracture of the sample increases and the apparent load temporarily decreases. The difference between the minimum value and the breaking load at this time is called brittle load. A large brittleness load indicates that the sample is brittle, and a small brittleness load indicates that the sample is sticky. As the load is further applied, the sample is finally completely broken. The load at this time is called the maximum final load.

From the breaking strength curve obtained from each sample, the breaking load, brittleness load, and maximum final load were read as described above, and the distribution diagram was prepared and shown in FIG. In FIG. 4, the X axis (left direction in the figure) indicates brittle load (gf), the Y axis (right direction in the figure) indicates fracture load (gf), and the Z axis (height direction in the figure). Indicates the maximum final load (gf).
As is clear from FIG. 4, the hot air dried brown rice of Comparative Example 3 was widely distributed centering around a breaking load of 332 gf (3.26 N) and a brittleness load of 38 gf (0.37 N), whereas Example 2 The brown rice dried by microwave ventilation was almost concentrated around a breaking load of 197 gf (1.93 N) and a brittleness load of 27 gf (0.265 N). As a result, it can be seen that the brown rice of Comparative Example 3 has a large breaking load, so its outer skin is hard, and its brittle load is large, so its inside is brittle. That is, since the outer skin is hard, the water absorption is poor, the gelatinization of starch is delayed, there is no sticky feeling or plump feeling, and the texture is bad. In contrast, the brown rice of Example 2 was found to be softer and more sticky than the brown rice of Comparative Example 3. That is, it was found that the brown rice of Example 2 was cooked softer than the brown rice of Comparative Example 3.

It is a graph which shows distribution of the amount of crude protein with respect to a polishing rate. It is a graph which shows the relationship between storage days and a crude protein amount. It is a graph which shows the breaking strength curve of a model. It is a distribution map of the breaking load, brittleness load, and maximum final load obtained from the breaking strength curve of each sample.

Claims (3)

  Moisture vapor content generated by the temperature difference between the inside and the surface of the dried rice while keeping the inside temperature high by microwave heating in a temperature range that does not impair its characteristics Due to the pressure difference, the moisture inside moves to the surface in the state of vapor, and other components remain inside only by the movement of moisture, preventing the formation of a hard film, high in protein retention, rich in amino acids, A method for producing soft brown rice.   The method for producing soft brown rice having a high protein retention and soft protein according to claim 1, wherein the temperature at which air is passed through the surface is 10 to 25 ° C.   A brown rice produced by the method according to claim 1 or 2 is dipped or conditioned in water to germinate 0.5 to 1 mm, washed and then dried by microwave ventilation again. Production method.

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