JPH0746972B2 - Cooling method of rice immediately after rice polishing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cooling rice immediately after rice polishing, which is mainly used in a rice polishing factory.

[0002]

2. Description of the Related Art Generally, when a process of removing bran layer and germ from brown rice is carried out by a rice polishing machine (rice polishing or whitening), the temperature of rice immediately after rice polishing is 1 compared to that of brown rice (including rice) before rice polishing.
It is known to rise near 0 to 20 degrees.

However, when the rice whose temperature has risen is sent to the subsequent steps as it is for the selection, blending, color selection, packaging, etc., the following various problems occur. A relatively large amount of water evaporates from the rice whose temperature has risen due to rice polishing, but when this water contacts a series of equipment in the subsequent process and cools, dew condensation occurs, and the dew condensation part causes rice powder, rice grains, etc. Adheres to the surface and causes mold and lumps. In some cases, such dew condensation or the like may cause malfunction of the post-process devices and even stop the devices themselves.

It takes a relatively long time for the temperature of rice after milling to naturally drop to room temperature (for example, 3 days to 4 days when naturally cooled in a large tank).
(Day), during that time, the taste is greatly reduced. When the temperature of milled rice is high, the amount of water evaporated from the surface is inevitably large as described above, so the milled rice is dried more than necessary after milling, resulting in a so-called overdried state, which results in poor eating quality, etc. It is easy to cause deterioration of quality.

Various techniques have been proposed in the past to avoid such a loss of water in polished rice and a deterioration in taste due to overdrying. As one of them, there is a method of applying cold and humid air or air containing a large amount of water mist to milled rice (see, for example, Japanese Patent Publication No. 60-17499). Further, as another method, a method has been proposed in which the grain of rice is brought into contact with a cooled roller body having good thermal conductivity to remove heat from the polished rice to lower the temperature (for example, JP-A-61-2).
35662 publication).

[0006]

However, the above-mentioned conventional methods are not practical as means for solving the above-mentioned problems (1) to (4).

That is, in the above-mentioned method of exposing the polished rice to cold wet air, it is difficult to properly control the rice polishing temperature and the water content of the cold wet air. It is easy to have too much or too little. In that case,
If the water content is large, cracking of the body occurs, and if the water content is small, the polished rice is rapidly dried and the surface of the rice grain is covered with fine cracks, which deteriorates the taste.

Further, in the case of the method of bringing the rice grains into contact with the roller body, dew condensation or bran adheres to the roller body, so that the heat absorbing property is poor but maintenance is troublesome, and it is not practical.

In addition to these methods, white rice tempering machines and the like for the purpose of compensating for water loss and overdrying of polished rice have been provided so far, but they are to reduce the temperature of rice in a short time immediately after rice polishing. Since it was not intended, the above problems 1 to 3 could not be solved.

The present invention has been made in view of the above-mentioned conventional circumstances, and it is possible to reduce the temperature of rice immediately after rice polishing easily and in a short time without impairing the taste by utilizing the so-called sprinkling water principle. The purpose of the present invention is to provide a method capable of reducing the taste of white rice caused by an increase in grain temperature associated with rice polishing and the problem of dew condensation on various devices used in a series of steps after rice polishing. And

[0011]

To achieve the above object, the method for cooling rice immediately after rice polishing according to the present invention is characterized in that it is constructed as follows. First, 0.4% to 1.5% by weight of water is added to rice whose temperature is higher than that before rice polishing due to rice polishing while the grain temperature immediately after the rice polishing is high, and water is added to the surface of the rice grain. Form a film. In this case, if the amount of water added is less than 0.4% by weight, the amount of water that evaporates is insufficient, and as a result, the shortage is compensated by evaporation of the water originally present in the polished rice, If over-dried rice is produced, and if it is more than 1.5%, the water film formed on the surface of the rice grain becomes too thick than necessary and drips from the rice grain group.

Further, the water added at this time has a poor dew-like rate and has a poor adhesion rate to rice grains, so it is preferable to keep it in a state of dripping water as much as possible. In order to spread the water in the form of a film,
It is desirable to mix and stir only the required amount.

Next, immediately after the formation of such a water film, air is supplied to vaporize the water on the surface of the rice grain, so that the heat of vaporization is taken from the surface of the rice grain to lower the temperature of the rice to room temperature. In this case, the air supply method is not particularly limited, and may be, for example, a blowing method using a blower or a rotating fan or an air suction method. However, in order to efficiently bring the wind into contact with the entire surface of the rice grain, as described in claim 2, the rice immediately after milling, which has a water film formed on the surface of the rice grain and is still higher than room temperature, is placed on the suction net conveyor. Then, a method of sucking air from under the conveyor is preferable. In that case, it is necessary to lower the temperature of the rice on the conveyor to room temperature in a short time. Specifically, it should be within 1 minute. This is because the water in the surface layer of the rice grain penetrates deep inside the rice grain with the lapse of time after mixing water, and if strong wind drying is performed in that state, cracks will occur and the taste will be significantly reduced, such a situation. This is because it is necessary to cool the rice while the water remains on the surface layer of the rice grains in order to avoid this.

Further, the speed of the air supplied to the rice after water addition is
It is preferably 1 m / sec or more and 15 m / sec or less.
If it is 1 m / sec or less, the variation of the rice grains spread on the net conveyor is too subtle to cause a problem in operability, and the drying time becomes long, and if it exceeds 15 m / sec, energy efficiency and drying are increased. This is because problems such as overdrying tend to occur due to variations in time.

Here, the reason why the amount of water added to rice immediately after rice polishing is limited to the above value is as follows. now,
1 kg of rice whose initial temperature was, for example, 30 ° C (apparent specific heat is 0.45-0.55c depending on the moisture content of brown rice)
It fluctuates within the range of al / g · deg, but here 0.5
cal / g · deg) is 5 by rice milling treatment.
It is assumed that the temperature has risen to 0 ° C. At this time, the amount of increase in heat of rice is as follows.

1000 × [(50-30) × 0.5] = 10000 (cal) The amount of water required to deprive the increased heat amount as the heat of vaporization of water is 539 cal of the heat of vaporization of water under normal temperature and normal pressure. Since it is / g, it becomes 10000/539 = 18.4 (g). Therefore, in this case, theoretically, when 1.84% by weight of water is added to 1 kg of rice and all of it is vaporized, the temperature of the rice immediately after rice polishing (50 ° C) becomes the initial temperature ( 30 ° C).

However, if the amount of water added to the rice exceeds about 1% by weight, the added water tends to drop as drops from the rice grain group after mixing and stirring, which is not preferable. Further, even if an ideal thick water film is formed on the surface of the rice grain, most of it will not be vaporized efficiently because it will be scattered with the air flow rubbing the surface of the rice grain under ventilation. Therefore, when the amount of water added exceeds 1% by weight and 1.5% at the maximum, it is difficult to remove a necessary amount of heat from the rice grains as heat of vaporization, and moreover, it is difficult to remove the heat of the apparatus used in the examples described later. If an apparatus having an exhaust duct or an exhaust blower is to be used as described above, for example, a product such as mold or drainage which is difficult to process is formed in the exhaust duct or the exhaust blower, which is bad in terms of disposal.

From this point of view, the inventor of the present invention practically judged that the amount of water added was 1% or less, and from the results of the examples described later, specifically, the amount was 0.4% to 1.5%. It is limited. In a practical rice milling machine, it is rare that the grain temperature rise during rice polishing exceeds 20 ° C throughout the year except for the winter period. Therefore, the conclusion derived from the above assumption is practically applicable. It is reasonable.

[0019]

According to the above structure, the temperature of rice raised by rice polishing is lowered to room temperature by removing heat of vaporization from the surface of rice grains when water added immediately after rice polishing is vaporized by the supply of wind. It That is, the temperature of rice immediately after rice polishing is lowered for the same reason as that of sprinkling water.

Since the amount of water added in this case is set to 0.4% to 1.5% by weight and spreads like a film on the surface of the rice grain, it is forcibly forced by ventilation. It is efficiently vaporized and takes necessary and sufficient heat from rice grains in a short time. Therefore, since the water added immediately after rice polishing does not permeate into the inside of the rice grain from the surface layer, the deterioration due to the permeation of water into the inside of the grain can be avoided.

As a result, the temperature of the rice immediately after the rice polishing can be lowered easily and in a short time, and the taste of the white rice is deteriorated due to the temperature rise during the rice polishing.
Problems such as dew condensation in various devices used in a series of steps after rice polishing will be solved.

[0022]

EXAMPLES Examples of the present invention will be described below. [Embodiment 1] First, a cooling system used in this embodiment will be described. FIG. 1 shows the overall configuration of the system. As shown in FIG. 1, the system 1 includes a level hopper 10 into which rice immediately after rice polishing and a motor 21.
The particle feeding mixed water stirring chamber 20 provided with the screw conveyor 22 driven by rotation, the turntable hopper 30 provided with the net conveyor 32 rotated by the drive motor 31 in the upper part, and the central processing unit (CPU) It has a built-in controller 40.

Of these, the level hopper 10 is provided with a rice input port 11 at the upper part and a discharge port 12 at the lower part, and branch plates 13, 13 for adjusting the flow rate of rice are set up at the discharge port 12. Are arranged in the direction.

The level hopper 10 has an upper flow rate level detecting sensor 14 for detecting the rice flow rate when the rice flow rate exceeds a predetermined upper limit value, and also when the rice flow rate is below a predetermined lower limit value. The lower limit flow rate detection sensor 15 for detecting this, the upper limit level detection sensor 16 arranged at a predetermined upper position so that a warning can be issued when the amount of rice in the hopper exceeds an allowable value, and the inside of the hopper. A lower limit level detection sensor 17 that detects when the amount of rice falls below a predetermined value, and an optimum level detection sensor 18 that detects it when the flow rate of rice is at a preset optimum value. ing. Then, the signals from these sensors 14 to 18 are input to the controller 40, and based on these input signals, the controller 40 causes the amount of water added to the particle feeding mixed water stirring chamber 20 and the rotation speed of the net conveyor 32, which will be described later. The suction amount of the exhaust blower 35 and the like are controlled.

Further, a water pump 25 for supplying a predetermined amount of water from a separately provided tank 23 through a water supply passage 24 is connected to the particle feeding mixed water stirring chamber 20. And
In the stirring chamber 20, the predetermined amount of water and rice grains are sent to the turntable hopper 30 while being stirred by the screw conveyor 22.

On the other hand, the turntable hopper 30 has a developing screw brush 33 on its upper part, which receives the rice after hydration sent from the grain-mixing and mixing water stirring chamber 20 and spreads it on the net conveyor 32, and its spreading. A pick-up screw 34 is provided to take out the removed rice from the discharge port 30a to the outside of the hopper 30 after the rice is rotated by a predetermined amount together with the net conveyor 32, and at the lower downstream opening end, the hopper side is provided. An exhaust blower 35 that sucks out the gas is connected to the outside. And the net conveyor 32
While the upper rice is rotated by a predetermined amount, the suction action of the exhaust blower 35 evaporates excess water from the surface of the rice grain,
It is configured to be discharged to the outside through the exhaust duct 35a on the downstream side.

The method of the present invention using such a system 1 is carried out as follows. First, milled rice whose temperature has risen from the initial temperature due to the milling process is fed into the hopper 10 through the feeding port 11 of the level hopper 10.

The rice introduced into the level hopper 10 is detected by a temperature sensor (not shown) additionally provided with the amount of temperature rise accompanying the rice polishing, and its flow rate is detected by each of the level sensors 14-18. Then, the water is supplied from the lower discharge port 12 to the particle-mixed water mixing chamber 20.

The detection results of the temperature sensor and the like are input to the controller 40, respectively, and the temperature of rice in the level hopper 10 and the flow rate of rice discharged from the lower discharge port 12 ( Based on the amount of polished rice, etc., the controller 40 weights a predetermined amount (1 in this embodiment:
%) Of water is determined so that water can be added, and the pump 25 is controlled based on this to supply the determined predetermined amount of water from the tank 23 into the particle feeding mixed water stirring chamber 20.

On the other hand, in the particle feeding and mixing water stirring chamber 20, by mixing and stirring a predetermined amount of rice and water supplied as described above, a water film is formed on the surface of these rice. , Turntable hopper 30 after the film formation
On the net conveyor 32.

The rice supplied onto the net conveyor 32 is expanded by the expansion screw 33, and then rotated by a predetermined amount (180 degrees in the illustrated example) together with the conveyor by the motor 31, and thereafter, by the take-out screw 34. It is taken out of the turntable hopper 30 through the discharge port 30. And in this way, the net conveyor 3
While rotating the rice with 2, the air in the turntable hopper 30 is exhausted by the exhaust blower 35 to the exhaust duct 3
By continuing to discharge to the 5a side for a predetermined time and with a predetermined air volume, the above water present in the form of a film on the surface of the rice grain is vaporized and evaporated on the air flow accompanying the suction of the exhaust blower 35 until the temperature of the rice drops to room temperature. .

According to such a structure, the rice whose temperature has been raised by the rice polishing process is sent to the grain-mixing and mixing water stirring chamber 20 through the level hopper 10, and in this stirring chamber 20, 1% by weight of water is added. A water film is formed on the surface of the rice grains by mixing and stirring with, and in that state, the water film is sent to the turntable hopper 30 and spread on the net conveyor 32. Then, the discharge port 30a of the turntable hopper 30
During a predetermined time from when the rice grain is discharged, the air flow (wind) generated by the suction action of the exhaust blower 35 scrapes the surface of the rice grain, so that the water present in a film form on the surface of the rice grain is rapidly vaporized.

In that case, as described above, the particle feeding mixed water stirring chamber 2
Since the amount of water added at 0 is set to 1% by weight with respect to rice, the water is efficiently evaporated from the surface of the rice grain by the wind sucked by the exhaust blower 35. At that time, necessary and sufficient heat is removed from the rice grains as evaporation heat in a short time, so that the rice on the net conveyor 32 is quickly cooled to room temperature. By rapidly lowering the temperature of rice in this way, it is possible to prevent water added immediately after rice polishing from penetrating from the surface layer of the rice grain into the inside of the rice grain. Deterioration due to will be avoided.

As a result, the temperature of rice immediately after rice polishing can be lowered easily and in a short period of time, which in turn causes the problem of deterioration in the taste of white rice caused by the temperature rise during rice polishing.
Problems such as dew condensation in various devices used in a series of steps after rice polishing will be solved.

Since the flow rate of rice discharged from the rice mill and the grain temperature after discharge change with time, it is necessary to automatically control the amount of water added and the ventilation time according to the change in the flow rate and the grain temperature. There is. Although such control is generally difficult, in the case of the present embodiment, the temperature of the rice after the change can be easily detected by a separately provided temperature sensor. Regarding the change in the flow rate, three sensors of an upper limit flow rate level detection sensor 14, a lower limit flow rate level detection sensor 15 and an optimum level detection sensor 18 are provided, and moreover, the discharge port of the level hopper 10 leading to the particle feeding mixed water stirring chamber 20. 1
Since 2 is divided into three by the branch plates 13 in the vertical direction, it is possible to easily detect a change in rice flow rate by, for example, appropriately adjusting the opening degree on the outlet 12 side. is there.

[Embodiment 2] Instead of the level hopper 10 in the above-mentioned Embodiment 1, an ordinary hopper was used, and in the same manner as in Embodiment 1, the high temperature rice immediately after rice polishing had a weight ratio of about 1%. After adding water, the rice was cooled. After cooling, the water content of the rice grains had decreased by 0.3%, but cracks could not be found with a magnifying glass. The grain temperature was 28 ° C.

[Examples 3 to 7] A large number of experiments of the same type were carried out by changing the numerical values in Example 2 by a predetermined amount, and the results shown in Table 1 were obtained.

[0038]

[Table 1]

[Examples 8 to 12] From Table 1, the cooling time is 1
It was determined that about 1 minute and about 1% of the amount of water were appropriate, and in order to investigate the vicinity thereof in more detail, an experiment similar to the comparative example was conducted by changing only the numerical values. The results are shown in Table 2.

[0040]

[Table 2] As shown in Table 2, 1% by weight of water was added to the rice immediately after milled and mixed, and the air was blown at a wind speed of 4 m / sec for 1 minute to cool the rice. It was confirmed that good results were obtained in all respects such as grain temperature drop.

[Comparative Example 1] Relative to rice that was milled in a state of over-whitening (whiteness 41.5 °) with an ordinary rice milling machine (grain temperature immediately after milling was 50 ° C) at room temperature of 30 ° C In a laboratory with a humidity of 60%, spread it in layers on a plastic tray,
In that state, it was left to cool for 1 hour. After that, when the state of rice was observed, it was recognized that thin lines ran in a mesh-like fashion for each starch compound constituting the rice grain. Also, the water content was 0.9% less than that immediately after whitening.

[Comparative Example 2] The same rice as the polished rice used in Comparative Example 1 was placed on a net, and the net was adjusted in the same laboratory as Comparative Example 1 so that the wind speed on the rice grain was 0.9 m / sec. The blower was operated from below to perform forced cooling for 5 minutes. As a result, cracks were formed on the surface of the so-called multi-grain body on the surface of the rice grain, to the extent that it was clearly visible to the naked eye. Moreover, the water content was 1.1% less than that immediately after rice polishing, and the grain temperature was slightly lower than room temperature of 30 ° C.

Comparative Example 3 In the state of Comparative Example 2, a high-concentration water mist was added into the blower using a humidifier. Then, when the relative humidity was set to 150% (converted value) and a sample similar to that of Comparative Example 2 was taken and examined, except that the water content of the rice grains was 1.0% less than that immediately after rice polishing, There was not much difference from the case of Comparative Example 2.

[0044]

As described above, according to the cooling method of the present invention, the temperature of rice immediately after rice polishing can be quickly lowered without causing a problem such as cracking on the surface of rice grain. As a result, it is possible to solve the problem of deterioration in the taste of white rice caused by the temperature rise during rice polishing and the problem of dew condensation in various devices used in a series of steps after rice polishing. In addition, it can be packaged as it is without any treatment after cooling.

In particular, according to the present invention, since the temperature of rice can be lowered to room temperature in a short time, it can be applied regardless of the amount of rice polished. Therefore, it can be used as a cooling means for rice immediately after rice polishing in a large-scale rice polishing machine, or as a cooling means for rice immediately after rice polishing in a small-sized and small-volume rice polishing machine.

[0046]

[Brief description of drawings]

FIG. 1 is a system diagram showing an overall configuration of a system used in a first embodiment of the present invention.

[Explanation of symbols]

 32 ... Suction net conveyor.

Claims (3)

[Claims] 1. For rice whose grain temperature has risen due to rice polishing,
While the grain temperature immediately after the rice polishing is high, 0.4% to 1.
Add 5% water to form a water film on the rice grain surface,
A method for cooling rice immediately after rice polishing, which comprises immediately supplying air to vaporize water on the surface of the rice grain to remove heat of vaporization from the surface of the rice grain to lower the temperature of the rice to room temperature. 2. The rice immediately after milling, which has a water film formed on the surface of the rice grain and is still higher than room temperature, is placed on a suction type net conveyor, and air is sucked from under the conveyor to the rice on the conveyor. The method for cooling rice immediately after rice polishing according to claim 1, wherein the time for cooling the temperature of the rice to room temperature by supplying air to cool the rice is within 1 minute. 3. The method for cooling rice immediately after rice polishing according to claim 1 or 2, wherein the velocity of the air supplied to the rice is 1 m / sec or more and 15 m / sec or less.