JPH03240452A - Processing of polished rice - Google Patents

Abstract

PURPOSE:To obtain polished rice having high preservability and cookable without washing by contacting polished rice with water or an aqueous solution for a short time and separating excess water or aqueous solution by centrifugal separation to increase the water-content of the rice by a specific ratio. CONSTITUTION:Polished rice is made to contact with water or an aqueous solution (e.g. solution of salt or sugar) for <=1min in an immersion tank 8 and attached excess water or solution is removed by centrifugal separator 16 to increase the watercontent of the rice by 1-5%.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for treating polished rice, and more specifically, the present invention relates to a method for treating polished rice, and more specifically, to remove excess moisture adhering to the surface of the polished rice grains by bringing water or an aqueous solution into contact with the surface of the polished rice grains. The present invention relates to a method for processing polished rice, which involves centrifuging to increase the moisture content of polished rice and removing the bran adhering to the polished rice and the remaining bran layer.

[Conventional technology]

The higher the moisture content of white rice, the better the taste of the rice after cooking.

The reason for this is as follows. When white rice is soaked in water, the water absorption rate is fast and the volumetric distortion is large, which causes cracks in the white rice grains.Excess water is absorbed into the cracks, and when cooked, the rice becomes sticky and sticky due to the excess water content. Become. On the other hand, Norano has a moisture content of 1526 or higher, and even when soaked, the water absorption rate is slow and the volume strain is small, so it absorbs a moderate amount of water without cracking, resulting in soft and sticky rice. It is.

In order to solve this problem, a method and apparatus for moisturizing polished rice have been invented in which water is added to polished rice with a low moisture content (over-dried) to bring it to a standard moisture content (15%).

These methods are disclosed, for example, in Japanese Unexamined Patent Publication No. 165146/1982, and the gist of the method is that since a small amount of humidification is continuously applied without leaving any water on the surface of polished rice,
This has the effect of preventing excessive water from rapidly absorbing moisture on the grain surface of polished rice and causing cracking and damage due to deterioration of quality.

However, this method takes a long time to humidify, making the device larger and requiring a fine mist generator, a steam generator, and the like.

In addition, since white rice is usually milled in a dry state, there is bran adhering to the surface of the white rice grains, and some rice grains have a layer of bran remaining due to uneven polishing. For this reason, rice is washed to remove these substances when cooking rice. In order to solve this problem, techniques for washing rice mechanically and drying the excess water absorbed, and techniques for increasing the shelf life of high-moisture white rice through various packaging and treatments were developed, for example, in JP-A-59-10.
It is disclosed in Japanese Patent No. 6260.

However, the former method requires a large amount of energy to re-dry the moisture-absorbed food, the latter method has poor storage stability, and both methods have the drawback that the rice tastes poor after cooking.

[Problem that the invention seeks to solve]

The object of the present invention is to solve the various problems of the above-mentioned conventional techniques, and it is possible to condition the humidity of polished rice to a standard moisture content in a short time and safely, and also to make the equipment compact and simple. To provide a processing method for obtaining polished rice with high commercial value by peeling off and removing the bran attached to polished rice and the bran layer remaining on the polished rice in a short time.

[Means to solve the problem]

In the present invention, after contacting polished rice with water or an aqueous solution for less than 1 minute, excess water or aqueous solution adhering to the polished rice is centrifuged through the porous wall of a rotary cylinder, so that the moisture content of the polished rice after treatment can be determined by After contacting water or an aqueous solution for less than 1 minute with white rice with a milling yield of 94% or less, the moisture content of white rice should increase by 1 to 5% from the moisture content of white rice. This problem was solved by centrifuging the free sugar and the remaining bran layer together with water or an aqueous solution to make the milling yield of polished rice after treatment lower than the milling yield before treatment.

[For production]

Water or an aqueous solution is applied in a very short time to the entire grain surface of white rice whose weight ratio (milling yield) to brown rice is 94 to 90%. An aqueous solution is one in which salt, sugar, and signal-soluble nutrients such as vitamins or enzymes are dissolved depending on the purpose. In addition, methods for adhesion include immersing rice grains in water or an aqueous solution in the process before feeding them to a centrifuge, or spouting water or an aqueous solution onto flowing rice grains, or spraying a mist of water or an aqueous solution with a nozzle, etc. , feeding rice and water or an aqueous solution into the centrifuge, etc. can be selected as appropriate. Polished rice whose entire grain surface is wetted with water or an aqueous solution has excess water attached to it, and this excess water is unevenly distributed even in each grain, and even more excess water is unevenly distributed in the contact area of the rice grains. If left in this state, the rate and amount of water absorbed into the rice grain will vary depending on the part of the rice grain, which may cause cracks in the rice grain or cause the rice grain to absorb more water than the target moisture content. Excess water adhering to the surface of the rice grains is separated and removed from the porous wall of the rotating cylinder in a short period of time by centrifugal force, forming a uniform water film of a certain amount on the surface layer of the rice grains. This uniform water film formed on the surface layer is absorbed into the rice grain at a uniform rate throughout the grain, so no cracks occur. The length of contact time needs to be adjusted depending on the moisture content of the polished rice raw material and the target moisture content after treatment. According to experiments, the appropriate contact time for processing polished rice with a moisture content of 13.5% and a milling yield of 91.5% was 10 seconds. The polished rice after this treatment had a moisture content of 14.8% and a yield of 90.3%.

As mentioned above, the second effect of this treatment method is that the yield of milled rice is reduced, that is, rice milling is performed. White rice that has been milled using normal rice milling processes has a milling yield of around 90%, but there are cases where bran adheres to the surface and a bran layer remains on some of the rice grains. When water is attached to the surface of the rice grains of this white rice or polished rice with a low milling yield of up to 94%, the bran and the bran layer become even softer and are peeled off by light contact between the rice grains, separating and removing the excess water, eliminating the need for washing the rice during cooking. It becomes white rice.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a flowchart for implementing the present invention. The front end of the grain lifting machine 1 is connected to a rice milling machine (not shown) through a hopper 2, and the discharge side is connected to a tank 3. Suction machines 4A and 4B are installed above the grain lifting machine 1 and tank 3. A rotary valve 6 for intermittently discharging rice grains is connected to a weighing machine 5 provided at the bottom of the tank 3, the valve 6 is connected to a grain lifting machine 7, and the discharge side of the grain lifting machine 7 is connected to a dipping tank 8. A water supply pipe 9 faces into the soaking tank 8, and a butterfly valve 11 is connected to a υ1 outlet pipe 10 at the bottom of the soaking tank 8, and the butterfly valve 11 is connected to a rice feeding pipe 13 via a pump 12. A water level gauge 14 and an overflow pipe 1 are installed at the top of the immersion tank 8.
5 will be provided.

The rice feeding pipe 1-3 is connected to a centrifugal separator 1-6, which will be described in detail later, and the undischarged port 17 of the centrifugal separator 16 is connected to a refined product tank 19 via a grain lifting machine 18.

It is desirable that the water or aqueous solution used in the present invention be partially circulated, and the solution separated and removed by the centrifuge 16 contains unnecessary solids such as rice bran. It connects to the sedimentation layer 22A of the liquid treatment device 21. 22A, 22B, and 22C are sedimentation layers, and when the aqueous liquid in the sedimentation layer 22A reaches the upper limit level, the water is connected to the sedimentation layer 22B sequentially.

It is configured to move to 22C. The outlet 23 provided in the middle of 22C communicates with the water supply pipe 9 of the immersion tank 8 via a flow control valve 24 and a pump 25.

A moisture content measuring device 26 is provided on one side of the tempering tongue 19, and the target moisture content set in the moisture content measuring device 2G is compared with the measured value of the polished rice moisture content after processing, so that the difference between the two is reduced. A control device 27 is provided which performs feedback control using a combination of the contact time with water, the amount of water added, the number of revolutions of the centrifuge (centrifugal acceleration), the amount of polished rice supplied, the water pressure, the direction of water injection, and the position of water addition. In addition, the control device 27 does not perform feedback control that controls the moisture content measuring device 26, but performs program control in which raw rice yield, raw material polished rice moisture content, and target polished rice moisture content are input and control is performed using a program created in advance through experiments. may also be used.

Next, the configuration of the centrifugal separator 16 will be explained with reference to FIGS. 2 and 3. In FIG. 2, a vertical shaft 29 is rotatably provided inside a machine frame 28, and a rotating cylinder 31 having a porous wall 30 through which rice grains do not pass is provided above the vertical shaft 29. Rotating tube 3
1 is open at the top, and a bottom plate 32 is provided at the bottom. Also,
At the center of the rotary cylinder 31 is a guide cylinder 33 having an opening at the bottom.
is erected on the bottom plate 32, and the supply 1.135 connected to the supply hopper 34 faces the upper part of the guide cylinder 33.

Furthermore, the centrifugal separator 1-6 is provided with a water supply device 36.

The water supply device 36 includes a water tank 37, a water pipe 38 for supplying water into the supply hopper 34, and a water pipe 39 having a nozzle 40 and a pump 41 for spraying water or an aqueous solution toward the rotating cylinder 31 of the centrifuge 1-6. configured.

In Fig. 2, the rotating cylinder 31 is configured such that the diameter of the upper part is larger than that of the lower part, and the rice grains fed into the rotating cylinder 31- are continuously moved upward by a component of centrifugal force and are continuously processed. The degree of taper is determined through experiments taking into account capacity, etc. However, in the case of intermittent processing (batch processing), the same diameter or a larger diameter at the bottom should be used, and when discharging, a rotating It is convenient to open the shutter provided at the lower part of the cylinder 31 and let out the rice grains by υ1. Reference numeral 42 is an additional element for raising the rice temperature or water temperature to promote uniform water absorption into the interior of the rice grain.

The centrifugal separator is not limited to the configuration shown in FIG. 2; for example, if it is a horizontally rotating cylinder type centrifuge, the influence of gravity is smaller than that of a vertical type, and continuous processing can be carried out more easily.

Next, the specific operation of the above embodiment will be explained. White rice milled to a suitable milling yield of 94 to 90% is supplied from a hopper 2 of a grain lifting machine 1 and temporarily stored in a tank 3. When a certain weight is measured and discharged using a measuring device 5 provided at the bottom of the tank 3, the flow rate is regulated to a constant level by the rotation of a rotary valve 6, and the polished rice is discharged and charged from the grain lifting machine 7 into the soaking tank 8. A set amount of water is supplied from the water supply pipe 9 to the weight of polished rice put into the soaking tank 8. Then, the entire surface layer of the polished rice comes into contact with the water.

The amount of water to be supplied is sufficient as long as it wets the entire surface of the polished rice grains, but when the soaking tank 8 was used, the amount of water was almost the same as the weight of the polished rice. Twice the amount of water based on the weight was added. 10 seconds after the start of soaking, the butterfly valve 11 is opened and the white rice is sent to the centrifuge 16 along with water by the pump 12, and water is separated and removed from the porous wall of the rotary cylinder 31 of the centrifuge 16, which is already rotating. However, during the contact of polished rice with water due to short-term soaking, the elution of the bran adhering to the surface of the polished rice grains, the peeling of the bran layer remaining on the polished rice, and the elution of free fatty acids occur due to the action of water and centrifugation. The water is generated and separated and removed outside the rotary cylinder 31 together with water.

The polished rice that has passed through the centrifuge 16 in a short time of 20 to 30 seconds is transported from the rice discharge port 17 to the tempering tank 19 via the grain fryer 18. In the tempering tank 19, a moisture content meter 26 is used to measure the moisture content of the polished rice after the treatment. Moisture content measuring device 26
Electrical resistance, capacitance, and optical methods can be used for this measurement, but because white rice has high moisture near the surface of the grain, it causes an error compared to the measurement of normal white rice, so it is necessary to correct it. When measured using a capacitance method, the value was 0.5% higher in the case of 15%.

A difference signal between the measured moisture content and the set moisture content is communicated to the control device 27, and the control device 27 controls the contact time of polished rice and water, the amount of added water, the rotation speed of the centrifuge, the amount of polished rice supplied,
Controls water pressure, water injection direction, water application position, etc. Also,
If the rice milling yield of treated white rice is to be the control target, replace the moisture content meter 26 with a white rice meter, measure the whiteness of the treated white rice, compare it with a set white charcoal, for example, 43% white rice, and calculate the difference. It communicates with the control device 27 as a signal and performs the same control as above.

In the above process, polished rice and water are brought into contact with each other in advance outside of centrifugation, but as shown in FIG. A method for separating and removing water by jetting water into contact with the rotary cylinder 31, and a supply hopper 3
A method of supplying polished rice from 4 and spraying high-pressure water droplets or mist water from a nozzle provided inside the rotary cylinder 31 can be appropriately selected and combined.

Although the above embodiment described continuous processing, if the rotating cylinder is made substantially vertical, intermittent centrifugal separation becomes possible, and although the operation and effect are the same, it is suitable for processing with a small capacity.

〔Effect of the invention〕

As described above, according to the method for treating polished rice of the present invention, after the polished rice is brought into contact with water or an aqueous solution for less than 1 minute, excess water or aqueous solution adhering to the polished rice is centrifuged through the porous wall of the rotary cylinder. The moisture content of polished rice can be increased by 1 to 5% compared to the moisture content before treatment, and compared to conventional polished rice processing methods, the humidity control speed is greatly improved, the equipment is smaller, and running costs are reduced. In addition, if polished rice with a milling yield of 94% or less is supplied and processed, the rice milling will progress due to the elution of adhering bran, peeling off of the remaining bran layer, and elution of free fatty acids, which will be the same as completely washed polished rice with a milling yield of 90%. It has exceptional effects such as removing unnecessary substances, increasing white discoloration, and having a standard moisture content, which makes it easy to store, and producing white rice that does not require washing during cooking.

[Brief explanation of drawings]

FIG. 1 is a flowchart of the present invention, and FIG. 2 is a front vertical sectional view showing an embodiment of a centrifugal separator that constitutes a part of the present invention. 1... Grain frying machine, 2... Hopper, 3... Tank,
4A, 4B... Suction machine, 5... Weighing machine, 6... Rotary valve, 7... Grain frying machine, 8... Soaking tank, 9... Water supply pipe, 10... Discharge Pipe, 11... Butterfly valve, 12... Pump, 13... Rice feeding pipe, 14
...Water level gauge, 15...Overflow pipe, 16...
Centrifugal separator, 17... Not discharged [1, 18... Grain frying machine, 19... Tempering tank, 20... Water discharge [1, 21... Water treatment device, 22A, 22B] , 22
C... Sedimentation tank, 23... Outlet, 24... Flow rate control valve, 25... Pump, 26... Moisture content measuring device, 2
7...Control device, 28...Machine frame, 29...Vertical axis,
30... Porous wall, 31... Rotating tube, 32... Bottom plate, 33... Guide tube, 34... Supply hopper, 35...
... Supply port, 36... Water supply device, 37... Water tank, 38... Water pipe, 39... Water pipe, 40... Nozzle, 41... Pump.

Claims (3)

[Claims] (1) After bringing water or an aqueous solution into contact with polished rice for less than 1 minute,
A method for processing polished rice, which comprises centrifuging excess water or aqueous solution adhering to the polished rice through the porous wall of a rotating cylinder, thereby increasing the moisture content of the polished rice after treatment by 1 to 5% over the moisture content before treatment. . (2) For white rice with a milling yield of 94% or less,
After contacting water or an aqueous solution for less than 1 minute, the free bran and remaining bran layer are centrifuged together with the water or aqueous solution adhering to the polished rice from the porous wall of the rotary cylinder. A method for processing polished rice, which is characterized by proceeding to a level lower than the rice milling yield. (3) After bringing water or aqueous solution into contact with polished rice of any milling yield of 94% or less for less than 1 minute, excess water or aqueous solution adhering to the polished rice is separated from the porous wall of the rotary cylinder, and after treatment, Reduce the moisture content of polished rice to 1 to 5% of the moisture content before treatment.
A method for treating polished rice, which comprises increasing the polishing yield of polished rice after treatment by eluating free bran and a residual bran layer into the aqueous solution to a value lower than the milling yield before treatment.