JPH03254648A - Method of polished rice treatment - Google Patents

Abstract

PURPOSE:To provide the title method through such processes that polished rice is washed with water, etc., put to mechanical dehydration, drying, moisture conditioning and then packaging, thereby accomplishing the moisture conditioning safely in a short time and preserving the resultant polished rice with high commercial value. CONSTITUTION:Polished rice is washed through e.g. immersion in water or an aqueous solution of common salt, saccharide, alcohol, etc., and fed in a short time (within one minute) into a centrifugal separator where it is dehydrated, and the resulting rice is put to drying and moisture conditioning processes followed by pref. addition of glucono delta-lactone and then vacuum packaging, thus accomplishing the objective treatment.

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 that increases the moisture content of polished rice by centrifugation and removes the bran and remaining bran layer attached to the polished rice.

[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, if the rice has a standard moisture content of 15% or higher, even when soaked, the water absorption rate is slow and the volume strain is small, so it absorbs an appropriate amount of water without cracking, resulting in soft and sticky rice.

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.

In addition, the rice disclosed in JP-A No. 59-10620 has a water content of about 32 to 35 by washing the rice, soaking it in water, draining it and drying it.
%, but because the moisture content is quite high, it is difficult to store after opening the bag, and it spoils easily, especially in the summer.

[Problem that the invention seeks to solve]

The object of the present invention is to solve the 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 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]

The present invention involves washing polished rice by contacting it with water or an aqueous solution for a short period of time, and then packaging the polished rice through a mechanical dehydration process followed by a drying process or a tempering process, and wherein the packaging is kept at an internal pressure lower than atmospheric pressure. The problem was solved by vacuum packaging and by adding glucono delta-lactone to polished rice that had gone through a drying or tempering process.

[For production]

Water or an aqueous solution is applied to the entire grain surface of polished rice in a very short period of time. The aqueous solution used is one in which salt, sugar, alcohol, starch, etc. are dissolved. When starch is used, a highly concentrated starch solution is heated and gelatinized and then dissolved in a solution of 2 to 5% based on the water weight, and a 10% alcohol solution is suitable. The main purpose of using an aqueous solution is to slow down the water absorption rate.

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. The dehydrated polished rice is then packaged after undergoing a drying process or a tempering process.

Vacuum packaging improves the shelf life of white rice, and adding glucono delta-lactone to white rice improves the taste of cooked 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 pulp 6 is connected to a grain lifting machine 7, and the discharge side of the grain lifting machine 7 is connected to a soaking tank 8. A water supply pipe 9 faces into the soaking tank 8, and a butterfly valve 11 is connected to a discharge 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 tube 13 is connected to a centrifugal separator 16 whose details will be described later.
An ice outlet 17 of the centrifugal separator 16 communicates with a tenburine tank 19 via a grain fryer 18.

It is desirable that the water or aqueous solution used in the present invention be configured to be partially circulated, and the solution separated and removed by the centrifuge 16 contains unnecessary solids such as bran, and the aqueous liquid outlet 20 is It is connected to the sedimentation layer 22A of the liquid processing device 21. 22A, 22B, 22C are precipitated layers, and the precipitate m2
When the 2A water reaches the upper limit level, the water changes to 22B.

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 Tenburin tank 19, and the target moisture content set in the moisture content measuring device 26 is compared with the measured value of the polished rice moisture content after processing, and the difference between the two is reduced. A control device 27 is provided which performs feedback control based on a combination of the contact time with water, the amount of water added, the number of rotations of the centrifuge (centrifugal acceleration), the amount of polished rice supplied, the water pressure, the water injection direction, and the water application position. The control device 27 does not use feedback control using the moisture content measuring device 26, but uses 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. It's okay. Further, 43 is a measuring vacuum packaging machine provided below the Tenbourine tank 19.

Next, the configuration of the centrifugal separator 16 will be explained with reference to FIG. 2. In FIG. 2, a vertical shaft 29 is located inside the machine frame 28.
is provided rotatably, and a rotary cylinder 31 having a porous wall 30 through which rice grains do not pass is provided above it. The upper part of the rotary cylinder 31 is open, and a bottom plate 32 is provided at the lower part. In addition, the rotating cylinder 31
In the center of the bottom plate 32 is a guide cylinder 33 having an opening at the bottom.
A supply port 35 connected to a supply hopper 34 faces the upper part of the guide cylinder 33.

Furthermore, the centrifugal separator 16 is provided with a water supply device 36. The water supply device 36 includes a water tank 37 , a water pipe 38 that supplies water into the supply hopper 34 , a nozzle 40 and a pump 4 for spraying water or an aqueous solution toward the rotating cylinder 31 of the centrifuge 16 .
1 and a water pipe 39.

In FIG. 2, the rotating cylinder 31 has an upper diameter larger than a lower diameter, and the rice grains fed into the rotating cylinder 31 are continuously moved upward by the centrifugal force and are continuously processed. The degree of taper is determined by experiment, taking into consideration the capacity, etc. However, when performing intermittent processing (batch processing), the same diameter or a larger diameter at the bottom should be used, and when discharging, a rotary cylinder should be used. It is convenient to have a structure in which the rice grains are discharged by opening a shutter provided at the lower part of the rice grains. Reference numeral 42 is a heating device that increases the rice temperature or water temperature to promote uniform water absorption into the interior of the rice grains.

The centrifugal separator is not limited to the configuration shown in FIG. 2; for example, if a horizontally rotating tube type centrifuge is used, 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, polished rice is discharged under a constant flow rate regulated by the rotation of the rotary pulp 6, and is fed 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 together with water to the centrifuge 16 by the pump 12.
Water is separated and removed from the porous wall 30 of the rotary cylinder 31 of the centrifugal separator 16 that is already rotating, but during the contact between the polished rice and water due to short-term immersion, the rice bran attached to the surface of the polished rice grains is eluted. , the peeling of the bran layer remaining in the polished rice and the elution of free fatty acids occur due to the action of water and centrifugation, and the rotary cylinder 31
It is separated and removed outside. The white rice that has passed through the centrifuge 16 for a short time of 20 to 30 seconds is sent from the rice discharge port 17 to the grain frying machine 18.
It is transported to the tempering tank 19 via. The white rice is tempered in the small ring tank 19, and the water content is homogenized throughout the grains of white rice. Therefore, cracks on the surface of the rice grains due to uneven moisture that occur during packaging (especially in the case of vacuum packaging) are prevented. The polished rice that has been tempered is then sent to the weighing vacuum packaging machine 42, where it is weighed at fixed weight intervals and then vacuum packed at an internal pressure lower than atmospheric pressure. A moisture content meter 26 provided in the tempering tank 19 measures the moisture content of the polished rice after the treatment. The moisture content measuring device 26 can be of an electrical resistance type, a capacitance type, or an optical type, but since white rice has a high moisture content near the grain surface layer, it will cause an error compared to the measurement of normal white rice, so it is necessary to correct it. be. When measured using a capacitance method, the value was 0.5% higher in the case of 15%.

The 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. In addition, if the milling yield of treated polished rice is to be the control target, replace the moisture content meter 26 with a whiteness meter, measure the whiteness of the treated polished rice, and compare it with a set whiteness, for example, 43% white charcoal. The difference is used as a signal to communicate with the control device 27 to perform the same control as described above.

In the above process, polished rice and water are brought into contact with each other in advance outside the centrifuge, but as shown in FIG. The rotating cylinder 31 is brought into contact with water by spouting water from the
A method of supplying polished rice from the supply hopper 34 and spraying water in the form of high-pressure water droplets or mist from a nozzle provided inside the rotary cylinder 31 is appropriately selected and combined. be able to.

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.

Furthermore, glucono delta-lactone can be added to the white rice tempered in the tempering tank 19 to improve its taste. In other words, glucono-delta-lactone acts on starch or protein during cooking, and in combination with the protein decomposition action, effectively gelatinizes the starch and cooks rice that is soft, sticky, and delicious. I can do it.

〔Effect of the invention〕

According to the method for treating white rice of the present invention, the white rice is washed by contacting water or an aqueous solution for a short time, followed by a mechanical dehydration process, followed by a drying process or a tempering process, and then packaged, so that the rice has a good shelf life and is cooked. It is possible to obtain white rice that does not require washing at the time of washing. In addition, the tempering effect homogenizes the moisture throughout the polished rice, which prevents cracks on the surface of the rice grains due to uneven moisture that occurs during packaging (especially in the case of vacuum packaging), and prevents stickiness during cooking. The rice will not become sticky.

Furthermore, vacuum packaging can improve the shelf life of polished rice.

Furthermore, by adding glucono delta-lactone to white rice that has undergone a drying or tempering process, the rice is cooked into soft, sticky, and delicious rice.

[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, IO... Discharge Pipe, 11... Butterfly valve, 12... Pump, 13... Rice feeding pipe, 14
...Water level gauge, 15...Overflow pipe, 16...
- Centrifugal separator, 17... Undischarge port, 18... Grain frying machine, 19... Tempering tank, 20... Water discharge port, 21... Water treatment device, 22A, 22B, 22C
... Sedimentation tank, 23 ... Outlet, 24 ... Flow rate control valve, 25 ... Pump, 26 - ... Moisture content measuring device, 27
...Control device, 28...Machine frame, 29...Vertical axis, 3
0... Porous wall, 31... Rotating cylinder, 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, 42... Warming device, 43... Weighing vacuum packaging machine.

Claims (3)

[Claims] (1) A method for processing polished rice, which comprises washing polished rice by contacting it with water or an aqueous solution for a short period of time, followed by a mechanical dehydration step, followed by a drying step or tempering step, and then packaging the polished rice. (2) The method for processing polished rice according to claim (1), characterized in that the packaging is vacuum packaging for packaging at an internal pressure lower than atmospheric pressure. (3) The method for treating polished rice according to claim (1), wherein glucono delta-lactone is added to the polished rice that has undergone a drying step or a tempering step.