Patent Publication Number: US-2004043120-A1

Title: Method of and apparatus for processing polished rice

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a method of and an apparatus for processing polished rice to obtain no-bran rice which requires no washing before cooking.  
       [0003] 2. Description of Related Art  
       [0004] There is known an apparatus for manufacturing no-bran cereal as shown in FIG. 6 from Japanese Patent No. 3206752. This no-bran cereal manufacturing apparatus comprises a wet processing section  105 , a mixing/stirring section  110  and a separating/drying section  116  which are arranged substantially parallel to one another and horizontal.  
       [0005] The wet processing section  105  includes a first screw cylinder  101 , a first screw shaft  103  rotatably supported in the first screw cylinder  101  and having stirring vanes  102 , a spray nozzle  104  for spraying water to the material polished rice at the proximal end portion of the first screw cylinder  101 . The mixing/stirring section  110  is arranged under the wet processing section  105  and comprises a second screw cylinder  106  having substantially the same size as the first screw cylinder  101  and a second screw shaft  108  rotatably supported in the second screw cylinder  106  and having stirring vanes  107 . A hopper  109  for supplying starchy granular material is connected to the proximal end portion of the second screw cylinder  106 . The separating/drying section  116  is arranged below the mixing/stirring section  110  and comprises a screen cylinder  111  having a number of slits, an air inlet  112  arranged above the screen cylinder  111 , a cylindrical casing  113  covering the screen cylinder  111 , an air discharge duct  114  connected to the bottom of the cylindrical casing  113 , and an outlet  115  for taking out the processed polished rice (no-bran rice) arranged at the distal end of the screen cylinder  111 .  
       [0006] In the wet processing section  105 , a predetermined amount of material polished rice is supplied into the first screw cylinder  101  and moisture of approximately 5% by weight in the form of mist is added to the material polished rice from the spray nozzle  104  so that the moisture permeates over each grain surface of the polished rice to soften bran stuck on each grain surface. In the mixing/stirring section  110 , the polished rice with moisture added is mixed and stirred with starchy granular material of high temperature of 60° C.- 120 ° C. from the hopper  109  in the second screw cylinder  106 .  
       [0007] The bran stuck on the grain surface of the polished rice which has been softened by the moisture added is gelatinized immediately after touching with the starchy granular material of high temperature and is caught by the granular material and removed from the surface of each grain of the polished rice. Since the bran  3  is securely caught by the starchy granular material  4 , the bran  3  does not adheres to the surface of the grains again.  
       [0008] In the separating/drying section  116 , the polished rice and the granular material fed into the screen cylinder  111  are stirred to be separated from each other. The polished rice is dried by the air of 40° C. from the air inlet  112  to assist separation of the polished rice from the granular material. The polished rice removed from the granular material is discharged outside from the processed polished rice outlet  115 , and the granular material dropped from the slits of the screen cylinder  111  is discharged from the blowing discharge duct  114 .  
       [0009] In the above apparatus for manufacturing no-bran cereal, the bran stuck on the softened rice is effectively absorbed by the starchy granular material to enhance whiteness of the no-bran rice, and friction among the grains of polished rice and the starchy granular material are low to suppress generation of powdered bran since the pressure in the second screw cylinder  106  of the mixing/stirring section  110  is relatively low such as 20 gf/cm 2 . However, there has been found a problem that the obtained no-bran rice has low brightness. It is considered that the low brightness is caused by inequalities of the grain surface of the no-bran rice. Since the bran is removed from minute grooves of commissure of the grain, the minute grooves are left on the grain surface to make inequalities of the surface. Thus, light impinged on the minute inequalities diffuses to increase the whiteness but lower the brightness, as shown in FIG. 5.  
       [0010] There is known a method of polishing rice from Japanese Patent Publication No. 54-13383 in which water in the form of liquid, moistened air, steam is added to material polished rice to be soften grain surfaces and the moistened rice is stirred to be subjected to polishing, removing of bran, heating, grinding to thus smooth the gain surfaces by friction among the grain surfaces softened by adding moisture, and dry the grain surfaces utilizing heat produced in this process, to produce brightness of the grain surfaces.  
       [0011] However, in this method of smoothing the grain surfaces by friction among grains with the surface softened by moistening, if the moisture is insufficient, the bran stuck on the grain surface is not effectively removed but embedded into minute grooves on the grain surfaces to fail in enhancing the whiteness.  
       SUMMARY OF THE INVENTION  
       [0012] The present invention provides a method of and an apparatus for processing polished rice capable of effectively removing bran stuck on grain surfaces of polished rice to enhance whiteness and also smoothing the grain surfaces to remove minute grooves thereon to have high brilliance.  
       [0013] A method of processing polished rice of the present invention comprises the steps of: adding moisture to the polished rice to soften grain surfaces thereof; mixing and stirring starchy granular material heated to have temperature not less than 60° C. with the moistened polished rice so that bran stuck on the grain surfaces of the polished rice is captured by the starchy granular material and removed; and separating the polished rice from the starchy granular material with bran captured, and smoothing the grain surfaces by eliminating minute inequalities thereof after the bran removed so as to enhance brilliance of the grain surfaces.  
       [0014] The starchy granular material may have granularity of 0.5 mm-1.7 mm, so that the bran stuck on the grain surface is easily captured by the starchy granular material and the starchy material mixed into the polished rice can be effectively separated from the polished rice.  
       [0015] The starchy granular material may have moisture not higher than 5% in weight, so that the bran moistened is easily caught by the starchy granular material having less moisture.  
       [0016] The starchy granular material may be selected from the group consisting of grinded wheat, grinded barleycorn, grinded millet, grinded buckwheat and grinded kaoliang, and may comprise pearl tapioca, which are all edible and available with low cost.  
       [0017] It is preferable to perform smoothing of the grain surfaces by eliminating minute inequalities thereof after the bran removed under pressure in a range between 40 μl/cm 2  and 100 gf/cm 2 .  
       [0018] The present invention also provides a polished rice processing apparatus comprising moisture adding means, mixing/stirring means and separating/smoothing means for carrying out the above respective steps of the polished rice processing method.  
       [0019] The moisture adding means may include a screw cylinder arranged horizontally, a screw shaft rotatably arranged in the screw cylinder and having stirring vanes, and a spray nozzle for spraying water to material polished rice. The mixing/stirring means may include a cylindrical casing arranged horizontally, a first hollow stirring shaft arranged rotatably in the cylindrical casing and having stirring slats, and a granular material supplying device for supplying the starchy granular material into the cylindrical casing through the hollow stirring shaft. The separating/smoothing means may include a porous wall cylinder arranged horizontally, a second hollow stirring shaft supported rotatably in the porous wall cylinder and having stirring slats, and an air blowing device for blowing air into the porous wall cylinder through the hollow stirring shaft.  
       [0020] The mixing/stirring means and the separating/smoothing means may be connected coaxially by aligning said cylindrical casing and said porous wall cylinder and joining said first hollow stirring shaft and said second hollow stirring shaft to extend coaxially as a unit, so as to make the apparatus compact.  
       [0021] The separating/smoothing means may have a grain discharge device at a distal end portion thereof, and a resistance device may be provided at the grain discharge device for adjusting pressure in the porous wall cylinder. It is preferable to set the pressure in the porous wall cylinder in a range between 40 gf/cm 2  and 100 gf/cm 2 . 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0022]FIG. 1 is an enlarged schematic view of a grain surface of polished rice softened by adding moisture when bran stuck on the grain surface is captured by starchy granular material;  
     [0023]FIG. 2 is an enlarged schematic view of the grain surface of no-bran rice with the bran removed from the grain surface;  
     [0024]FIG. 3 is an enlarged schematic view of the grain surface of the no-bran rice after subjected to smoothing process;  
     [0025]FIG. 4 is a vertical sectional view of a polished rice processing apparatus according to the present invention;  
     [0026]FIG. 5 is a schematic diagram of a grain of the polished rice showing diffusion of light by minute inequalities of a grain surface; and  
     [0027]FIG. 6 is a vertical sectional view of a no-bran cereal manufacturing apparatus according to prior art. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
     [0028] First, a principle of the method of the present invention will be described referring to FIGS.  1 - 3 .  
     [0029] There remains bran  3  on a grain surface  1  of polished rice comprising commissure after subjected to an ordinary polishing process. The bran  3  comprises a part of aleurone of the aleurone layer remaining on the grain surface  1 , and a part of the aleurone powdered after removed form the grain surface  1  by the polishing process and adhered thereon. By adding moisture to the grain surface  1  of the polished rice, moisture in the bran stuck on the grain surface  1  is increased so that the bran  3  is swelled with moisture and softened to form a gap between the bran  3  and the grain surface  1 .  
     [0030] The starchy granular material  4  having temperature not less than 60° C. preferably in a range of 60° C.-120° C. is mixed to the moistened rice and stirred. The bran  3  on the grain surface  1  is gelatinized by heat from the starchy granular material  4  immediately after touching with the starchy granular material  4 . An appetence between the gelatinized bran  3  and the starchy granular material  4  gelatinized by heat as well is enhanced and thus a cross link is formed between the bran  3  and the starchy granular material  4 , so that the bran  3  adheres to and caught by the starchy granular material  4 , as shown in FIG. 1.  
     [0031] The bran  3  is easily removed as being caught by the starchy granular material  4  form the grain surface  1  without causing any damage on the grain surface  1 , as shown in FIG. 2. The grains of polished rice with the bran  3  removed are separated form the granular material  4  catching the bran  3  so that no-bran rice with no bran remaining in the minute recesses or grooves of the grains is obtained.  
     [0032] However, although the bran  3  is removed from the grain surface  1 , parts of the commissure remain on the grain surface  1  as protrusions  2  to form minute grooves  5  between the protrusions  2 , as shown in FIG. 2. Light impinged on the grain surface  1  diffuses on the surface because of the protrusions  2  and the minute grooves  5  to lower brilliance of the grain surface  1 . According to the method of the present invention, the protrusions  2  are scraped to even the grooves  5  to smooth the grain surface  1  by mutual friction among the grains to have high brilliance, as shown in FIG. 3. It is preferable to set pressure of mutual friction in the smoothing process in a range of 40-100 gf/cm 2 .  
     [0033] As the starchy granular material  4 , grinded rice, grinded wheat or barleycorn, grinding millet, buckwheat and kaoliang with granularity adjusted in a range from 0.5 mm to 1.7 mm and dried to have moisture not higher than 5% can be used. Also, granular material such as pearl tapioca obtained by processing starch of cassava to be pre-gelatinized and being dried and formed into balls is preferably used.  
     [0034] A polished rice processing apparatus for carrying out the method of processing the polished rice will be explained referring to FIG. 4.  
     [0035] The polished rice processing apparatus  6  comprises a moisture adding section  7  for adding moisture to the material polished rice so as to soften bran remaining on the grain surfaces of the material polished rice, a mixing/stirring section  8  for mixing and stirring preheated starchy granular material with the moistened polished rice so that the granular material captures the softened bran on the surfaces of the polished rice, and a separating/smoothing section  9  for separating the processed polished rice from the starchy granular material and burnishing the grain surface.  
     [0036] In this embodiment, the moisture adding section  7  is arranged at the uppermost position in the polished rice processing apparatus  6 , the mixing/stirring section  8  and the separating/smoothing section  9  are connected with each other to extend coaxially at the middle position of the polished rice processing apparatus  6  so as to make the apparatus compact.  
     [0037] The moisture adding section  7 , the mixing/stirring section  8  and the separating/smoothing section  9  may be provided separately and connected by appropriate grain shifters. Further, the moisture adding section  7  may be arranged at the uppermost position, the mixing/stirring section  8  may be arranged at the middle position and the separating/smoothing section  9  may be arranged at the lowermost position in one polished rice processing apparatus.  
     [0038] The moisture adding section  7  comprises a screw cylinder  10  arranged horizontally and a screw shaft  11  rotatably supported in the screw cylinder  10 . A supply cylinder  13  for supplying the material polished rice into the screw cylinder  10  is arranged at the proximal end portion of an upper circumference of the screw cylinder  10 , and a communicating pipe  15  communicating an outlet  14  at the distal end portion of the screw cylinder  10  and an inlet  24  at the proximal portion of the mixing/stirring section  8 .  
     [0039] The screw shaft  11  has a screw blade  16  at the proximal portion under the supply cylinder  13  and a plurality of stirring vanes  17  in the region between the screw blade  16 . A spray nozzle  19  is arranged to be directed into the supply cylinder  13  to spray water to the material polished rice fed into the supply cylinder  13 , and a motor  18  for driving a feeder (not shown) for feeding the material polished rice is provided at the supply cylinder  13 . A pulley  20  fixed to the distal end of the screw shaft  11  is connected with a motor  21  through a belt  23  in a casing  22 .  
     [0040] The mixing/stirring section  8  and the separating/smoothing section  9  are arranged coaxially under the moisture adding section  7 . The mixing/stirring section  8  comprises a cylindrical casing  25  communicating with the communicating pipe  15  at the proximal end and a hollow stirring shaft  26  rotatably supported in the cylindrical casing  25 . The proximal part of the hollow stirring shaft  26  serves as a granular material supplying pipe  27  having granular material supply holes in the vicinity of a partition wall  37  at a distal end of the proximal part. A grain feeding rotor  29  for feeding the grains of the material rice supplied from the inlet  24  is fixed to an outer circumference of the proximal part of the hollow stirring shaft  26 , and stirring slats  30  are fixed to an outer circumference in a forward region between the grain feeding rotor  29  and the distal end of the hollow stirring shaft  26 . A mixing/stirring chamber  31  is formed between the grain feeding rotor  29  and the stirring slats  30  and an inner circumferential of the cylindrical casing  25 .  
     [0041] One end of a granular material supply pipe  33  is connected to the proximal end of the hollow stirring shaft  26  and the other end is connected to a blower  34  for air-conveying the granular material. A hopper  36  for supplying the granular material is connected to the granular material supply pipe  33  at the middle thereof through an adjusting valve  35  for adjusting feeding rate of granular material. The granular material supply pipe  33 , the blower  34 , the hopper  36 , and the adjusting valve  35  constitutes a granular material supplying device. The partition wall  37  separates an inner space of the hollow stirring shaft  26  into a granular material supply passage and an air supply passage at an approximately middle position of the hollow stirring shaft  26 .  
     [0042] The separating/smoothing section  9  is arranged continuously and coaxially with the mixing/stirring section  8 . The separating/smoothing section  9  is constituted by a porous wall cylinder  39  connected coaxially with the distal end of the cylindrical casing  25  projecting into a machine frame  38 , and the distal portion of the hollow stirring shaft  26  having a number of through holes  48 . A separating/smoothing chamber  40  is formed between the distal portion of the stirring shaft  26  and an inner circumference of the porous wall cylinder  39  connected with the cylindrical casing  25 .  
     [0043] A grain discharge device  43  comprising a discharge pipe  42  with an opening  41  is arranged at the distal end of the separating/smoothing chamber  40  in an outlet flume  53 . A resistance device  46  for adjusting pressure in the separating/finishing chamber  40  is provided at the grain discharge device  43 . The resistance device  46  comprises a resistant lid  44  for applying resistive force on the grains being discharged from the discharge pipe  42  and a weight  45  for producing the resistive force of the resistant lid  44 . The inner pressure of the separating/smoothing chamber  40  can be adjusted in a range of 40-100 gf/cm 2  by the resistance device  46 .  
     [0044] An air inlet  47  for taking open air is provided at the distal end of the hollow stirring shaft  26 , and a number of through holes  48  are formed on circumference of the hollow stirring shaft  26  confronting the porous wall cylinder  39 . A funnel  49  for collecting the granular material separated from the processed polished rice (no-bran rice) is provided under the porous wall cylinder  39 , and connected with a conducting pipe  50  and a suction fan (not shown). Air introduced into the stirring shaft  26  from the inlet  47  flows through the through holes  48 , the separating/smoothing chamber  40 , the porous wall cylinder  39 , the funnel  49  and the conducting pipe  50  to the suction fan.  
     [0045] A pulley  51  fixed to one end of the stirring shaft  26  is connected with the motor  21  through a belt  52  in the casing  22 .  
     [0046] A conveying device having a screw conveyer  54  and a conveyer cylinder  55  is arranged below the separating/smoothing section  9  to be connected to the outlet flume  53  of the separating/smoothing section  9  is connected to a proximal end portion of the conveyer cylinder  55 , and an outlet  56  for taking out the processed polished rice (no-bran rice) is arranged at the distal end of the conveyer cylinder  55 . A pulley  59  fixed to one end of the rotary shaft  57  is connected with the motor  21  through a belt  59  in the casing  22 .  
     [0047] A recycle device  60  is connected to the conducting pipe  50  through the pipe  61  for scraping the bran captured on the granular material and recycling the granular material with the bran scraped to be fed to the hopper  36  through the pipe  62  and the heating device  63  for preheating the granular material to have temperature of 100° C.- 120 ° C.  
     [0048] An operation of the polished rice processing apparatus  6  will be described.  
     [0049] Predetermined amount of material polished rice, which is obtained by polishing brawn rice by an rice polishing machine, is supplied into the screw cylinder  10  from the supplying cylinder  13  by the feeding device driven by the motor  18 . Moisture of approximately 5% by weight is added to the material polished rice by the mist sprayed from the spray nozzle  19  arranged near the inlet  12 . The polished rice with moisture added is stirred by the stirring vanes  17  while being fed towards the distal end portion of the screw cylinder  10  by the screw blade  16  rotating at 500 rpm. By the stirring, moisture supplied in the form of mist permeates over a surface of each grain of the polished rice to soften bran remaining on each grain of the polished rice.  
     [0050] Subsequently, the polished rice is discharged from the screw cylinder  10  through the outlet  14  and fed into the cylindrical casing  25  of the mixing/stirring section  8  from the inlet  24  through the discharge cylinder  15 , and is stirred by the feeding rotor  29  and the stirring slats  30 . At the same time, the starchy granular material in the hopper  36  is fed into the supply pipe  33  through the feed valve  35  and also pressurized air from the air conveying blower  34  is supplied into the supply pipe  33 , so that the starchy granular material is fed into the hollow stirring shaft  26 . Since the starchy granular material may be small grains such as pearl tapioca obtained by processing starch to be pre-gelatinized and dried to be form to a ball having a hardness of 2-5 kgf/cm 2  and a standard granularity of 0.5 mm-1.7 mm, the granular material is conveyed by the air supplied from the blower  34 . The granular material is preheated by the heating device  63  to have high temperature of 100° C.-120° C. and supplied into the granular material supply pipe  33 . The granular material conveyed into the hollow stirring shaft  26  is blocked by the partition wall  37  and discharged through the through holes  28  to be fed into the mixing/stirring chamber  31 .  
     [0051] In the mixing/stirring chamber  31 , the starchy granular material which has temperature of 60° C.-100° C. reduced from the temperature of 100° C.-120° C. at the heating device  63  is mixed and stirred with the polished rice. The bran on the surface of each grain of the polished rice which has been softened by the moisture added in the moisture adding section  7  is gelatinized immediately after touching with the granular material of high temperature and is caught by the granular material and removed from the surface of each grain of the polished rice. Since the bran is securely caught by the granular material, the bran does not adheres to the surface of the grains again. The moisture of the bran is evaporated to absorb heat from the surface of each grain to lower the temperature thereof.  
     [0052] The polished rice and the starchy granular material move into the separating/smoothing chamber  40  of the separating/smoothing section  9  and the starchy granular material passes the porous wall cylinder  39  through the through holes to drop into the funnel  49  and the grains of the polished rice remain in the separating/smoothing chamber  40  being restrained by the porous wall cylinder  39  to thus separated from the granular material. The grains of the polished rice remaining in the separating/smoothing chamber  40  are subjected to stirring by the stirring slats  30 . At the same time, the air taken from the inlet  47  is introduced into the separating/smoothing chamber  40  through the hollow stirring shaft  26  and the through holes  48  to assist separation of the polished rice from the granular material.  
     [0053] The grains of the polished rice remaining in the separating/smoothing chamber  40  is subjected to stirring by the stirring slats  30  at the pressure in a range between 40 gf/cm 2  and 100 gf/cm 2  adjusted by the resistance device  46  provided at the grain discharge portion  42 . With this stirring of the grains at the appropriate pressure, the friction mutually acting among the grains scrapes the protrusions  2  on each grain surface of the polished rice to be burnished.  
     [0054] The grains discharged from the grain discharge tube  42  are with bran removed from the surface to enhance whiteness and the protrusions of the grooves are burnished to provide high brightness.  
     [0055] The polished rice passed through the lid  44  drops onto the outlet flume  53  is conveyed by the conveying device and discharged from the outlet  56 .  
     [0056] The processes and products by the conventional polished rice processing apparatus as shown in FIG. 6 and the polished rice processing apparatus of the present invention as shown in FIG. 4 are compared as follows;  
               TABLE 1                          (abundance and pressure of mixture of rice gains and starchy       granular material)                             Prior art   Present invention                                             Abundance   Approximately 30%   Approximately 90%           Pressure   20 gf/cm 2     40 gf/cm 2 -100 gf/cm 2                        
 
     [0057]               TABLE 2                          (brilliance, whiteness and turbidness of processed rice grain       surfaces)                             Prior art   Present invention                                             Brilliance   Low   High           Whiteness   45%-47%   45%-47%           Turbidness   60 ppm-70 ppm   60 ppm-70 ppm                        
     [0058] As described, according to the present invention, bran stuck on grain surfaces of polished rice is effectively removed to enhance whiteness of obtained no-bran rice and also the grain surfaces are smoothed to remove minute grooves thereon to have high brilliance.