CA1219771A - Method and apparatus for the removal of bran from rice and like cereal grains - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method for removing bran from cereal grains, particularly rice, wherein dehusked cereal grains to be debranned are fed under controlled pressure through a chamber wherein they are laterally confined by an apertured screen while being worked by a special blade rotor providing pockets of grain which rotate with the rotor within and relative to the confined grain body so that the debranning action is effected Mainly by grains rubbing together whereby to produce high grade unbroken polished grains efficiently and economically.

Description

~ 7~ 70627-lD

This invention relates to the processing o:E rice and other cereal grains and is particularly concerned with a method wherein bran is efficiently removed from the grains.
This applica.tion is divi.ded from applicants copending Canadian application serial No. 39~,13~ filed January 22, 1982, the latter application being directed to apparatus for removing bran from rice and like cereal grains comprising an annular wall defining an open-ended grain processing chamber, a power driven rotor assembly within said chamber surrounded by said wall, means for introducing grains to be debranned between the wall and rotor assembly at one end of said chamber and applying controlled pressure to move said grains through sald chamber longitudinally o:E sa:id rotor assembly to a discharge opening at the other end, ancl means :Eor rotat:ing sa:id rotor assembly Eor e:E-Eecting bran-removil-g abrasion Oe ~:rni.ll :in snl.d ch.~lb~r; characte~rl~èd by said rotor ass~ b.ly be:illg Eorm~d w:itll :inwllrclly c:los~cl ~)ock~ts :E.Icing thc operat:ional dir~ct:ion oE rotat:ion o:E sa:i.cl roto:r asse~lllb.ly to r~ta:ill .llld convey some o:E tlle gru.ills a:roullcl w:itll :it du:r:i.llg rotat.ioll, w:ith the graills ca:rried by said rotor asselllb.ly cont:illua:l.ly directly ellgclging the surrowlcling bocly o:E
grain.
Rice is a major crop and food in many countries. In some countries the most desirable rice, usually that destined for food, is so-called polished rice which has the bran surface layers removed and appears as a more or less colorless smooth unbroken grain. Rice which has been debranned without breaking or otherwise damaging the grain is more highly desired than broken grain rice. Therefore a continuing problem in the industry is to improve the production of unbroken rice free of bran as economically and as efficiently as possible.
Machines for removing bran developed over the years include generally the abrasive type wherein the rice grains are subjected to the Case #LN-A957 - 1 -~2~7~

positive action of abrasive sur:Eaced rollers, and friction type wherein the rice grains are rubbed on metal surfaces and each other.
In its preferred embodiment the invention will be described in relation to rice milling apparatus, of -the friction type, wherein rice grains are fed axially through a chamber defined by an apertured confining screen surrounding a milling rotor, and wherein bran is removed from the surfaces of the rice grains in the chamber and separated from the resultant polished rice grains.
Apparatus of the foregoing type has been proposed and is widely used. Probably the most well known comprises machines sometimes known as Satake macllilles that incorporate principles disclosed in the United States patents to Satake Nos. 3,078,89~; 3,179,1~0; 3,485,280;
3,628,582; 3,750,88~ 8,25l allcl~l,l55,295. A related improvement to Satakc macllilles ls clisclosecl i.n hlor:L Unitecl States l'atellt 3,~35,865.
Know~ rt also illcllldes IlllgcLberg lJnitccl States Patellt No. ~Z~,602 where a rotor milLs rice in u conl~ lillg cyLilldr:ic;ll perEoratecl casing ~mcl Staton No. ~,05l,773 whereill the rotor is mocl:iE:ic(l to provide :r:ice grain passages througll it.
The Satake and like mach:ines clo produce clebranned rice, but experiellce has shown that commercially available milling apparatus also produces a considerable percentage of less desirable broken rice grains.
The term "milling" as used herein means the removal of bran from the rice grain.
Analyzing these conventional friction type machines it appears that the debranning and accompanying grain-breaking action takes place to a very large extent as the rice grains are forced outwardly by the rotor and moved in rubbing contact against the metal screen surrounding the rotor.
Additionally there appears to be considerab]e wide area abrasive contact of the metal ribs of the Satake type rotor with the grains. These observations are derived from examining the wear patterns of the rotor and ~ ~2~ t;~

screen in Satake machines. In fact in such conventional machines the interior of the screen is usually initially provided with rows of surface projections to cause abrasive action of the screen on the grains, and with continued use of the machine abrasive wear on the screen results in polishing of the inner screen surface with the projections being worn and removed. It has been found that when the screen becomes so smooth as to lose its abrasive action on the grains the efficiency of bran removal reduces considerably. In the conventional machines as the screen 'becomes worn the bran removal efficiency may be retained for a time by lengthening the resistance increasing resistance to passage of the rice through the machine, but this often subjects the rice to undue forces that cause an increase in breakage and also accelerates screen wear. It is therefore common practice to replace smooth scre~ens, at every three months or so in those installations.
It is th~ major obj e~ct o:E tll:is :invention to provide novel meth-ocls of removing bran Eron~ rice or like cereal gralns .for producing a higher y:ielcl o:E unbrok~ )ol:ished griL:ins.
Accorcl:ing to one aspect of the presellt invelltion there is provicled a metllod o:E processing ce:real grains for efficiently removing bran with a minim~un o:E individucll grain breakage characterized by the steps of continuously supplying dehusked grains into a chamber having a wall confining a body of said grains against a driven rotor formed to retain and convey some of said grains around with it during rotation whi.le applying force moving the grains surrounding the rotor with respect thereto, with grains carried by the rotor continually directly engaging the surrounding grains whereby all of said grains in passing through the chamber move in a changing dynamic pattern wherein they are subjected to bran removing contact with other grains with the separated bran and the processed grains being discharged from said chamber.

The grain is pre.ferably moved longitudinally of the rotor under controlled axial pressure.

317~
Abrasive action upon the grains by the rotor and screen is minimized and substan-tially all of the abrasive action causing removal of the bran from the grains results from rubbing of the grzins against each other.
In another aspect, the invention provides a body of milled rice weighing at least 200 grams in which substantially all of the grains are free of bran and germ and in which the germ seat region is intact.
The present invention, together with that of applicants aforementioned Canadian application Serial No. 39~,134, will now be further described, with reference to the accompanying drawings, which illustrate an exemplary apparatus for use in carrying out the method of the present inventloll:
I:igure 1 is a slde elevation partly in section showing a rice polislllllg apparatus l)ccorcl:ing to a preter:red embodimellt of the invention;
I:igure 2 is n geller.llLy persl)~ctive view showillg the relat:ive urr.lllgelllellt ol` tlle sl)ec:ill.l bklcl~l ul:illlllg rotor LLlld the surrouuldillg screen in the nl)parat~ls of l~:ig~lre L, p.lrts bcillg relllovecl ~or clar:ity of disclosure;
Figure 3 :is all enklrged sectioll substanticllly on l:ine 3-3 of Figure 2 showing the rotor, IDilling challlber and screen association in the apparatus of Figure l;
Figure ~ is a generally perspective view showing the rotor apart from the other apparatus;
Figure 5 is a photomicrograph illustrating unbroken polished rice grains, produced by the invention;
Figure 6 is a photomicrograph illustrating a broken rice grain, illustrative of broken grains produced by hitherto conventional machines, particularly showing that the grain tip is broken off at the germ end of the grain; and Figure 7 is a reproduction of a photomicrograph showing several broken off fragments for scale comparison to a normal size grain of rice.
PREFERRED EMBODIMENTS
Figure 1 shows a rice milling apparatus containing a preferred embodiment of the invention.
A housing 11 is mounted on a stand 12 suitably bolted or otherwise rigidly secured on a floor support. An internal structure 13 provides a space 14 within one end of the housing and a generally hori7~olltal mainly hollow shaft 15 is journalled in structure 13.

Withi.n the housing space 14 shaft 15 is provided with one or more rows of air aclmission openings 16 and space 14 may be connected through opening 17 to a compressor 1~ or like source of air under pressure. Compressor l~ ls clriven by a belt 19 Erom the shaEt 15 which is pow~recl by an electric motor 21.
Witl~ th~ hollsillg at th~ oth~r sicl~ oE structure l3 the shlft L5 carr:ies a ll~licul rice gr.lill Eeecl scrcw 22 allcl L rice mi:lling rotor 23. A housillg ol)ell:illg 20 I)erllli-ts ~lltry ot rice to be milled. Screw 22 is keyecl to shaEt l5 Eor rotution the:r~witll. Rotor 25 is longitudinally slidably nlountecl over the end of sha:Et 15 and may be Eormed with end clrive lugs 24 (see Figure 4) engageable with corresponding recesses in the end of screw 22. Rotor 23 is axially held on shaft 15 by a plug and abutment device 25 that is secured in place by bolt 26 to close the hollow shaft at that end and axially engage the end of the rotor. Detail of a special rotor structure that is particularly advantageous in the invention will follow.
The rotor 23 is coaxially surrounded by a fixed screen assembly 27 which as shown in ~igure 2 comprises an apertured screen 28 mounted in a rigid cage formed by parallel annular end members 29 and 31 between which extend a plurality of bars 32 one of which is indicated in ~æ~ 7~

Figure 2. As shown best in Figures 2 and 3 screen 28, which may be formed of sheet metal suitably p~lched or otherwise provided with a multiplicity of bran discharge apertures 33, defines a regular hexagonal envelope or confini.ng wall in spaced relation around the rotor. Screen 28 thus establishes a milling chamber 34 around the rotor, and apertures 33 are of such size that they will not pass a grain of rice and are oriented so as not to obstruct rice grain movement axially of the chamber.
Preferably the inner peripheries 30 of the members 29 and 31 are suitably hexagonal to snugly receive the screen ends, and the screen includes folds or ends indicated at 36 into slots 37, all for anchoring the screen against rotation.
The screell assembly 27 is seated in housillg recesses 38 and suitably ile.ld against movement thereill.
As sllown i.TI l::ig~lre 1 the houslllg ls Eormed wlth a bottom open:ing 41 p:re:Ee:r;lbLy coextells:ive~ly extelldi.ng the lengtll o:E the rotor~ and w:ith a coax:ia:L pol:Lshed r:i.c~ d:i.sclll:rge elld OpOII:illg ~2 that ls valved by a coaxial p.klte ~3 p:ivo~e(l ut ~ on the hOllS:i.llg allCl hav:ing Ull adjustable biasillg coullterwe:igllt 45 carried by a tllreadecl extellsioll 46. As plate 43 may rock about lts p:ivot i-t changes its d:istance relative to opening 42 in operation oE the machille as will appear to oppose the rice graln feeding pressure of screw 22 and control the time and rate of passage of rice through chamber 34. A housing outer wall 47 extends air tlght around the cage and collects the dlscharge bran and directs it to opening 41.
The shaft 15 is formed with two or more longitudinal rows of air exit openlngs 48 each row extendlng substantially coextenslve wlth the length of the rotor.
In operatlon generally brown rice to be debranned is continuously fed into the houslng through opening 20 and axlally advanced lnto the mllllng chamber 34 by the rotating screw 22. Screw 22 thus exerts a continuous pressure axially feeding the rlce through chamber 34 toward discharge opening 42. Valve disc 43 is biased toward opening 42 by a counter force dependent upon the adjusted position of weight 45, which counter force effects a pressure in opposition to that of screw 22 and tends to oppose and control axial displacement of the rice column in chamber 34. Weight 45 in operation is adjusted to position plate 43 to allow a predetermined rate of discharge of rice grains through opening 42.
The rice entering and passing through chamber 34 is peripherally confined by screen 28 and subjected to the action of rotor 23. This removes bran from the rice grain surfaces and the removed bran which is powdery is eventually discharged through opening 41 and collected. Air entering shaft opening 16 exits at openings 48 as shown by arrows in Figure 1 to pass through the rotor and thereby cool the rice being milled and to force the removed bran through screen openings 33 for collection and discharge at 41. Polished bran-free rice is continuously discharged at 42.
While for purposes of clarity of disclosure a compressed air system is shown for forcing the bran through the screen, a reversely operating suction system wherein suction is applied around the exterior of screen 28 and a filtered air admission opening provided at 47 may be employed.

The invention is here concerned with a novel method of bran removal and novel components for carrying out that method. The relative arrangement of parts is as shown in Figure 1, but the invention embodies improvements in the rotor, screen and action at chamber 34 which result in overall improvement and efEiciency o-f operation of the entire milling operation.
ROTOR
The bladed rotor assembly 23 is mounted on shaft 15. This rotor assembly comprises similar annular rectangular cross section end rings 51 and 52 that are parallel and rigidly interconnected by four identical longitudinal flat blades 53 welded at opposite ends to the respective end rings.

The number and disposition of the blades 53 is important. As shown in Figure 3 there are pre:Eerably :~:our equally spaced blades 90 apart and each blade extends outwardly substantially tangentially to the inner circular periphery 5~ of each end ring to traverse the flat inner surfaces 55 of the end rings, and projects beyond -the cylindrical envelope defined by the outer cylindrical surfaces 56 of the end rings to appear as parallel longitudinal outward projections 57 along the rotor.
In a preferred embodiment the rings 51 and 52 each have an inner cylindrical periphery about 2 3/~ inches in diameter and a radial 10 thickness of about 3/4" and about 1/2" axial thickness. The blades 53 are made of rectangular stock about 1/~" thick 1 7/8" wide and 8 l/'i" long.
The :Elnt planar inner sur:Eace of each blade indicated at 59 in Figure 3 extends fl distance o:E about 1/~l" beyolld -the cy:L:Lnclrical envelope cont~ g sur:Ences 56 ;l.lld tlle parn:L:Ie~:L p:Lullnr outer sur:Eace 60 of eacl b:lacle extellcls u d:istil.nc~) cl' of about .l./2" beyollcl tlr.lt c~nvelope.
lhe :i.nll~3r por:i.l)llc~:r;l.:l. di.~ ctt~r o:t tl~e rotor cncl rings is such tll.lt the :roto:r ussollll).ly 23 hils a snug sL:icl:illg E:lt uL)on shaEt :L5 so that the inncr corn/~:r 58 o:E ~acll b:Lacle .L:it~s substilllt:il:Lly on a sh lft di mleter.
For :I:i:E:E~rellt sha:Et diumeters the end ring inner peripheral dimensions n~ay bc-~ varied to suit but the :Eoregoing relationship is correspondingly Inaintained.
In any event when the rotor is mounted on the shaft 15 as shown in ligure 3 the flat inner face 59 of each blade defines with the outer cylindrical periphery 61 of the shaft and to some extent with the inner end of the next adjacent blade to establish an effective grain pocket indicated at 62 and in the preferred embodiment there are four of these pockets.
SCREEN
The screen inner surface defines a polygon or like shape capable of defining inwardly open pocket-like areas. The currently best known mode contour of the screen is hexagonal as shown, with the inner rice grain contacting surface 70 being desirably smooth and non-abrasive. The inner surface of the screen is of such a shape, in cross section, as not to permit mere free unimpeded rotation of the rice grain body as a whole in the chamber without relative movement of the rice grains when the rotor is turned. The inner contour of the screen is such as to allow the rice body in the chamber to continually change its effective radial thickness as the rotor acts therein.
Por use with a rotor of the dimensions given above, the screen 28 has a maximum dimensioll across :Elats of about six inches. In practice the screen may be 1 scre~ll used in prior machines, except that it .i5 preEerably :initially polish~(l smootll on its inner surface~ A screen bearing tlle usual int~rrlaL pro;jectiolls as :in prior Satake mach:ines work Eairly wcll :initiaLLy, al-l~l exl)~riellce h;ls showll that :in coaction Witil the presellt rotor th~ yiol~l oE ullL)rokcll poLisllecl gra:ins actualLy :increases as such scr~ell wear talces placc all~l th~ scre~ll b~colllcs smootll. AEter the screen becomes smootll e(luivlLellt to all in:iti,ll pol:ish little or no Eur-ther wear is obse-rve(l, an~ optimutn opcrat:ioll ensues, as compared to conventional machines that become ineEicient when the screen wears smooth.
OYER~TION
In use, brown rice is fed through housing opening 20 to be advanced by screw 22 into and through chamber 34. In order to improve the abrasive action within the chamber calcium carbonate, usually in the form of ground limestone, is mixed with the brown rice being introduced, preferably in the proportion of about 1.6% of the weight of the rice. Weighted plate 43 valves the rice discharge opening si.milarly to operation in conventional machines~ although it has been observed that less counterforce is necessary in operation of the machine of the invention.
Motor 21 may rotate shaft 15 at the same speed as in conventional machines, namely about 575-600 rpm. It has been observed _ g ~l2~9~

however that the shaft, a.nd thereEore rotor, speed may be increased greatly, up to double, and still obtain efficient debranning with a higher throughput and increased yield of unbroken polished rice. By the same token it has been noted that less power may be required to drive the rotor at the conventional machine speeds, thus obtaining the improved results of the invention using less energy and more economically.
Referring to Figure 3, the rotor 23 moves in chamber 34 counterclockwise as indicated by the arrow. Clockwise rotation has proved unsatisfactory.

As the rotor rotates the leading blade edges 71 delve vigorously into and through the surrounding grain body and debranning is accomplished using mainly :Eorces derived frolll rotor rotation and coacting with the screen wh:icll althougll 1t has no abrasive fwlction imparts dynamic movement to the gra:i.ns s~lrroullclillg the rotor. In l~ractlce i.t has beetl observed that, as tlle rotor rotates it l)icks ul) nl~(l estrlb:L:i.slles on :its pcripllery a plura.lity ol~ ere :tour, long:itlld.i.ll;llly extell(l~ g pockets ot :r:ico graills ~62 :in ligure~ 3) that ~re car:r:ied as sucll aroullcl at the sl~eed oE the rotor.
:Ct is :importlllt that the :inller :Eace 59 o:E each blade extend to provide as shown an ef:Eective L)ocket closure association w:ith the periphery 61 of the shaft. Should there be a substantial space between the inner edge of the blade and the shaft grain will discharge through that space and this will result in less efficient debranning operation~
Grains in these pockets are in direct dynamic contact with the main body of grain being fed axially through chamber 34 while that body is continually subjected to an apparently pulsating generally lateral action due to rotor Eorces and the shaped contour, here polygonal, of the retaining screen. The resultant is a dynamic interaction of grains in chamber 34 that results in complete debranning oE the grain substantially without breakage, the bran being removed from the grain essentially only by grain against grain rubbing friction. The removed bran which is about 10% by weight of the rice is discharged laterally outwardly through the screen apertures 33 due to the air pressure differential. The calcium carbonate which absorbs oil produced during abrasion of the grain is removed with the bran.
The exact theory o:E operation and pattern of rice movement is not known. What is known is that the above described bladed rotor acting within a smooth surfaced screen produces a higher yield of unbroken polished rice than in conventional machines, particularly those of the Sa-take type.
In support of a possible theory of operation observed wear patterns are noted. In conventional machines wear patterns on the surfaces of the rotor and the screen indicate that most of the abrasive debranning action takes place during passage of the grain longitudinally through the first third of chamber 3~. In the present apparatus observation shows no perceptib:le wear on the screen inntr surface, and some abrasive wear is shown Oll the b:lades 53 but only at tht :le~acl~ g edge 71 and tha.t mllinly along tllt tllir(l of tll~ :Itllgtl~ l.r tllt gl~c~ tltr~lllc~ tlld ldjlc~llt scrt~w 22.
Tll-15 SillCe thtre :is J10 re.l:ill1CC Ul)OII lbrasioll at tht screen, and -thtre a.re m1nor ilrels o:~ surflcc wear on tlle rotor, tllt uct:ive abras:ioll thclt removes the brm .is believ~cl ~o talce p.lclce~ substallt:il11y only in grain to grain rubbing :Eriction. S.ince gra:in to grain rubb:ing fr:iction is less damagillg than grain to metal .E:riction such :is probably the reason the present method and apparatus are more efficient than conventional machines. As the grain advances in chamber 3~ toward the discharge outlet ~2, the coefficient of friction of the grain surfaces reduces and these more slippery grains move to the discharge opening.
In a machine having the foregoing dimensions and operated at the conventional speeds of about 600 rpm brown rice which weighs about forty-eight pounds per cubic foot passes through the chamber 3~, which has a volume of about one cubic foot at a rate of about thirty-nine cubic feet per hour, the residence time of rice grains in the chamber being about one and one-hal-f minutes.

~2~ 7~7~
PR RTIONATE YIELD OF UNBRO~EN RICE
Pigure 5 shows a number of polished unbroken rice grains 80 produced iJI the present machine and it will be noted that each grain exhibits at one end a reduced size hook-like tip 81 that may be identified by a white scar in the region 82. T}lis scar results from processing of the grain during debranning and it represents generally the region where the ge-rm indicated in dotted lines at 83 at one of the grains has been removed.
In the conventional machines such as Satake and also in the present machine the g~rm is removed in the debranning processing and is takell off with the bran.
Pigure 6 shows a number oE debranned grains oE rice 8~ that eacll have the ti.p 81 brokell ol`E, thereby represellt:ing a consiclerable loss of size ancl weigllt oE the~ graill. 'rhis brokell grain was processed :in a Sntake type IllaCIl:in~. P:igure 7 illustr.ltes the relat:ive s:iæe of the brolcell Irnglllents Eor exclmple tips relative to the rice gra:in.
Tests h.lv~ showll that the~re :is a very much larger proportionate yield oE unbrokell graills in the cl~brallnecl rice procluced by the present metllod and apparatus than in the convelltional machines. This fact has been established by microscopically examining the polished rice and the separated bran and most accurately by counting rice Eragments that are found in the bran in the respective cases. The tips 81 that break off are usually small enough to pass through the screen apertures and appear as fragments in the collected bran. If some of the tips broken off are too large to pass through apertures in the screen they are retained and discharged with the rice grains and later extracted as by aspiration. Actually the bran collected from the conventional machines exhibits a different, more grayish color, from that produced in the present machine probably due to the presence of more of the colorless rice fragments. The bran resulting from the present machine has a smoother feel when rubbed between the fingers, as compared to that o:f conventional machines where the presence of relatively small rice fragments is sufficient to impart a granular feel.
A typical sample oE rice processed from a given batch of brown rice in a conventional commercial Satake machine exhibits an intact grain content of only about 75%. A grain count on another sample of the same batch oE brown rice processed comparably, but according to the present method, shows that 98% of the milled grains are intact, i.e., are free of bran and germ and are characterised by the presence of an intact germ seat region (thus, substantially all, that is at least 90%, desirably 95% and preferably at least about 98% o:E the milled rice grains are intact).
Milled rice produced by the present apparatus may also contain a sma:ll, signif-:icant content o:f chalky grains, i.e., up to ~1% by weig11t. 'I'his conte1lt of chaLky grai1ls, which are hig11ly Eragile, is typic~1lly up to twicc t11e COlltCllt Ol' ch1lLky gra~ s l)res~1lt in rice Ero~n t1~ ).Itc~ L~l COllV~ lt:iOll.l.l ~y.
1~or e.~ )Lc i11 a body of ricc produced by the pre~sellt apparatus COrr~`spOlldillg to .l COllVCllt:iOIICl.l packtlge s.ize we~ig1~ g at Least about 200 gra1Ds substa1ltially all oE th~L~roduct rice grains we:re unbroke1l and the germ seat reg:ion was intact.

h~AJOR ADVANI'AGES OF T11E PRESENT METHOD AND APPARATUS
l) Higher yield oE unbroken polished rice.

2) Increased efficiency of entire milling operation.

3) Reduced energy requirements during debranning.

4) Economy in debranning increased.

5) Screen life increased since no need to replace polished worn screens.

6) Faster debranning. No need to pass through different pressure machines repeatedly.

7) Rotor wear low and less critical.

8) Improved product grain.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are there:fore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of processing cereal grains for efficiently removing bran with a minimum of individual grain breakage characterised by the steps of continuously supplying dehusked grains into a chamber having an internally smooth wall confining a body of said grains against a driven rotor formed with inwardly closed pockets to retain and convey some of said grains around with it during rotation while applying force moving the grains surrounding the rotor with respect thereto, with grains carried by the rotor continually directly engaging the surrounding grains whereby all of said grains in passing through the chamber move in a changing dynamic pattern wherein they are subjected to bran removing contact with other grains with the separated bran and the processed grains being discharged from said chamber separately.

2. The method defined in claim 1 wherein the internal grain contacting surfaces of said wall are non-abrasive.

3. The method defined in claim 1, wherein a plurality of longitudinally extending pockets of grain are retained upon and rotated with said rotor.

4. The method defined in claim 1 wherein said wall is an apertured screen.

5. The method defined in claim 4 wherein the separated bran passes through said apertured screen and the processed grain are separately discharged from said chamber.

6. A method of processing rice grains for efficiently removing bran with a minimum of individual grain breakage characterised by the steps of continuously supplying brown rice into a chamber having an internally smooth wall confining a body of rice grains surrounding a driven rotor peripherally formed with inwardly closed pockets to retain and convey some of said rice grains around with it during rotation while applying force moving rice grains longitudinally of said rotor, with rice grains carried by the rotor continually directly engaging the surrounding rice grains whereby all of said rice grains in passing through the chamber move in a changing dynamic pattern wherein they are subjected to bran removing contact with other rice grains with the separated bran and the processed rice grains being discharged from said chamber separately.

7. The method defined in claim 4 wherein the internal rice grain contacting surfaces of said wall are non-abrasive.

8. The method defined in claim 4 wherein a plurality of longitudinally extending pockets of grain are retained upon and rotated with said rotor.

9. The method defined in claim 6 wherein said wall is an apertured screen.

10. The method defined in claim 9 wherein the separated bran passes through said apertured screen and the processed grains are separately discharged from said chamber.