CA1161328A - Grain milling and degerminating process - Google Patents
Grain milling and degerminating processInfo
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- CA1161328A CA1161328A CA000405872A CA405872A CA1161328A CA 1161328 A CA1161328 A CA 1161328A CA 000405872 A CA000405872 A CA 000405872A CA 405872 A CA405872 A CA 405872A CA 1161328 A CA1161328 A CA 1161328A
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- kernel
- germ
- disc
- grain
- endosperm
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Abstract
ABSTRACT OF THE DISCLOSURE
An improved degerminating process wherein the grain kernels are crushed from the thin edges toward the center while avoiding crushing of the relatively flat side surfaces. The crushing force fractures the endosperm under and around the germ and squeezes the germ away from the endosperm in a whole condition. A machine for carrying out the degermination includes relatively rotating discs having corrugations in their facing surfaces in which the kernels are caught and crushed from the thin edges toward the center. An alternative degerminator machine includes a single rotating disc having curved guide vanes on its, upper surface for guiding the kernels, as, they are propelled outwardly by centrifugal force. The vanes orient each kernel with its top or bottom edge in position to impinge upon flat impact surfaces which results in a crushing force applied from the thin edge toward the center of the kernel. Milling processes employing the improved method of degermination utilize, at the front end of the mill, rollers, with fine corrugations which are normally used only at the end of a long succession of rollers in a conventional differential milling operation.
The rollers are adjusted to minimize penetration of the germ to thereby maintain it in a whole condition and produce high quality fines that remain in the prime product streams.
An improved degerminating process wherein the grain kernels are crushed from the thin edges toward the center while avoiding crushing of the relatively flat side surfaces. The crushing force fractures the endosperm under and around the germ and squeezes the germ away from the endosperm in a whole condition. A machine for carrying out the degermination includes relatively rotating discs having corrugations in their facing surfaces in which the kernels are caught and crushed from the thin edges toward the center. An alternative degerminator machine includes a single rotating disc having curved guide vanes on its, upper surface for guiding the kernels, as, they are propelled outwardly by centrifugal force. The vanes orient each kernel with its top or bottom edge in position to impinge upon flat impact surfaces which results in a crushing force applied from the thin edge toward the center of the kernel. Milling processes employing the improved method of degermination utilize, at the front end of the mill, rollers, with fine corrugations which are normally used only at the end of a long succession of rollers in a conventional differential milling operation.
The rollers are adjusted to minimize penetration of the germ to thereby maintain it in a whole condition and produce high quality fines that remain in the prime product streams.
Description
l 161328 This invention relates to grain milling generall~, and more particularly to imp:roved milling apparatus and processes ~hich accomplish separation of the grain components in a novel manner resulting in substantial economic savings and increased ~ield. The invention also deals with an improved method and ap-paratus for degerminating grain such as corn.
Conventional milling techniques utilize a gradual reduction process wherein successive differential grinding and shifting separates the basic com-ponents of the whole kernel grain, na~el~ bran, endosperm and germ. The grain is first cleaned ~ith care being taken to maintain the grain intact. With relatively tough grains such as wheat, impact deinfestation may be utilized under proper conditions without the danger of cracking the grain. ~ith most brittle grains such as corn under most conditions, a water ~ash is normally performed to remove foreign materials ~hile protecting the grain rom damage Using prior art proc0dures, the cleaned grain is then subjected to tempering wherein water absorption magnifies the differences in grinding charac-teristics of the grain components, Finall~, the gradual reduction process sub-~ects the grain to multiple grinding and separating steps until the components have been ground to the desired size and purityO The g~ound product is dried if necessar~ to meet market specifications, cooled and graded. A typical milling process for highly purified products utilizing conventional techniques has from 50 to 60 séparate steps before the end products are reached In addition to the expense of the large number of rollers needed in the gradual reduction process, the stock must be elevated each time it is to ~e pas;sed through a~other set of rollers, thus requiring expensive conveying equlpment. Further, since tempering i5 necessary to achieve separation of the gra~n components, the components must be dried to the proper moisture content.
t 161328 Again, this increases the cost and co~plexit~ of the milling process and delays its completion. The high fat content and conse~uent lo~ quality of the "fines"
resul~lng from the conventional process neces$itates that the~ be separated and removed from the stock, which further adds to the difficulty and expense involved.
The degree of separation of germ from endosperm that is achieved wlth conventional degerminating mach~nes is; lacking some~hat and this incomplete-ness of the degermination causes manr of the problems that are encountered in the overall milling process. In the Beall degerminator, ~hich is used exten-sively in the United States, the grain kernels are rubbed more against one another than against the metal of the machlne. As a consequence, even though relatively good separation of the germ is achieved, a large quantit~ of fines ~s generated and the fines are high in at content since they contain much germ.Impact type degerminatars are used for speciflc purposes such as where finished products having high ~at c~ntent are acceptable (table meal) and where smaller granulation of the finished products is involved ~no large grits~. The impact degerminators that have been used in the past ge~erate fewer ~ines than the Beall degerminator and provide higher yields of recovered oil;
however, the separation of the germ that is achieved vith i~pact machines is poor and for this reason they have not been widely used. All degerminators that have been proposed or used in the past break the germ and the qualit~
of the product is thus reduced in comparison to products in w~ich the germ is ina whole condition.
It is a primary object of the present invention to provide a method af milllng grain which completes the milling process in a minimum number of steps and is therefore more economical than processes employing gradual differential grinding techniques.
An additional object of the inventlon la to provide an improvedmethod and apparatus for degerminating grain ~herein a high degree of separation of the germ is achieved without the germ being broken.
A still further object of the invention is to provide a method and apparatus, for degerminating grain wherein the grain kernels are crushed from the thin edges to~ard the center in a manner to pop the germ component out of the kernel in a substantiall~ whole condition.
Yet another object of the invention is to provide a degerminating apparatus of the character described which ass,ures, that crushing forces, are applied onl~ to the thin edges: and not to the relativel~ large side surfaces.
There are numerous other a~antages; and objects of the present invention which will be discus;sed or become apparent from a reading o the 20110~ing s;pecification and claims:
The invention encompas,ses a mill~ng process for grain kernels ~hich includes the s,teps, of fracturing the grain kernels into a plurality of relatively large particles and then grinding the endos,perm portion of each fractured particle while s,u~stantiall~ avoiding grinding of the germ thereby effecting s,eparation of the endosperm from the germ without substantial size reduction of the germ. The ground particles are then separated within a pres,elected ~ize range and the separated particles; are s,-ubjected to a grinding action applied in a manner to grind the endosperm while s,ubstantially avoiding grinding of thegerm thereb~ effecting s;ize reduction of the endos,perm without s,ubstantiall~
reduclng the s,ize ~f the germ. Finall~, the ground particles are sorted into a portion rich,in endosperm and a portion rich in germ and bran.
In another aspect, the invention encompasses a machine for degermi~
....
l 161328 nating a kernel o grain s,uch as corn having relatively large side surfaces andrelativel~ thin s;ide edges. The machine comprlses, a frame, a disc member sup-ported on the frame in a generall~ horizontal orientation for rotation about a subs:tantially vertical axis, and a plurality of guide vanes on the upper s,urface of the disc member for guiding the kernel generally outwardl~ thereon.
A~ impac~ surface is supported on the frame at a location outwardly of the vane and means is provided for rotating the dis,c member about its axis at a speed s,ufficient to centrifugall~ propel a kernel dis,posed on the disc mem~er out-~ardly along one of the guide vanes and against the impact surface. There is als,o means; for ori.enting the kernel s,uGh that one of its thin s:ide edges impacts agalnst the impact surface whereb~ a compressive crushing force is applied to the kernel from one edge to~ard the center to fracture the endos,perm portion away from the germ portionO
In the accompanying drawings ~hich form a part of the speciication and are to ~e read in con~unction therew,~th and in which like reference numeral~. are used to indicate like parts, of the various, views:
Pigure 1 is, a to,p plan view s,howing one of the corrugated disc mem~ers included in a degerminator machine constructed according to one em~odi-ment of the invention, with the ~roken line~, indicating that the corrugations 2Q extend along the entire s,urface of the dis,c;
F~gure 2 is a fragmentary sectional view on an enlarged scale taken generall~ along line 2-2 of Figure 1 in the direction of the arro~s, with corn kernels sho~n in broken lines;
Pigure 3 is a ~ide elevational view, partially in s,ection, showing a degerminator machine constructed according to a s,econd embodiment of the invention;
l 161328 Figure 4 is a sectional vie~ taken generall~ along line 4-4 of Pigure 3 in the direction of the arro~s;
~ igure 5 ls a diagrammatic flow: sheet of a conventional milling procesci of the type commonly employed in the prior art;
Figure 6 is, a diagrammati,c flow sheet of a milling process carried out according to one embodiment of the invention;
Pigure 7 is a diagrammatic flo~ sheet of a modified milling process carried out according to the invention;
Figure 8 is a diagrammatic flo~ sheet of another modified milling process, of the inventlon;
Pigure 9 is, a diagrammatic flow s,heet of still another modified milling process, of the invention;
Pigure 10 is a side elevational vie~ of the grain kernel s,hown in Pigure 2; and Pigure 11 is a top plan vie~of the kernel sho~n in Figure 10.
Reerring initiall~ to Pigure S w.hich depicts the conventional milling Rroces,s, des,cribed briefl~ above, it is; to be emphas,ized that the illustration of Pigure 5 forms no part of the pres;ent invention and is included herein merelr for pur,pos,esi of comparis,on to allow for a more complete understanding2Q of the pres,ent inventionO In the interes,t of brevity, the process shown in ~igure 5 ~i11 not be described in intricate detail as a complete understanding w,i,ll be readily apparent to anyone s,-killed in the art. Briefl~, ho~ever, referring to Figure 5, it is, seen that corn i~, first introduced to a cleaning station ~herein foreign materials, s,uch as stones,, sticks, sand and foreign s,eeds are removed. The grain is. then subjected to a ~ater ~a~h for removal of d~rt and other foreign materials. Next, a tempering s,tep is utilized to condition the grain ~or the s;u~sequent grinding ~perations. The tempering procedure allo~s the whole kernel grain to absorb moisture and thereby magnifies the different grinding characteristics of the grain components. Since moisture is absorbed primaril~ through the germ tip of the grain, the tempering proceture normally lasts for about one and up to several hours depending upon the end product des,ired and the age and moisture content of the grain being processed. Tempering is achieved in a single or several steps over given time periods us,ing simple water absorption or a combination of water and heat as hot water or steam.
The tempering process res,ults in a relatively highly absorptive germ and bran becoming tough and pliable as these components take on water.
On the other hand, the endosperm, which absorbs moisture much more slowly, will remain relatively unchanged although somewhat less brittle. This procedure also helps, to commence parting of the endosperm from the germ and bran components.
The next step in the conventional proces,s is to pas,s the tempered grain to a degerminator which breaks the whole kernel grain in a manner to achieve initial separation o germ, bran and endosperm. By far the mos,t w,~dely used type o degerminator is the Beall degerminator ~hich is well kno~n to those in the trade and which generall~ requires tempering of the grain to a moisture level of from 19% to 25%, depending on the degree o degermination and debranning soughtO Also used at times i9 an impact type degerminator which generates less fines although the degree of germ separation is reduced ln comparison to the Beall machine. In anr case, the design of the degerminator is; such that the germ is intended to be broken out from the endosperm to the extent pos,sI~le without excessivel~ grinding the,germ component. Consideration i~ given to bran removal in this step depending on the final use of the end product. The goal of the degerminator, namelr to remove the germ without --6--, l 161328 grinding it undul~, is not actuall~ reached with existing degerminators, and an additional problem is that lo~ ~ualit~ fines are produced which must be removed prior to further processing of the stock.
~ enerall~ the product out of the degerminator is separated into "tail" and "thru" streams, the former being relativelr rich in endosperm and the latter being relativel~ rich in germ and bran. The two streams are then dried and cooled to reduce the moisture content to approximately 17%. Prior to commencing the grinding steps, the t~o degerminator streams are preferably placed on gravit~ tables (or aspirators) as indicated in the flo~ diagram to achieve some further initial sorting out of germ and endosperm.
The roll grinders in the conventional milling process are set up in two series as indicated in the drawing. One series is or the endosperm rich streams and the other series is ~or the germ rich streams. In the drawing, the various sets of roller mills are indicated diagrammaticallr and given the conventional designation of break ~"brk") rollers and germ rollers.
The concept utilized in each series of roller mills in the conventional milling process is to match particle size with individual roller mill characteris-tics. Thus, relatively large particles; from the gravity tables ~or aspirators) are dlrected to the first break and germ rollers respectively, according to particle size classification. These first rollers are characterized by relativel~ large corrugations with inherent coarse grinding characteristics.
The smaller particles from the gravit~ tables are directed according to the ~uccess;ivelr finer series of rollersO Por example, the stock going to thè
number one break roll mar be that pass;ing through a sieve with 3~ wires per inch and over one with 5 ~ires: per inch. The roller corrugation used for this stock is 6 per ~nch. Next, stock passing through a 5 wires per inch mesh but l 161328 pass,ing over one with 8 per inch is; pass~ed to a ~reak roll with 8 corrugations per inch of roll circumferenceO The procedure is continued up to rolls with 20-24 corrugations per inch.
In general, rollers, grinding the s,treams rich in endosperm have a higher roll speed differential than those grinding the germ rich streams, the reason being that the relativel~ ragile germ requires the gentler treatment afforded b~ a lo~er roll speed differentialO This is the reason that two series of roller mills are employed.
Because of the different grinding characteristics of the components, as dis,cuss,ed above, the roller mills, in each series, ~ill proceed to reduce the size of the endos,perm relative to the s,ize of the germ and bran. The mill s,tock that does not meet final product s,~eciication ~excepting moisture) is, continuously reclass,ified by size, as,pirated to remove bran, and then passed to ~che next roller mi,ll which is set up to receive the stock according to its primar~ component and particle size. The proce~s is repeated over and over until the desired separating and sorting is accomplished.
The final steps in the conventional milling process are to dry the milled grain to a maximum moisture content of approximately 12% or to market-ing and ~nd use specifications, cool it, and aspirate off any remaining bran.
The end product is then graded according to size into various component products.
h~th a vi~ to unders,tanding the present invention, reference is f~rst of all made to Pigures 10 and~ here it is seen that a corn kernel is de~ignated b,y the numeral 20 and has a germ portion 20a that is surrounded by an endosperm portion 20b. Pigure 11 shows, in full one o the relatively large 1at s;ide suraces, o the kernel ~hich has been designated by the D eral 21.
A s,econd large flat side surface (not s,hown) is opposite and parallel surface 21.
-8~
l 161328 The two side surfaces 21 are separated ~ relatlvel~ thin side edges 23a, 23b and 23co Side edge 23a extends the length of the kernel on opposite sides (only one side being visible in Pigure 10). The top side edge is designated 23b and the bottom side edge or tip is designated 23c Manifestly, the width of the side edges is equal to the thickness of the grain kernel.
~ ith reference now to Pigures 1 and 2, one embodiment of an improved degerminator 10 is shown, which is constructed to crush the grain from its thin edges toward the center area of the kernel. The compressive force accompanying this crushing action fractures the endosperm under and around the germ to release it in a manner providing approximatel~ 95% separation from the endosperm while maintaining the germ in a substantiall~ whole condition.
The degerminator machine 10 includes a stationar~ upper metal disc 12 and a lower disc 14 whlch is mounted on a vertical shaft 16. The shaft may be driven by any type of drive system (not shown~ in order to rotate the lower disc 14 re~ative to the stationary upper disc 12. The discs are parallel to one another in horizontal planes, and their facing surfaces a~e spaced apart in a manner that will be more full~ explained.
The stationary upper ~isc 12 has a central opening 18 through which the grain is introduced to the area between the discs. Each disc 12 and 14 is provided ~ith a plurality-of radiall~ extending corrugations 12a and 14a, respectivel~. The corrugations 12a and 14a extend over the entire facing surfaces of the discs. As shown in Figure 1, the corrugations are greater in number on the outer portion of the discs than on the inner portions to accommodate the larger surface areas of the outer disc portion50 Referring to ~igure 2 particularl~, corrugations 12a and 14a are incllned and are sized so that a corn kernel 20 in an inclined orientation can l 161328 fit with Qne of its thin s,-ide edge~ 23a ~n the groove of an upper corrugation 12a and w~th the oppos,ite s-ide edge 23a of the kernel located in the groove of a lower corrugation 14a ~see the kernel ~n the right portion ~f Pigure 2). ~owever, when the grooves of the corrugations are located directl~ above one another, they are spaced apart a dis,tance less than the width of kernel 20 bet~een its opposite side edges, 23a. The respective peaks and valleys of each corrugation are rounded to avoid piercing the kernel at the point of contact. The ridges o corrugations, 12a and 14a are vertically spaced apart a distance at least as great as, the thickness of kernel 20 ~et~een its xelativel~ large opposite s,ide s,urfaces 21. Prefera~ly, the pitch of each corrugation 12a and 14a is about the width of the kernel (or slightl~ longer), and the depth of each corrugation is approximately e~ual to the thicknes;s of the kernel. The corrugations are smoothly rounded on their ridges and grooves to avoid presenting sharp edges or corners that might cut the grain.
In operation, grain is introduced between discs 12 and 14 through opening 18, and shaft 16 is rotated to rotate disc 14 relative to disc 12 in the direction indicated by the directional arrow- in Pigure 2~ When a kernel positioned ~,etween the discs, is orlented with its large flat sides 21 facing up and do~n (as s,hown for the kernel in the left hand portion of Pigure 2), the kernel pass-es freel~ bet~een the ridges of corrugations 12a and 14a and no crushing occurs. Ho~ever, when the kernel is displaced in any fashion from this orientation, the thin opposite side edges 23a or 23b and 23c of the kernel catch in the grooves of opposed corrugations, 12a and 14a. This is the position of the kernel shown in the right hand portion of Pigure 2.
Continued motion of dis,c 14 relatlve to dis,c 12 su~jects the kernel caught b,etw:een the corrugations: to a compressive crushing force that is applied l 161328 from the thin oppos;ite s,ide edges of the kernel to~ard the center. The magnitude of this crush~ng force is: su~ficient to fracture the endosperm under and around the germ 20a to thereb,~ s,~ueeze or pop the germ 20a out of the side of the kernel in a s-uhstantially whole, undamaged condi,tion. The crushing action terminates when the corrugations move past one another. Since the released germ 20a is small enough to pass freely between the ridges of the corrugations, it is not crushed and is carried outwardl~ b~ centrifugal force along with the fragments of the endosperm resulting from the crushing action. The fines result-ing from the degermination contain very little ge~m since the germ is maintained whole.
The grain ma~ be tempered prior to the degermination, although tempering is not es~sential. The amount of whole and relatively undamaged germ that is released and the exten~'to which the germ and endosperm are separated is a function of a number of factGrs., including the moisture content of the ~crm, the type and condition o the corn, the configuration of the corrugations 12a and 14a, or combinations of these and other factors.
Exemplifying the improved results obtained by the degerminating method of this invention, it has been found that midwestern hybrid corn of about 12% moisture and average condition and age yields approximately 85% whole germ and slightly more than 95% separation of germ and endosperm. Tempering the same type of corn to about 17% moisture content for about 3 hours increases the yield to about 95% ~hole germ and about 97% complete separation of germ and endos,perm. The degerminator fines that will pass through a 16 mesh screen var~ in quantity from a high of ab,out 20% of the corn degerminated to a low of a'~out 10%, and from a fat content of ab,out 1% to about 5%, depending on the tempering proces:s, the moisture content of the germ and endosperm, the kind of l 161328 corn, the condition and age of the corn, the relative speed of rota~ion of discs 12 and 14, the spacIng bet~een the discs, the configuration and arrangement of the corrugations, and the condition of the disc surfaces.
Although the degerminator machine 10 is similar in construction to a conventional attrition mill, its operational characteristics differ considerably.
The main difference is that the discs; 12 and 14 are carefully spaced and the corrugations are arranged to achieve only a crushing effect on the kernel which is; applied ~nly- from the opposite thin edges in~ardlr to~ard the center, in contrast to the grinding and cutting action of an attrition mill. Since discs 12 and 14 are spaced apart such that a kernel oriented with its flat sides parallel to the planes of the discs passes freely between the ridges of the cor-rugations, the machine avoids crushing the kernels from the relatively large flat sides thereof, thus assuring that the crushing occurs only at the thin edges in a manner to squeeze the germ free of the endosperm.
Referring now to Pigures 3 and 4, a degerminator constructed in ac-cordance with a second embodiment of the invention is generally designated by numeral 22. Degerminator 22 applies a crushing force similar to that applied by degerminator 10, although in the case of degerminator 22, the force is applied rom only one of the thin edges of the kernel toward the center.
The degerminator 22 includes an upright wall 24 having a generally c~lindrical shape and surmounted b~ a frustoconical roof portion 26. A
vertical tube 28 extends through roo 26 and is hollo~ in order to receive and d~rect grain into the machine. The lo~er end of tube 28 is open and is located centrallr above a horizontal disc 30, Disc 30 is rigidly mounted on top of a vertical shat 32 ~hich may be rotated by any suitable drive system ~not shown).
A pluralitr of spaced apart guide vanes 34 are located on the upper l 161328 s,urface of disc 3Q. Each vane 34 extends, outwardl~ along the disc from tube 28 to the peripher~ of the disc. Vanes; 34 are curved members each having a sharpll~ curving outer end portion which approaches a tangent line at the edge of the disc.
The inside surface of ~all 2~ is, located outwardl~ of the periphery of disc 30 a dis,tance less- than the thicknes,s of a grain kernel. The inside surface of the ~all is formed in a manner to present a plurality of flat linear surfaces 24a against which the corn kernels impact when propelled outwardl~
off of disc 30. Each impact surface 24a is; oriented such that a kernel propelled off of the peripher~ of disc 30 and moving in a direction generallr tangent to the dis,c impacts against surface 24a at a right angle. Surfaces 24b of wall 24 extend bet~een each adjacent pair of impact surfaces 24a to assist in directing the grain kernels against surfaces 24a at substantially a right angle.In operatlon, grain is introduced throug~ the ~ube 28 and onto the upper surace of disc 30. The disc is rotated at a rate of speed high enough to propel the grain outwardly thereon b~ centrifugal force. As it moves out-w æ dly, the grain is guided along the curved leading suraces o the guide vanes 34 until the grain is eventually propelled off of the edge of the disc against the impact surfaces 24a~
The guide vanes are constructed to orient the grain such that one of the thin top or bottom edges of each kernel impacts against surface 24a, there~ appl~ing a compressive crushing orce to the grain from the thin edge to~ard the center and not at one of the relatively large side surfaces of the kernel. As each kernel is propelled outw.ardly along vane 34, it may be orientedeither with one of its large flat sides; agains;t the vane or with one of its thin ~ide edges against the vane. In elther case, the top or bottom edge o the kernel l 161328 ~ill be on it$ leading portion in the direction o motion at the time it ~eaves the disc, b~ vlrtue of the sharpl~ curving shape of the outer portions of vanes 34. Consequentl~, the thin top or bottom edge of the kernel impinges on surface24a and a crushing force is thereb~ applied from the edge to~ard the center. Inthis manner, vanes 34 orient the kernel so that only thin edges engage surfaces 24a, and the crushing force is not applied to the flat sides as would sometimes occur ~ith straight radlal vanes.
The crushing force applied on the edge of the kernel toward the center s,quee~es the germ out from the endosperm in a substantiall~ ~hole condition. Due to the space bet~een wall 24 and dis,c 30, only the fragments of broken kernels can pass, betw.een the wall and the edge of the disc for further processing. Un-b,roken kernels, are too large to fall bet~een the wall and disc and ma~ be recirculated through the machine, It is to be understood th~t variou5, additional types o machines ma~ be employed to carr~ out the degerminating method of this invention. How-ever, the machines 10 and 22 are preferred slnce they effectively apply crushingorces to the s,ide edges of the gra~n while avoiding the application of crushing forces; to the relatively large side surfacés, In addltion to the effectiveness of the germ separation, the process of this; invention separates the bran from the endosperm with excellent results.A~ the moisture content of the bran increas,es, its separation becomes more comRlete. It has been found that if dr~ corn of about 14% moisture is tempered or 4 to 8 minutes with addition o water o about 2% to 8% by weight of the corn,"90% to 98% of the bran is removed b~ the degerminating process as a resultof the crushing fcrces applied to the cornO The degree of debranning is affectedb,~ the kind and condition of the corn, the amount of water and heat added and the length of time held, the speed of the discs, and the coniguration of cor-rugations, 12a and 14a or the shape o vanes 34. Since on a practical level only the ~ran is tempered and not the remalnder of the corn, drying is simpliPied because only the bran needs to ~,e s,orted out by screens and/or as,piration and sent to dryers. Conventional methods of debranning require tempering of the germ ~lso and/or separate equipment to perform this function.
In carrying out the method of the present invention, the po~er requirements are about 2~ HP per hour per ton of corn, as compared with requirements of conventional processes of from 15 to 25 HP per hour per ton of corn for degerming and de~,ranning, Another important result obtained by the degerminating process of this invention is the relativel~ high ~uality of the degerminator fines which, as, previously indicated, have a fat content of about 1% to 5%. In comparison, the ines generated in conventional degerminating processes are so high in fat that they are either sold as, a low value ~yproduct animal feed or are reproces-sed to upgrade their quality, Such reprocessing involves the use of sifters, aspirators, gravity tables, purifiers or various combinations of these and other costly devices. Upgrading the quality of the fines with such devices allows the fines to move into industrial uses or other markets where they yleld a higher price than animal feed but a lo~er price than prime products from the mill. In addition, separation of the fines from the prime product is costly and time consuming.
The pres-ent invention also provides improved grain milling processes w,hich are illus,trated in flow sheet form in ~igures 6-9, The ~hole grain or a ma~or part oP it ma~ be tempered in some oP the processes, although temper~ng i,s~not alwa~s required if the prePerred degerminating process described above ~s -15~`
used, due to the high degree of deger~ina~lon and the high qualit~ of the fines.
The particular process that ma~ be employed to the best advantage in each set of circumstances depends upon a variet~ of factors, including the end products desired, the type and condition of the grain, and economic considerations such a~ operating costs and marketing objectives.
Referring first to Figure 6, the process sho~n therein involves cleaning of the corn followed by a prebreaking in a prebreak mill. The prebreak mill ma~ be an~ suitable type that breaks the grain by subjecting it to a crushing action that breaks the endosperm while preferabl~ although not necessaril~
maintaining a substantial amount of the ge~m in a whole condition. The grain should be broken along the germ so the germ is exposed. The crushing action should fracture the grain into at least four and preferably six or more major pieces, The germ should be separated ~rom the endosperm to as great an extent a~ possible because the fat content of the finished products is reduced as the degree of separation increases. The actual degree of separation of the germ and the extent to which the germ remains whole depend upon the particular prebreaking process utilized and the end product desiredO
Tempering of the ~rain may be carried out in advance of the prebreak or after the prebreak, or bothO Tempering before the prebreak better controls the germ separation. ~or example, corn havlng a moisture content of 15% to 20%
~ ~eight w~ll, when broken, provide better release of the germ with a cor~
responding reduction in fines and fat content than corn having a moisture content below about 15%. The tempering can be carried out using known techniques.
Tempering after prebreaking may be carried out if the moisture content of the germ and bran was: not ad~usted b~ a tempering step prior to prebreak, or if additional moisture ad~ustment ~s neces~sary or desired after ~ 161328 prebreak. The moisture content of the germ and bran prior to passage of the stock to the first roller mill should be a~out 15% to 35% b~ ~eight. Tempering after prebreak results in an appreciable shortening of the tempering tîme because the prebréaking exposes the germ and bran. Tempering can be as short as 2 ~inute~ if heat is used and in no case ~ill it exceed about 30 minutes when performed subsequent to prebreak.
Although a main advantage of the proces,s of this invention is that it avoids, the need to remove fines prlor to milling, it ma~ be desirable in s,ome instances to remove the fines; after prebreak and before milling in order 1~ to reduce the water requirements for the tempering step. This can be done in a sifter which sifts the stock after prebreak and before tempering if tempering occurs only after prebreak. The fines are then separated and returned to the stock after it has been tempered and passed through the first set of break rolls if this is desirable to simpliy the flow.
The près,ent invention departs from the technique of the conventional grain milling process which, as pr~viously indicated, attempts to match particle size with individual roller mill characteristics~ In the conventional gradual reduction process, the particles are first passed through roller mills having relativel~ large corrugations and then to successive additional roller mills 2Q having increasingl~ finer corrugations. It has heretofore been thought that an~ attempt to utilize rollers having fine corrugations at the front end of the mill ~ould result in smashing of the grain kernels which would make ultimate ~eparation of germ, bran and endosperm exceedingl~ difficult.
Instead of passing the grain through a long succession of rollers as is done in the conventional prGcess, gri,nding is accomplished in the present invention b~ passing the broken grain directl~ to ine rollers of the type that l 161328 no mall~ characterize onl~ the end of a dierential milling process.
rn accordance ~ith the inventlon, the prebreaking and tempering steps are effected, and the grain is then passed through a first set of break rolls which may be of the modified Dawson type having 20 corrugations per inch and a spiral of about ~ inch per linear oot. The rollers are arranged dull to dull and have a differential roll speed of 2 to 1. The first break roller mill is adjusted ~o that at least approximatelr 50% of the product through is small enough to pass through a United States #12 sieve. The spacing bet~een the rollers is $ufficient to substantiall~ prevent appreciable penetration of the roller corrugations inta the germ, thereb~ avoiding size reduction of the germ in contrast to the conventional practice of placing fine rollers closer together in accordance with the fine particles being processed. Those particles from the prebreak mill, ~ith the exception o the "fines", are large enough sa that the~ are sub~ected to a grinding action when passed between the rollers o~ the ~irst break mill and those of the second break mill.
Due to the fineness of the roller corrugations and their spacing, the endosperm is severely and abruptly ground up and thereby separated from the germ and bran without resulting in the germ being fractured excessivel~. The prQduct from the first break rolls, together with the fines if they have been removed prior to temper, is shifted through a United States #8 sieve and a United States #12 sieve. The relatively large size particles over the #8 ~ieve are primaril~ germ and bran and may be directed to feed or oil recover~
or to further processing as described below. The portion passing through the #}2 screen is less than 1% in fat content, and it is therefore passed to finished praduct. Particlesi through the #8 screen but over the #12 screen are principally endosperm, although there is; enough germ present that this portion is not market--18_ able as a pri~e product. This portion i~ passed to a second set of break rolls which effect further size reduction of the endosperm and ~hich further separate the endosperm from the germ and bran components.
The rollers of the second break mill have corrugations of the same size as the first set or slightl~ smaller, and the spacing between the rolls is again sufficient to avoid excessive penetration of the germ. The differential speed of the rollers in the second break mill ma~ be reduced to about 1.75 to 1. After passing through the second set of break rolls, the product is sifted through a #14 wire. The particles over the ~ire are rich in germ and bran and go to animal feed or oil recover~. The s-tock passing through the wire is rich ln endosperm and goes to finished product along with the endosperm rich stock rom the first break mill. The endosperm rich stream is dried and cooled if necessaryi and is inally passed to a grading station where grits and meal are Braded according to a size and any remaining bran is removed by aspiration.
The free germ ma~ be removed prior to the first break rolls by utilizing gravit~ tablesO This optional step lowers the fat content of the throughs from the sifter wires, and it aids in making the milling process superior to conventional processes both in quality and product yield.
Although the specific operating parameters for the process depend
Conventional milling techniques utilize a gradual reduction process wherein successive differential grinding and shifting separates the basic com-ponents of the whole kernel grain, na~el~ bran, endosperm and germ. The grain is first cleaned ~ith care being taken to maintain the grain intact. With relatively tough grains such as wheat, impact deinfestation may be utilized under proper conditions without the danger of cracking the grain. ~ith most brittle grains such as corn under most conditions, a water ~ash is normally performed to remove foreign materials ~hile protecting the grain rom damage Using prior art proc0dures, the cleaned grain is then subjected to tempering wherein water absorption magnifies the differences in grinding charac-teristics of the grain components, Finall~, the gradual reduction process sub-~ects the grain to multiple grinding and separating steps until the components have been ground to the desired size and purityO The g~ound product is dried if necessar~ to meet market specifications, cooled and graded. A typical milling process for highly purified products utilizing conventional techniques has from 50 to 60 séparate steps before the end products are reached In addition to the expense of the large number of rollers needed in the gradual reduction process, the stock must be elevated each time it is to ~e pas;sed through a~other set of rollers, thus requiring expensive conveying equlpment. Further, since tempering i5 necessary to achieve separation of the gra~n components, the components must be dried to the proper moisture content.
t 161328 Again, this increases the cost and co~plexit~ of the milling process and delays its completion. The high fat content and conse~uent lo~ quality of the "fines"
resul~lng from the conventional process neces$itates that the~ be separated and removed from the stock, which further adds to the difficulty and expense involved.
The degree of separation of germ from endosperm that is achieved wlth conventional degerminating mach~nes is; lacking some~hat and this incomplete-ness of the degermination causes manr of the problems that are encountered in the overall milling process. In the Beall degerminator, ~hich is used exten-sively in the United States, the grain kernels are rubbed more against one another than against the metal of the machlne. As a consequence, even though relatively good separation of the germ is achieved, a large quantit~ of fines ~s generated and the fines are high in at content since they contain much germ.Impact type degerminatars are used for speciflc purposes such as where finished products having high ~at c~ntent are acceptable (table meal) and where smaller granulation of the finished products is involved ~no large grits~. The impact degerminators that have been used in the past ge~erate fewer ~ines than the Beall degerminator and provide higher yields of recovered oil;
however, the separation of the germ that is achieved vith i~pact machines is poor and for this reason they have not been widely used. All degerminators that have been proposed or used in the past break the germ and the qualit~
of the product is thus reduced in comparison to products in w~ich the germ is ina whole condition.
It is a primary object of the present invention to provide a method af milllng grain which completes the milling process in a minimum number of steps and is therefore more economical than processes employing gradual differential grinding techniques.
An additional object of the inventlon la to provide an improvedmethod and apparatus for degerminating grain ~herein a high degree of separation of the germ is achieved without the germ being broken.
A still further object of the invention is to provide a method and apparatus, for degerminating grain wherein the grain kernels are crushed from the thin edges to~ard the center in a manner to pop the germ component out of the kernel in a substantiall~ whole condition.
Yet another object of the invention is to provide a degerminating apparatus of the character described which ass,ures, that crushing forces, are applied onl~ to the thin edges: and not to the relativel~ large side surfaces.
There are numerous other a~antages; and objects of the present invention which will be discus;sed or become apparent from a reading o the 20110~ing s;pecification and claims:
The invention encompas,ses a mill~ng process for grain kernels ~hich includes the s,teps, of fracturing the grain kernels into a plurality of relatively large particles and then grinding the endos,perm portion of each fractured particle while s,u~stantiall~ avoiding grinding of the germ thereby effecting s,eparation of the endosperm from the germ without substantial size reduction of the germ. The ground particles are then separated within a pres,elected ~ize range and the separated particles; are s,-ubjected to a grinding action applied in a manner to grind the endosperm while s,ubstantially avoiding grinding of thegerm thereb~ effecting s;ize reduction of the endos,perm without s,ubstantiall~
reduclng the s,ize ~f the germ. Finall~, the ground particles are sorted into a portion rich,in endosperm and a portion rich in germ and bran.
In another aspect, the invention encompasses a machine for degermi~
....
l 161328 nating a kernel o grain s,uch as corn having relatively large side surfaces andrelativel~ thin s;ide edges. The machine comprlses, a frame, a disc member sup-ported on the frame in a generall~ horizontal orientation for rotation about a subs:tantially vertical axis, and a plurality of guide vanes on the upper s,urface of the disc member for guiding the kernel generally outwardl~ thereon.
A~ impac~ surface is supported on the frame at a location outwardly of the vane and means is provided for rotating the dis,c member about its axis at a speed s,ufficient to centrifugall~ propel a kernel dis,posed on the disc mem~er out-~ardly along one of the guide vanes and against the impact surface. There is als,o means; for ori.enting the kernel s,uGh that one of its thin s:ide edges impacts agalnst the impact surface whereb~ a compressive crushing force is applied to the kernel from one edge to~ard the center to fracture the endos,perm portion away from the germ portionO
In the accompanying drawings ~hich form a part of the speciication and are to ~e read in con~unction therew,~th and in which like reference numeral~. are used to indicate like parts, of the various, views:
Pigure 1 is, a to,p plan view s,howing one of the corrugated disc mem~ers included in a degerminator machine constructed according to one em~odi-ment of the invention, with the ~roken line~, indicating that the corrugations 2Q extend along the entire s,urface of the dis,c;
F~gure 2 is a fragmentary sectional view on an enlarged scale taken generall~ along line 2-2 of Figure 1 in the direction of the arro~s, with corn kernels sho~n in broken lines;
Pigure 3 is a ~ide elevational view, partially in s,ection, showing a degerminator machine constructed according to a s,econd embodiment of the invention;
l 161328 Figure 4 is a sectional vie~ taken generall~ along line 4-4 of Pigure 3 in the direction of the arro~s;
~ igure 5 ls a diagrammatic flow: sheet of a conventional milling procesci of the type commonly employed in the prior art;
Figure 6 is, a diagrammati,c flow sheet of a milling process carried out according to one embodiment of the invention;
Pigure 7 is a diagrammatic flo~ sheet of a modified milling process carried out according to the invention;
Figure 8 is a diagrammatic flo~ sheet of another modified milling process, of the inventlon;
Pigure 9 is, a diagrammatic flow s,heet of still another modified milling process, of the invention;
Pigure 10 is a side elevational vie~ of the grain kernel s,hown in Pigure 2; and Pigure 11 is a top plan vie~of the kernel sho~n in Figure 10.
Reerring initiall~ to Pigure S w.hich depicts the conventional milling Rroces,s, des,cribed briefl~ above, it is; to be emphas,ized that the illustration of Pigure 5 forms no part of the pres;ent invention and is included herein merelr for pur,pos,esi of comparis,on to allow for a more complete understanding2Q of the pres,ent inventionO In the interes,t of brevity, the process shown in ~igure 5 ~i11 not be described in intricate detail as a complete understanding w,i,ll be readily apparent to anyone s,-killed in the art. Briefl~, ho~ever, referring to Figure 5, it is, seen that corn i~, first introduced to a cleaning station ~herein foreign materials, s,uch as stones,, sticks, sand and foreign s,eeds are removed. The grain is. then subjected to a ~ater ~a~h for removal of d~rt and other foreign materials. Next, a tempering s,tep is utilized to condition the grain ~or the s;u~sequent grinding ~perations. The tempering procedure allo~s the whole kernel grain to absorb moisture and thereby magnifies the different grinding characteristics of the grain components. Since moisture is absorbed primaril~ through the germ tip of the grain, the tempering proceture normally lasts for about one and up to several hours depending upon the end product des,ired and the age and moisture content of the grain being processed. Tempering is achieved in a single or several steps over given time periods us,ing simple water absorption or a combination of water and heat as hot water or steam.
The tempering process res,ults in a relatively highly absorptive germ and bran becoming tough and pliable as these components take on water.
On the other hand, the endosperm, which absorbs moisture much more slowly, will remain relatively unchanged although somewhat less brittle. This procedure also helps, to commence parting of the endosperm from the germ and bran components.
The next step in the conventional proces,s is to pas,s the tempered grain to a degerminator which breaks the whole kernel grain in a manner to achieve initial separation o germ, bran and endosperm. By far the mos,t w,~dely used type o degerminator is the Beall degerminator ~hich is well kno~n to those in the trade and which generall~ requires tempering of the grain to a moisture level of from 19% to 25%, depending on the degree o degermination and debranning soughtO Also used at times i9 an impact type degerminator which generates less fines although the degree of germ separation is reduced ln comparison to the Beall machine. In anr case, the design of the degerminator is; such that the germ is intended to be broken out from the endosperm to the extent pos,sI~le without excessivel~ grinding the,germ component. Consideration i~ given to bran removal in this step depending on the final use of the end product. The goal of the degerminator, namelr to remove the germ without --6--, l 161328 grinding it undul~, is not actuall~ reached with existing degerminators, and an additional problem is that lo~ ~ualit~ fines are produced which must be removed prior to further processing of the stock.
~ enerall~ the product out of the degerminator is separated into "tail" and "thru" streams, the former being relativelr rich in endosperm and the latter being relativel~ rich in germ and bran. The two streams are then dried and cooled to reduce the moisture content to approximately 17%. Prior to commencing the grinding steps, the t~o degerminator streams are preferably placed on gravit~ tables (or aspirators) as indicated in the flo~ diagram to achieve some further initial sorting out of germ and endosperm.
The roll grinders in the conventional milling process are set up in two series as indicated in the drawing. One series is or the endosperm rich streams and the other series is ~or the germ rich streams. In the drawing, the various sets of roller mills are indicated diagrammaticallr and given the conventional designation of break ~"brk") rollers and germ rollers.
The concept utilized in each series of roller mills in the conventional milling process is to match particle size with individual roller mill characteris-tics. Thus, relatively large particles; from the gravity tables ~or aspirators) are dlrected to the first break and germ rollers respectively, according to particle size classification. These first rollers are characterized by relativel~ large corrugations with inherent coarse grinding characteristics.
The smaller particles from the gravit~ tables are directed according to the ~uccess;ivelr finer series of rollersO Por example, the stock going to thè
number one break roll mar be that pass;ing through a sieve with 3~ wires per inch and over one with 5 ~ires: per inch. The roller corrugation used for this stock is 6 per ~nch. Next, stock passing through a 5 wires per inch mesh but l 161328 pass,ing over one with 8 per inch is; pass~ed to a ~reak roll with 8 corrugations per inch of roll circumferenceO The procedure is continued up to rolls with 20-24 corrugations per inch.
In general, rollers, grinding the s,treams rich in endosperm have a higher roll speed differential than those grinding the germ rich streams, the reason being that the relativel~ ragile germ requires the gentler treatment afforded b~ a lo~er roll speed differentialO This is the reason that two series of roller mills are employed.
Because of the different grinding characteristics of the components, as dis,cuss,ed above, the roller mills, in each series, ~ill proceed to reduce the size of the endos,perm relative to the s,ize of the germ and bran. The mill s,tock that does not meet final product s,~eciication ~excepting moisture) is, continuously reclass,ified by size, as,pirated to remove bran, and then passed to ~che next roller mi,ll which is set up to receive the stock according to its primar~ component and particle size. The proce~s is repeated over and over until the desired separating and sorting is accomplished.
The final steps in the conventional milling process are to dry the milled grain to a maximum moisture content of approximately 12% or to market-ing and ~nd use specifications, cool it, and aspirate off any remaining bran.
The end product is then graded according to size into various component products.
h~th a vi~ to unders,tanding the present invention, reference is f~rst of all made to Pigures 10 and~ here it is seen that a corn kernel is de~ignated b,y the numeral 20 and has a germ portion 20a that is surrounded by an endosperm portion 20b. Pigure 11 shows, in full one o the relatively large 1at s;ide suraces, o the kernel ~hich has been designated by the D eral 21.
A s,econd large flat side surface (not s,hown) is opposite and parallel surface 21.
-8~
l 161328 The two side surfaces 21 are separated ~ relatlvel~ thin side edges 23a, 23b and 23co Side edge 23a extends the length of the kernel on opposite sides (only one side being visible in Pigure 10). The top side edge is designated 23b and the bottom side edge or tip is designated 23c Manifestly, the width of the side edges is equal to the thickness of the grain kernel.
~ ith reference now to Pigures 1 and 2, one embodiment of an improved degerminator 10 is shown, which is constructed to crush the grain from its thin edges toward the center area of the kernel. The compressive force accompanying this crushing action fractures the endosperm under and around the germ to release it in a manner providing approximatel~ 95% separation from the endosperm while maintaining the germ in a substantiall~ whole condition.
The degerminator machine 10 includes a stationar~ upper metal disc 12 and a lower disc 14 whlch is mounted on a vertical shaft 16. The shaft may be driven by any type of drive system (not shown~ in order to rotate the lower disc 14 re~ative to the stationary upper disc 12. The discs are parallel to one another in horizontal planes, and their facing surfaces a~e spaced apart in a manner that will be more full~ explained.
The stationary upper ~isc 12 has a central opening 18 through which the grain is introduced to the area between the discs. Each disc 12 and 14 is provided ~ith a plurality-of radiall~ extending corrugations 12a and 14a, respectivel~. The corrugations 12a and 14a extend over the entire facing surfaces of the discs. As shown in Figure 1, the corrugations are greater in number on the outer portion of the discs than on the inner portions to accommodate the larger surface areas of the outer disc portion50 Referring to ~igure 2 particularl~, corrugations 12a and 14a are incllned and are sized so that a corn kernel 20 in an inclined orientation can l 161328 fit with Qne of its thin s,-ide edge~ 23a ~n the groove of an upper corrugation 12a and w~th the oppos,ite s-ide edge 23a of the kernel located in the groove of a lower corrugation 14a ~see the kernel ~n the right portion ~f Pigure 2). ~owever, when the grooves of the corrugations are located directl~ above one another, they are spaced apart a dis,tance less than the width of kernel 20 bet~een its opposite side edges, 23a. The respective peaks and valleys of each corrugation are rounded to avoid piercing the kernel at the point of contact. The ridges o corrugations, 12a and 14a are vertically spaced apart a distance at least as great as, the thickness of kernel 20 ~et~een its xelativel~ large opposite s,ide s,urfaces 21. Prefera~ly, the pitch of each corrugation 12a and 14a is about the width of the kernel (or slightl~ longer), and the depth of each corrugation is approximately e~ual to the thicknes;s of the kernel. The corrugations are smoothly rounded on their ridges and grooves to avoid presenting sharp edges or corners that might cut the grain.
In operation, grain is introduced between discs 12 and 14 through opening 18, and shaft 16 is rotated to rotate disc 14 relative to disc 12 in the direction indicated by the directional arrow- in Pigure 2~ When a kernel positioned ~,etween the discs, is orlented with its large flat sides 21 facing up and do~n (as s,hown for the kernel in the left hand portion of Pigure 2), the kernel pass-es freel~ bet~een the ridges of corrugations 12a and 14a and no crushing occurs. Ho~ever, when the kernel is displaced in any fashion from this orientation, the thin opposite side edges 23a or 23b and 23c of the kernel catch in the grooves of opposed corrugations, 12a and 14a. This is the position of the kernel shown in the right hand portion of Pigure 2.
Continued motion of dis,c 14 relatlve to dis,c 12 su~jects the kernel caught b,etw:een the corrugations: to a compressive crushing force that is applied l 161328 from the thin oppos;ite s,ide edges of the kernel to~ard the center. The magnitude of this crush~ng force is: su~ficient to fracture the endosperm under and around the germ 20a to thereb,~ s,~ueeze or pop the germ 20a out of the side of the kernel in a s-uhstantially whole, undamaged condi,tion. The crushing action terminates when the corrugations move past one another. Since the released germ 20a is small enough to pass freely between the ridges of the corrugations, it is not crushed and is carried outwardl~ b~ centrifugal force along with the fragments of the endosperm resulting from the crushing action. The fines result-ing from the degermination contain very little ge~m since the germ is maintained whole.
The grain ma~ be tempered prior to the degermination, although tempering is not es~sential. The amount of whole and relatively undamaged germ that is released and the exten~'to which the germ and endosperm are separated is a function of a number of factGrs., including the moisture content of the ~crm, the type and condition o the corn, the configuration of the corrugations 12a and 14a, or combinations of these and other factors.
Exemplifying the improved results obtained by the degerminating method of this invention, it has been found that midwestern hybrid corn of about 12% moisture and average condition and age yields approximately 85% whole germ and slightly more than 95% separation of germ and endosperm. Tempering the same type of corn to about 17% moisture content for about 3 hours increases the yield to about 95% ~hole germ and about 97% complete separation of germ and endos,perm. The degerminator fines that will pass through a 16 mesh screen var~ in quantity from a high of ab,out 20% of the corn degerminated to a low of a'~out 10%, and from a fat content of ab,out 1% to about 5%, depending on the tempering proces:s, the moisture content of the germ and endosperm, the kind of l 161328 corn, the condition and age of the corn, the relative speed of rota~ion of discs 12 and 14, the spacIng bet~een the discs, the configuration and arrangement of the corrugations, and the condition of the disc surfaces.
Although the degerminator machine 10 is similar in construction to a conventional attrition mill, its operational characteristics differ considerably.
The main difference is that the discs; 12 and 14 are carefully spaced and the corrugations are arranged to achieve only a crushing effect on the kernel which is; applied ~nly- from the opposite thin edges in~ardlr to~ard the center, in contrast to the grinding and cutting action of an attrition mill. Since discs 12 and 14 are spaced apart such that a kernel oriented with its flat sides parallel to the planes of the discs passes freely between the ridges of the cor-rugations, the machine avoids crushing the kernels from the relatively large flat sides thereof, thus assuring that the crushing occurs only at the thin edges in a manner to squeeze the germ free of the endosperm.
Referring now to Pigures 3 and 4, a degerminator constructed in ac-cordance with a second embodiment of the invention is generally designated by numeral 22. Degerminator 22 applies a crushing force similar to that applied by degerminator 10, although in the case of degerminator 22, the force is applied rom only one of the thin edges of the kernel toward the center.
The degerminator 22 includes an upright wall 24 having a generally c~lindrical shape and surmounted b~ a frustoconical roof portion 26. A
vertical tube 28 extends through roo 26 and is hollo~ in order to receive and d~rect grain into the machine. The lo~er end of tube 28 is open and is located centrallr above a horizontal disc 30, Disc 30 is rigidly mounted on top of a vertical shat 32 ~hich may be rotated by any suitable drive system ~not shown).
A pluralitr of spaced apart guide vanes 34 are located on the upper l 161328 s,urface of disc 3Q. Each vane 34 extends, outwardl~ along the disc from tube 28 to the peripher~ of the disc. Vanes; 34 are curved members each having a sharpll~ curving outer end portion which approaches a tangent line at the edge of the disc.
The inside surface of ~all 2~ is, located outwardl~ of the periphery of disc 30 a dis,tance less- than the thicknes,s of a grain kernel. The inside surface of the ~all is formed in a manner to present a plurality of flat linear surfaces 24a against which the corn kernels impact when propelled outwardl~
off of disc 30. Each impact surface 24a is; oriented such that a kernel propelled off of the peripher~ of disc 30 and moving in a direction generallr tangent to the dis,c impacts against surface 24a at a right angle. Surfaces 24b of wall 24 extend bet~een each adjacent pair of impact surfaces 24a to assist in directing the grain kernels against surfaces 24a at substantially a right angle.In operatlon, grain is introduced throug~ the ~ube 28 and onto the upper surace of disc 30. The disc is rotated at a rate of speed high enough to propel the grain outwardly thereon b~ centrifugal force. As it moves out-w æ dly, the grain is guided along the curved leading suraces o the guide vanes 34 until the grain is eventually propelled off of the edge of the disc against the impact surfaces 24a~
The guide vanes are constructed to orient the grain such that one of the thin top or bottom edges of each kernel impacts against surface 24a, there~ appl~ing a compressive crushing orce to the grain from the thin edge to~ard the center and not at one of the relatively large side surfaces of the kernel. As each kernel is propelled outw.ardly along vane 34, it may be orientedeither with one of its large flat sides; agains;t the vane or with one of its thin ~ide edges against the vane. In elther case, the top or bottom edge o the kernel l 161328 ~ill be on it$ leading portion in the direction o motion at the time it ~eaves the disc, b~ vlrtue of the sharpl~ curving shape of the outer portions of vanes 34. Consequentl~, the thin top or bottom edge of the kernel impinges on surface24a and a crushing force is thereb~ applied from the edge to~ard the center. Inthis manner, vanes 34 orient the kernel so that only thin edges engage surfaces 24a, and the crushing force is not applied to the flat sides as would sometimes occur ~ith straight radlal vanes.
The crushing force applied on the edge of the kernel toward the center s,quee~es the germ out from the endosperm in a substantiall~ ~hole condition. Due to the space bet~een wall 24 and dis,c 30, only the fragments of broken kernels can pass, betw.een the wall and the edge of the disc for further processing. Un-b,roken kernels, are too large to fall bet~een the wall and disc and ma~ be recirculated through the machine, It is to be understood th~t variou5, additional types o machines ma~ be employed to carr~ out the degerminating method of this invention. How-ever, the machines 10 and 22 are preferred slnce they effectively apply crushingorces to the s,ide edges of the gra~n while avoiding the application of crushing forces; to the relatively large side surfacés, In addltion to the effectiveness of the germ separation, the process of this; invention separates the bran from the endosperm with excellent results.A~ the moisture content of the bran increas,es, its separation becomes more comRlete. It has been found that if dr~ corn of about 14% moisture is tempered or 4 to 8 minutes with addition o water o about 2% to 8% by weight of the corn,"90% to 98% of the bran is removed b~ the degerminating process as a resultof the crushing fcrces applied to the cornO The degree of debranning is affectedb,~ the kind and condition of the corn, the amount of water and heat added and the length of time held, the speed of the discs, and the coniguration of cor-rugations, 12a and 14a or the shape o vanes 34. Since on a practical level only the ~ran is tempered and not the remalnder of the corn, drying is simpliPied because only the bran needs to ~,e s,orted out by screens and/or as,piration and sent to dryers. Conventional methods of debranning require tempering of the germ ~lso and/or separate equipment to perform this function.
In carrying out the method of the present invention, the po~er requirements are about 2~ HP per hour per ton of corn, as compared with requirements of conventional processes of from 15 to 25 HP per hour per ton of corn for degerming and de~,ranning, Another important result obtained by the degerminating process of this invention is the relativel~ high ~uality of the degerminator fines which, as, previously indicated, have a fat content of about 1% to 5%. In comparison, the ines generated in conventional degerminating processes are so high in fat that they are either sold as, a low value ~yproduct animal feed or are reproces-sed to upgrade their quality, Such reprocessing involves the use of sifters, aspirators, gravity tables, purifiers or various combinations of these and other costly devices. Upgrading the quality of the fines with such devices allows the fines to move into industrial uses or other markets where they yleld a higher price than animal feed but a lo~er price than prime products from the mill. In addition, separation of the fines from the prime product is costly and time consuming.
The pres-ent invention also provides improved grain milling processes w,hich are illus,trated in flow sheet form in ~igures 6-9, The ~hole grain or a ma~or part oP it ma~ be tempered in some oP the processes, although temper~ng i,s~not alwa~s required if the prePerred degerminating process described above ~s -15~`
used, due to the high degree of deger~ina~lon and the high qualit~ of the fines.
The particular process that ma~ be employed to the best advantage in each set of circumstances depends upon a variet~ of factors, including the end products desired, the type and condition of the grain, and economic considerations such a~ operating costs and marketing objectives.
Referring first to Figure 6, the process sho~n therein involves cleaning of the corn followed by a prebreaking in a prebreak mill. The prebreak mill ma~ be an~ suitable type that breaks the grain by subjecting it to a crushing action that breaks the endosperm while preferabl~ although not necessaril~
maintaining a substantial amount of the ge~m in a whole condition. The grain should be broken along the germ so the germ is exposed. The crushing action should fracture the grain into at least four and preferably six or more major pieces, The germ should be separated ~rom the endosperm to as great an extent a~ possible because the fat content of the finished products is reduced as the degree of separation increases. The actual degree of separation of the germ and the extent to which the germ remains whole depend upon the particular prebreaking process utilized and the end product desiredO
Tempering of the ~rain may be carried out in advance of the prebreak or after the prebreak, or bothO Tempering before the prebreak better controls the germ separation. ~or example, corn havlng a moisture content of 15% to 20%
~ ~eight w~ll, when broken, provide better release of the germ with a cor~
responding reduction in fines and fat content than corn having a moisture content below about 15%. The tempering can be carried out using known techniques.
Tempering after prebreaking may be carried out if the moisture content of the germ and bran was: not ad~usted b~ a tempering step prior to prebreak, or if additional moisture ad~ustment ~s neces~sary or desired after ~ 161328 prebreak. The moisture content of the germ and bran prior to passage of the stock to the first roller mill should be a~out 15% to 35% b~ ~eight. Tempering after prebreak results in an appreciable shortening of the tempering tîme because the prebréaking exposes the germ and bran. Tempering can be as short as 2 ~inute~ if heat is used and in no case ~ill it exceed about 30 minutes when performed subsequent to prebreak.
Although a main advantage of the proces,s of this invention is that it avoids, the need to remove fines prlor to milling, it ma~ be desirable in s,ome instances to remove the fines; after prebreak and before milling in order 1~ to reduce the water requirements for the tempering step. This can be done in a sifter which sifts the stock after prebreak and before tempering if tempering occurs only after prebreak. The fines are then separated and returned to the stock after it has been tempered and passed through the first set of break rolls if this is desirable to simpliy the flow.
The près,ent invention departs from the technique of the conventional grain milling process which, as pr~viously indicated, attempts to match particle size with individual roller mill characteristics~ In the conventional gradual reduction process, the particles are first passed through roller mills having relativel~ large corrugations and then to successive additional roller mills 2Q having increasingl~ finer corrugations. It has heretofore been thought that an~ attempt to utilize rollers having fine corrugations at the front end of the mill ~ould result in smashing of the grain kernels which would make ultimate ~eparation of germ, bran and endosperm exceedingl~ difficult.
Instead of passing the grain through a long succession of rollers as is done in the conventional prGcess, gri,nding is accomplished in the present invention b~ passing the broken grain directl~ to ine rollers of the type that l 161328 no mall~ characterize onl~ the end of a dierential milling process.
rn accordance ~ith the inventlon, the prebreaking and tempering steps are effected, and the grain is then passed through a first set of break rolls which may be of the modified Dawson type having 20 corrugations per inch and a spiral of about ~ inch per linear oot. The rollers are arranged dull to dull and have a differential roll speed of 2 to 1. The first break roller mill is adjusted ~o that at least approximatelr 50% of the product through is small enough to pass through a United States #12 sieve. The spacing bet~een the rollers is $ufficient to substantiall~ prevent appreciable penetration of the roller corrugations inta the germ, thereb~ avoiding size reduction of the germ in contrast to the conventional practice of placing fine rollers closer together in accordance with the fine particles being processed. Those particles from the prebreak mill, ~ith the exception o the "fines", are large enough sa that the~ are sub~ected to a grinding action when passed between the rollers o~ the ~irst break mill and those of the second break mill.
Due to the fineness of the roller corrugations and their spacing, the endosperm is severely and abruptly ground up and thereby separated from the germ and bran without resulting in the germ being fractured excessivel~. The prQduct from the first break rolls, together with the fines if they have been removed prior to temper, is shifted through a United States #8 sieve and a United States #12 sieve. The relatively large size particles over the #8 ~ieve are primaril~ germ and bran and may be directed to feed or oil recover~
or to further processing as described below. The portion passing through the #}2 screen is less than 1% in fat content, and it is therefore passed to finished praduct. Particlesi through the #8 screen but over the #12 screen are principally endosperm, although there is; enough germ present that this portion is not market--18_ able as a pri~e product. This portion i~ passed to a second set of break rolls which effect further size reduction of the endosperm and ~hich further separate the endosperm from the germ and bran components.
The rollers of the second break mill have corrugations of the same size as the first set or slightl~ smaller, and the spacing between the rolls is again sufficient to avoid excessive penetration of the germ. The differential speed of the rollers in the second break mill ma~ be reduced to about 1.75 to 1. After passing through the second set of break rolls, the product is sifted through a #14 wire. The particles over the ~ire are rich in germ and bran and go to animal feed or oil recover~. The s-tock passing through the wire is rich ln endosperm and goes to finished product along with the endosperm rich stock rom the first break mill. The endosperm rich stream is dried and cooled if necessaryi and is inally passed to a grading station where grits and meal are Braded according to a size and any remaining bran is removed by aspiration.
The free germ ma~ be removed prior to the first break rolls by utilizing gravit~ tablesO This optional step lowers the fat content of the throughs from the sifter wires, and it aids in making the milling process superior to conventional processes both in quality and product yield.
Although the specific operating parameters for the process depend
2~ upon the age of the grain, its moisture content and grade, and the end products desired, it has been found, by wa~ of example, that United States grade #2 corn having a moisture content of 13% yields approximately 62% brewer's grits on a United States #30 sieve at 1% maximum oil, 8% meal through a United States #30 sieve at less than 1.5% oil, 3% 10ur through a United States #80 sieve at about 2% maximum oil, and a brewer~s extract on the grits of 80.5% as is basic and prescribed b~ the American Association of Brewing Chemist Methods. The total ~lg-l 161328 prime product y~eld ig 73%. In compar~son, a typical yleld of equal quality pro-ducts from the conventional process of pigure 5 is 47% bre~er's grits, 9% meal and 5% flour. The total prime product yield ~ 63% ln the conventional process. In additlon to providing a higher yield in the more valuable bre~er's grits, the pro-cess of this invention yields a cereal grit and flour product of higher quality ~ecause of a reduction in "black specks"O This is attributable to the reduced grinding which leaves most of the germ tip ~black speck) attached to the bran or germ, although the extent to which this occurs decreases ~ith a diminishing of the tempering.
Pigure 7 illustrates a mod~fied grain milling process which involves no tempering and has the objective of producing a maximum amount of brewer's grits. After the corn is cleaned, it is degerminated by subjecting it to the pre~erred degermination process described previously. The grain is thereby crushed from its thin edges toward the center to achieve a high degree of separ-ation o the germ from the endosperm while maintaining the germ in a substantially whole condition.
The degerminator stock is pas~ed to a degerminator sifter which grades it into four streams containing particles of different sizes. A first stream con-sists of relatively large particles of whole corn or incompletely degerminated 2Q pieces of cornO It may not be necessar~ to separate out this first stream or fraction, depending on the scalp sieve size, the degerminator setting, the con-dition of the corn, and/or the object of the milling operation. The first stream is recycled or pass;ed again through the degerminator.
The bulk of the degerminator ~tock is; the second coarse~t fractlon which contains bran, the whole germ and the larger broken germ particles, as well as the pieces; of ~roken endosperm passlng over the second sieve. Pepending upon a variet~ of factors, the second sleve can be from S to 9 mesh. The second fraction is passed to gravitr table ~1 where the germ and bran are sorted -20-l 161328 from the endos,perm and d~rected to feed or o~l recover~. If large ~uantities of corn are being processed so that sheer volume requires the use of a number of grawit~ tables, more efficient gravit~ table operation can be obtained by closer s,izing of s,tream #2 into s-everal streams and/or employing asplration prior to pas,sing the s,treams, to the gravit~ tables. This ~ill upgrade the inished product in both quality and quantity;
The third fraction includes broken germ, endosperm and bran normall~
making up between 5% and 25% of the total ~eight of the corn. This stream goes to gravitr table ~2 which sorts the germ and bran from the endosperm and directs them to animal feed or an oil recoverr s~stem. The endosperm is combined ~ith the endosperm rich s,tream f~om gravit~ table #l and passed to break rolls, having fine corrugations that ma~ be identical with those of the firs,t break roll mill described in connection ~ith the proces,s of Figure 6.
The stock rom the break rolls is, comb~ned with the fourth and inest fraction from the degerminator sifter, In a grits grade sifter, mos,t of the germ and bran still remaining in s,tock are scalped off and d~rected to feed or oil recover~. The s,calp sieve is about 10 to 16 mesh, depending upon the mesh of the sieve for the fourth fraction from the degerminator sifter. The grits grade sifter size cla$si,fies the remainder of the roller mill s,tock ~hich is aspirated conventionally.
It has been found that with United States Grade #2 ~orn having a mo~sture content of 13%, the process o ~igure 7 rields about 57% brewer's grits over a United States #30 sleve with a fat content of 1~ or less, about 2% meal through a United States #30 s,ieve and over a United States #80 sieve wi,th 1.5% fat or les;s, and about 5% flour through a #80 sieve at 2.5% maximum fat and a lo~ at less, than 1%. The prime product rield is about 71% of the total ~eight of the cleaned corn, as compared to about 63% for the conventional -21_ mi,lling process;.
Referring now to Figure 8, the milllng process, shown therein employs tempering and the preferrsd degerminating method described above. The object of the process is to produce a maximum ~ield of brewer's, gritsO The process of Pigure 8 is similar to that of Pigure 7, the main difference heing that only one gravity table is needed and optional tempering of all or part of the grain may be carried outc If a particularlr high quantit~ of whole germ is desired from the degerminator or if a small amount of ines and low fat is, sought, the grain is, tempered af~er being cleaned and before degermination. Tempering at this point produces high ~ields and oil quality as, compared to the process of Figure 7. However, the moisture added penetrates, deeply into all parts of the corn s,o that relatively long and extens,ive drying is re~uired, A small amount of tcmpering is particularly b~neflcial i ths mois,ture o the corn is low becaus,e in this cas,e the degerminatlon is enhanced appreciab,ly due to the tempering step.
Degermination is eected b.~ the preferred degerminating method described above, and the degerminator stock is fed to a degerminator sifter which provides four fractions, as in the process, of Pigure 7, However, instead Qf directing fraction #3 to a gravity table, it is tempered, if there was no tempering previousl~, to bring its germ moisture content in the range of about 15% to 35%.
A~ter te~e~,i,n~ of th0 #3 f~a,cti,on, it is, combined with the endosperm rich grit stream from the gravity table o fraction #2, and the combined streams are then sent to fine break rolls which may be identical with those employed in the process: of Figure 7. The s,tream from the roller mill ma~ be passed directly _22-l 161328 to the grits; grader stter or ta a dr~ing station and a cooling station if necessary due to marketing or end u~e ob~ectivesO If the grain was tempered ~eforc degsrmination, the fine fraction ~4 is comblned with the roller mill stock before dr~ing and cooling. The fine fraction ~4 from the degerminator sifter can bypass the dry~ng and cooling stations in a situation where only raction #3 was tempered, since fraction #4 need not be dried in this case.
~raction #4 is then combined with the roller mill stock after dr~ing and cooling. The grits grader sifter and æspiration operations are carried out in the same manner as in the process of Pigure 7.
~inimal témpering ~ields res;ults simllar to and usually somewhat better than are obtained with the process of ~igure 7. More complete tempering gives results better than those of the process; of Plgure 6, with yields of prime products running as high as 75% o the cleaned corn.
Pigure 9 illustrates still another milling process in which the degermination proce~s of the invention is used to debran as ~ell as to degerminate.
This process is used primarily to produce extra coarse grits such as those used to make cereal cornflakes in the breakfas;t food industry~ If the objective of the process is to maximize grit size, impact deinestation is not used to advantage in the eorn cleaning operation because the broken corn that results from impact deinfestation is not debranned easil~ and the yield of larger grits is reduced accordingl~.
After the corn isi ~leaned, it is tempered using water, hot water, and/or steam and is held long enough for the moisture to penetrate and loosen the b.ran. Unlike the conventional debxanning processes which re~uire tempering of the entixe kernel, onl~ the bran is tempered and the tempering time is reduced appreciabl~ as a result. Aftsr tempering, the grain is degerminated by the l 1613~8 preferred method of degermination descri~ed previouslr, res,ulting in the germ being separated from the endosperm and the endosperm being crushed out of the pliable tempered bran.
The degerminator stock is sited b~ the degerminator sifter wherein the top or coarsest fraction i,s scalped o and passed through an aspirator to remove the bran. The bran that is removed ma~ be sent to a dryer if necessary before it isi directed to animal feed or to another use. Undegerminated corn or large particles that need to be degermed andtor debranned are recycled from the as,priator back to the degerminator.
The remaining fractions, from the degerminator sifter are separated acGording to size and according to market and/or use objectives and efficient gravity table operation, These fractions are s~nt to gravit~ tables which may be preced~d by aspirators, depending upon the desired efficienc~ of the gravit~
tables for separating the grain for drying or other reasons,. The aspirating, s~fting and gravity table operations are carried out conventionally. It has b,een found that for particularly efffcient bran removal, most of the bran is scalped off in the recycle fraction from the degerminator sifter.
The process of Pigure 9 efficiently and economically produces extra large grits meeting the marketing specifications of fat and bran content. The fraction of extra large grits not used as, grits can be reduced in size for ~,re~-er's grits and/or meal and added to the products of the degerminating process.
In each of the process,es of the present invention, the fines from the degerminator are relativel~ lo~ in fat content since the germ is maintained in a s,u~stantfally ~hole condition. Accordfngly, the fines are high enough in quality~that they can remain in the prime product stock and need not be separated qut and s,ent to feed as is necessary in the conventional milling process. It i5 -24-, l 161328 also apparent that fewer steps are requlred ln the milling process of this invention as a result primarily of the high degree of degermination and dehramling that is achieved in the degermination process.
The processes illustrated in Pigures 6~9 can be combined to produce virtually all dry corn milled products ~ith a maximum of flexibilit~ and economy.
In addition, in situations, where the desired product is cornmeal having a fat level of about 1.2% to 1.5%, even higher yields than those ~ith lo~er fat products can be achieved ~y using size reduction equipment to break down the grlts~.
By virtue of the reduced nu~ber o steps required, the process of this, invention permits; the overall size of the mill to ~e reduced substantially.
Also, the reduction in the amount of equipment provides considerable economy and decreas,es- the maintenance and repair requirements. Since the process stock does not need to be siifted repeatedly- as i5 necessar~ in the conventional gradual reduction method of milling, only a relatively small amount of sifter cloth is required. ~e~er roller mills are needed, and the reduced length of the flow path correspondingly reduces the need for conveying equipment. Further economic henefits result from the reduced power requirements and the decreased need for heating, cooling and drying equipment. The simplicity of the processes has the added benefit of reducing the level of s,ki,ll and training necessar~ to operate a mill in which the processes are carried out.
~hile the processes, have been described ~ith particular reference to corn milling, the~ find application als,o in connection with other grains such as wheat and grain sorghum. Maniestly, ~ith a much smaller sized grain such as milo, rollers, having finer corrugations are utllized to achieve the desired s,eparation o components in a minimum number of steps.
l 161328 The process;es of this invention ma~ find application for "clean up"
of a stream of broken grain in a conventional milling process. It should also be apparent in connection with the process of ~igure 6 that more than one or two breaks may be made in the prebreak mill and that higher yields or higher quality products may be obtained b~ using three or more break~i depending upon the results desired and the nature of the grainO
~ y virtue of the economic beneflts obtained by using the milling proces.ses of the present invention, dr~ milling techni~ues ma~ be extended into areas that have heretofore been thought to be economically impractical. For example, since yields o prime products over 70% are obtained ~ith fat content as low as: .4%, it is practical to appl~ the dry milling processes to replace the long, extensive steeping step employed in the wet milling of corn, thereby shortening the proces;s and cutting costs. Another economic advantage of the present invention is the high ratc of germ recovery which results in a higher oil yield per bushel of corn than is obtained with conventional dry milling processes.
~rom the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure.
It will be understood that certain features and subcombinations are o~ utility~and may be employed without reference tocther features and subcom-B~nations. This is contemplated b~ and is wi.thin the scope of the claims.
Since man~ pos;sible embodiments; ma~ be made of the invention without departing from the scope thereof, it ls to be understood that all matter herein s:et forth or sho~n in the accompanying draw.~ngs is to be interpreted as illus-trative and not in a limiting sense.
Pigure 7 illustrates a mod~fied grain milling process which involves no tempering and has the objective of producing a maximum amount of brewer's grits. After the corn is cleaned, it is degerminated by subjecting it to the pre~erred degermination process described previously. The grain is thereby crushed from its thin edges toward the center to achieve a high degree of separ-ation o the germ from the endosperm while maintaining the germ in a substantially whole condition.
The degerminator stock is pas~ed to a degerminator sifter which grades it into four streams containing particles of different sizes. A first stream con-sists of relatively large particles of whole corn or incompletely degerminated 2Q pieces of cornO It may not be necessar~ to separate out this first stream or fraction, depending on the scalp sieve size, the degerminator setting, the con-dition of the corn, and/or the object of the milling operation. The first stream is recycled or pass;ed again through the degerminator.
The bulk of the degerminator ~tock is; the second coarse~t fractlon which contains bran, the whole germ and the larger broken germ particles, as well as the pieces; of ~roken endosperm passlng over the second sieve. Pepending upon a variet~ of factors, the second sleve can be from S to 9 mesh. The second fraction is passed to gravitr table ~1 where the germ and bran are sorted -20-l 161328 from the endos,perm and d~rected to feed or o~l recover~. If large ~uantities of corn are being processed so that sheer volume requires the use of a number of grawit~ tables, more efficient gravit~ table operation can be obtained by closer s,izing of s,tream #2 into s-everal streams and/or employing asplration prior to pas,sing the s,treams, to the gravit~ tables. This ~ill upgrade the inished product in both quality and quantity;
The third fraction includes broken germ, endosperm and bran normall~
making up between 5% and 25% of the total ~eight of the corn. This stream goes to gravitr table ~2 which sorts the germ and bran from the endosperm and directs them to animal feed or an oil recoverr s~stem. The endosperm is combined ~ith the endosperm rich s,tream f~om gravit~ table #l and passed to break rolls, having fine corrugations that ma~ be identical with those of the firs,t break roll mill described in connection ~ith the proces,s of Figure 6.
The stock rom the break rolls is, comb~ned with the fourth and inest fraction from the degerminator sifter, In a grits grade sifter, mos,t of the germ and bran still remaining in s,tock are scalped off and d~rected to feed or oil recover~. The s,calp sieve is about 10 to 16 mesh, depending upon the mesh of the sieve for the fourth fraction from the degerminator sifter. The grits grade sifter size cla$si,fies the remainder of the roller mill s,tock ~hich is aspirated conventionally.
It has been found that with United States Grade #2 ~orn having a mo~sture content of 13%, the process o ~igure 7 rields about 57% brewer's grits over a United States #30 sleve with a fat content of 1~ or less, about 2% meal through a United States #30 s,ieve and over a United States #80 sieve wi,th 1.5% fat or les;s, and about 5% flour through a #80 sieve at 2.5% maximum fat and a lo~ at less, than 1%. The prime product rield is about 71% of the total ~eight of the cleaned corn, as compared to about 63% for the conventional -21_ mi,lling process;.
Referring now to Figure 8, the milllng process, shown therein employs tempering and the preferrsd degerminating method described above. The object of the process is to produce a maximum ~ield of brewer's, gritsO The process of Pigure 8 is similar to that of Pigure 7, the main difference heing that only one gravity table is needed and optional tempering of all or part of the grain may be carried outc If a particularlr high quantit~ of whole germ is desired from the degerminator or if a small amount of ines and low fat is, sought, the grain is, tempered af~er being cleaned and before degermination. Tempering at this point produces high ~ields and oil quality as, compared to the process of Figure 7. However, the moisture added penetrates, deeply into all parts of the corn s,o that relatively long and extens,ive drying is re~uired, A small amount of tcmpering is particularly b~neflcial i ths mois,ture o the corn is low becaus,e in this cas,e the degerminatlon is enhanced appreciab,ly due to the tempering step.
Degermination is eected b.~ the preferred degerminating method described above, and the degerminator stock is fed to a degerminator sifter which provides four fractions, as in the process, of Pigure 7, However, instead Qf directing fraction #3 to a gravity table, it is tempered, if there was no tempering previousl~, to bring its germ moisture content in the range of about 15% to 35%.
A~ter te~e~,i,n~ of th0 #3 f~a,cti,on, it is, combined with the endosperm rich grit stream from the gravity table o fraction #2, and the combined streams are then sent to fine break rolls which may be identical with those employed in the process: of Figure 7. The s,tream from the roller mill ma~ be passed directly _22-l 161328 to the grits; grader stter or ta a dr~ing station and a cooling station if necessary due to marketing or end u~e ob~ectivesO If the grain was tempered ~eforc degsrmination, the fine fraction ~4 is comblned with the roller mill stock before dr~ing and cooling. The fine fraction ~4 from the degerminator sifter can bypass the dry~ng and cooling stations in a situation where only raction #3 was tempered, since fraction #4 need not be dried in this case.
~raction #4 is then combined with the roller mill stock after dr~ing and cooling. The grits grader sifter and æspiration operations are carried out in the same manner as in the process of Pigure 7.
~inimal témpering ~ields res;ults simllar to and usually somewhat better than are obtained with the process of ~igure 7. More complete tempering gives results better than those of the process; of Plgure 6, with yields of prime products running as high as 75% o the cleaned corn.
Pigure 9 illustrates still another milling process in which the degermination proce~s of the invention is used to debran as ~ell as to degerminate.
This process is used primarily to produce extra coarse grits such as those used to make cereal cornflakes in the breakfas;t food industry~ If the objective of the process is to maximize grit size, impact deinestation is not used to advantage in the eorn cleaning operation because the broken corn that results from impact deinfestation is not debranned easil~ and the yield of larger grits is reduced accordingl~.
After the corn isi ~leaned, it is tempered using water, hot water, and/or steam and is held long enough for the moisture to penetrate and loosen the b.ran. Unlike the conventional debxanning processes which re~uire tempering of the entixe kernel, onl~ the bran is tempered and the tempering time is reduced appreciabl~ as a result. Aftsr tempering, the grain is degerminated by the l 1613~8 preferred method of degermination descri~ed previouslr, res,ulting in the germ being separated from the endosperm and the endosperm being crushed out of the pliable tempered bran.
The degerminator stock is sited b~ the degerminator sifter wherein the top or coarsest fraction i,s scalped o and passed through an aspirator to remove the bran. The bran that is removed ma~ be sent to a dryer if necessary before it isi directed to animal feed or to another use. Undegerminated corn or large particles that need to be degermed andtor debranned are recycled from the as,priator back to the degerminator.
The remaining fractions, from the degerminator sifter are separated acGording to size and according to market and/or use objectives and efficient gravity table operation, These fractions are s~nt to gravit~ tables which may be preced~d by aspirators, depending upon the desired efficienc~ of the gravit~
tables for separating the grain for drying or other reasons,. The aspirating, s~fting and gravity table operations are carried out conventionally. It has b,een found that for particularly efffcient bran removal, most of the bran is scalped off in the recycle fraction from the degerminator sifter.
The process of Pigure 9 efficiently and economically produces extra large grits meeting the marketing specifications of fat and bran content. The fraction of extra large grits not used as, grits can be reduced in size for ~,re~-er's grits and/or meal and added to the products of the degerminating process.
In each of the process,es of the present invention, the fines from the degerminator are relativel~ lo~ in fat content since the germ is maintained in a s,u~stantfally ~hole condition. Accordfngly, the fines are high enough in quality~that they can remain in the prime product stock and need not be separated qut and s,ent to feed as is necessary in the conventional milling process. It i5 -24-, l 161328 also apparent that fewer steps are requlred ln the milling process of this invention as a result primarily of the high degree of degermination and dehramling that is achieved in the degermination process.
The processes illustrated in Pigures 6~9 can be combined to produce virtually all dry corn milled products ~ith a maximum of flexibilit~ and economy.
In addition, in situations, where the desired product is cornmeal having a fat level of about 1.2% to 1.5%, even higher yields than those ~ith lo~er fat products can be achieved ~y using size reduction equipment to break down the grlts~.
By virtue of the reduced nu~ber o steps required, the process of this, invention permits; the overall size of the mill to ~e reduced substantially.
Also, the reduction in the amount of equipment provides considerable economy and decreas,es- the maintenance and repair requirements. Since the process stock does not need to be siifted repeatedly- as i5 necessar~ in the conventional gradual reduction method of milling, only a relatively small amount of sifter cloth is required. ~e~er roller mills are needed, and the reduced length of the flow path correspondingly reduces the need for conveying equipment. Further economic henefits result from the reduced power requirements and the decreased need for heating, cooling and drying equipment. The simplicity of the processes has the added benefit of reducing the level of s,ki,ll and training necessar~ to operate a mill in which the processes are carried out.
~hile the processes, have been described ~ith particular reference to corn milling, the~ find application als,o in connection with other grains such as wheat and grain sorghum. Maniestly, ~ith a much smaller sized grain such as milo, rollers, having finer corrugations are utllized to achieve the desired s,eparation o components in a minimum number of steps.
l 161328 The process;es of this invention ma~ find application for "clean up"
of a stream of broken grain in a conventional milling process. It should also be apparent in connection with the process of ~igure 6 that more than one or two breaks may be made in the prebreak mill and that higher yields or higher quality products may be obtained b~ using three or more break~i depending upon the results desired and the nature of the grainO
~ y virtue of the economic beneflts obtained by using the milling proces.ses of the present invention, dr~ milling techni~ues ma~ be extended into areas that have heretofore been thought to be economically impractical. For example, since yields o prime products over 70% are obtained ~ith fat content as low as: .4%, it is practical to appl~ the dry milling processes to replace the long, extensive steeping step employed in the wet milling of corn, thereby shortening the proces;s and cutting costs. Another economic advantage of the present invention is the high ratc of germ recovery which results in a higher oil yield per bushel of corn than is obtained with conventional dry milling processes.
~rom the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure.
It will be understood that certain features and subcombinations are o~ utility~and may be employed without reference tocther features and subcom-B~nations. This is contemplated b~ and is wi.thin the scope of the claims.
Since man~ pos;sible embodiments; ma~ be made of the invention without departing from the scope thereof, it ls to be understood that all matter herein s:et forth or sho~n in the accompanying draw.~ngs is to be interpreted as illus-trative and not in a limiting sense.
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a machine for degerminating a kernel of grain such as corn having relatively large side sur-faces and relatively thin edges, the improvement com-prising: a frame; a disc member supported on said frame in a generally horizontal orientation for rotation about a substantially vertical axis; a plurality of guide vanes on the upper surface of said disc member for guiding the kernel generally outwardly thereon, each of said vanes extending in a curvilinear path and terminating in an end portion that is substantially parallel to a tangent of said disc whereby a kernel impelled by said disc will be aligned by one of said vanes so that a side edge will be the leading edge of the kernel as it moves along said vane and is released by said disc; means for presenting a plurality of impact surfaces in the same horizontal plane as said disc, each of said surfaces being substan-tially linear and extending transversely of the path of travel of a kernel impelled by said disc, said means presenting said impact surfaces being positioned away from the periphery of said disc a distance greater than the largest dimension of the kernel thereby precluding the application of crushing forces to said kernels as the latter pass between said disc and said surfaces;
means for feeding said kernals, at a controlled rate, from an initial overhead position onto the disc at a point near the center of the disc; and means for rotating said disc member about said axis in a direction opposite to the direction of said guide vanes at a speed sufficient to centrifugally propel a kernel disposed in the disc member outwardly along one of the guide vanes and against said impact surface, whereby a compressive crushing force is applied to the kernel from said one side edge toward the center to fracture the endosperm portion away from the germ portion.
means for feeding said kernals, at a controlled rate, from an initial overhead position onto the disc at a point near the center of the disc; and means for rotating said disc member about said axis in a direction opposite to the direction of said guide vanes at a speed sufficient to centrifugally propel a kernel disposed in the disc member outwardly along one of the guide vanes and against said impact surface, whereby a compressive crushing force is applied to the kernel from said one side edge toward the center to fracture the endosperm portion away from the germ portion.
2. In a machine as set forth in claim 1, means for adjusting the angular orientation of said impact surfaces relative to the path of travel of said kernel to provide for maximum impact force.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000405872A CA1161328A (en) | 1981-06-18 | 1982-06-23 | Grain milling and degerminating process |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA380,157A CA1133353A (en) | 1979-11-28 | 1981-06-18 | Grain milling and degerminating process |
| CA000405872A CA1161328A (en) | 1981-06-18 | 1982-06-23 | Grain milling and degerminating process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1161328A true CA1161328A (en) | 1984-01-31 |
Family
ID=25669352
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000405872A Expired CA1161328A (en) | 1981-06-18 | 1982-06-23 | Grain milling and degerminating process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1161328A (en) |
-
1982
- 1982-06-23 CA CA000405872A patent/CA1161328A/en not_active Expired
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| MKEX | Expiry |