RECOVERY OF PROTEIN, PROTEIN ISOLATE AND/OR STARCH FROM CEREAL GRAINS

Abstract: The protein/starch bond is broken mechanically by wet attrition milling rather than by cooking or with chemicals alone. The grain particles are milled to a particle size sufficiently small to break the bond between starch and protein and sufficiently large to retain substantially all of the starch granules intact. The protein is then extracted with ethanol and alkali solvents, separated and dried to form protein and/or protein isolate. The intact starch granules are cleaned and dried.

Description: RECOVERY OF PROTEIN, PROTEIN ISOLATE AND/OR STARCH FROM CEREAL GRAINS Reference to Related Applications This application is a continuation-in-part of my copending U.S. Application Serial No. 487,739 filed March 2 , 1990 entitled Method of Producing Protein and Protein Isolates from Cereal Grains. Field and Background of the Invention This invention relates generally to the production of protein or protein isolates and/or starch from cereal grains. In particular, this invention relates to a technique in which the bond between starch, on the one hand, and protein on the other is broken mechanically rather than by the conventional process of cooking. As a result, there is realized an increased recovery of a higher quality protein and intact granules of a high¬ er quality pure starch. It has been proposed heretofore to obtain a protein isolate from corn or other cereal grains. As is well known to nutritionists, agricultural commodities, such as cereal grains, may contain complete or nearly com¬ plete proteins and thus, if the protein were isolated, would be capable of providing a balanced diet for hu¬ mans. Heretofore, the extraction of isolated proteins from agricultural commodities has been made difficult by the chemical bonding which exists between protein and the starch constituents of the commodities. In prior, well known processes which involve some bio¬ chemical treatment or steps using one of these consti¬ tuents, such as the yeast fermentation of corn or grains to produce ethanol, the starch/protein bond is broken by hydrolysis through cooking. However, break¬ ing the bond by cooking, while making the starch and sugar content available for other uses, destroys the possibility of recovering the protein in a form useful as food. James T. Lawhorn proposed, in .United States Patent 4,624,805, that, after an initial grinding step in which the grain is ground to "meal" size (250-600 microns), protein be isolated prior to the use of starches and sugars in an ethanol fermentation process. The protein is extracted with an alkali/alcohol solu- tion either with or without sonification. La horn teaches that the protein is recovered by ultrafiltra- tion, with the dissolved sugars and starches in a per¬ meate being concentrated by reverse osmosis for use in alcohol production. It has been discovered by attempts to practice the Lawhorn process that the process as disclosed in the patent simply does not work on a commercial scale. First, by relying on chemicals and sonification to break the protein/starch bond, only minimal percentages of the available protein is extracted. Secondly, the ultrafiltration membranes described by Lawhorn foul and clog, and the desired continuous operation does not occur. However, the Lawhorn process does propose the separation of protein and other components of agricul- tural commodities by a process which avoids cooking and thereby would permit the recovery of a food graded pro¬ tein isolate, if it worked on a commercial scale. On a dry basis, the endosperm of corn makes up ap¬ proximately 83% of the kernel and contains the bulk of the starch. Other cereal grains may vary somewhat in percentages of endosperm but are conceptually similar. The starch is present as granules of roughly 5-35 mi- crons in size with the space therebetween filled with protein. This protein/starch matrix has to be broken to be able to recover either or both starch or protein. Intact starch granules are much more valuable than starch granules which are not intact. It should be noted that the structure of the granules themselves depends on the way in which amylose and amylopection are associated by intermolecular hydrogen bonds. Strong bonds give rise to crystalline areas and weak bonds to amorphous areas. Normal corn starch has a crystallinity in the range of 15-39%. In the known processes for separating protein from starch, either the usefulness of protein and starch have been destroyed by the cooking and/or steeping proc- ess, or else the protein has been ineffectively recov¬ ered in the Lawhorn process. In my prior application Serial No. 487,739, while a technique for mechanically breaking the starch/ protein matrix, the starch gran¬ ules are generally not left intact. Therefore, a proc- ess which effectively recovers quality protein and maintains starch granules intact has not been hereto¬ fore accomplished. Brief Description of the Invention With the foregoing in mind, the present invention reduces the grain kernels to particles of an optimum size to be treated more effectively with a solvent to extract the protein from the starch. Toward this end, it has been found experimentally that particle sizes in the range of 1-100 microns realize enhanced recovery of the available protein (greater than 80%). Further, af¬ ter subsequent microfiltration, the end product has a protein concentration of over 90%, qualifying it as protein isolate, a much more valuable type of protein suitable for use in baby food, food for the elderly, as a fortifying agent for snack food, milk shakes, nutri¬ tional drinks, pizza, and the like, as well as a sub- stitute yeast in hamburger meat. It has also been determined that if such particle sizes are in the higher end of the acceptable range (35-100 microns), all of the starch granules may remain intact, which makes them more valuable,- as they are suitable for new industrial and commercial uses such as, for example, in biodegradable plastics, surgical dusting powders, antiperspirant sprays, disposable san¬ itary products, instant laundry starches and others. Other applications are also envisioned where cross- linking for instance overcomes the sensitivity of the granules to disruption and improves the strength of swollen granules. In the process of the present invention, the grain is first subjected to a dry milling process to reduce the particle size to a range that can be easily intro¬ duced to the second operation after defatting: disk attrition wet milling. It is in this operation that the starch/protein matrix is broken. In the attrition mill (Koruma, for example), two carborundum disks are used, one stationary and one rotating at a high speed. The dry ground kernels are fed in aqueous slurry form through the center of the upper disk, and grinding occurs in the horizontal plane between the disks. The clearance between the disks is adjustable, as well as the rate of feed. Thus, the particle size can be close¬ ly controlled. The clearance between mill disks, speed of feed, and pumping pressure are adjusted to yield in conjunction with sufficient feed pressure, particle sizes of 1-50 microns, if the resulting starch is to be used in the production of ethanol where disruption of the starch granule is not a factor. However, where it is desirable to maintain the starch granule intact, the spacing between the disks should be above the particle size of the largest granules (between 35 and 100 mi¬ crons and preferably approximately 50 microns). It is desired to set spacing between the disks at slightly above the largest particle size expected (depending on the type of grain being processes. After the conventional extraction phase in which one or more solvents are added, and after settling (with or without centrifugation) , the clear supernatant containing the protein is decanted and the starch cake remains. The starch cake is washed to remove further protein and then slurried in water and cleaned up in a set of hydroclones in which all non-starch particles are separated. Thereafter the slurry is centrifuged to 40-70% by weight dry solids and dried in a flash dryer or drum dryer or other dryer. The pH is reduced to 6-7 with hydrochloric or other acid. The end result is a high quality pure starch of intact granules. The protein containing supernatant is processed through a continuous cross-flow microfilter having in¬ organic membranes. Preferably the membranes are alu¬ minum oxide or other inorganic membranes. (Note that there are also presently being developed but not yet commercially available some forms of organic membranes which may become available in the future.) The pH of the protein or protein isolate is reduced to any de¬ sired value through diafiltration with deionized water, which simultaneously increases the purity. Protein isolate is that material which has a pro¬ tein purity of 90% or more. Protein purity below 90% is considered to be protein concentrate. In corn, for example, the available protein is made up of approxima¬ tely 10% albumins and globulins (soluble respectively in water and neutral salt solutions), 35+% glutelins (soluble in alkali) and 50+% prolamines (mainly zein and soluble in high ethanol concentrations) . The system of the present invention recovers most of* the prolamines and glutelins, as well as some of the globu¬ lins. The overall extraction efficiency of protein is greater than 80%. With the foregoing in mind, it is an object of this invention to isolate from cereal grains the food value protein and starch present while enabling the maximum recovery of other useful by-products. In realizing this object, the starch constituents are separated from the protein constituents mechanically in a two-step grinding process. In the first step, the kernels are subjected to a dry milling operation in which the ker¬ nels are broken down to a particle size on the order of 5/64" or less in diameter. There follows a wet attri¬ tion milling process which reduces the particle size of the commodity to a very fine range. During this opera¬ tion, the protein/starch matrix is broken resulting in a more efficient extraction of protein. A further object of this invention is to produce protein isolate from corn or other grain while enabling use of the remaining constituents of the corn or other grain in further process which yield useful by-products, such as bacterial or yeast fermentation. In realizing this object of the present invention, the separation of protein and other constituents is accomplished while avoiding cooking of the agricultural commodity which would otherwise limit the usefulness of the constitu- ents of the commodity. Yet another object of this invention is to separ¬ ate the protein and starch constituents of cereal grains in such a manner that the protein recovery is maximized without destroying the integrity of the starch granules. In the case of corn, current varieties convention¬ ally processed are normally deficient in lysine and tryptophan. A high lysine corn is known (Crow's Opaque 2) which is only slightly deficient in tryptophan. However, new varieties of corn will become available soon with high protein content and all eight a ino ac¬ ids essential for human nutrition present in sufficient quantities to meet FAO/WHO standards. While the proc¬ ess to be described hereinafter will work with any va- riety of corn, it is contemplated as being most useful with such high protein content, essentially complete protein corn. Brief Description of the Drawings Some of the objects of the invention having been stated, other objects will appear as the description proceeds, when taken in connection with the accompany¬ ing drawing in which a schematic flow diagram of the process of this invention is shown. Detailed Description of the Invention While the present invention will be described more fully hereinafter with reference to the accompanying drawing, in which a preferred embodiment of the present invention is shown, it is to be understood at the out¬ set of the description which follows that persons of skill in the appropriate arts may modify the invention here described while still achieving the favorable re- suits of this invention. Accordingly, the description which follows is to be understood as being a broad, teaching disclosure directed to persons of skill in the appropriate arts, and not as limiting as in the present invention. A process for isolating protein from an agricultur¬ al commodity such as cereal grains in accordance with this invention preferably begins with a suitable com¬ modity which contains all eight essential amino acids in sufficient quantities to provide a complete protein as understood in accordance with the standards of the Food and Agricultural Organization of the United Na¬ tions. Such a commodity may be whole corn or some other cereal grain or vegetable matter. Such vegetable matter, or a suitable grain, is provided as the first step in the process, indicated at 10 in the drawing. It is contemplated that the process may possibly be practiced with other commodities which might supply less than complete protein. However, the maximum bene¬ fit is to be obtained where the commodity used does provide a complete protein, and thus that is the pre¬ ferred practice of this invention. As will be appre¬ ciated, the process may begin with whole corn, in which event protein is produced from both the germ and endo¬ sperm, or . with degerminated corn. Generally, a protein isolate produced from the germ alone will be a better quality isolate. The corn (in the preferred practice) or other is first dry ground in a hammer mill or the like to a par¬ ticle size of from about one sixteenth inch to three sixteenth inch nominal diameter. The ground corn is now defatted. The ground and defatted corn or other particulate vegetable matter containing bound-together protein and starch is then mixed with water to form a slurry in which the vegetable matter constitutes up to at least about 35 percent of the slurry by weight. The slurry is then fed to a special attrition mill for wet grinding which reduces the particles to a size in- the range of 1-100 microns such that the bond between starch and protein constituents is broken mechanically. A suitable mill is manufactured by Koruma Maschinenbau of the Federal Republic of Germany and sold for use in the cosmetic and drug industries. Such a mill also disperses the vegetable oils contained in the starting vegetable matter, such as corn oil, if not removed, to such an extent that no serious membrane fouling of sig¬ nificance occurs in subsequent process steps to be des- cribed hereinafter. Both wet and dry milling can pro¬ ceed at essentially ambient room temperatures. In cases where the starch constituent is to be used for the production of ethanol, the spacing between the disks of the mill, the pumping pressure, and the speed of the feed .are adjusted to yield particles in the range of approximately 1-10 microns. Where intact starch granules are desired, the parameters are adjus¬ ted to yield particles in the range of 35-100 microns. After wet milling, the slurry is subjected to pro- tein extraction. The specific sequence of the protein extraction steps may vary depending upon the specific nature of the starting vegetable matter, and the person of skill in the applicable arts practicing this inven¬ tion will discover that, as starting materials vary from those described here as most preferred, at least certain process variables must be varied to maximize yields. Attention will be directed to some of these matters hereinafter. In the presently preferred form of this invention, the temperature of the slurry is raised to about 125° Fahrenheit for the extraction steps which follow. Such heating will be a side effect of the wet milling and/or may be accomplished by supplying heat to the slurry. Temperatures much above 125° will result in denaturing the proteins rendering the process ineffective for re¬ covering high quality protein with good functionality. In the preferred process, the first step of extrac¬ tion involves the solubilization of the glutelins. This step involves adjusting the pH of the slurry to a range of from about 9 to about 12 by the addition of a suitable alkali. The step of adjusting the pH may com- prise adding at least one of sodium hydroxide and pot¬ assium hydroxide in a quantity sufficient for adjusting the pH of the slurry to the specified range. Where it is important that a low sodium end product be obtained, then potassium hydroxide is the preferred agent. The slurry is agitated during the addition of the pH ad¬ justing hydroxide. The pH adjusted alcohol/water/corn slurry is then allowed to dwell while being agitated for a predeter¬ mined interval of time to allow for the solubilization of protein. A residence time of from thirty to sixty minutes is generally sufficient. The slurry is then stirred and sufficient alcohol is added to achieve a solution in which the ethanol constitutes at least about 50% of the slurry by weight. The upper limit of alcohol content preferably is not more than 80% by weight. The alcohol/water/corn slurry is-.. then allowed to dwell while being agitated for a predetermined interval of time to allow for the solubilization of protein. At this point in the process, the proLa.mines or zein con¬ taining proteins enter solution. A residence time of from thirty to sixty minutes is generally sufficient. These two steps for extracting prolamines and glu¬ telins and globulins may, with some starting vegetable matter, produce a higher yield of end product if re¬ versed in sequence. That is, while the preferred se- quence for a high lysine corn is as described herein- above, it is contemplated that other starting materials may provide a higher yield if the first extraction is for glutelin and the second for prolamines. Further, while here described as two separate and sequential steps, it may be possible with some materials to essen¬ tially combine the two treatment steps and permit only a single period of residence or resting for extraction of all proteins. In any event, the steps of extraction are followed by a step of separating the slurry into two portions, a high solids content portion and a high liquids content portion. The two portions are here described in that manner out of a recognition that it is not easily poss¬ ible to complete the entire separation into wet and dry portions in a single step. Thus any attempt to separate solids from the slurry will of necessity carry a small quantity of liquids, and vice versa. The separation should be by settling, possibly with the use of aids such as biopolymers and rapid settling equipment, and may be with the further aid of devices such as a centri¬ fuge. The high liquid portion, or supernatant, is withdrawn following the separation process. The withdrawn supernatant contains the proteins which are in the process of becoming separated, and is next purified in a cross-flow microfiltration step with inorganic or organic membranes. At the present time, an inorganic membrane, namely aluminum oxide " , is preferred. This microfiltration yields a retentate with a high purity protein content, which upon under¬ going diafiltration will yield protein isolates with purities exceeding 90%. The zeta-potential of the alu- minum oxide membrane is zero around pH 8-9, and of the prevailing high pH-values of 9-12, both the membrane and the proteins are charged negatively, thus repelling one another and yielding the retentate as. being the product. The retentate is then concentrated until the degree of concentration is acceptable for spray drying or some other drying procedure which will yield a dry powder isolate useful as a foodstuff or food supple¬ ment. A liquid protein concentrate or isolate may also be produced for use in, for instance, nutritional bev- erages or pharmaceutical applications. After recovery of the ethanol solvent before or af¬ ter microfiltration, for concentration and recycling, the high solids content portion of the slurry is con¬ centrated and, where ethanol is the desired end prod- uct, then passed to a fermentation process as a feed¬ stock. The fermentation process may be any of those known to persons skilled in the applicable arts, in- cluding a bacterial fermentation process for the pro¬ duction of butanol or a yeast fermentation process for the production of ethanol. Such processes and their other by-products being known from other disclosures, they will not be here discussed at length. The fermen¬ tation process may be concluded with distillation or with other separation procedures such as pervaporation to yield the product streams desired. Alternatively, when intact starch granules is the desired end product, the high solids content portion of the slurry is washed, cleaned, dried, and the pH re¬ duced to approximately 6. If the corn or other starting material used has an incomplete amino acid balance, it is, of course, poss- ible to add some natural or synthetic amino acid of the deficient type to bring the end product into appropri¬ ate balance. Such additions may be made to the dry isolate powder along with any other materials necessary or appropriate for flowability, handling or the like. In regular corn, the ethanol soluble protein fraction is larger than the alkali soluble fraction, with the two together making up some 80-90% of the total protein of the corn. In a high lysine corn, the Opaque 2 gene changes both proportions of these protein fractions as well as the lysine content within the various protein groups. It is for this reason that, with various starting materials, various process parameters must be adjusted to optimize the yield obtained from the parti¬ cular starting material. Example I In development of this invention, a quantity of Crow's high lysine corn was ground in a roller mill to a particle size of about one sixteenth inch and six pounds of such dry ground corn was mixed with 5.1 li¬ ters of pure water to form a slurry. The corn con¬ tained 9.5% moisture and 8.56% protein, thus starting the example with 233 grams of protein in the slurry. The slurry is then passed through an attrition mill where the corn was further ground to a sufficiently small particle size (approximately 1-50 micron) that the bond between the protein and starch in the starch/ protein matrix was broken. The slurry was stirred, heated to 125° Fahrenheit, the pH adjusted to 11.4 with NaOH, and sufficient ethanol added to increase the to¬ tal volume to 18 liters. The slurry was agitated for thirty-five minutes for protein extraction, and was then allowed to settle for two hours, fifteen minutes. Careful decantation yielded over 10 liters of super¬ natant containing 18.9 g/L of protein (an 82% extrac¬ tion), which was then fed to a microfiltration module. The microfiltration module was equipped with a 0.2 mi- cron aluminim oxide membrane. During filtration, tem¬ perature was maintained at 123° Fahrenheit and feed pump pressure at about 90 psig. The cross-velocity was 8.36 M/sec and average transmembrane pressure was about 60 psig. An 18 second backwash with 120° water at pH 12 was applied every four minutes. The flux obtained was 170 L/M 2 /H. The retentate from the process con¬ tained 5.8 g/L of protein with a purity of 75%. The remaining impurities were minerals and some fat which were removed by dialysis to bring the protein purity to 90.4%. The retentate was then concentrated to about 50 g/L in a rotary vacuum evaporator and spray dried to form a powder isolate with about 12% moisture content and over 90% purity. A small amount of a silica based antistatic agent was added to facilitate the spray dry¬ ing step. After the process was completed, the filter membrane was regenerated to achieve the same flux using water as had been the case prior to the process illus¬ trated. A later study with defatted (as described in Example II) corn resulted in the extraction of 83.4% of the pro¬ tein originally present in the corn in the two-step ex- traction process (60 minutes at 125°F and pH 11.6; 60 minutes at 125°F and 68% v/v ethanol. After settling and centrifugation of the supernatant (15 minutes at 15,100 x g) a 68.2% pure protein solution was obtained. Following microfiltration with a 0.2 micron aluminum oxide membrane and backflush with compressed air plus diafiltration with 5.6 times the original volume of feed as Dl-water, the retentate yielded a 98% purer protein isolate at pH 6.9. Spray drying resulted in a 98% pure protein isolate with 7.1% moisture. Example II 13 pounds of whole corn (hi-ly Opaque 2 from Crow) with 8.5% (weight to weight) protein on an as is basis were ground in a hammer mill with a 5/64" screen. Total available protein was thus 502 grams. The corn was defatted with n-hexane under high vac¬ uum in a modified Crown Iron Works machine at tempera¬ tures not exceeding 52°C (125.6°F) so as not to dena¬ ture the protein. Ethanol or other solvents may be used for the defatting operations. The ground and de- fatted corn was mixed with deionized water into a 31 weight % slurry, which was then milled in a Koruma attrition mill to a particle size of 50-100 microns. In doing so, the protein/starch matrix was broken. Next, under continuous stirring and at temperatures not exceeding 125°F, the protein was extracted in a two-step process. In the first step, the pH was raised to 11.3 with sodium hydroxide and a 45 minute extrac¬ tion time allowed. In the second step, ethanol was added to a final concentration of 60% by volume and another 45 minute extraction time allowed. The mixture was allowed to settle for 2 hours, and the supernatant decanted. A total of 82.1% of the available protein had been obtained in solution. Of the supernatant, 12.0 liters were centrifuged at 17,000 x g. The centrate contained 17.43 g/kg of total solids with 10.97 g/kg of total protein (determined as total Kjeldahl nitrogen times 6.25). Its purity was 62.9%. There followed cross-flow microfiltration and dialysis with a 0.2 micron aluminum oxide membrane (Alcoa) yielding retentate (product in this case) of 6.5 liters with 15.58 g/kg of total sol- ids and 14.08 g/kg of protein. Hence, the purity was 90.4%. The pH of the retentate was 7.3 after 63.6 li¬ ters of Dl-water were used for dialysis. This product was spray dried concurrently at exit temperatures of 218°F, yielding a fluffy powder with 8.0% moisture. The protein in the permeate was not recovered here, however, that may be done in a membrane unit with smaller pore size. Utilizing a 100 Angstrom aluminum oxide membrane, a total of approximately 85% of the protein in the feed was recovered. Depending upon the protein content and make-up of the protein in the corn, from three to over four pounds of protein isolate prod¬ uct may be produced per bushel. The product pH may be at or near neutral. By controlling the purity through diafiltration until the proper pH (an almost linear re¬ lationship) is obtained,products with different func¬ tionalities may be produced. Functional properties as viscosity, water and oil absorption, gel strength, emulsification, solubility, wettability, etc. can be varied this way. The starch is cleaned and dried (spray dried). Due to the mild processing conditions, the starch granules are still intact. This is determined by electron mi¬ croscopy, x-ray diffraction, digital scanning calori- metry, electron microscopy and Congo red application to a sample under a microscope. Such intact starch granu¬ les are appropriate raw material for new biodegradable plastics which will contain up to 75% starch. It may be used to produce pyrodextrins. It may be cross- linked to overcome the sensitivity of the granules to disruption while it improves the strength of the swol¬ len granules. This way it can be used in surgical dust- ing powders, disposable sanitary products, antiperspir- ant sprays, etc. It may be extruded to yield instant laundry starches or pregelatinized for specialty food applications, etc. As will be understood, the present invention has disclosed processes capable of producing protein iso¬ lates, intact starch granules, and other by-products. The other products include butanol, ethanol, corn oil, dietary fiber, etc. and are produced by applying other¬ wise known technology. In the drawings and specifica- tions, there has been set forth a preferred embodiment of the invention and, although specific terms are used, the description thus given uses terminology in a gener- ic and descriptive sense only and not the purposes of limitation.

Claims: WHAT IS CLAIMED IS: 1. A process for isolating protein from cereal grains containing starch and protein bound into a matrix, the process comprising the steps of: wet attrition milling particles of said grain to a size sufficiently small to break the bond between starch and protein, then extracting the broken bond protein from the starch with at least one solvent, then separating the resulting high liquid content portion containing the extracted protein from the resulting high solids content portion containing the starch, and then subjecting the high liquid content portion of the extracted protein to continuous cross-flow micro- filtration with inorganic membranes for isolating the protein constituent, concentrating the protein into a dry powder. 2. A process for isolating protein from corn comprising the steps of: wet attrition milling particles of said grain to a size sufficiently small to break the bond between starch and protein, then extracting the broken bond protein from the starch with at least one solvent, then separating the resulting high liquid content portion containing the extracted protein from the starch, and then content portion containing the starch, and then subjecting the high liquid content portion of the extracted protein to continuous cross-flow micro- filtration with inorganic membranes for isolating the protein constituent, concentrating the protein into a dry powder. 3. A process according to one of Claim 1 or Claim 2 wherein step of breaking by wet attrition milling comprises grinding particles of vegetable matter to a particle size in the range of about one [micron] to 100 microns. 4. A process according to one of Claim 1 or Claim 2 . further comprising the step of passing starch separ¬ ated from the protein isolate to a fermentation process as a feedstock. 5. A process according to Claim wherein said step of passing starch to a fermentation process com¬ prises passing the starch to a bacterial fermentation process for the production of butanol. 6. A process according to Claim 4 wherein said step of passing starch to a fermentation process com¬ prises passing the starch to a yeast fermentation proc¬ ess for the production of ethanol. 7. A process for isolating protein from cereal grains comprising the steps of: adding water to ground participate vegetable matter obtained from said cereal grains containing bound together protein and starch for making a slurry in which the vegetable matter constitutes up to about 35 percent of the slurry by weight, passing the slurry through an attrition mill and grinding the particulate vegetable matter to a par- ticle size effective to break, by physical action, the bond between protein and starch in the starch-protein matrix of the vegetable matter, adding alcohol to the slurry for making the slurry in which the alcohol constitutes at least about 50 percent of the slurry by weight, adjusting the pH of the slurry to a range of from about 9 to about 12, permitting the slurry to dwell for a suffi¬ cient time interval to cause solubilization of protein, then separating the slurry into high solids content and high liquid content portions, subjecting the high liquid content portion of the slurry which contains the solubilized protein to continuous cross-flow microfiltration with inorganic membranes for isolating the protein constituent, and then concentrating and drying the protein isolate. 8. A process for producing protein isolate from corn comprising the steps of: grinding corn to a particle size in the range of from about one sixteenth to about three sixteenths inch nominal diameter, then adding water to the ground corn particles for making a slurry having corn constituting from about 30 to about 35 weight percent of the slurry, passing the slurry through a wet attrition mill and grinding the corn particles to a particle size effective to break the bond between protein and starch in the corn by physical actions, then adding alcohol to the slurry for making a slurry in which the alcohol constitutes at least about 0 percent of the slurry by weight, adjusting the pH of the slurry to a range of from about 9 to about 12, permitting the slurry to dwell for a suffi¬ cient time interval to cause solubilization of protein, then separating the slurry into high solids content and high liquid content portions, subjecting the high liquid content portion of the slurry which contains the solubilized protein to microfiltration for isolating the protein constituent, and then concentrating and drying the protein isolate. 9. A process according to one of Claim 7 or Claim 8 wherein said step of adjusting the pH of the slurry to a range of from about 9 to about 12 comprises adding an. alkali. step of adjusting the pH comprises adding at least one of sodium hydroxide and potassium hydroxide in a quan¬ tity sufficient for adjusting the pH of the slurry to said range. 11. A process according to Claim 10 wherein said step of adding a quantity of at least one of sodium hydroxide and potassium hydroxide further comprises agitating the slurry while adding, the pH adjusting hydroxide. 12. A process according to one of Claim 7 or Claim 8 further comprising the step of adjusting the pH of the slurry to about 8 after passage of said time inter¬ val. 13. A process according to Claim 12 wherein said step of adjusting the pH of the slurry to about 8 com¬ prises adding a quantity of sulfuric acid sufficient for adjusting the pH of the slurry to said range. 14. A process according to one of Claim 7 or Claim 8 wherein said step of grinding to a particle size eff¬ ective to break, by physical action, the bond between protein and starch comprises grinding to a particle size in the range of about one to 100 microns. 15. A process according to one of Claim 7 or Claim 8 further comprising, prior to the step of adding alco¬ hol, the step of adjusting the temperature of the slurry to about 125° Fahrenheit and maintaining the temperature of the slurry and the high liquid content portion thereof within five degrees of 125° Fahrenheit throughout the process. 16. A process according to one of Claim 7 or Claim 8 wherein said step of permitting the slurry to dwell for a predetermined interval of time comprises per¬ mitting the slurry to dwell for an interval in the range of from about thirty minutes to about two hours and agitating the slurry during the interval of dwell. 17. A process according to one of Claim 7 or Claim 8 further comprising the step of passing starch separ¬ ated from the protein isolate to a fermentation process as feedstocks. 18. A process according to Claim 17 further com¬ prising the step of passing starch to a bacterial fer¬ mentation process for the production of butanol. 19. A process according to Claim 17 further com¬ prising the step of passing starch to a yeast fermen¬ tation process for the production of ethanol. 20. A process for producing protein isolate from high lysine corn comprising the steps of: grinding high lysine corn having prolamine, glutelin, sugar and starch constituents into particles having a size in the range of from about one sixteenth to about three sixteenths inch nominal diameter, then adding water to the ground corn particles for making a slurry having corn particles constituting from about 30 to about 35 weight percent of the slurry, passing the slurry through an attrition mill and grinding the corn particles to a sufficiently fine particle size to mechanically break the chemical bond between the prolamine and glutelin and starch consti¬ tuents by physical action, then : extracting the prolamine and glutelin consti¬ tuents of the corn from the finely ground particles into a solution, then separating the slurry into a high solids con¬ tent portion containing sugar and starch and a high liquid content portion which contains the extracted prolamine and glutelin constituents of the corn, subjecting the high liquid content portion of the slurry to continuous cross-flow microfiltration with inorganic membranes for isolating the protein constituents, and then concentrating and drying ther protein constituents to form the protein isolate. 21. Protein made by a process comprising the steps of: adding water to the ground particulate vege¬ table matter containing bound together protein and starch for making a slurry in which the vegetable matter constitutes up to about 35 percent of the slurry by weight, passing the slurry through an attrition mill and grinding the particulate vegetable matter to a par- ticle size effective to break, by physical action, the bond between protein and starch in the starch-protein matrix of the vegetable matter, then adding ethanol to the slurry for making a slurry in which the ethanol constitutes at least about 50 percent of the slurry by weight, adjusting the pH of the slurry to a range of from about 9 to about 12, permitting the slurry to dwell a sufficient time interval to cause solubilization of protein, .then separating the slurry into high solids content and high liquid content portions, subjecting the high liquid content portion of the slurry to continuous cross-flow microfiltration with inorganic membranes for isolating the protein constituent, and then concentrating and drying protein constituents to form the protein isolate. 22. Protein made by a process comprising the steps of: grinding corn to a particle size in the range of from about one sixteenth to about three sixteenths inch nominal diameter, then adding water to the ground corn particles for making a slurry having corn constituting from about 30 to about 35 weight percent of the slurry, passing the slurry through an attrition mill and grinding the corn particles to a particle size effective to break the bond between protein and starch in the corn by physical action, then adding ethanol to the slurry for making the slurry in which the ethanol constitutes at least about 50 percent of the slurry by weight, adjusting the pH of the slurry to a range of from about 9 to about 12, permitting the slurry to dwell a sufficient time interval to cause solubilization of protein, then separating the slurry into high solids content and high liquid content portions, subjecting the high liquid content portion of the slurry to continuous cross-flow microfiltration with inorganic membranes for isolating the protein constituent, and then concentrating and drying the protein constit¬ uents to form the protein isolate. 23. A process for recovering intact starch gran¬ ules from cereal grains containing starch and protein bound into a matrix, the process comprising the steps of: _ wet attrition milling particles of said cereal grain to a size sufficiently small to break the bond between starch and protein and sufficiently large to retain substantailly all of the starch granules intact; extracting the broken bond protein with at least one solvent; separating the resulting high liquid content portion containing the extracted protein and the re¬ sulting high solids content portion containing the starch granules; and cleaning and drying the starch granules. 24. The process according to Claim 23 wherein said particle size resulting from said wet attrition milling step is in the range of about 35-100 microns. 25. The process according to Claim 23 wherein said particle size resulting from said wet attrition milling step is in the range of 50-100 microns. 26. The process according to Claim 23 wherein, after cleaning and before drying, the pH of the starch granules is reduced to approximately 6-7. 27. A process for producing protein and intact starch granules from cereal grains comprising the steps of: grinding the cereal grain to a particle size in the range of from about one-sixteenth to about three-sixteenths inch nominal diameter; adding water to ther ground grain particles for making a slurry in which the grain constitutes from about 25% to about 35% by weight of the slurry; passing the slurry through a wet attrition mill and further milling the ground grain particles to a particle size sufficiently small to break the bond between starch and protein and sufficiently large to retain substantially all of the starch granules intact by physical actions; adding alcohol to the slurry for making a slurry in which the alcohol constitutes at least about 50% of the slurry by weight; adjusting the pH of the slurry to a range of from about 9 to about 12; permitting the slurry to dwell for a suf¬ ficient interval to caused solubilization of protein; separating the resulting high liquid content portion containing the extracted protein and the re- suiting high solids content portion containing the starch granules; subjecting the high liquid content portion of the slurry which contains the solubilized protein to cross-flow microfiltration with inorganic membranes for isolating the protein constituent; concentrating and drying the protein isolate; and cleaning and drying the starch granules. 28. The process according to Claim 27 wherein the step of adjusting the pH of the slurry to a range of from about 9 to about 12 comprises adding alkali. 29. The process according to Claim 28 wherein said step of adjusting the pH of the slurry to a range of from about 9 to 12 comprises adding at least one of sodium hydroxide and potassium hydroxide in a quantity sufficient for adjusting the pH of the slurry to the specified range. 30. The process according to Claim 26 wherein af¬ ter step (b), the step of defatting the cereal grain at temperatures not exceeding 52°C. 31. The process according to Claim 30 wherein said step of adjusting the pH of the slurry to about 8 com¬ prises adding a quantity of sulfuric acid sufficient for adjusting the pH of the slurry to the specified range. 32. The process according to Claim 27 wherein the particle size resulting from said wet attrition milling step is in the range of about 35-100 microns. 33. The process according to Claim 27 wherein said particle size resulting from said wet attrition milling step is in the range of 50-100 microns. 34. The process according to Claim 27 wherein, after cleaning and drying step, the pH of the starch granules is reduced to approximately 6. 35. The process according to Claim 27 wherein dur- ing the extraction steps set forth in sub-paragraphs (d)-(f) the temperature is maintained within 5° of 125° Fahrenheit. 36. The process according to Claim 27 wherein said step of permitting the slurry to dwell for a predeter¬ mined interval of time comprises permitting the slurry to dwell for an interval of time in the range of from about 30 minutes to about 2 hours and agitating the slurry during the interval of dwell. 37. The process according to Claim 27 and further after step (g) centrifuging the high liquid content portion of the slurry at a g-force in the range of 10,000-15,000 xg to recover dispersed particulate matter. 38. The process according to Claim 27 wherein the cross-flow microfiltration step includes diafiltration in conjunction therewith. 39. A slurry formed from ground cereal grain and comprising a high liquid content portion containing protein isolate and a high solids content portion con¬ taining intact starch granules. 40. A process for producing protein isolate from cereal grains containing starch and protein bound into a matrix, the process comprising the steps of: grinding corn to a particle size in the range of from about one sixteenth to about three sixteenths inch nominal diameter; defatting the ground corn particles; adding water to the ground corn particles for making a slurry having corn constituting from a about to about 35 weight % of the slurry; passing the slurry through a wet attrition mill and grinding the corn particles to a particle size effective to break the bond between protein and starch in the corn by physical actions; adding alcohol to the slurry for making a slurry in which the alcohol constitutes at least about 50% of the slurry by weight; adjusting the pH of the slurry to a range of from about 9 to about 12; permitting the slurry to dwell for a suf¬ ficient time interval to cause solubilization of protein; separating the slurry into high solids content and high liquid content portions; subjecting the high liquid content portion of the slurry which contains the solubilized protein to microfiltration and diafiltration for isolating the protein constituent; concentrating an drying the protein isolate. 41. The process according to Claim 40 wherein said step of wet attrition milling to a particle size effec¬ tive to break, by physical action, the bond between protein and starch comprises milling to a particle size in the range of about 1 to 100 microns. 42. The process according to Claim 40 wherein said step of microfiltration and diafiltration comprises subjecting the high liquid content portion of the slurry which contains the solubilized protein to a cross-flow microfiltering unit with inorganic membranes.

Inventors: KAMPEN WILLEM H, KAMPEN, WILLEM, H.
Applicants: ENERGENETICS INC, ENERGENETICS, INC.
Application year: 1991
Main classification: A23J1
IPC codes: A23J1, A23L1, C07K1, C07K14, C08B30