GB2176487A - Process for extracting proteins from brewer's grain - Google Patents

Abstract

A process for extracting protein solids from spent brewer's grains includes alkaline extractions of the grains followed by ultrafiltration of the product to yield a highly purified protein solid. An enzymatic treatment step in the process modifies the protein solid.

Description

SPECIFICATION Improved process for extracting proteins from brewer's grain This invention is directed to an improved process for isolating protein solids from brewer's grain.

In my prior United States patent 3,846,397,1 summarized the processes of making beers, ales, and stouts utilizing barley malt and other vegetable products. In one of the earlier steps ofthis brewing process, the starch within the barley malt or othervegetable ingredient is enzymatically converted to a sugar which is soluble in the processing liquid noted asthe wort. The remaining portions of the barley malt or othervegetable ingredient remain as spent grains or brewer's grains once the wort is separated from them. These spent grains or brewer's grains include coagulated and precipitated proteins, as well as other insoluble components.

The brewer's grains can be utilized directly as animal feed. However, they contain some high quality protein which, if separated from other components, have other higher order uses other than simplythat as a crude animal feed.

In my prior process described in my U.S. patent 3,846,397, a protein containing solid is isolated. In addition to protein,this solid contains othercomponents such as salts, lipids, and other organic residues from the barley malt or other vegetable ingredient.

The non-protein content of the solids isolated on a dried weight basis constitutes about 50% of the weight ofthis solid. While this is a significant increase in concentrate of the protein compared to its concentration in the brewer's grains, it is desirable in many instances to further increase the protein concentration in the recovered solids.

In many instances it is further desirable to alterthe protein which can be recovered from the brewer's grain to increase the nitrogen soluble index ofthe protein and to orgenoleptically modify it whereby it can be utilized in high quality food or beverage products.

In view ofthe above, the present invention provides for improved processes for recovering protein solids from spent grains or brewer's grains. This is achieved in a process for recovering protein solids from brewer's grains in which said grains are treated with a hot alkaline solutionto solubilizethe protein fraction of said brewer's grains in said solution and in which said solution is thereafter treated to recover protein solids, the improvement which comprises: treating said solution to remove gross particulate matterfrom said solution; passing said solution through an ultrafiltration device to separate said solution into a permeate and a retentate; dewatering said retentateto recover a solid having a high protein content based on the dry weight of said recovered solid.

Further, this is achieved in a process for recovering protein solids from brewer's grains in which said grains are treated with a hot alkaline solution to solubilize the protein fraction of said brewer's grains in said solution and in which said solution is thereafter treated to recover protein solids, the improvement which comprises: treating said solution to remove gross particulate matterfrom said solution; treating said solution with a proteolytic enzyme for a time sufficientto at least partially hydrolyze said proteins; acidifying said enzymatic treated solution to acid pre cipitatesaid protein solids.

The drawing is a flow chart showing the utilization of brewer's grains as a starting material to yield high quality protein solids therefrom by following the va rioustreatment path outlined.

In making beers, ales, and stout, hereinafter collec tivelyidentified bytheterminology"beer", barley malt is first soaked in water and allowed to germinate, afterwhich it is dried and ground toflour. Theflouris then fed into mashtubswherein its starch is for mented into sugar. Other vegetable ingredients, as are noted in my U.S. patent 3,846,397, can also be added to the barley malt to supply starchesforfer- mentation.

After fermentation, the material now noted as a mash is brought to a boil to stop the enzymatic action utilized during fermentation, and to coagulate and percipitate proteins leached from the barley malt, which, if carried over into the liquid portion designatedasthewortwouldimpartundesirableprop erties to the resulting beer. The wort is suitably separated from the solid components ofthe mash and further processed into beer. The solids from the mash, which after separation from the wort are noted as brewer's grains or spent grains, constitutes the starting material for the processes ofthis invention.

The brewer's grains 10 after separation from the wort, can be utilized directly. Alternately, they can be dried and milled to a very fine powder to facilitate increase yields of protein solids by breaking down the vegetable residues into smaller units to facilitate the extraction ofthe proteins. In any event, the brewer's grains, whether used directly after separation ofthe wort, or after being intermediately processed, are treated with an alkaline solution 12.

The brewer's grains 10 are diluted with water so that they consitute about 10% solids, and then are heated. An alkaline solution 12, asforinstance a 0.1 normal sodium hydroxide solution, is added to the slurry ofthe brewer's grain lOin the water. As perthe teachings of my U.S. patent 3,846,397, heating can preferentially be carried out so astoconcurrently raise both the temperature and the pH of the slurry of the brewer's grains 10.

The initial pH of the brewer's grains in the water is approximately pH 6, and this is raised by the alkaline solution 12toa pH of about pH 10 over the course of the heating period. The heating is effectively carried out on a suitable industrial scale by the infusion of steam into the suspension ofthe brewer's grain lOin the water and alkaline solution 12.

When the slurry of the brewer's grains 10 the water with the addition ofthe alkaline solution 12 has reached a temperature of about 1 80" to 21 2"F, the pH is effectively raised to about a pH 10, the remaining unsolubilized solids are separated at step 14 in the flow chart by appropriate techniques such as filtering centrifugation and the like. These solids can then be utilized as animal feed 16 after appropriate drying of the like.

The solution 18, from the separation step 14, can then be treated utilizing several processescomprising the several interrelated embodiments ofthe invention.

In a first ofthese processes, the solution 18 is en zymatically treated at step 20. Enzymatic treatment is performed utilizing proteolytic enzymes. For this enzymatictreatment, the solution 18 can be utilized directly as received during the separation step 14, or alternately, the pH ofthe solution 18 can be adjusted downwardly within a pH range of pH 7to pH 8. Itis preferable, however, to utilize the solution 18 simply as it is received from the separation step 14. Generally, as received, the solution 18 will have a pH of about pH 9 or pH 10, because itis atthis pH rangethat maximum protein subtraction from the brewer's grains 10 is obtained.

In any event, enzymatic treatment will be for a time period sufficient to partially hydrolyze the proteins within the solution 18. Normally, the amount of enzyme utilisedwould be based upon the expected amount ofdryweight ofthe protein solids eventually recovered. The enzyme would be present in a concentration of about.001%to about 1% by weight ofthe enzyme per weight ofthe dry weight of the recovered protein solids.

Preferably, the proteolytic enzyme is a fungal protease enzyme. Mentioned as preferable enzymes for thisenzymatictreatmentare enzymes sold underthe tradename of Milezymes AFP and Nutrase. Milezymes AFP enzymes are available from Miles Laboratory, Eckhart, Indiana; and Nutrase is availablefrom Novalabs, Division of Nova, a Danish company having U.S. offices in Connecticut. The Milezymes enzymes would include milezyme AFP 1,000,2,000, 3,000, andfungal protease31,000.

Technical literature supplied by the producers of these enzymes indicatethatenzymaticactivityatthe preferred pH ranges of pH 9 or pH 10 noted above is exceedingly low. However, contrary to this, I have found that enzymatictreatment atthis high pH yields a product having superior properties with respectto certain orgenolepticcriteria.

Insofar as extremely high heattends to denature and inactivate these proteolyticenzymes, prior to en zymatictreatmentthe solution 18 should be cool below at least 1000 F. The enzymatic treatment 20 can be conducted from room temperature to below 100" F.

Afterthe enzymatic treatment 20, the resulting solution can be briefly heated to above 1 60" F, preferably around 1900 F, to heatkill the enzyme. Depending upon other process steps, as is outlined below, a separate heattreatmentstepto kill the enzyme after enzymatictreatment 20, may or may not be included in the processing scheme.

In a first embodiment ofthe invention, after en zymatictreatment 20, the resulting solution is then acidified at acidification step 22 below pH 7, preferably pH 6 or lower. This acidification causes acid precipitation of the proteins in the solution. The precipitated proteins are appropriately removed from the reaction liquors, and are de-watered at step 24 utilizing appropriate techniques such as filtration, centrifugation, and the like, to yield protein solids 26.

The protein solid 26 can be suitably dried for storage orfor use as a high quality protein. The resulting liquors 28 from the acidification step 22 can befurther treated, if desired, to yield other products 30, not forming a portion of the instant invention, which are leached from the brewer's grains 10 by the akaline solution 12.

In a further embodiment, after completion of the enzymatic treatment 20, the protein solutions are passedthrough an ultrafiltration device to perform an ultrafiltration step 32.

In even a further embodiment of the processing steps ofthe invention, the enzymatic treatment 20 is not utilized inbetween the separation step 14 and the ultrafiltration step 32, but instead the solution 18 is directly passed through the ultrafiltration device for the ultrafiltration step 32.

Forthe ultrafiltration step 32, any one of a number of commercially available ultra filtration membranes can be utilized. Typically, a large pore ultrafiltration membrane ableto separate the large molecular weight proteins from smaller components, will be utilized. As for instance, a ultra filtration membrane having a cutoff point of approximately 100,000 molecularweight units. This allows retention of the desired proteins while passing through salts, lipids, and other smaller organic molecules which are originally leached from the brewer's grain 10 by the alkaline solution 12. In thisway,the large molecularweight proteins can be freed ofthe other materials leached from the brewer's grains 10.Withoutthe ultrafiltration step 32, many ofthese materials are carried over into the protein product which restricts the final product to containing only abut 50% protein. By utilizing the ultrafiltration step 32, the percentage of protein in the final product can be raised significantly to at least aboutthe 80% level, and preferably higher, as for instance 90%.

In any event, the solution 18, with orwithoutthe enzymatic treatment step 20, is passed through a suitable ultrafiltration device as a diluted solution wherein the solids contents would be in the range of about one part solid matter from the brewer's grains 10 to about 10 to 50 parts water In the ultrafiltration device, the solution 18, with or without enzymatic treatment step 20, is separated into a permeate 34, which passes through the ultrafiltration membrane, and a retentate 36 which is retained by the membrane based upon the molecular weight cutoff point of the membrane. The permeate 34 can be processed to yield other products 38 if desired.If an enzymatic treatment 20 is included with- in the process steps, these other products 38 might also include certain very small proteins chains and individual amino acids which might be cleaved from the larger proteins. If a particular amino acid our a small protein were desired, appropriate choice ofthe enzymes for utilization in the enzymatic treatment 20 could be made so as to yield the desired products in the other products 38.

For the purposes of this invention, however, the desired protein solids constitute the retentate 36. The retentate 36 can be further de-watered at step 39 to yield a protein solid 40 of the invention. Insofar as the protein solid 40 is, in fact, water soluble because of the previous alkaline treatment 12, it has certain desirable characteristics for utilization in otherfood pro ducts. Depending upon the particular alkali utilized to form the alkaline solution 12, the protein solid 40 would be as an alkali proteinate. Such a proteinate would be very water soluble, and, if desired, residual water could be maintained on the product40 tofacili- tate resolubilization ofthis product our further processing into high quality foodstuffs and the like.

It is preferable to perform the ultrafiltration 32 utilizing a warm solution, as for instance, a solution of about 140 F. Preferably during the leaching ofthe brewer's grain 10with the alkaline solution 12,the solution is heated. Therefore, after separation step 14, the resulting heated solution 18 can be directly utilized forth ultrafiltration step 32.

An acidification step 42 can be introduced in be tween the solution step 18 and the ultrafiltration step 32, or after the enzymatic treatment 20 and before the ultrafiltration step 32. If the acidification step 42 is utilized, the solution 18 is directly acidified, or is acidified after enzymatic treatment 20, as was discussed with respect to acidification step 22. However, the solid products are not separated, but the total contents ofthe acidification step 42 are passed through the untrafiltration device for the ultrafiltration step 32.

The presence ofthe solid protein particles from the acidification step 42 can enhance the ultrafiltration step 32 by preventing pore blockage of the ultrafiltration membrane. The precipitated protein from the acidification step 42 is retained in the retentate36, and the mother liquors from the acidification step 42 are passed into the permeate 34. Contrary to the acidification step 22, however, the acidification step 42 can, if desired, by only a partial acidification to only partially precipitate the protein contents of the solution 18, with the remainder of the protein contents of the solution being separated during the ultrafiltration step 32 based upontheirmolecularweight.

Alternately, to utilize the retentate 36 directly for production of the protein solid 40, the retentate 36 can be solubilized at step 44 by the addition of water46.

The resulting solution from the solubilization step 44 can then be enzymaticallytreated at step 48 in a like manner as with the enzymatic treatment step 20, followed by acidification at step 50; or the resulting solution from the solubilization step 44 can be directly acidified at step 50.

The acidification step 50 is as was described forthe acidification step 22. The mother liquors 52from this acidification step can be further treated, if desired, to yield other products 54 as was described for the other products 30. The acid precipitated protein from the acidification step 50 is de-watered at step 56 yielding the protein solid 58.

The protein 58will differslightlyfrom the protein solid 40 in that it has been acid precipitated and, thus, will have different solubility characteristics from the protein solid 40. After drying, however, both the protein solid 40 and the protein solid 58 will be dry, white, bland-flavored proteins suitable for utilization in high quality food products such as milk substitutes, or protein additives for other food products. This dis tinguishes them from other protein products which have not been subjected to the ultrafiltration step 32, which generally are darker in colorand less mild.

The protein product 30, which, while not having undergone the ultrafiltration treatment step 32, has undergone the enzymatic treatment step 20 and will also exhibit certain improvements in both its color and flavor characteristics.

The protein solids 40 and 58 exhibit protein concentrations based on a dry weight basis of at least 80% protein content. Generally, this protein content will be ofthe order of 90% protein content. The protein solids 40 and 58 will have an increased nitrogen solu ble index compared to other protein products from brewer's grain 10 as, for instance, the protein pro ducts of my patent 3,846,397. Further, if enzymatic treatment, such as enzymatic treatment steps 28 or 48, is utilized in the process flow scheme, the resultant protein solids 26,40, and 58 will have a decrease of certain amino acid constitutants thereof which have been split off by the enzymatic treatment.It is believed that this loss of certain ofthe amino acid components ofthe protein solids yields betterflavor characteristics resulting in protein solids which are very bland compared to protein solids which have not been enzymaticallytreated in a like manner.

While a single ultrafiltration step 32 has been shown in the flow chart ofthe drawing, additional ultrafiltration steps might be introduced at other points in the flow scheme such as after the enzymatic treatment step 48 to yield a retentate and, thus, bypassing the acidification step 50. By introducing an ultrafiltration step afterthe enzymatictreatmentstep 48, any amino acids which might be split offfrom the protein would be small enough to not be retained in the retentate in the ultrafiltration step utilized after the enzymatic treatment step 48, and, as such, the protein isolate from the retentate of any such filtration step would differ because of the loss of the hydrolyzed amino acids.

Example 1 Five hundred grams of wet, spent grain comprising approximately 100 grams of dry,spentgrain and 400 grams ofwaterwere mixed with 1000 mIs of additional water. The pH was raised to pH 10 utilizing sodium hydroxide concurrently with heating ofthesolution to 140% The heating and raising ofthe pH is as is set forth in my U.S. patent 3,846,397, the entire contents of which are herein incorporated by reference. The solution at this point contains 13.5% solid content.

755 m Is ofthis material was passed through an appropriate ultrafiltration device to yield 350 m Is of retentate having 6.8% solids.

Example 2 In a like mannerto the procedure of Example 1, prior to ultrafiltration, .5 parts milezymes AFP was added to the solution from the alkaline extraction of the brewer's grains after cooling ofthe solution to about 1000 F. After enzymatic treatment, the solution was heated to 1400 for separation in the ultrafiltration device, as per Example 1.

Example 3 In a like mannerto Example 1,the solutionfromthe alkaline extraction ofthe brewer's grains was passed through an ultrafiltration device, and the retentate was taken up in 10 partswaterto which would be added a milezyme AFP enzyme. After appropriate treatment, the resulting enzymatic treated solution was acidified to below pH 6to acid precipitate the resultant protein solid.

Claims (20)

1. In a process for recovering protein solidsfrom brewer's grains in which said grains are treated with a hot alkaline solution to solubilize the protein fraction of said brewer's grains in said solution and in which said solution is thereafter treated to recover protein solids, the improvement which comprises: treating said solution to remove gross particulate matter from said solution; passing said solution through an ultrafiltration device to seperate said solution into a permeate and a retentate; de-watering said retentateto recover a solid having a high protein content based on the dry weight of said recovered solid.

2. The process of claim 1 wherein: said protein in present in a concentration of at least 80 percent of the dryweight of said recovered solid.

3. A process of ciaim 1 orclaim2wherein: the pH of said solution is from about pH 7 to about pH 10 priorto passing said solution through said ultrafiltration device.

4. The process of claim 1 or claim 2 wherein: said solution is acidified to a pH of about 6 to precipitate at least a portion of said protein solids priorto passing through said ultrafiltration device and where said precipitate protein is retained in said retentate.

5. The process of any of claims 1 to 3wherein: said solution is treated with a proteolytic enzyme priorto passing said solution through said ultrafiltration device.

6. The process of claim Swherein: said solution has a pH offrom pH 7 to about pH 10 duringtreatmentwith said proteolytic enzyme.

7. The process of claim 6wherein: said solution has a pH offrom pH 7to aboutpH 8 during said treatment with said proteolytic enzyme.

8. The process of any one of the preceding claims including: adding waterto said retentate to resolubilize said retentate; treating said resolubilized retentate with a proteolytic enzyme; acidifying said enzymatic treated resolubilized retentate to acid precipitate said protein solids.

9. The process of any one of the preceding claims including: milling said brewer's grains priorto treating with said alkaline solution.

10. The process of eitherclaim 1 orclaim2in- cluding: heating said solution to at least 1 40"F (60"C) and adjusting the pH to at least about pH 10 priorto passing said solution through said ultrafiltration device.

11. The process of any one of claims 1 to 7 including: adding waterto said retentateto resolubilizesaid retentate; acidifying said resolubilized retentateto acid precipitate said protein solids.

12. The process of claim 11 wherein: said resolubilized retentate is acidified to about pH 6 and belowto acid precipitate said protein solids.

13. The process ofclaim 8wherein: said resolubilized retentate is acidified to about pH 6 and belowto acid precipitate said protein solids.

14. The process of any one of claims 5to 7 wherein: said proteolytic enzyme is chosen from the group consisting of milezyme AFP enzymes and Nutrase.

15. The process any one of claims 5,6,7 or 14 wherein: said enzyme is present in a concentration offrom about0.001%to about 1% by weight of said enzyme per weight ofthe dry weight of said recovered protein solids.

16. In a process for recovering protein solids from brewer's grains in which said grains are treated with a hot alkaline solution to solubilize the protein fraction of said brewer's grains in said solution and in which said solution is thereafter treated to recover protein solids, the improvement which comprises: treating said solution to remove gross particulate matterfrom said solution; treating said solution with a proteolytic enzyme for a time sufficient to at least partially hydrolyze said proteins; acidifying said enzymatic treated solution to acid precipitate said protein solids.

17. The process ofclaim l6including: heating said solution to at least 1 00"F (38"C) and adjusting the pH to at least about pH 10 priorto treating said solution with said proteolytic enzyme.

18. The process of claim 16 or claim 17 wherein: said enzyme is present in a concentration of from about0.001%to about 1 % by weight of said enzyme per weight ofthe dry weight of said recovered protein solids.

19. The process of any one of claims 16to 18 wherein: said proteolytic enzyme is a fungal protease enzyme.

20. A process for recovering protein solids from brewer's grains substantially as described herein.