IE46362B1 - Process for the production of high protein whey products - Google Patents

Abstract

PROCESS FOR THE PRODUCTION OF HIGH PROTEIN WHEY PRODUCTS of which the following is a specification. A process for the treatment of whey to produce products containing whey protein to a desired predetermined level. Whey is subjected to treatment for removing a portion of its lactose content by lactose crystallization and the resulting mother liquor, which has a protein level higher than that of the original whey, is then subjected to ultrafiltration carried out in such a controlled manner as to produce a protein rich fraction having the desired protein content. The process produces products standardized with respect to protein content, irrespective of variations in the protein level of the source whey, which may vary from time to time.

Description

' This invention relates to processes for the treatment of whey derived from a source that is subject to variations in protein ' content to produce products having whey protein to desiredpredetermined levels.

It is recognized in the food industry that edible whey contains valuable nutrients, including whey protein. Wheyssuch as are produced in the manufacture of Cheddar, cheese (e.g., sweet whey) and other types of cheeses, have relatively high mineral salt contents which'in many food formulations cannot he tolerated.

Various processing treatments can be applied to remove some of the mineral salts whereby the whey is more acceptable in various formulations. Particular reference can be made to reduction In the mineral salt content: (i.e., ash content) by ion exchange columns or electrodialysis. Removal of say 50% or more of the mineral salt content also serves to increase the protein level (e.g., from 12 to 14.5% dry solids basis [DSB]). There is a commercial demand for whey derived products having a relatively high-protein content, as for example from 25 to80% (DSB).It has also been known that whey can be fractionated by ultrafiltration to produce a permeate that is rich in lactose and a fraction rich in protein .(see Canadian Patent 996,361 dated April 22,1975). By application of ultrafiltration it is possible to produce whey products having protein levels well above 25%. Ultrafiltration tends to be subject to some difficulties when applied to whey, such as rapid reduction in the flux rate and relatively short life for the membranes. In general it has been found that to attain a given protein level in the 25 to 35% range (DSB), it is more economical to employ removal of lactose by crystallization. A complicating factor in the production of high protein whey products is that the protein content of raw natural whey available for processing varies from day to day and from season to season, whereas it is important for a commercial high protein whey product to have a fixed predetermined protein content which complies with product specifications. It is difficult to control a lactose crystallizing operation, followed by removal of lactose crystals, in such a manner as to provide a mother liquor having a predetermined protein level, since the protein level tends to vary dependent upon variations in the protein level of the natural whey and other processing factors such as those that affect the lactose yield.

We have now found a process for the treatment of whey which makes possible production of products that are standardized with respect to their protein levels, irrespective of variations in the protein level of the source whey by the application of ultrafiltration processing operations which are relatively simple, economical and readily controllable.

We have found that by using such a controlled ultrafiltration step it is possible to provide an acceptable and economical flux rate and relatively long operating cycles before it is necessary to replace or regenerate the ultrafiltration membrane.

According to the present invention there is provided a process for the treatment of whey derived from a source that is subject to variations in protein content to produce a product having whey protein to a desired predetermined level, comprising removing from 45 to 55% of the lactose content of the source whey by crystallization of the lactose from the source whey and removal of the lactose crystals, whereby the resulting mother liquor has a protein level subject to variations due to variations in the source whey but higher than the untreated whey and - 3 thereafter subjecting the mother liquor to ultrafiltration under conditions sufficient to produce a protein rich fraction and a lactose rich permeate, the ultrafiltration operation being controlled to provide a desired predetermined protein level that is higher than that of the mother liquor.

Additional objects and features of the invention will appear from the following description in which the preferred embodiments have been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing; Figure 1 is a flow diagram illustrating one procedure for carrying out the process.

Figure 2 is a flow diagram illustrating another 15 embodiment of the process.

Figure 3 is a flow diagram illustrating another embodiment of the process.

Figure 4 is a diagram illustrating ultrafiltration equipment. - 4 46362 The source material employed is preferably produced as a by-product in the manufacture of cheese.

It is considered preferable to use so-called sweet whey such as that produced in the manufacture of Cheddar cheese. Typical sweet wheys range from pH 5.7 to 6.4, whereas acid wheys such as are produced in the manufacture of cottage cheese range from pH 4.3 to 4.8. Cottage cheese wheys have an ash content which may range from 9.5 to 13.0¾ (DSB). Sweet wheys such as are produced in the manufacture of Cheddar cheese may have ash contents ranging from 8.0 to 10.0¾. and lactose contents from to 76¾ (DSB). As previously mentioned, the general composition of whey produced in a particular cheese plant may vary from day to day and from season to season, due to variations in the milk used in the cheese manufacturing process. Likewise the protein level varies with the type of processing used in the cheese manufacturing plants in which tho wheys are derived. Particularly, when products are being produced for human consumption, it is necessary for the whey to be of edible quality, and it is desirable that the heat denaturable protein remains substantially undenatured(i.e., low heat whey.

In the procedure outlined in Figure 1, it is assumed that the whey is a low heat sweet whey of edible quality produced in the manufacture of Cheddar cheese.

In step 10 the whey is concentrated, preferably by vacuum evaporation, to a solids concentration of from 20 to 30¾. It is then subjected to clarifying in step 11, which can 6 3 63 be carried out by passing the whey through a suitable centrifuge capable of removing any undisSolved solids, such as curd fragments. The clarified concentrate is then partially demineralized in step 12, which can be carried out by known methods, such as contact with ion exchange resins or electrodialysis. Electrodialysis is preferred because it is relatively economical and subject to control. More particularly, it is desirable to utilize the electrodialyzing process and apparatus dis10 closed in U.S. Patents 3,544,436 dated December 1,1970 and 3,755,134 dated August 28,1973. In step 12, a predetermined amount of mineral salts are removed, depending upon the specifications for the finished product being manufactured. In general, from 20 to 90½ of the ash con15 tent can be removed, Tlu partially demineralized whey from step 12 has a solids content somewhat less than the solids content Of the concentrate produced in Step 10. For example, the solids content may range from·19 to 255 where the whey in step 10 is concentrated to a solids content of from 20 to 30%. In step 13 the partially demineralized whey is further concentrated, preferably by vacuum evaporation,to a solids content of from 50 to 60%. The concentrate is then subjected to lactose crystallization in stop 14 which can be carried, out by known methods involving cooling the concentrate to effect lactose crystallization, after which the lactose crystals are removed as by screening, hydraulic separation or centrifuging. The amount of lactose removed in this manner depends upon various controlling factors of the crystal6 lizing operation, including particularly the concentration of tho whey before cyrstallization, but is in the range of from 45 to 55% of the lactose content of the concentrate.

Removal of lactose results in a corresponding increase in the protein content. Thus, whereas the whey supplied to the process may have a protein level of the order of 12% (DSB), after reducing the lactose content by some 45 to 555, the protein level in the remaining solids may range from 25 to 405. According to the present process, step 14 is carried out under such conditions as to remove an amount of lactose which will result in a protein level of the remaining solids that is less than that required in the finished product, but is as high as can be economically produced by the step 14. For example, if the specifications call for a protein level of 355 for the finished product, then the amount of lactose removed in step 14 may be such that the protein level of the remaining mother liquor is from to 325.

Xn step 15 the mother liquor from step 14 is subjected to separating as by use of a suitable centrifuge for removing a portion of the butterfat that may be present. Generally, wheys derived from the manufacture of cheese have a fat content of the order of 1.0 to 2.5% (DSB). In step 15 it is desirable to reduce the fat content to a level of the order of 0.3 to 0.35% (DSB). Centrifuging also serves to remove a sludge containing relatively fine sized lactose crystals that are not removed in step 14. Following step 15, the material is subjected to ultrafiltration in step 16. It is desirable that the material being supplied to and during ultrafiltration be at a temperature level of the order of 110 to 120“F.

Ultrafiltration equipment can be obtained from a number of manufacturers, and is characterized by membranes thcough which the liquid material is forced under con5 trolled pressure to remove water and smaller molecules present, and resulting in the concentration of the larger molecules on the pressure side of the membrane. An equipment unit may consist of a.-plurality of serially connected modules manifolded in such a manner that the feed flows successively from one module to the next, while the liquid (i.e., permeate) expressed from all the modules is merged together for separate discharge. There are a number of ultrafiltration membrane concepts available - tubular, hollow fibers, plate and frame? leaf design- and spiral wound. Any of these should be suitable for this application. With the proper selection of pressures and membranes, ultrafiltration can be applied to produce a lactose rich permeate and a protein rich fraction. Most of the various kinds of mineral salts present are removed with the lactose permeate, whereby on a dry solids basis the level of mineral salts in the protein rich fraction is less than the mineral salt level of the feed material. For example, if the mineral salt level of the mother liquor from step 14 corresponds to an ash content of 4.0% (DSB), then step 16 may produce a protein fraction having an ash content of 3.0% (DSB). Good results have been obtained by use of equipment made by ABCOR,INC. of Cambridge, Massachusetts sold under the trade designation ABCOR.

In operation of ultrafiltration equipment,there are certain factors which can be varied to cohtrol the protein level of the protein rich fraction. These factors include the pressure at which the feed is supplied to the membranes, the temperature of the feed/ and the duration of the operating. cycle. Tho equipment is usually operated to process predetermined measured batches of tho feed material, with recirculation of the protein fraction back to the feed, and with the duration of the cycle being such as to attain the desired protein level. Making use of the ABCOR equipment previously mentioned, one can obtain protein levels in one stage as high as 50%, or any lesser level which one may desire to comply with the product specifications. The equipment may include a feed tank of sufficient size to accommodate the batch of feed material, a feed pump which supplies the feed material to the modules of the ultrafiltration equipment at a predetermined pressure or pressures, and means for recirculating the protein fraction. The equipment may also include a heat exchanger for heating or cooling the feed material to a desired temperature level. Such equipment can be operated on either a batch or continuous cyclo.

In some instances the protein fraction from a first equipment stage may be routed to a second equipment stage 17, with the second stage operating in the same manner as the first stage. When two or more equipment stages are used the protein fraction from a preceding stage may be diluted with water to provide the feed to the next stage. The amount of diluting water can be another controlling factor to determine the protein level of the protein fraction produced.

By way of example, the amount Of diluting water may be about the same volume as the volume of protein fraction supplied as feed to step 17. An increase in the amount of dilution serves to increase the protein level produced by the second stage. Assuming that care is taken throughout processing to - 9 46363 avoid heating to temperatures of the order of 150°F. or higher for prolonged periods, the protein of the products obtained is substantially undenatured.

The protein fraction from step 16 produces product 5 A which can be used as such, or which can be subjected to drying 18 to produce the dry product B. Known methods of spray drying can be used to produce product B in powdered form. Likewise, the protein fraction from a second stage 17 produces product C, which again can be dried at 19 to produce product D.

Assuming that the products produced by the process of Figure 1 are to be supplied to various food manufacturers for formulating with other ingredients, the lactose crystallizing and removal step 14 and the ultrafiltration step 16 can be controlled to meet such specifications. For example, the specifications may call for a series of products ranging from 25 to 80% protein. Also the specifications for each such product may call for ash contents ranging from 1.5 to 6.0 Such specifications of ash content can be met by control20 ling the demineralizing step 12. Thus although stops 12,.14 and 16 are interrelated, they can he accurately controlled to meet the desired specifications to a high degree of accuracy. The process is economical, particularly in that a substantial part of the protein level increase is obtained by removal of crystallized lactose in step 14, and the remaining increase is attained to a high degree of accuracy by ultrafiltration. The process can-be operated to accommodate variations in the protein content of the incoming whey. Thus analyses can be 3.0 made of the whey recei ved by the processing plant, and - 10 46362 depending upon the percentage of protein present in the whey solids, the process can be controlled to meet the desired specifications. Ultrafiltration as used in the process not only serves to increase the protein level, but in addition functions as a method of standardization of the finished product to meet the specifications.

As is understood by those familiar with ultrafiltration equipment, economical operation is dependent in part upon the flux rate that can be maintained. With the present process, relatively high flux rates can be maintained, due in part to the absence of a substantial amount of ash which is removed in step 12, and also to the reduction in the fat content by step 15. Also it has been found that undesirable fat present in the whey can most economically be removed after the crystallization and removal of lactose in step 14, as distinguished from removing the undesired fat by centrifuging the incoming whey.

Figure 2 illustrates another embodiment of the process in which crystallization of lactose and removal of lactose crystals is carried out before demineralizing.

Thus the incoming whey is concentrated at 21, preferably by vacuum evaporation, to a solids content of from 50 to 60% or higher. In step 22 this concentrate is subjected to lactose crystallization and removal of lactose crystals, and the mother liquor subjected to separating and clarifying in step 23. This material is then supplied to the electrodialyzing operation 24 for reducing the mineral salt content to the desired level. Thereafter it is subjected to ultrafiltration 25 to produce the product E.

Also this material can be spray dried at 26 to produce the product F. The separating step 23 serves to remove fine lactose crystals not removed in step 22, and also removes a certain amount of fat which may be in excess of that desired.

In both the processes of Figures 1 and 2, making use of sweet whey, it i,s generally unnecessary to adjust the pH of the material being supplied to the demineralizing step. However,in the event that acid wheys are used, it is desirable to neutralize acid by the addition of a suitable neutralizing agent, such as sodium or potassium hydroxide.

It is desirable to neutralize to a pH level of the order of 6.-1 to 6.5, with the incoming whey being neutralized before processing.

Another embodiment of the process is shown in Figure 3. This is applicable where the product specifications do not call for a reduction in the mineral salt content. Thus with such products, the incoming whey is concentrated in step 31 to 40 to 60% solids, and subjected to crystallizing and removal of lactose crystals in step 32. Thereafter the mother liquor is subjected to separating and clarifying in step 33, and then to ultrafiltration 34. Both the steps 32 and 34 are controlled to produce the desired protein level in the final products. Product G is the protein fraction from step 34, and product H is the same material after drying 35. By the use of the process shown in Figure 3, it is possible to produce final products having protein levels ranging from 22 to 75%.

Figure 4 schematically illustrates one way in which ultrafiltration equipment has been operated. The equipment includes a feed tank 41 which is of sufficient 6 3 6 2 size to accommodate a batch of material to be processed introduced through the feed line 42. Pump 43 delivers material from tank 41 to the ultrafiltration equipment 44 at a predetermined pressure. The protein fraction is recirculated by line 45 and pump 46 to the discharge side of the pump and permeate is discharged through line 47. The draw off of the protein fraction through line 48 is controlled by the three-way valve 49.

The equipment shown in Figure 4 can be operated continuously. Thus whey is pumped from tank 41 at a continuous rate and delivered to the ultrafiltration unit 44 at a fixed predetermined rate and temperature. Pump 46 continuously recirculates the protein fraction with flow rates such as to maintain the desired flux performance.

When the protein level reaches the desired value, the product is bled off at a controlled rate through valve 47 and line 48. If it is desired to employ a second equipment stage, the fraction bled off through line 48 is delivered by a pressure pump to a second equipment stage operating in the same manner as just described. The feed to the second equipment stage may be diluted as previously described.

Examples of the invention are as follows: The source material was sweet whey of edible quality obtained from the manufacture of Cheddar cheese.

Its protein level was 11.5% (DSB), and the ash content of the solids was 10%. As received for processing, it was at pH 5.8. By use of a vacuum evaporator it was concentrated to 20% solids, after which the concentrate was clarified by centrifuging. It was then subjected to elec 4636 2 trodialyzing, making use of the method and apparatus disclosed in said D.S. Patents 3,544,436 and 3,755,134. The pH was adjusted to pH 6.1 with sodium hydroxide and during electrodialysis it remained between the limits of 6.1 to 6.5. Also it was at a temperature between the limits of 100 to 110°F. Electrodialyzing was carried out to the_ extent of.reducing the ash content to 4.5¾ (DSB). The electrodialyzed material had a solids content of 20¾. This material was then subjected to concentration to 50 to 555 and then crystallization of lactose by cooling, after which lactose crystals were removed by hydraulic separation. The amount of lactose thus removed reduced the lactose content of the mother liquor to 555 (DSB). The mother liquor was then subjected to separation by centrifuging to reduce. the fat content to 2.55. Thereafter the batch was diluted to 155 solids and subjected to ultrafiltration, making use of equipment manufactured by ABCOR,INC. of Cambridge, Massachusetts, identified as AB COR UF 480. The equipment was operated with recirculation of the protein fraction in the manner described in connection with Figure 4. The product specifications to be met in this instance was a dry powdered product having aft ash content of Π5, and a protein level of ^35% (DSB) . The controlling factors of the'ultrafiltration operation were controlled whereby these specifications were met accurately both with respect to mineral salt content and protein level. Control involved maintaining the inflow pressure constant, and controlling the duration time of the cycle. During the course of this example, it was observed that the ultrafiltration equipment maintained a relatively high flux rate, which is attributed to the fact that the whey hid been partially - 14 4 6 3 6 2 demineralized and had a relatively low fat level. The final product in this instance corresponded with Product B of Figure 1.

Example 2.

Example 1 was repeated, but control of the crystallization of lactose and its removal and of the ultrafiltration operation were modified to produce a product of higher protein value, namely ?50% (DSB). Thus in this instance crystallization of lactose and lactose removal were carried out to remove a higher percentage of lactose, whereby the lactose remaining in the mother liquor was 50% (DSB). This was done by increasing the concentration of the whey before crystallization. The resulting mother liquor had a protein level of ?32%. Ultrafiltration was then carried out under controlled conditions to meet the specification of -50% protein in the final product.

Example 3.

To carry out the process illustrated in Figure 2, the whey employed can be the same as in Example 1. It is concentrated by vacuum evaporation to 55% solids content, after which it is subjected to crystallization and removal of lactose crystals to the extent of providing a mother liquor having a lactose content of 5.0%, and a protein level of 13%. The mother liquor is then subjected to the separating and clarifying step 23 carried out by use of a centrifuge, and tho clarified material then subjected to electrodialyzing 24 carried out in the same manner as in Example 1. Electrodialyzing is continued to reduce the ash content to the level of 4% (DSB).

The electrodialyzed material is then fed to the ' ; A6362 ultrafiltration step 25 which is controlled to meet the product specifications. These specifications may call for an ash content of 13% and a protein level of Ϊ35%.

The specifications as to protein level can be readily at5 tained by controlling the ultrafiltration operation. The product produced in this example would correspond with the product F of Figure 2.

Example 4.

The product specifications ih this instance called 10 for a mineral salt content corresponding to that present in untreated whey, and a protein level of 12%. In other words, the product specifications did not require reduction in the ash content. The whey in this instance was the same as employed in Example 1. It was concentrated by vacuum evaporation to a 55% solids, after which it was subjected to crystallization of lactose and removal of lactose crystals to reduce the lactose content of the mother liquor to 50%, Also the level of protein in the mother liquor was increased to 18% (DSB). The mother liquor Was then subjected to separating and clarifying by use of a centrifuge, which served to remove fine lactose crystals as a sludge, together with some fat. The clarified material was then subjected to ultrafiltration carried out as previously described to produce a protein fraction having a protein level corresponding to the specifications, namely -35%. This product when spray dried corresponded with the product Ή of Figure 3. Here again there was no difficulty iri accurately manufacturing to the desired protein specifications.

With respect to the procedure of Example 4, the - 16 4 6 3 6 2 protein fraction produced by ultrafiltration can be subjected to demineralizing as by electrodialysis to reduce the ash content to a desired level to meet product specifications. Likewise in carrying out procedures as in Figures 1 and 2, or as in Examples 1, 2 or 3, demineralizing can be applied to the protein fraction produced by ultrafiltration. However, when demineralizing is employed, we prefer that it be applied before removal of lactose and before ultrafiltration as in Figure 1. Such practice reduces the amount of mineral salt contamination of the lactose crystals removed in step 14 and the salt -level in both the protein fraction and permeate from step 16.

Claims (7)

1. A process for the treatment of whey derived from a source that is subject to variations in protein content to produce a product having whey protein to a desired predetermined protein level, 5 comprising removing from 45 to 55% of the lactose content of the source whey by crystallization of the lactose from the source and removal of the lactose crystals, whereby the resulting mother liquor has a protein level subject to variations due to variations in the source whey but higher than the untreated whey, χ ο - and thereafter subjecting the mother liquor to ultrafiltration under conditions sufficient to produce a protein rich fraction and a lactose rich permeate, the ultrafiltration operation being controlled to provide a desired predetermined protein level that is higher than that of the mother liquor. 15 2. A process, as in Claim 1 in which during the processing of the material some of the mineral salts content is removed. 3. A process as in Claim 2 in which mineral salts are removed by electrodialysis.

2. O 4. A method as in Claim 1 in which some of the mineral salts are removed from the material being processed before the removal of part of the lactose by crystallization.

3. 5. A process as in Claim 2 in which a part of the mineral salt content is removed after removal of some of the lactose by 25 crystallization. - .

4. 6. A process as in Claim 1 in which the removal of a part of the mineral salts is carried out before removal of lactose by crystallization and ultrafiltration is carried out after removal of lactose crystals. - 18 46362

5. 7. A process for the treatment of whey substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

6. 8. A process for the treatment of whey as set forth in any of the foregoing Examples.

7. 9. A product of a process as claimed in any one of the preceding claims.