GB2130069A - Whey treatment process and product - Google Patents

Abstract

Cheese whey is subjected to reverse osmosis, preferably carried out by use of a membrane having a salt (NaCl) rejection characteristic of 35 to 75%, with the whey being applied to the membrane at pressures which provide flux rates of about 8 to 18 GFD. The resulting permeate consists of water together with mineral salts derived from the whey and the retentate is a concentrated modified whey having a reduced ash content. The mineral salt content of the permeate consists mainly of monovalent salts, with the remainder of the mineral salts consisting mainly of mineral bivalent salts, remaining with the whey. The protein level of the retentate whey may be increased by ultrafiltration, to produce modified whey products of high protein value.

Description

SPECIFICATION Whey treatment process and product This invention relates generally to processes for the treatment of cheese wheys, and to modified whey products resulting from such processes.

Various processes have been used commercially for the production of what is known in the trade as modified wheys, which products may differ from natural wheys with respect to ash content, protein level, and/or lactose content. Reduction in ash content of cheese whey has been carried out by contact with ion exchange resin, and by electrodialysis. Protein concentrates have been produced from whey by fractionation processes such as ultrafiltration which reduce the lactose and ash content, or by concentration and removal of a portion of the lactose by crystaliization. As a part of such processing concentration of the whey may be carried out by conventional membrane reverse osmosis or vacuum evaporation.Since modified whey, and particularly modified whey having protein levels ranging from 2090%, are dietetically important for humans and animals, it is important to provide processes for their production which will produce products of high quality to predetermined specifications, without excessive processing costs.

The present invention provides a process for producing modified cheese whey comprising subjecting cheese whey to membrane reverse osmosis, the salt (NaCI) rejection characteristics of the membrane being such that the resulting permeate is water together with the major portion of the monovalent mineral salts of the whey and the whey retentate is concentrated and its mineral salt content substantially reduced.

The invention includes a method as described inciuding the further step of subjecting the modified whey produced to membrane ultra-filtration to provide a lactose-rich permeate and a proteinrich modified whey retentate having a protein content of from 35 to 90% (DSB) and an ash content of about 1.4 to 3.5% (DSB).

In accordance with preferred embodiments of the present process cheese whey is pre-treated to reduce its fat content to 0.1% or less, and is then subjected to a special form of reverse osmosis. This is carried out by use of membrane having a salt (NaCI) rejection characteristic of about 35% to 75%, with the whey being applied to the membrane at pressures which provide flux rates of about 8 to 18 GFD.

The resulting permeate consists of water together with mineral salts derived from the whey and the retentate is a concentrated modified whey having a reduced ash content. The mineral salt content of the permeate consists mainly (e.g. of monovalent salts, with the remainder of the mineral salts consisting mainly of mineral bivalent salts), remaining with the whey. The protein level of the retentate whey may be increased by ultrafiltration, to produce modified whey products of high protein value.

The invention will be illustrated by the following description in which the preferred embodiments have been set forth in detail in conjunction with the accompanying drawings.

Referring to the drawing Figure 1 is a flow sheet illustrating the process in its simplest form.

Figure 2 is a flow sheet illustrating a process in which a whey protein concentrate is produced.

Assuming that the modified whey product to be produced by the process is to be used for human consumption, the raw source whey should be of edible quality with a protein content that is substantially undenatured. A typical analysis of a suitable edible whey is as follows.

Whey protein 13.1% DSB Lactose 77.9% DSB Mineral salts (ash content) 8.3% DSB Fat 0.7% DSB Non-protein nitrogen (NPN) 0.50% DSB Total solids 6.3% The above analysis may vary somewhat depending upon the cheese processing operations, and the type of cheese being manufactured. The non-protein nitrogen is a part of the indicated whey protein content.

As previously stated the present process is characterized by a novel form of reverse osmosis applied to the whey. Reverse osmosis as generally applied to milk products, employs membranes having a 9398% salt rejection characteristics, and serves to concentrate the feed material.

Assuming for example that the source whey employed is one of edible quality, it is first subjected to pretreatment step 10. This may include pasteurizing, and removal of fat or lipid complexes whereby the fat content is reduced to about 0.1% or less. The fat content can be reduced by various methods such as filtration, centrifuging, or both, or by precipitation followed by filtration or centrifuing.

Pretreatment may also involve pH adjustment to near neutrality, as for example to a pH value of 6.2 to 6.4. Pasteurization should be at temperatures and for periods of time insufficient to cause any substantial denaturing of the whey protein. Pasteurization equipment of the continuous type may be used which may heat the whey to a temperature of about 1 61--1 66"F. for a short period of about 1 5-20 seconds.

The pretreated whey is then subjected to membrane reverse osmosis step 11 making use of standard commercially available reverse osmosis equipment, but equipped with membranes differing in porosity from those ordinarily used for reverse osmosis. More specifically the membranes that are employed have a salt (NaCI) rejection characteristic of 35 to 75%, whereas membranes customarily used for reverse osmosis have a salt rejection characteristic of 93 to 98%.

The osmosis equipment may vary in its details of construction and arrangement of membrane modules, depending upon the desired capacity and other requirements. As is well known to those familiar with commercial membrane reverse osmosis equipment, the membrane modules may be in groups, with the groups connected in series/parallel arrangements, and with the feed being supplied by a pump having provision for adjusting the applied fluid pressure. The equipment may be of the one pass type, or may be provided with a feed tank in which a quantity of whey is introduced for an operating cycle with retentate being recirculated back into the feed tank.

With respect to conventional commercial reverse osmosis as applied to whey, the permeate consists mainly of water, with only minor amounts of mineral salts and whey solids. Thus conventional osmosis serves simply to concentrate the whey to a solids content of the order of 12 to 30%, which generally is suitable for further processing.

When reverse osmosis is practiced using membranes having salt (NaCI) rejection characteristics in the order of 3575%, new and advantageous results are produced, and the mode of operation differs radically from standard commercial reverse osmosis. More specifically when reverse osmosis of whey is carried out according to the present invention, fractionation takes place in such a manner that the whey retentate is substantially demineralized, simultaneously with concentration. In addition fractionation occurs with respect to the mineral salt content, whereby the major part of the monovalent salts pass out with the permeate, and the mineral salts remaining with the retentate are mainly bivalent salts.This is advantageous when the retentate is used in connection with food products, because bivalent mineral salts are considered dietetically superior for such purposes compared to the monovalent salts. A further advantage of the present invention is that the flux rate is substantially higher than is experienced with conventional reverse osmosis. Thus whereas concentional osmosis may have flux rates of the order of 4 to 9 GFD, with the present invention the flux rates can be maintained from about 9-to 1 8 GFD. Such higher flux rates make for greater capacity for a given osmosis equipment and total membrane area. This feature makes for a highly efficient operation and tends to reduce overall processing costs.

In a typical instance making use of the present invention, the retentate forming product A may analyze as follows.

Protein 13.2% DSB Lactose 80.5% DSB Ash content 6.31% DSB Non-protein nitrogen* 0.49% DSB Fat less than 0.1% Total solids 18.0% The permeate may analyze as follows.

Lactose 0.66% DSB Ash content 0.34% DSB Non-protein nitrogen* Not determined Whey protein Not determined Fat Not determined Total solids 1.00% *A'part of the whey protein content.

Of the ash content present in the above permeate, about 85% (by analysis) comprises monovalent salts. Assuming that the ash content of 8.3% in the source whey comprised about 57% monovalent salts and 43% bivalent salts, it is evident that the major portion of the monovalent mineral salts are removed and are present in the permeate. The remainder of the ash content remains with the retentate, and here the major portion of the ash consists of bivalent mineral salts.

In the typical instance referred to above, the retentate product A consists of a modified whey which has a substantially lower ash content than the original source whey; it is a concentrate with respect to total solids content, its ash content is substantially reduced, the major part of the ash content of the product consists mainly of bivalent salts, and the protein and lactose contents are slightly higher than the source whey, due primarily to removal of a substantial portion of the ash.

Product A is a commercially saleable product, and can be used as an additive in many food products. The process can be readily controlled to produce a particular degree of demineralization, which for example may range from 1 5-25% of the ash content of the source whey. Concentration of the whey may range from about 12 to 30% solids, as in conventional reverse osmosis of whey. If higher percentages of ash removal are desired, this can be carried out by conventional methods, such as by ion exchange, or electrodialysis. It may be used in fluid form or spray dried to produce a dry powder product.

The procedure illustrated in Figure 2 of the drawing makes use of the invention described above, together with ultrafiltration to produce whey protein concentrates. Thus whey in this instance is subjected to pretreatment 1 2 which may be the.same as pretreatment 10 of Figure 1. The whey is then subjected to reverse osmosis 13, carried out in the same manner as step 11 of Figure 1. The retentate from step 13 is then subjected to ultrafiltration 14. This can be carried out by use of conventional commercial ultrafiltration equipment, provided with membrane having a porosity as commonly used in such operations. Fractionation by ultrafiltration produces a lactose-rich permeate, and a protein-rich retentate.Depending upon the manner in which ultrafiltration is controlled and carried out, the protein content of the retentate may range from 2090%, thus providing a whey protein concentrate which has commercial value for many purposes, including use as an additive in food products. In a typical instance making use of the process as shown in Figure 2, the retentdte from step 1 3 may analyze substantially the same as the retentate from step 11 of Figure 1, and the permeate from step 1 3 substantially the same as that from step 11. The permeate from step 14 may in a typical instance analyze as follows.

Protein 5.4% DSB Lactose 87.1% DSB Ash content 7.5% DSB Non-protein nitrogen 0.52% DSB Total solids 20.0% The analysis of the retentate product B from step 14 may range as follows.

Whey protein 3590% DSB Lactose 8.561.25% DSB Ash content 1.43.5% DSB Non-protein nitrogen 0.10.25% DSB Fat 0.30.7% Total solids 1 5-30% Examples of the invention are as follows.

Example 1 The source material is a raw fresh low acid swiss cheese whey of edible quality. It should be low heat whey in that there must be no significant denaturization of the protein content. The pH value of such whey may be about 6.3, and the total solids contents about 7%. The whey may analyze as follows.

Protein 13.1% DSB Lactose 77.9% DSB Fat 0.7% DSB Ash 8.3% -DSB NPN 0.5% DSB Total solids 6.3% The pretreatment may be carried out in accordance with U.S. Patent 3,447,930 dated June 3, 1969 to reduce the fat content to about 0.1% or less. Specifically the whey is pasteurized by passing it through a preheater where it is rapidly heated to about 161 "F. and held for a period of about 1 5 seconds. Subsequently it is cooled and the pH value adjusted within the iimits of about pH 6.2 to 6.4 by the addition of potassium hydroxide. The concentrate is then clarified by centrifuging in a bowl-type intermittent unloading clarifier. This serves to remove small quantities of insoluble suspended casein, and also removes a part of the fat content.After such pretreatment the fat content should not be more than 0.1% (DSB). According to the procedure shown in Figure 1 this pretreated whey is then subjected to reverse osmosis, which may be carried out by the use of commercial membrane osmosis equipment such as is manufactured by Patterson Candy International. This equipment is provided with membrane having salt (NaCI) rejection characteristics of 3575%. The arrangement of membranes may be such as to provide 1 8 square feet of membrane area. The retentate from step 1 3 is a whey concentrate having a total solids content of about 20%, and corresponding in analysis to the typical retentate referred to above in connection with step 11 of Figure 1.

The ultrafiltration step 1 4 is applied to the retentate from step 13, employing commercial ultrafiltration equipment, such as that produced by Aktieselskabet De Danske Sukkerfabrikker, Copenhagen, Denmark (DDS). The membranes may be customary membranes such as are presently employed in the commercial fractionation of whey.

Depending upon the manner in which step 1 4 is controlled, the whey protein concentrate product B produced as in this example may have an analysis ranging as follows.

Protein 3590% DSB Lactose 8.561.25% DSB Ash 1.43.5% DSB NPN* 0.10.25% DSB Fat 0.30.7% Total solids 1 5-30% *A part of the whey protein content.

The lactose-rich permeate from step 1 4 may analyze as follows.

Lactose 5.4% DSB Whey protein 87.1% DSB Ash 7.5% DSB NPN* 0.52% DSB Total solids 1 5-20% *A part of the whey protein content.

Because the major part of the monovalent mineral salts are removed in the permeate, from step 13, only a small percentage of such salts appear in the permeate from step 14. The bivalent salts which remained with the retentate from step 13, likewise appear in the retentate from step 1 4.

Product B produced in the second example is a high quality whey protein concentrate which is dietetically valuable as a food product, with or without being blended with other food ingredients. It may be spray dried to form a dry power product. The permeate may be processed to produce a lactose of desired purity.

The method described in the above Example iilustrate the production of modified wheys by methods which involve minimum processing costs, both with respect to the processing steps and the equipment required for the process, with reference particularly to modified wheys which are demineralized to a desired degree, and modified wheys in the form of whey protein concentrates with specific levels of protein content.

Claims (12)

Claims

1. A process for producing modified cheese whey comprising subjecting cheese whey to membrane reverse osmosis, the salt (NaCI) rejection characteristics of the membrane being such that the resulting permeate is water together with the major portion of the monovalent mineral salts of the whey and the whey retentate is concentrated and its mineral salt content substantially reduced.

2. A process as claimed in Claim 1 in which the membrane salt (NaCI) rejection characteristics are of the order of 3575%.

3. A process as claimed in Claim 1 or Claim 2 in which the source whey has a solids content of about 6.0 to 7.0%, and reverse osmosis is carried out to concentrate the whey retentate to a solids content of about 12 to 30% at a flux rate of about 9 to 18 GFD.

4. A process as claimed in Claim 3 in which the reverse osmosis is carried out to produce a whey concentrate having a whey protein content of about 13.0 to 13.5% and an ash content of about 5.8 to 6.8% (DSB).

5. A process for producing modified cheese whey from a source whey having an ash content of about 8.0 to 8.5% (DSB) and a total solids content of about 6.0 to 7.0%, comprising pretreating the whey whereby its fat content is reduced to 0.1% or less, subjecting the whey to membrane reverse osmosis making use of membrane salt (NaCI) rejection characteristics of about 3575%, the whey being applied to the membrane at pressures which provide a flux rate in the range of about 8 to 18 GFD, the resulting permeate being water together with mineral salts derived from the whey and the retentate being a modified whey having an ash content of about 5.8 to 6.8% (DSB) and a total solids content of about 12.0 to 30.0%.

6. A process as claimed in Claim 1 substantially as hereinbefore described with reference to Figure 1 of the drawing.

7. A process as claimed in any one of Claims 1 to 6 including the further step of subjecting the modified whey produced to membrane ultrafiltration to provide a lactose-rich permeate and a protein rich modified whey retentate having a protein content of from 35 to 90% (DSB) and an ash content of about 1.4 to 3.5% (DSB).

8. A process as claimed in Claim 1 substantially as hereinbefore described with reference to Figure 2 of the accompanying drawing or substantially as described in the Example.

9. A modified cheese whey having a protein content of from 35 to 90% (DSB), an ash content of

1.4 to 3.5% (DSB), the ash content comprising mainly bivalent mineral salts.

10. A modified cheese whey produced by a process as claimed in any one of Claims 1 to 8.

11. A modified cheese whey substantially as hereinbefore described as Product A or Product B of the Example.

12. A food product made from or incorporating a modified cheese whey as claimed in any one of Claims 9 to 11.