Membrane Processing in Cheese ManufactureV V Mistry, South Dakota State University, Brookings, SD, USA

ª 2002 Elsevier Ltd. All rights reserved.

This article is reproduced from the previous edition, Volume 1,

pp 300–306, ª 2002, Elsevier Ltd.

Introduction

Cheesemaking is a process of controlled removal ofmoisture from milk by acid and temperature manipula-tion. Ultimately, most of the casein, fat and insolubleminerals along with some water are retained in the cheese.The efficiency with which these components are retainedis of great interest to cheese-makers because of the impacton cheese yield and therefore on the cost of production.Membrane processing provides the potential for improv-ing the efficiency of cheesemaking and therefore offerscapabilities that are of value in terms of economics andquality, and also provides opportunities for the develop-ment of new cheeses.

Membrane processing, including reverse osmosis (alsoknown as hyperfiltration), nanofiltration, ultrafiltrationand microfiltration, are pressure-driven separation/con-centration operations which employ organic or inorganicmembranes. Reverse osmosis of milk or whey will removeonly water and is therefore similar to thermal evaporation(Table 1). Nanofiltration removes water and small mono-valent ions, such as sodium, potassium and chloride.Ultrafiltration achieves greater separation; in addition towater and smaller minerals, it also removes lactoseand most water-soluble minerals and vitamins.Microfiltration, on the other hand, is able to separatelarger components of milk such as proteins. It is thereforepossible to separate caseins and whey proteins. Bacterialcells and spores can also be removed from milk with thisprocess.

This diverse range of separation capabilities is possiblewith the help of membranes of specific pore sizes andprocess parameters (pressure) (see Milk ProteinProducts: Membrane-Based Fractionation). Membrane-processed milk or whey possesses unique compositionaland physical characteristics that enable applications in themanufacture of various products. Cheese manufactureusing membrane processing has been practiced commer-cially since the early 1970s but the manner in which it isused has evolved over time owing to experience gainedby cheese-makers and the development of new mem-branes and applications.

Membrane processes can be used in cheese manufac-ture to accomplish various specific tasks. The effects ofreverse osmosis of milk are similar to those of thermal

concentration of milk or fortification of milk with milkpowder. The objective of such methods is to concentrateall milk components equally to a predetermined level.The later two methods (thermal concentration andfortification) are practiced in commercial cheese manu-facture to improve the efficiency of cheesemaking andincrease cheese yield. Reverse osmosis is generally notused for such applications because current multiple-effectevaporators equipped with vapor recompression systemsoffer greater efficiencies of operation, although combina-tions of thermal evaporation and reverse osmosis havebeen suggested for process optimization (see Plant andEquipment: Evaporators).

Ultrafiltration and microfiltration are the most com-mon membrane processes used in the cheese industry.Applications for nanofiltration, which is a relatively newmembrane process in cheesemaking, are also beingdeveloped.

Ultrafiltration

Ultrafiltration of milk is conducted at approximately50 �C but a lower or slightly higher temperature mayalso be used. The feed runs under pressure tangentiallyacross an ultrafiltration membrane with a molecularweight cutoff of 10 000 to 100 000 Da. Low molecularweight materials, i.e. water, lactose, soluble minerals andvitamins, pass through the membrane and form thepermeate stream. The membrane retains the remainingcomponents and this mass, called retentate (or concen-trate), is used for cheesemaking. The concentration of theretentate is varied by continually recycling the feed acrossthe membrane until the desired concentration of milkproteins is achieved or by using a very large surface areaof membrane, as in large commercial operations.

There are three major methods for using ultrafiltrationfor cheesemaking; low concentration (also known as pro-tein standardization), medium concentration, and highconcentration (precheese concept). The latter (precheeseconcept) paved the way for the application of ultrafiltra-tion in cheesemaking. This process, commonly known asthe MMV process after its inventors Maubois, Mocquotand Vassal of INRA, France, was originally developed for

618

Camembert cheese in the late 1960s and has been adaptedfor other cheeses, such as Feta.

Certain physicochemical properties of ultrafilteredmilk are particularly critical in cheesemaking applicationsand should be understood. These include viscosity, buf-fering capacity and rennet coagulation properties. As theprotein content of milk is increased by ultrafiltration,there is an increase in viscosity. This aspect is of particu-lar importance in the pumping requirements ofultrafiltered milk at high protein levels. For example, insome cheesemaking procedures where fermented milk isconcentrated to a high level in a multistage ultrafiltrationunit, positive displacement pumps have to be used totransport efficiently the viscous retentate across the laterstages of the membrane unit. Further, mixing of ingredi-ents such as starter, rennet and salt requires attention toprevent localized coagulation.

During ultrafiltration of milk, proteins and colloidalsalts are concentrated simultaneously. This causes anincrease in the buffering capacity, and hence directlyinfluences acid production characteristics of lactic acidbacteria, the pH of cheese, ripening characteristics andrennet coagulation. Under conditions of high buffering, itis difficult to obtain the desired pH even with the produc-tion of large amounts of lactic acid by the starter bacteria(Figure 1). Such a reduction in the rate at which the pHfalls allows lactic acid bacteria to grow to large numbersbut also offers the potential for growth of spoilage andpathogenic organisms. The large amount of lactic acid

produced results in an acid-tasting product and an imbal-ance in calcium will cause poor cheese texture andfunctionality, such as stretching. It is possible to lowerthe buffering capacity of ultrafiltered milk by removingsome of the colloidal salts by solubilization. This can beaccomplished by reducing the pH of milk to 5.6–6 duringultrafiltration.

Another property of concern is rennet coagulation.Generally, concentration reduces the rennet coagulationtime and increases the firmness of the coagulum. Thefirmness of rennet curd from unconcentrated wholemilk, as measured by a formagraph, is approximately8 mm after 40min while that of 6% protein ultrafilteredmilk is 58 mm. This is in part because of increased proteinand calcium in the retentate and also because in ultrafil-tered milk (4�) hydrolysis of only 50% of the �-casein isrequired for curd formation compared to 97% for uncon-centrated milk. This phenomenon is useful where hightemperature treatment of milk, such as UHT, is used. It iswell known that severely heated milk has poor rennetcoagulation properties, i.e. the coagulum is very weak.French workers have demonstrated that if milk is ultra-filtered prior to UHT treatment, its rennet coagulationproperties are restored.

Low-Concentration Retentates (ProteinStandardization)

At present, this is probably the most widely used applica-tion of ultrafiltration for cheesemaking because it is easilyadaptable to most cheese varieties while at the same timeproviding economical benefits. In this method, milk isultrafiltered to a concentration of no more than 2� andconventional cheesemaking equipment is used. A com-mon practice is to increase the milk protein concentrationto 3.7–4.5% prior to cheesemaking. This enables unifor-mity in the composition of milk, hence the term ‘proteinstandardization’ for this application of ultrafiltration.Other terms used include low-concentrated retentates(LCR). This method is used for various cheeses, includingCamembert, Cheddar and Mozzarella. Advantages ofusing this procedure include uniformity in milk composi-tion from day to day, a firm coagulum and therefore lowerlosses of casein to whey, increased cheese yield (approxi-mately 6% on a protein basis), improved cheesemakingefficiency (more cheese per vat) and, importantly, there isno need for additional specialized cheesemaking equip-ment other than an ultrafiltration unit (Figure 2). Theincrease in cheese yield is attributed to better fat andprotein recovery and the retention of some whey proteins.

For cheeses such as Cheddar, concentration of up to1.6 to 1.7� is used. At higher levels, the rennet coagulumis extremely firm and difficult to handle and fat losses inthe whey may be high. The moisture content of Cheddar

Table 1 Composition of milk concentrated approximately

threefold by reverse osmosis and ultrafiltration

Component MilkReverseosmosis (%) Ultrafiltration

Total solids 12.2 36.6 28.0

Fat 3.50 10.5 10.5

Total protein 3.20 9.6 9.5Lactose 4.80 14.4 4.1

Ash 0.70 2.1 1.3

Hours

pH

%TA

4.6

5.0

5.4

5.8

6.2

6.6

7.0

0

0.4

0.8

1.2

1.6

2

0 1 2 3 4 5 6 7 8 9 10 11

Figure 1 Relationship between lactic acid production (solid

line) and pH (broken line) during lactic fermentation of

unconcentrated milk (N ) and 4.3x ultrafiltered milk (&).

Cheese | Membrane Processing in Cheese Manufacture 619

1

2

6

4

5

7

8

9

3

10

Figure 2 Typical plant layout for Cheddar cheese manufacture using ultrafiitration for protein standardization. 1, Pasteurization and fat standardization; 2, protein standardization usingUF; 3, cheesemaking; 4, draining conveyer; 5, cheddaring conveyor; 6, salting/mellowing conveyor; 7, block former; 8, vacuum packaging; 9, cheese block packing; 10, main process

control panel. (Courtesy APV Nordic, Aarhus, Denmark.)

cheese made with this process tends to decrease withprotein content in milk; suggested reasons for this effectinclude rapid syneresis because of the coarser network ofthe protein gel. Using standard procedures such as low-temperature cooking can increase moisture content.Researchers in the United States have demonstrated thathomogenization of the cream can readily increase thelevel of cheese moisture. This method can also be usedto increase further the yield of Cheddar cheese madefrom ultrafiltered milk. Recovery of fat in Cheddar cheesemade from milk ultrafiltered to 4.6% protein and withoutcream homogenization was 94.7%, whereas that withcream homogenization was 96.8%.

Maubois and colleagues in France developed the con-cept of ultrafiltration of milk on farms for cheesemakingin the late 1970s. This method used the LCR approachand involved the ultrafiltration of milk to less than 2� onthe farm prior to transportation to the cheese factory.Permeate was fed to cows at the farm. The objective wasto reduce the cost of transport of milk and to increasecheese yield. The economics of the process should alsotake into account the disposal of permeate that is pro-duced on the farm. Subsequent studies in the UnitedStates suggested that this process would be economicalfor farms with 100 to 1000 cows. This method of ultra-filtering milk on the farm is now being used in the UnitedStates where milk is ultrafiltered cold to 3.5� at a collec-tion centre and then transported long distances (>500 km)to cheese factories, at which the retentate is used to raisethe total solids content of cheese milk to 13.5–15%.

Medium-Concentration Retentates

In this method, milk is concentrated to 2 to 5� prior tocheesemaking. In some instances, diafiltration may beadopted to adjust the mineral content and buffering capa-city. Much higher quantities of whey proteins are retainedin the cheese and the yield is also higher than with theLCR method. The changes in the physicochemical prop-erties of milk are large enough to warrant the use ofspecially designed equipment. The rennet-induced coa-gulum, for example, is very firm and difficult to handlewith conventional equipment.

After various industrial trials, commercial applicationof this method for cheesemaking is currently limited; themost notable example includes the APV-SiroCurd pro-cess for Cheddar cheese. This method was developed inAustralia and involved continuous rennet coagulation ofmilk ultrafiltered to 40–45% solids. A small portion of theultrafiltered milk was prefermented with lactic acid bac-teria and used as bulk starter at the level of 10–12%. Thecontinually forming coagulum was cut with speciallydesigned wire knives and cubed curd pieces transferredinto a rotating drum where syneresis took place during

heating to 38 �C over a 30–40 min period. Automated

cheddaring occurred at the optimum pH, followed by

milling and salting. Yield increases of 6–8% were claimed

with this process. After several years of operation, how-

ever, this process is no longer used because of technical

difficulties and poor economics.

Production of Liquid Precheese

This method was the earliest of all ultrafiltration applica-

tions for cheesemaking. Milk is ultrafiltered to a

concentration that is equal to the composition of the

cheese being manufactured. It is then set with rennet,

and acid development takes place, followed by additional

treatments required for the specific cheese variety and

there is very little whey separation. Thus, this process is

unique in that practically no conventional cheesemaking

equipment is required and of all the ultrafiltration meth-

ods, this method has the highest yield potential because of

maximum whey protein retention in the cheese.While the protein standardization technique can be

adapted to most cheese varieties, the liquid precheese

concept is more limited in its applicability because it is

not possible to achieve the composition of all cheeses by

ultrafiltration. The process developed for this method was

originally for Camembert cheese. It has also been applied

to Feta cheese. New cheeses, such as Pave d’Affinois, have

also been developed using the liquid precheese concept.For Camembert cheesemaking using this method,

pasteurized milk is ultrafiltered to 5� and at 20 �C a

mesophilic lactic culture and salt are added at 2% and

0.75%, respectively. After a pH of 5.5 is reached, rennet is

added and the mixture transferred to forms in which the

coagulum is formed. At the proper firmness, the coagulum

is removed from the molds, brined for 30min, sprayed

with Penicillium camemberti spores and ripened at 11–12 �Cfor 12 days at high humidity for mold growth on the

surface of the cheese wheels. This process results in a

yield increase of 12% to 15%.A high level of success with the liquid precheese con-

cept has also been achieved with Feta cheese. In this

Danish procedure, 5� ultrafiltered whole milk is homo-

genized, blended with lactic starter, salt and a lipase-

rennet mixture and poured into 18-kg tins where curd

forms. The curd is then covered with salt or 6% brine and

held for ripening. This process is an example in which the

cheese is actually manufactured in its retail package.Recently, a process for the manufacture of blue

cheese was commercialized in France in which standar-

dized milk is ultrafiltered to 6�. Starter and rennet are

added and continuous coagulation, cutting and molding

follow.

Cheese | Membrane Processing in Cheese Manufacture 621

Application of Ultrafiltration for FreshCheeses

The manufacture of fresh acid-type cheeses, such ascream cheese, quark and Ricotta, was particularly chal-lenging until mineral and ceramic membranes becameavailable. These membranes made it possible to ultra-filter acid curd to a high solids level with few foulingproblems. The general principle is to ferment high-heat-treated milk to pH 4.6 to 4.8 and then ultrafilter thecurd to the desired concentration. Traditionally, forquark, a centrifugal separator is used to separate curdand whey. The advantage of the ultrafiltration proce-dure is that whey proteins are retained and thereforecheese yield is increased. For cream cheese, the Cornellprocedure involves the blending of heavy cream with27.5% solids skim milk retentate to achieve the compo-sition of cream cheese. This mixture is pasteurized andhomogenized, then fermented, mixed with stabilizersand pasteurized.

Characteristics of Cheese fromUltrafiltered Milk

While the retention of whey proteins is advantageousfrom the cheese yield perspective, its impact on cheesequality should also be taken into account. Whey proteinsgenerally are inert filler materials and undergo very littleproteolysis during ageing. Flavor development is there-fore slow. Retarded proteolysis, along with the high waterbinding capacity of whey proteins, also influences thetexture of cheese. Furthermore, the high buffering capa-city of such cheese retards autolysis of lactic starter cellsand the breakdown of casein. These effects become morepronounced as the concentration of whey proteins incheese is increased (LCR cheese versus liquid precheeseconcept).

The impact of high mineral retention on cheese func-tionality and flavor is also of concern. Excessive retentionof calcium makes it difficult to obtain optimal function-ality in cheeses such as Mozzarella and may lead tobitterness in fresh acid-curd cheeses. Bitterness also arisesbecause of increased buffering, which leads to high levelsof starter cells. Preacidification during ultrafiltration cancontrol the mineral content of cheese.

Microfiltration

Microfiltration of milk for cheesemaking is a relativelynew concept but is rapidly gaining commercial accep-tance because of the potential to use a wide range ofmembrane pore sizes (0.05–10 mm). This flexibility

makes it possible to achieve the desired specific separa-tion, as well as fractionation, of milk constituents.Ceramic microfiltration membranes are commonly usedbut polysulfone membranes are also available.

The current direct applications of microfiltration forcheesemaking include a process for the removal of bac-teria and casein standardization of cheese milk. Both theseapproaches are commercialized.

Removal of Bacteria

Reducing the microbial load of milk prior to cheesemak-ing by processes such as pasteurization is a commonpractice and in some cases even mandatory. On theother hand, high heat treatment of milk is believed toalter the cheesemaking characteristics of milk and flavorcharacteristics of cheese. High-speed centrifugation ofmilk (bactofugation) was developed to remove bacteria,particularly spores of Clostridium tyrobutyricum, from milkbut the process is not as efficient as newly developedmicrofiltration procedures.

The microfiltration process of Alfa Laval (now TetraPak) for removing bacteria and spores is called theBactocatch� process (Figure 3). Raw skim milk is micro-filtered using a membrane with a pore size of 1.4 mm at35–50 �C. The retentate contains bacteria and thepermeate is the bacteria-free milk. This bacteria-freemilk can be blended with heated cream for standardiza-tion of fat. Bacteria removal efficiencies of 99.6–99.98%are reported, i.e. almost sterile milk is obtained. In theoriginal Alfa Laval (Tetra Pak) procedure, the retentate(which contains bacteria and some milk components)was heated to a high temperature to kill the bacteriaand blended with cream. In a modification developed by

Heat

Blend

Cheesemilk

Raw whole milk

Cream(10 parts)

Skim milk(90 parts)

Microfilter(1.4 µm pore size)

Microfiltrate (81 parts)(protein)

Retentate(9 parts)(bacteria)

Figure 3 Process for removal of bacteria from milk by micro-

filtration.

622 Cheese | Membrane Processing in Cheese Manufacture

APV, this bacterial concentrate is recycled through the

self-desludging separator prior to microfiltration. Hence,

bacteria are removed as sludge and milk components arerecovered.

This process is particularly suitable for fluid milkproduction (see Milk Protein Products: Membrane-

Based Fractionation) but is attractive for the manufac-ture of cheeses such as Swiss because of the possibility

of removal of spores of Cl. tyrobutyricum without using

nitrates or excessively high heat. On the other hand,French researchers have demonstrated that under

normal circumstances, microfiltered milk is not idealfor eye formation in Swiss cheese because of the

removal of non-starter lactic acid bacteria by microfil-

tration. This has been overcome by modifying thestarter system. Specific heterolactic strains with

mesophilic, thermophilic and propionic starters are

recommended.

Casein Standardization

Separation of casein and whey proteins can be accom-plished by using a microfiltration membrane of 0.1 mm

pore size. When skim milk is microfiltered in this manner,casein is concentrated and whey proteins are in the

permeate. The casein content of milk is increased from

2.5% to 3.5% and hence cheese yield is increased.Furthermore, the microfiltrate (permeate) generated

from this process contains whey proteins but no glyco-

macropeptide, which is normally found in whey fromconventional cheesemaking procedures. With this

method, it is therefore possible to standardize the caseincontent of cheese milk while producing an ‘ideal whey’

that has better functional characteristics than whey con-

taining glycomacropeptides.In recent work, French workers have used this

approach in combination with ultrafiltration to improve

the cheesemaking properties of dried milk. In this

patented process, whey proteins are completely or par-tially removed from milk by microfiltration, as above.

The microfiltration permeate, which contains the whey

proteins, is ultrafiltered and the permeate from ultrafil-tration, which contains lactose, minerals and water, is

blended with the retentate of microfiltration. The micro-filtration retentate contains casein, and when blended

with ultrafiltration permeate yields milk with low or no

whey protein. This milk is evaporated and spray-dried.The spray-dried product can be used for cheesemaking

after reconstitution without the typical difficulties

encountered with conventional powder, which containsdenatured whey proteins because of the heat treatments

employed during manufacture.

Nanofiltration

Dairy applications of nanofiltration are very recent andmajor use is currently in the area of whey processing.Such use includes demineralization and concentration ofwhey and reduction of salt from salt whey (see WheyProcessing: Demineralization). Interesting applicationsfor cheese are also emerging. High permeability of mono-valent ions (40–90%) and low permeability of polyvalentions (5–20%) typically characterize nanofiltration.Consequently, it is possible to concentrate milk by nano-filtration to obtain an altered mineral balance.Experimental work suggests that this would offer poten-tial for soft cheese manufacture.

Future Potential

Over the past 35 years, membrane processing of milk hasallowed the introduction of many innovations for cheese-making. Not only has cheesemaking efficiency improvedbut also new cheeses have been developed. The processthat led the development of membrane applications incheesemaking, MMV process for Camembert cheese, isno longer used for this cheese because of difficulties inmeeting consumer expectations for the appearance of thecheese. However, that process inspired the development ofapplications for other cheeses, namely, Feta, Paved’Affinois, Le Petit Moule, La Roche (blue cheese) andothers. Since the early days, significant improvements havebeen made in membrane design and processes that havefurther enhanced cheesemaking applications. As newmembrane processes and applications are developed, inno-vations in cheesemaking will continue. Unfortunately, notall countries have taken advantage of the applications ofmembranes for cheesemaking because the standards ofidentity pertaining to membrane-processed milk have notbeen fully resolved in individual countries but CodexAlimentarius regulations do permit the use of such milkand progress will continue.

See also: Milk Protein Products: Membrane-Based

Fractionation; Plant and Equipment: Evaporators; Whey

Processing: Demineralization.

Further Reading

Bylund G (1995) Dairy Processing Handbook. Lund, Sweden: Tetra PakProcessing Systems AB.

Garem A, Schuck P, and Maubois JL (2000) Cheese-making propertiesof a new dairy based powder made by a combination ofmicrofiltration and ultrafiltration. Lait 80: 25–32.

Guinee TP, O’Callaghan DJ, Mulholland EO, and Harrington D (1996)Milk protein standardization by ultrafiltration for Cheddar cheesemanufacture. Journal of Dairy Research 63: 281–293.

Cheese | Membrane Processing in Cheese Manufacture 623

IDF (1992) New Applications of Membrane Processes. Special Issue no.9201. Brussels: IDF.

Kosikowski FV and Mistry W (1997) Cheese and Fermented Milk Poods,3rd edn. Great Falls: FV Kosikowski LLC.

Lawrence RC (1989) The Use of Ultrafiltration Technology inCheesemaking. International Dairy Federation Bulletin no. 240.Brussels: IDF.

Maubois JL (1998) Fractionation of milk proteins. Proceedings of the25th International Dairy Congress, Aarhus: Denmark. pp. 74–86.

Maubois JL, Mocquot G and Vassal L (1969) A Method for ProcessingMilk and Milk Products. French Patent no. 2 052 121.

Mistry VV and Maubois JL (1993) Application of membrane separationtechnology to cheese production. In: Fox PF (ed.) Cheese:Chemistry, Physics and Microbiology, vol. 1, pp. 493–522.New York: Chapman & Hall.

Oommen BS, Mistry VV, and Nair MG (2000) Effect of homogenization ofcream on composition, yield, and functionality of Cheddar cheesemade from milk supplemented with ultrafiltered milk. Lait 80: 77–92.

Rattray W and Jelen P (1996) Protein standardization of milk and dairyproducts. Trends in Food Science and Technology 7: 227–234.

Saboya LV and Maubois JL (2000) Current developments ofmicrofiltration technology in the dairy industry. Lait 80: 541–554.

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