Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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the ripening of such cheeses is extended, they will

probably develop off-flavors. It is possible to develop

an intense flavor in internal bacterially ripened

cheeses, such as hard and semihard varieties, only if

the moisture content is low and if they are ripened for

a long period, e.g., 2–3 years. Owing to the high cost

of ripening facilities and stocks, the ripening of extra-

mature, low-moisture cheese is expensive, and there is

commercial interest in accelerating the ripening

process. Most of the work on accelerating cheese

ripening has been on Cheddar.

0060 Methods for accelerating cheese ripening fall into

six categories:

0061 elevated ripening temperature;

0062 exogenous enzymes;

0063 chemically or physically modified cells;

0064 genetically modified starters;

0065 adjunct starters.

0067 Ripening at an elevated temperature, e.g., up to



C, is the simplest and cheapest method for accel-

erating the ripening of Cheddar cheese, but modified

primary starters and adjunct cultures appear to be

very promising. Techniques for accelerating ripening

may also be applicable to low-fat cheeses, which tend

to ripen slowly.

See also: Cheeses: Types of Cheese; Enzymes:

Functions and Characteristics; Goat: Milk; Lactic Acid

Bacteria; Milk: Physical and Chemical Properties;

Pasteurization: Pasteurization of Liquid Products;

Sheep: Milk; Starter Cultures

Further Reading

Eck A and Gilles JC (2000) Cheesemaking: From Science to

Quality Assurance, 2nd edn. Paris: Technique et Docu-

mentation (Lavoisier).

Fox PF (ed.) (1993) Cheese: Chemistry, Physics and Micro-

biology, 2nd edn., vols. 1 and 2. London: Chapman &

Hall.

Fox PF, Guinee TP, Cogan TM and McSweeney PLH (2000)

Fundamentals of Cheese Science. Gaithersburg, MD:

Aspen.

Fox PF and Wallace JM (1997) Formation of flavour com-

pounds in cheese. Advances in Applied Microbiology 45:

17–85.

Fox PF, Wallace JM, Morgan S et al. (1996) Acceleration of

cheese ripening. Antonie van Leeuwenhoek 70: 271–

297.

Kosikowski FV and Mistry VV (1997) Cheese and Fer-

mented Milk Foods, 3rd edn., vols. 1 and 2, Westport,

CT: F.V. Kosikowski LLC.

McSweeney PLH and Sousa MJ (2000) Biochemical path-

ways for the production of flavour compounds in cheese

during ripening. Lait 80: 293–324.

Robinson RK (ed.) (1995) A Colour Guide to Cheese and

Fermented Milks. London: Chapman & Hall.

Robinson RK and Wilbey RA (1998) Cheesemaking Prac-

tice, R. Scott, 3rd edn., Gaithersburg, MD: Aspen.

Scott R (1986) Cheesemaking Practice. London: Elsevier

Applied Science.

Smit G, van Hylckama Vlieg JET, Smit BA, Ayad EHE and

Engels WJM (2002) Fermentative formation of flavour

compounds by lactic acid bacteria. Australian Journal of

Dairy Technology 57: 61–68.

Yvon M and Rijnen L (2001) Cheese flavour formation by

amino acid catabolism. International Dairy Journal 11:

185–201.

Strecker Aldehyde

(a)

Amino acid

(b)

Isobutanal

2-Methylpropanal

(from Val)

Phenylacetaldehyde

(from Phe)

α-Ketoglutaric acid

Methional

3-Methylthiopropanal

(from Met)

R H

ROH

2-Methylbutanal

(from Ile)

3-Methylbutanal

(from Leu)

fig0008 Figure 8 (a) Strecker reaction between an amino acid and an a-keto acid (e.g., a-keto glutaric acid) and (b) structures of some

Strecker aldehydes found in cheese.

1086 CHEESES/Manufacture of Hard and Semi-hard Varieties of Cheese

Cheeses with ‘Eyes’

P L H McSweeney, University College, Cork, Ireland

Synopsis

0001 Mechanical openings (resulting from the incomplete

fusion of curd pieces) are common in many cheese

varieties where they may be considered desirable

(e.g., Monterey) or a defect (e.g., Cheddar). However,

some internal bacterially ripened varieties are charac-

terized by the development of ‘eyes’ caused by gas

(CO

), produced by bacterial metabolism, being

trapped in the curd. The development of eyes in

cheese is governed by the rate of gas production by

bacteria and the ability of the curd to retain the gas.

There are two main families of cheeses with eyes:

Dutch types (Edam, Gouda, and related varieties),

which have small eyes, and Swiss types, which are

characterized by large eyes. In the case of Edam and

Gouda cheeses, CO

is produced by the action of

Leuconostoc spp. or citrate-utilizing (Cit

) lactococci

on citrate (See Cheeses: Dutch-type Cheeses),

whereas in Swiss varieties, CO

is produced by Pro-

pionibacterium freudenreichii from lactate. These

two families of cheeses are quite different in terms

of their manufacturing protocol, ripening conditions,

and flavor and appearance of the final product.

0002 The most popular Swiss-type cheese is Emmental

(Figure 1), which originated in the Emm river valley

in Switzerland, but is now made world-wide. This

article will concentrate on the manufacturing proto-

col for, and the ripening of, Emmental. A number of

other related Swiss-type cheeses will be discussed

briefly.

General Characteristics of Emmental

Cheese

0003Typically, Emmental contains c. 30.5% fat, 35.5%

moisture, 27.5% protein, 0.5–0.7% salt, and 3.5%

ash, and has a pH of c. 5.6. It has a mild, sweet, and

somewhat nutty flavor. Emmental cheese is character-

ized by large eyes that are caused by CO

produced by

P. freudenreichii, which metabolizes lactate to propi-

onate, acetate, and CO

. Propionibacteria do not

grow in the milk during cheesemaking but grow in

the curd during the early stages of maturation when

the cheeses are transferred to a ‘hot room’ (*20



to promote their growth. The texture of Emmental is

quite rubbery and entraps the CO

(which migrates

through the curd until it reaches a fissure or weakness

at which an eye develops). The texture of Emmental

cheese results from a high cooking temperature

(*55



C), which inactivates much of the coagulant,

and a high pH at draining, leading to a high Ca

2þ

content in the curd. Emmental cheese is brine-salted.

0004The manufacturing protocol for Emmental is

shown Figure 2. Traditionally, Emmental is made

from raw cows’ milk, which is acidified through the

action of a mixed thermophilic starter consisting of

Streptococcus thermophilus and a Lactobacillus sp.

Lb. helveticus was used traditionally, but Lb. del-

brueckii sp. bulgaricus and Lb. delbrueckii sp. lactis

are now common also. Propionibacteria are added

to the milk (usually to c.10

–10

cfu ml

1

) or gain

access to the milk from the environment (which is

often the case in traditional manufacture). The milk,

at 30



C, is coagulated using calf rennet, and the

coagulum is cut into small pieces and cooked to

*55



C until the curd pieces are of the desired firm-

ness. The curds–whey mixture is transferred into

molds where the whey is drawn off. The mold is

sufficiently large to give a cheese wheel weighing up

to c. 100 kg and with a diameter of up to 1 m. The size

of the Emmental wheel is far from cosmetic. The large

size of the wheel means that Emmental has a rela-

tively low surface area-to-volume ratio. This is of

significance, since it determines the rate of cooling

of the curd (and thus the activity of the starter) and

salt diffusion throughout the cheese mass, and helps

to trap gas within the cheese and allows gas pressure

to increase within the cheese until eye formation

occurs. Over the next 1–2 days, the wheels are

pressed and turned frequently. During this time, the

curd cools, and acid production by the starter (which

was dormant during the scalding step) recommences.

Lactic acid fermentation in Emmental takes c.12h.

After pressing, the cheese wheels are brine-salted.

Swiss cheeses have the lowest NaCl content of

all cheese varieties, permitting the growth of its

fig0001 Figure 1 Emmental cheese. Reprinted with permission from

Roginski H, Fuquay JW and Fox PF (eds) (1992) Encyclopedia of

Dairy Sciences. Academic Press: London.

CHEESES/Cheeses with ‘Eyes’ 1087

secondary flora during ripening (P. freudenreichii).

Propionibacterium freudenreichii is very sensitive to

NaCl and will not grow at a

values below 0.96

(c. 1.2% NaCl).

0005 Although Emmental is manufactured in industry

by this traditional process, a rindless product is now

produced in large factories and, in many countries

with a developed dairy industry, is the major type of

Emmental produced. Rindless, or ‘block,’ Emmental

is manufactured by a process generally similar to that

described for traditional Emmental, but this cheese is

manufactured from milk with a lower fat content

(c. 2.5%) and cooked to a lower temperature. The

cheese is molded in the form of blocks that are

wrapped in plastic film; thus, no rind develops during

ripening.

Ripening of Swiss Cheese

0006In common with most, if not all, rennet-coagulated

cheeses, immediately after manufacture, Swiss cheese

has a bland flavor and a texture and appearance quite

different from the mature cheese. The characteristic

flavor, texture, and appearance of Swiss cheese de-

velop during ripening. The ripening of Swiss

cheese typically starts with storage in a cool room

and 10–15



C and 90% equilibrium relative humidity

(ERH) for 10–14 days; in traditional practice, the

cheeses are brushed, dry salt is rubbed on to the

surface, and the cheeses are turned daily until a

smooth rind develops. The cheeses are then trans-

ferred to a hot room (20–24



C, 80–83% ERH) and

held there for 3 weeks to 2 months. The cheeses are

held in the hot room until adequate eye formation

occurs (which is assessed traditionally by tapping the

cheese and listening to the hollow sound produced);

cheeses are then transferred to another ripening

room at about 7



C and matured for 1 or 2 months

for further flavor development.

0007During the ripening of Swiss cheese, protein and, to

a lesser extent, lipid in the cheese are degraded

to flavor compounds, lactate is metabolized with

important consequences for flavor and eye develop-

ment, and changes occur to the microflora of the

cheese. The ripening agents in Swiss cheese originate

from the milk (particularly the principal indigenous

proteinase in milk, plasmin), from the microflora of

the cheese (starter, nonstarter bacteria, and propionic

acid bacteria in addition to a minor contribution from

the coagulant (usually chymosin). The ripening of

Swiss cheese is summarized in Figure 3.

0008Starter bacteria reach maximum numbers in Swiss

cheese soon after manufacture. Thereafter, their

numbers decline rapidly as a result of the lack of

a readily fermentable carbohydrate and low pH.

Numbers of viable Sc. thermophilus decline at a

slightly faster rate than those of the Lactobacillus sp.

However, the importance of the starter to cheese

ripening does not end with their death. After death,

cells lyse at a strain-dependent rate, releasing their

intracellular enzymes, which are of great importance

in the ripening of Swiss cheese. Starter activity during

acidification also has a major indirect effect on

ripening since it is their action, together with the

buffering capacity of the cheese, that controls pH

and oxidation–reduction potential (E

) which, in

turn, have a very important effect on the rate of

30−32 ⬚C

Rennet,

thermophilic starter,

propionibacteria

Cows' Milk

Coagulum

Cut coagulum,

cook to c. 55 ⬚C

Curds−whey pitched into molds

Whey

Pressing

Dry cheese surface

Salt applied to the surface

1−2 days

Brine salting

c. 2 days, 8−10 ⬚C

Cool storage

Dry rind forms

10−14 days

10−15 ⬚C, 90% ERH

Hot room

20−24 ⬚C, 80−83% ERH

Cool storage

1−2 months

7 ⬚C

3 weeks to 2 months

Eye development

Emmental cheese

fig0002 Figure 2 Traditional manufacturing protocol for Emmental

cheese. Reprinted with permission from P.F. Fox, T.P. Guinee,

T.M. Cogan and P.L.H. McSweeney. Fundamentals of Cheese

Science, ß 2000, Aspen Publishers, Gaithersburg, MD.

1088 CHEESES/Cheeses with ‘Eyes’

COOH

D-Lactate

COOH

L-Lactate

Eyes

Propionate Acetate

Propionic acid bacteria

Lactose

Galactose

(c)(b)(a)

Lactobacillus sp.

Str. thermophilus

Caseins

Intermediate-sized

peptides

Proteinases from

starter

Plasmin and

chymosin

Short peptides

Peptidases

Free fatty acid

Free amino acids

Enzymatic and chemical

modifications

Volatile flavor compounds

Lipase

Triglyceride

fig0003 Figure 3 Schematic representation of the principal biochemical events occurring during the ripening of Swiss-type cheese. (a) Proteolysis and catabolism of amino acids, (b) lipolysis and

many ripening reactions. Most, if not all, ripened

cheeses develop an adventitious secondary flora

during ripening. These ‘non-starter lactic acid bac-

teria’ (NSLAB), typically mesophilic lactobacilli, are

present in the raw milk or gain entry from the cheese-

making environment; in the case of cheese made from

pasteurized milk, they may survive pasteurization,

perhaps in a heat-shocked state, or gain entry from

the environment. NSLAB are quite different from the

thermophilic lactobacilli used as starters in the manu-

facture of Swiss cheese, and include species of lacto-

bacilli such as Lb. casei and Lb. paracasei. As with all

other cheeses, the NSLAB flora of Swiss cheese is

uncontrolled, but increases from very low numbers

(particularly in the case of cheeses made from pas-

teurized milk) to c.10

cfu g

1

cheese. Studies on the

role of the NSLAB flora in Swiss cheese suggest that

they contribute to the differences in flavor between

raw and pasteurized milk cheeses and play a minor

role in ripening.

0009 The level of lactose in Swiss cheese decreases rap-

idly during the latter stages of manufacture and early

in ripening, reaching very low levels after 24 h. Soon

after manufacture, Emmental cheese typically con-

tains *1.7% lactose which is metabolized rapidly by

Sc. thermophilus to l-lactate; after 24 h, the level of

lactose in Swiss cheese is usually very low (Figure 4).

However, Sc. thermophilus metabolizes only the glu-

cose moiety of lactose and thus galactose levels in the

curd increase initially, reaching a maximum c.10h

after manufacture; galactose is then metabolized by

the lactobacilli to d/l-lactate. It is important to use a

Gal

Lactobacillus sp. in the starter mix or galactose

will accumulate in the curd, the metabolism of which

by NSLAB can lead to off-flavors. Metabolism of

galactose is usually complete after 14 days. During

the early stages of ripening, there is significantly more

l-lactate than d-lactate in the curd.

0010Lactate metabolism is more important in Swiss

cheese than in any other variety, with the exception

of surface mold-ripened cheeses such as Camembert

and Brie. Pr. freudenreichii added to, or contamin-

ating, the milk for Swiss-type cheeses grow once the

cheeses are transferred to the warm room after

brining and metabolize l-lactate during ripening via

a complex pathway to propionate, acetate, CO

and

O(Figure 5). The pathway for lactate metabolism

by Propionibacterium freudenreichii (Figure 6) in-

volves two separate cycles, one producing propionate

and the other acetate. In general, propionic acid bac-

teria are able to metabolize both l- and d-lactate, but

usually, they metabolize the former preferentially to

, and so levels of l-lactate decrease with a con-

comitant increase in the levels of propionate and

acetate (Figure 4). Later in ripening, the propionic

acid bacteria utilize d-lactate, at which point, the

concentration begins to decline. Carbon dioxide pro-

duced is essential for eye development, and the pro-

pionate and, to a lesser extent, acetate contribute to

the flavor of these cheeses. Eyes are a characteristic

sensory feature of Swiss-type cheeses and are a par-

ameter used by the consumer to identify these cheeses.

0011An undesirable pathway for lactate metabolism in

Swiss and many other cheeses is its anaerobic fermen-

tation to butyrate and H

by Clostridium spp.,

resulting in a serious defect known as ‘late gas blow-

ing.’ Spores of clostridia, which survive pasteuriza-

tion of milk and cooking of Swiss cheese, may be

removed from milk by bactofugation or microfiltra-

tion. Other approaches to avoid this problem include

the use of lysozyme or NO



(which degrade the cell

612182414 21 28 35

0.3

0.6

0.9

1.2

1.5

1.8

Glucose

Galactose

D-Lactate

L-Lactate

Lactose

Propionate

Propionibacteria

Acetate

DaysHours

P+ 4 h P+10 h 1 day

P+ h

fig0004 Figure 4 Lactose and lactate metabolism in Swiss-type cheese

manufactured using Streptococcus thermophilus and a galactose-

positive strain of Lactobacillus helveticus as starters. Lactose (s),

glucose (n), galactose (m), D-lactate (h), L-lactate (&), acetate

(!), propionate (!) and numbers of propionic acid bacteria (

.).

Reprinted with permission from P.F. Fox, T.P. Guinee, T.M.

Cogan and P.L.H. McSweeney. Fundamentals of Cheese Science,

ß 2000, Aspen Publishers, Gaithersburg, MD.

++CO

Lactate Propionate Acetate

−

fig0005Figure 5 Overall equation for the metabolism of lactate by

Propionibacterium freudenreichii in Swiss-type cheeses during

ripening. Reprinted with permission from P.F. Fox, T.P. Guinee,

T.M. Cogan and P.L.H. McSweeney. Fundamentals of Cheese

Science, ß 2000, Aspen Publishers, Gaithersburg, MD.

1090 CHEESES/Cheeses with ‘Eyes’

wall of Gram-positive bacteria and inhibit germin-

ation of spores, respectively) and good hygiene. In

particular, feeding silage to cows, whose milk will

be used in the manufacture of Swiss cheese, is forbid-

den in some regions.

0012 Because of the absence of strongly lipolytic agents,

lipolysis is quite limited in Swiss cheese. However,

lipolysis does contribute to the flavor of Swiss

cheese. Short-chain fatty acids contribute directly

to cheese flavor, and low levels are desirable in Swiss

cheese. However, high levels of free fatty acids give an

undesirable, rancid off-flavor to Swiss cheese. Fatty

acids also act as precursors for a range of further

reactions (e.g., the formation of fatty acid lactones,

hydroxyacids, esters, thioesters, and methyl ketones)

that contribute to cheese flavor. Lipolysis in Swiss

cheese is catalyzed by the indigenous milk lipoprotein

lipase (LPL; particularly in the case of raw milk

cheese, since this enzyme is extensively inactivated

by pasteurization). The action of LPL is probably

less important in raw milk Swiss cheese than in

other raw milk varieties, since it is partially inacti-

vated during the cooking step. Other sources of

lipases and esterases in Swiss cheese are the starter

and NSLAB; Pr. freudenreichii has also been shown to

possess a lipase.

Glucose

Glucose-6-P

Fructose-6-P

Fructose-1,6-diP

Glyceraldehyde-3-P

Glucokinase

3-P-Glycerate

P-Enolpyruvate

Oxaloacetate

Malate

Fumarate

Succinate

Poly-P

n −1

Poly-P

Phosphohexose isomerase

Pyrophosphate phosphofructokinase

Aldolase

Glyceraldehyde 3-phosphate dehydrogenase

Enolase

Pyruvate

Lactate

Phosphotransacetylase

Acetate

Citrate

Fumarase

Fumarate reductase

CoA transferase

Methylmalonyl CoA

Transcarboxylase

Propionyl CoA

6-P-Gluconate

Pentose-P

Pyruvate phosphate dikinase

ATP

LDH

ATP

AMP

ADP

Pyruvate

dehydrogenase

Acetyl CoA

Acetyl-P

Acetyl kinase

α-Ketoglutarate

Malic dehydrogenase

Methylmalonyl mutase

Propionate

Phosphoenol carboxytransphosphorylase

Succinyl CoA

fig0006 Figure 6 Cycles involved in the propionic acid fermentation by Propionibacterium sp. (LDH, lactate dehydrogenase; Poly-PN,

polyphosphate; Ppi, pyrophosphate.) For reasons of clarity, only the pyrophosphate-dependent conversion of fructose-6-P to fruc-

tose-1,6-diP is shown, and the generation of ATP by the electron transfer system is omitted. All reactions are directed towards

production of propionate, even though the reactions are reversible. Reprinted with permission from P.F. Fox, T.P. Guinee, T.M. Cogan

and P.L.H. McSweeney. Fundamentals of Cheese Science, ß 2000, Aspen Publishers, Gaithersburg, MD.

CHEESES/Cheeses with ‘Eyes’ 1091

0013 Proteolysis is a major series of events during the

ripening of Swiss cheese. Proteolysis in Swiss cheese is

catalyzed by enzymes indigenous to the milk and

from the cheese microflora and, to a much lesser

extent, from the coagulant. The principal indigenous

proteinase in milk, plasmin, is particularly important

for proteolysis in Swiss-type cheese. Plasmin (fibrino-

lysin, EC 3.4.21.7) is a serine proteinase with an

alkaline pH optimum that is formed from an inactive

precursor, plasminogen, by limited proteolysis. The

activation of plasminogen and plasmin activity in

milk are controlled by a system of plasminogen acti-

vators, plasmin inhibitors, and inhibitors of plasmi-

nogen activators. Plasmin is a particularly heat-stable

proteinase, and hence its activity relative to other

proteolytic enzymes (especially chymosin) is higher

in Swiss cheese than in other varieties, since it survives

the cooking step. Plasmin acts during ripening to

degrade b-casein to g-caseins; the latter accumulate

to greater levels in Swiss cheese than in most other

varieties. Chymosin, or other enzymes from the co-

agulant, are the most important enzymes for the ini-

tial degradation of the caseins during the ripening of

most internal, bacterially ripened varieties. However,

since chymosin is denatured extensively during the

cooking step of Swiss cheese, its action is less import-

ant in this variety than in varieties such as Cheddar.

0014 Intermediate-sized peptides produced by the action

of plasmin or chymosin are hydrolyzed by proteinases

and peptidases from the cheese microflora. Lactic

acid bacteria are auxotrophic for a number of amino

acids and therefore possess a range of proteolytic

enzymes capable of liberating amino acids from

the caseins. Although less well studied than the lacto-

cocci, thermophilic lactobacilli and streptococci used

as starters in Swiss cheese possess generally similar

proteinase and peptidase systems, including a cell

envelope-associated proteinase that is responsible

for degrading many of the intermediate-sized peptides

produced by plasmin and chymosin to shorter pep-

tides. Lactic acid bacteria, including those used as

starters in Swiss cheese, possess a wide range of intra-

cellular peptidases. These enzymes are released into

the cheese matrix following cell lysis, which occurs

during ripening, and are essential for the liberation of

amino acids (AA). Pr. freudenreichii is weakly proteo-

lytic, although it does possess intracellular peptidases

that contribute to ripening.

0015 Proteolysis results ultimately in the liberation of

AA. AA contribute directly to the background flavor

of cheese; some are sweet, some are sour, and many

are bitter. However, the major role of AA in the

development of cheese flavor is now thought to be

as precursor molecules for a range of poorly under-

stood catabolic reactions that lead to the formation of

many volatile flavor compounds. Although amino

acid catabolism has not been studied extensively in

Swiss cheese, it is highly likely that it follows the same

general pathways as in other internal, bacterially

ripened varieties such as Cheddar and Gouda.

Amino acid catabolic reactions include deamination

(to yield NH

and a-keto acids), decarboxylation (to

yield amines), formation of alkyl pyrazines, and ca-

tabolism of sulfur-containing and aromatic amino

acids.

Other Swiss-type Cheeses

0016Although Emmental is the Swiss-type variety pro-

duced in the largest amount world-wide, there are

several related Swiss cheese varieties. Gruye

re is a

popular Swiss-type cheese that differs from Emmental

in being smaller, with a somewhat stronger flavor and

fewer eyes, and is characterized by the development

of a surface flora. This surface flora (similar to that

which develops on smear-ripened varieties such as

Tilsit and Limburger) is encouraged by ripening for

2–3 weeks at 10



C and for 2–3 months at 15–20



and 90–95% ERH. During the hot-room stage, the

cheeses are rubbed with a brine-soaked cloth. Further

ripening at 12–15



C is required before retail; the

cheese is ripe in 8–12 months. Varieties similar to

Gruye

re include Raclette (which is manufactured

from raw milk and is acidified by the natural flora

of the milk) and Gruye

re de Comte

, which is pro-

duced in eastern France. Comte

has smaller eyes

than Emmental as a consequence of a low ripening

temperature (c.18



C). The surface of this cheese is

covered by an orange smear (‘morge’); cell numbers at

the surface are typically 10

cfu cm

2

, and the micro-

flora is very complex, consisting of coryneform

bacteria, micrococci, and yeasts. Beaufort is a French

variety that is similar to, but larger than (c. 45 kg),

Gruye

re and usually develops fewer eyes (as a result

of the growth of mesophilic starter acting on citrate at

a low ripening temperature) than Gruye

re. Appenzel-

ler, which originated in Switzerland, is a small cheese

(c. 30 cm) with a soft texture and propionic acid

fermentation that results in the development of a

few eyes. The curds are cooked at 43–45



C. Appen-

zeller is immersed in cider or spiced wine or coated

with a mixture of salt and spices during ripening,

which imparts a distinctive flavor to the cheese.

Maasdammer, a variety developed recently in The

Netherlands, is characterized by the use of a meso-

philic starter and extensive propionic acid fermenta-

tion, which gives large eyes and a domed appearance

to the cheese wheels. Jarlsberg is a Swiss-type cheese

produced in Scandinavia, which is characterized by

large eyes.

1092 CHEESES/Cheeses with ‘Eyes’

See also: Cheeses: Chemistry and Microbiology of

Maturation; Dutch-type Cheeses

Further Reading

Christensen JE, Dudley EG, Pederson JA and Steele JA

(1999) Peptidases and amino acid catabolism in lactic

acid bacteria. Antonie van Leeuwenhoek 76: 217–246.

Fox PF (ed.) (1993) Cheese: Chemistry, Physics and Micro-

biology, 2nd edn. vols 1 and 2, London: Chapman &

Hall.

Fox PF, Guinee TP, Cogan TM and McSweeney PLH (2000)

Fundamentals of Cheese Science. Gaithersburg, MD:

Aspen.

Fox PF, Lucey JA and Cogan TM (1990) Glycolysis and

related reactions during cheese manufacture and

ripening. Critical Reviews in Food Science and Nutrition

29: 237–253.

Fox PF and McSweeney PLH (1996) Proteolysis in cheese

during ripening. Food Reviews International 12: 457–

509.

Kosikowski FV and Mistry VV (1997) Cheese and Fer-

mented Milk Foods, 3rd edn. vols 1 and 2, Westport,

CT: F.V. Kosikowski.

Kunji ERS, Mierau I, Hagting A, Poolman B and Konings

WN (1996) The proteolytic system of lactic acid bac-

teria. Antonie van Leeuwenhoek 70: 187–221.

McSweeney PLH and Sousa MJ (2000) Biochemical path-

ways for the production of flavour compounds in

cheeses during ripening: A review. Lait 80: 293–324.

Polychroniadou A (2001) Eyes in cheese: a concise review.

Milchwissenschaft 56: 74–77.

Robinson RK and Wilbey RA (1998) Cheesemaking Prac-

tice. R. Scott. Gaithersburg, MD: Aspen.

Steffen C, Eberhard P, Bosset JO and Ru

egg M (1993)

Swiss-type varieties. In: Fox PF (ed.) Cheese: Chemistry,

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London: Chapman & Hall.

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and Technology 18: 117–123.

Soft and Special Varieties

R C Chandan, New Brighton, MN, USA

Introduction

0001 This article contains terse description of cottage

cheese, cream cheese, and cheese varieties commonly

used in South Asia and Latin America. The typical

composition of these products, compared with fresh

Cheddar cheese, is shown in Table 1.

Cottage Cheese

0002Cottage cheese belongs to the class of natural, unrip-

ened, soft cheeses. Since it has a significantly lower fat

content than most cheeses and is a good source of

protein, it is a popular part of low-calorie diets. This

cheese is made from pasteurized skim milk, concen-

trated nonfat milk or reconstituted nonfat dry milk.

Coagulation of skim milk is accomplished by fermen-

tation with Lactococcus lactis ssp. lactis or Lc. lactis

ssp. cremoris. Alternatively, food-grade acids may be

used to set the milk, but the product must be labeled

‘Direct Acid set.’ It is marketed as a small-curd (< 4 cm

diameter) or large-curd (> 8 cm diameter) product.

0003Cottage cheese is a major dairy product in North

America. In 2000, total sales of cottage cheese in the

US were 333.8 million kilograms, with average per

caput sales of 1.18 kg. The market value exceeds one

billion US dollars. The US Food and Drug Adminis-

tration standards define cottage cheese as the product

containing moisture not exceeding 80% and milk fat

not less than 4%. Cottage cheese may be labeled as

reduced fat if it contains at least 25% less fat than

creamed cottage cheese. To qualify for a low-fat label,

the product must contain not more than 3 g of fat per

serving of 28.35 g. Fat-free or nonfat cheese must

contain less than 0.5 g of fat perserving of 28.35 g.

Certain preservatives, including sorbates, are allowed

to extend the shelf-life of Cottage cheese. Cottage

cheese may contain fruits, seafood, meats, or vege-

tables.

0004Cottage cheese is a major ingredient of salads and

is used as a filling in the preparation of breakfast

food, blintze. Good-quality cottage cheese should

have a clean, creamy, cultured milk flavor, a natural,

creamy color, and a meaty, soft texture. It should have

a reasonably uniform curd size and should not be

pasty or too firm. It should have a uniform cream

layer around the curd particles with a little free cream.

tbl0001Table 1 Composition (%) of some soft cheeses

Cheese Moisture Protein Fat Lactose

Cottage cheese curd 79.8 17.3 0.4 1.9

Creamed cottage cheese 79.0 12.5 4.5 2.7

Neufchatel cheese 62.9 10.1 26.1 3.3

Cream cheese 53.8 7.6 34.9 2.7

Ricotta (whole milk) 71.7 11.3 12.9 3.1

Chhana – cow milk 53.4 17.4 24.8 2.6

Paneer – buffalo milk 51.3 17.3 27.0 2.6

Queso Blanco 55.0 23.0 15.0 2.7

Cheddar cheese curd 37.0 25.0 32.2 1.3

Cheddar is included for comparison.

Sources: USDA (1998). Nutrient Database for Standard Reference,

Release 12, Nutrient Data Laboratory. www.nal.usda.gov/fnic/foodcomp,

and Kosikowski FV and Mistry VV (1997). Cheese and Fermented Milk

Foods, 3rd edn. Westport, CT: FV Kosikowski LLC.

CHEESES/Soft and Special Varieties 1093

Manufacturing Process

0005 Depending on the plant schedule, a short-set,

medium-set, or long-set method may be used. The

long-set method involves using 1% starter, incubation

at 22



C for 12–16 h, whereas the short-set method

uses 5–7% starter at 32



C for 4–6h.

0006 The manufacturing operation may involve the use

of simple cheese vat and equipment for whey removal,

curd washing, draining, and creaming. The creamed

curd is pumped to a filler for packaging. However,

large-scale operations use automated systems to

continuously carry out the various steps outlined

below.

0007 Setting Raw skim milk is pasteurized at 73



C for

16.5 s. It is desirable to avoid previously heated milk

because a minimal heat treatment is needed to avoid

the formation of weak coagulum and subsequent

shattering of the curd. The pasteurized milk is cooled

to 32



C and pumped into a cheese vat, where the

jacket temperature is adjusted to maintain the milk

temperature at 32



C. Bulk culture is added at the

level of 5–7% and mixed thoroughly. The titratable

acidity is measured at this point. Stirring is continued

at intervals of 30 min for 1.5 h. The increase in acidity

at this point should be 0.05–0.07%. If not, 1% more

culture is added for each 0.01% increment below

0.05%. Next, rennet, diluted 1 to 40 with water, is

added at a level of 40 ml for a large curd and 12–

20 ml for a small curd per 454 kg of skim milk. After

mixing thoroughly, the vat is covered for about 2 h for

fermentation, during which time the pH should drop

to 4.6–4.7.

0008 Cutting When the coagulum is ready, it is cut first

along the length of the vat using appropriate horizon-

tal knives to yield the desired small- or large-curd

product. Wire knives with a 0.62-cm spacing are

used for the small-curd product and with 1.86 cm

spacing for the large-curd product. Next, the coagu-

lum is cut lengthwise with the vertical knife and then

crosswise with the vertical knife.

0009 Cooking After cutting, the curd is allowed to heal

for 10 min. The jacket water temperature is raised to

44–50



C to initiate cooking of the curds. The tem-

perature of curd is raised slowly to 54



C over 1.5 h.

The curd-whey is hand-stirred every 5–10 min, and a

mechanical agitator is used after the temperature has

reached 38–41



C. The agitation speed is increased

slowly to avoid matting of curd particles. Small curd

particles cook faster than large particles. Agitation is

continued until the curds become reasonably firm;

the curd is adequately cooked when a handful of

water-chilled curd springs apart when squeezed to-

gether with moderate pressure.

0010Washing After completion of cooking, the jacket

water is drained off. Whey is removed until the curd

begins to appear above the surface. Wash water, acid-

ified with phosphoric acid to pH 4.6 and chlorinated

to 10–20 mg kg

1

is then added to a volume equal to

that of the whey removed. The temperature of curd

should decrease to 27–30



C. After agitation for

10 min, the water is drained off. Washing is repeated

twice with chilled water to reduce the temperature of

the curd to 13–16



C and finally to 5



C or lower. The

curd is trenched and allowed to drain for 30–60 min

before creaming.

0011Creaming The curd is blended with cream dressing

in a blender or in the cheese vat. The dressing is

formulated to contain 12.5% fat, 8.5% solids-not-

fat (SNF), 2.7% salt, and 0.25% stabilizer. The stabil-

izer is especially designed for the dressing to achieve a

high viscosity and to avoid wheying off. The dressing

is pasteurized at 75–77



C for 30 min and homogen-

ized at 57



C at a pressure of 13.8 MPa, single stage,

followed by cooling to 4



C or below. One part of the

dressing is blended with two parts of curd to give at

least 4% fat in creamed cottage cheese. The dressing

can be treated further to enhance the shelf-life of

cottage cheese to control the growth of spoilage psy-

chrotrophic organisms. Cultures inhibitory to spoil-

age organisms may be added and the dressing itself

may be fermented. Several bacteriocin-containing

preservatives are commercially available to extend

the shelf-life of cottage cheese. The typical shelf-life

of cottage cheese packaged in moisture-barrier con-

tainers is 3–4 weeks at 4



0012The yield of cottage cheese curd is typically around

15.5% kg per 100 kg of skim milk of 9% SNF. A

fortified skim milk containing 12% SNF should give

21.6 kg of curd per 100 kg of starting material.

0013Quarg, also called Quark, Kwarg, Koarg, Twarog,

Tvorog, Taho, or Topfen, is a popular fresh cheese of

central Europe. It has a slightly sour flavor owing to

its low pH. It is generally made from skim milk. In

some cases, some variations may be made from hom-

ogenized full-fat milk. Buttermilk is also used as a raw

material. In a process similar to cottage cheese, the

milk is cultured with selected strains of Lactococcus

and Leuconostoc species. After fermentation, the

curd is collected by centrifugation in a special separ-

ator. It may be also be produced by direct acidifica-

tion with lactic acid, lemon juice, or vinegar. The curd

is blended with cream to yield low-fat or full-fat

Quarg.

1094 CHEESES/Soft and Special Varieties

Cream Cheese

0014 Cream cheese contains at least 33% fat and not more

than 55% moisture. It is a soft, unripened lactic acid-

coagulated cheese, made by a process similar to that

for cottage cheese. It has a mild, acid, and creamy

flavor with a buttery aroma. The manufacturing pro-

cedures are similar for cream and Neufchatel cheese,

but, compared with a fat content of 35% in cream

cheese, Neufchatel cheese contains 23% fat.

0015 Cream cheese is an important variety in North

America. In 2000, cream and Neufchatel cheese

production in the USA exceeded 331.8 million kilo-

grams. Cream cheese is mostly used as a spread on

bagels and toasted bread or as an ingredient of

cheesecakes. At present, cream cheese is marketed in

flavors like strawberry and other fruits. It is also

flavored with vegetables, condiments, spices, and

herbs. Low-fat versions are available.

Manufacturing Procedure

0016 Several processes are used to produce cream cheese.

Typically, the process involves standardizing cream

to 11% fat, followed by pasteurization at time–

temperature combinations (e.g., 68



C/30 min) similar

to normal pasteurization. Using a starter consisting of

Lactococcus lactis ssp. lactis/cremoris and Leuconos-

toc cremoris at a level of 5–6%, the cream is cultured

at 30–32



C for 5 h. A long-set process uses 1%

starter and incubation for 16 h at 22



C. Leuconostoc

sp. imparts a buttery aroma. In some plants, rennet is

added at a low level. Fermentation is continued until

a pH of 4.4–4.5 is attained.

0017 In the traditional process, the cultured cream is

drained in muslin bags by hanging overnight in a cold

room. However, most modern plants are equipped

with centrifuges to remove the whey. Cream cheese

collects in the bowl. Membrane processes are also

used for separation of whey. The cheese is subse-

quently packed by a cold-pack procedure without

additives or heat. Cold-pack cream cheese has more

aroma and flavor and lacks a pasty/sticky body than

the hot-packed product. However, it lacks the long

shelf-life obtained by the more commonly used hot-

pack procedure. This procedure involves heat treat-

ment of cream cheese in a kettle or scraped surface

heat exchanger. Cream cheese is mixed mechanically

with a stabilizer (0.35% locust bean gum) and 1%

salt and brought to 70



C. The hot mixture is hom-

ogenized at 13.8 MPa and transferred to the pack-

aging machine for hot packaging. The hot process

imparts a shelf-life of at least 2 months under refriger-

ated storage.

Cheeses Produced by Direct Addition of

Acid and Heat

0018Worldwide, curd formation during cheese making is

effected by the use of coagulating enzymes isolated

from various sources in combination with or without

a fermentation step. Alternatively, curd can be formed

by direct acidification of hot milk with food-grade

acids. Generally, the directly acidified cheeses are

consumed in fresh, unripened form. The cheese var-

ieties included in this category are quite diverse. From

the standpoint of commercial importance, Ricotta,

Chhana, Paneer, and Latin American cheeses will be

discussed briefly.

Ricotta Cheese

0019Like cottage cheese, Ricotta cheese is high-moisture,

unpressed cheese. Its composition varies, depending

on whether it is made exclusively from whey or from

a blend of whey and milk. Ricotta is also prepared

from whole milk, with no addition of whey. When

made from a blend of 95% sweet whey and 5% milk,

Ricotta contains 68–73% moisture, 16% protein,

4–10% fat, and 4% lactose.

0020Ricotta has a bland to slightly cooked, but pleasing,

flavor. Its texture is soft and creamy. It is consumed as

such as a spread and may be used as a replacement for

cream cheese or sour cream in dips. It is basically a

nonmelting cheese. Its major use is in Italian cuisine,

as in Lasagna and Ravioli, for example. (See Whey

and Whey Powders: Production and Uses.)

0021Manufacturing Procedure Most Ricotta is pro-

duced by a batch process. Traditionally, open kettles

are used. Heating may be direct, or steam jackets may

provide heat transfer. Sweet whey from Italian cheese

manufacture is suitable as long as its pH is 6.2 or

higher. Ten to 25% milk is often blended to neutralize

acid in the whey, enhance yield, and curd cohesive-

ness. The mixture is heated in a kettle to 82–93



followed by the addition of sufficient food-grade

acid, e.g., lactic, acetic, or citric, to reduce the pH of

the mixture to 5.9–6.1. In some plants, cultured milk/

whey may be used as a source of lactic acid. This pH

range is crucial to maintain the sweet flavor of the

cheese. As a result of heat and acidity, the proteins are

denatured, and a foam-type curd ascends to the sur-

face. The curd is then dipped with a perforated ladle

and collected in muslin bags. The bags are allowed to

drip and cool in a cold room. Alternatively, the curds

are drained in perforated stainless hoops and allowed

to dry. The curd is soft, fragile, and grainy, and may

be pressed slightly to achieve cohesiveness. The yield

of Ricotta is low, around 5–6% if no milk is mixed

CHEESES/Soft and Special Varieties 1095