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of the protein network. When the lactic acid has been

exhausted, P. camemberti catabolizes amino acids

released from the caseins with the production of

, which diffuses inward, further increasing the

pH. Deacidification of the cheese surface has a major

impact on the growth of coryneform bacteria (Br.

linens does not grow below pH 5.8), plasmin activity

(which is optimally active at alkaline pH), and coagu-

lant activity (the activity of which decreases with

increasing pH).

Lipolysis and Catabolism of Fatty Acids

0017 In most cheese varieties, relatively little lipolysis

occurs during ripening. Lipases and esterases in

cheese can originate from milk, rennet preparation,

starter bacteria, secondary nonstarter bacteria and

secondary cultures (e.g. P. camemberti). The limited

lipolysis is a consequence of the fact that there is

normally no significant exogenous or endogenous

lipases in pasteurized cheese milk, and the starters

used are only weakly lipolytic. The extent of lipolysis

in surface mold ripened cheeses (e.g., Brie and Cam-

embert) is generally between 6 and 10% of the total

fatty acids. However, significantly lower levels of

free fatty acids are present in surface-mold cheeses

than in blue-veined cheeses, in which lipases have

more contact with fat because of the development of

molds in the interior of the cheese and their longer

ripening time. Lipolysis tends to be highest towards

the surface, suggesting that Penicillium is the princi-

pal lipolytic agent in Camembert. P. camemberti

produces a high level of extracellular lipase, which is

optimally active at about pH 9.0 and 35



C, resulting

in an increase in lipase activity as the mold develops

during ripening. Most free fatty acids between C

and

are produced via lipolysis of triglycerides by

fungal lipases, but a smaller proportion of acids

between C

and C

originate from the degradation

of lactose and amino acids.

0018 In addition to their direct impact on cheese flavor,

free fatty acids act as precursors for series of catabolic

reactions, which lead to the production of other fla-

vour compounds (Figure 4). Molds play an important

role in the degradation of fatty acids to methyl

ketones and their reduction products (secondary alco-

hols) by a pathway related to b-oxidation. P. camem-

berti and G. candidum possess an enzymatic system

that oxidizes free fatty acids to b-ketoacyl-coenzyme

A, and the action of a thiolase yields a b-ketoacid

that is rapidly decarboxylated by a b-keto-acyl-

decarboxylase to give a methyl ketone with one less

carbon than the initial fatty acid.

0019 A complex array of compounds are produced as a

result of lipolytic activity, which contributes to flavor.

However, lipolysis is not accompanied by a rancid

taste, probably because the fatty acids are neutralized

on elevation of the pH.

Proteolysis

0020Proteolysis makes a direct contribution to the flavor,

and perhaps to off-flavor (e.g., bitterness), of cheese

through the formation of peptides and amino acids,

liberation of substrates (amino acids) for catabolic

changes (e.g., deamination, decarboxylation, transa-

mination, desulfuration, catabolism of aromatic com-

pounds such as phenylalanine, tyrosine, and

tryptophan, and reactions of amino acids with other

compounds), and textural changes in the cheese curd,

owing to breakdown of the protein network, a de-

crease in a

through water binding by formed

carboxyl and amino groups and an increase in pH.

0021Surface mold-ripened cheeses undergo consider-

able proteolysis during ripening due to the activity

of proteinases from starter microorganisms, rennet,

milk and, especially, the proteinases and exo- and

endopeptidases secreted by the Penicillium species.

The progression of proteolysis can be summarized

as follows: initial breakdown of caseins, which is

catalyzed mainly by the residual coagulant, plasmin,

and perhaps cathepsin D and other somatic cell

proteinases, followed by the production of large

water-insoluble polypeptides and intermediate-

sized water-soluble peptides, which are degraded by

proteinases and peptidases and peptidases from the

starter, nonstarter bacteria, and secondary microflora

(P. camemberti) of the cheese to small water-soluble

peptides and amino acids.

0022As in other cheeses, coagulant is considered to be

essential for the development of the correct texture in

surface mold-ripened cheeses. Since plasmin is not

inactivated by pasteurization, proteolytic activity

owing to plasmin is high in the surface of these

cheeses owing to their high pH (*7) and higher

Triglyceride

Lipase

Fatty acidFree fatty acids

β-Ketoacids

Methyl ketones

Secondary alcohols

β-Oxidation

γ-Hydroxyacids

Lactones

Unsaturated fatty acids

Hydroperoxides

Aldehydes

Acids Alcohols

fig0004Figure 4 Lipolysis and catabolism of fatty acids during ripening

of surface mold-ripened cheeses.

1126 CHEESES/Surface Mold-ripened Cheese Varieties

than in cheese varieties without molds. the increase in

pH may also increase the proteolytic activity of sec-

ondary microorganisms.

0023 While rennet, plasmin, enzymes from starter or

nonstarter microflora have an effect on proteolysis,

enzymes of Penicillium spp. are the principal proteo-

lytic agents in surface mold-ripened cheeses. These

molds have very potent proteolytic systems, which

include an aspartyl proteinase, a metalloproteinase,

an acid carboxypeptidase, and an alkaline aminopep-

tidase. The aspartyl proteinase is the principal enzyme

produced by cultures at grown pH 4.0; its optimum

pH is *5.0 on casein as substrate. It is generally

stable between pH 3.5 and 5.5. It is active on a

b- and k-caseins with different pH optima, but it

tends to be most active on a

-casein. It releases a

number of short peptides (soluble in 12% trichloro-

acetic acid, TCA) from a

-casein, whereas it releases

predominantly 12% TCA-insoluble peptides from

b-casein. The metalloproteinase has a pH optimum

of 5.5–6.0 and is stable over the range pH 4.5–8.5,

which suits the conditions in Camembert and other

surface mold-ripened cheeses. The metalloproteinase

hydrolyses a

-casein better than b-ork-casein.

Quantitative studies show that the aspartyl protein-

ase is more active than the metalloproteinase during

ripening. Penicillium spp. also have carboxy- and

aminopeptidase activities. There are two carboxypep-

tidases, one with an acid and the other with an alka-

line pH optimum. The carboxypeptidase activity

shows differences in behavior, depending on whether

its origin is intra- or extracellular; the extracellular

carboxypeptidase is a serine enzyme optimally active

on X–Glu–Tyr substrate at pH 3.5, whereas the intra-

cellular carboxypeptidase is optimally active on X–

Gly–Val at pH 6. Owing to their broad specificity, the

acid carboxypeptidases of Penicillium spp. may con-

tribute to the breakdown of bitter peptides in surface

mold-ripened cheese. The aminopeptidase has an

optimum pH around 8.0–8.5; it is a metalloenzyme

with the ability to release apolar amino acids, but

peptides with glycine in the penultimate position or

N-terminal are hydrolyzed slowly.

0024Proteolytic activity at the center of Camembert and

other surface-ripened cheeses is low, but it is high at

the surface, indicating that the migration of Penicil-

lium proteinases in the curd is limited. However,

peptides produced by the aspartyl proteinase have

been detected inside the cheese at a depth greater

than 7 mm at the end of ripening. This is probably

due to the migration of peptides produced by the

aspartyl proteinase, rather than of the enzyme.

0025The final products of proteolysis are free amino

acids, and their concentration at any stage of cheese

ripening is the net result of the liberation of amino

acids from casein and their catabolism to a number of

compounds, including ammonia, amines, aldehydes,

phenols, indole, and alcohols (Figure 5), all of which

contribute to the flavor of all cheese varieties,

especially surface mold-ripened cheeses.

Flavor of Surface Mold-Ripened Cheeses

0026Numerous compounds contribute to the flavor

of surface mold-ripened cheeses including fatty acids,

methyl ketones, ketones, alcohols, sulfur compounds,

amines, lactones, esters, aldehydes and pyrazines,

derived mainly from the three metabolic pathways

described above.

0027Fatty acids are important to the aroma of surface

mold-ripened cheeses, not only directly, but also as

precursors of methyl ketones, alcohols, lactones,

and esters. Short- and medium-chain, even-numbered

fatty acids (C

to C

) have low perception thresh-

olds, and each has a characteristic flavor. Acetic acid

has a typical vinegar odor, butyric has a rancid,

cheesy aroma, isobutyric and isovaleric acids have a

mild aroma, suggestive of sweet or rotten fruit, and

Amino acids

Transamination

Decarboxylation

Amines

Sulfur compounds

Phenol

Indole

Degradation

Oxidative

deamination

α-Keto acids

Aldehydes

Reduction

Oxidation

Acids Alcohols

Oxidative

deamination

fig0005 Figure 5 Pathways for the catabolism of free amino acids in surface mold-ripened cheeses.

CHEESES/Surface Mold-ripened Cheese Varieties 1127

octanoic, 4-methyloctanoic and 4-ethyloctanoic acids

have a goaty aroma. Long-chain free fatty acids

(> C

) play a minor direct role in cheese flavor

because of their high perception thresholds.

0028 Ketones have different perception thresholds and

different odor characteristics. The most important

ketone in Camembert cheese is octan-1-en-3-one,

which has mushroom note; octan-2-one, nona-

2-one, and decan-2-one are described as having a

musty note, and diacetyl and acetoin are well

known for their buttery aromas.

0029 Methyl ketones (C

to C

, odd chain) are the most

abundant aromatic compounds in surface mold-

ripened cheeses and are present in Camembert

and Brie cheeses from the eighth day of ripening.

Several methyl ketones (e.g., 3-methylpentan-2-one,

4-methylpentan-2-one, non-1-en-2-one, and undec-

1-en-2-one) have been identified in Camembert, but

the two major methyl ketones are nonan-2-one and

heptan-2-one, produced by P. camemberti from long-

chain fatty acids by b-oxidation, and their con-

centrations increase during ripening G. candidum

produces methyl ketones, such as pentan-2-one,

hepta-2-one, nonan-2-one, undeca-2-one, and pen-

tan-3-one. Octan-2-one, nonan-2-one, decan-2-one,

undecan-2-one, and tridecan-2-one are described as

having fruity, floral, and musty notes, whereas

heptan-2-one has a blue cheese note. Methyl ketones

with even-numbered carbon chains (except butan-2-

one) appear later during ripening and are never pre-

sent in large amounts, except in extra-ripe cheese.

0030 Primary and secondary alcohols, along with

ketones, are considered to be the most important

compounds in the aroma of surface mold-ripened

cheeses. 3-Methylbutan-1-ol is present at a relatively

high concentration in Camembert cheese and gives it

an alcoholic floral aroma. The principal secondary

alcohols present are heptan-2-ol and nonan-2-ol,

which are derived from their respective methyl

ketones. Oct-1-en-3-ol, which is well known for its

raw mushroom aroma, is produced by P. camemberti

during ripening and represents 5–10% of the aroma

compounds in ripened Camembert. This alcohol

has a low perception threshold and is one of the

key compounds in the aroma of Camembert.

Phenyl-2-ethanol is one of the major compounds in

Camembert after 7 days of ripening; it exhibits a

characteristic rose floral note, and its ester, pheny-

lethylacetate, plays an important role in the flavor

of raw milk Camembert.

0031 Sulfur compounds (2,4-dithiopentane, diethyldisul-

fide, 2,4,5-trithiohexane and 3-methylthio-2,4-dithia-

pentane) also play important roles in the flavor of

surface mold-ripened cheeses; they cause the strong

garlic notes characteristic of the mature cheese.

Coryneform bacteria are thought to be the key con-

tributors to the formation of sulfur compounds in

surface-mold-ripened cheeses. Br. linens can produce

methanethiol, because these bacteria have a methio-

nine-g-lyase, which produces methanethiol from

methionine, although methanethiol can also be pro-

duced from methionine by cystathionine-b-lyase,

methionine-a-deaminase or methionine-a-transami-

nase. P. camemberti and G. candidum produce metha-

nethiol and other sulfur compounds.

0032Numerous volatile amines have been identified in

Camembert cheese (e.g., methylamine, ethylamine,

dimethylamine, isopropylamine, or n-butylamine).

Ammonia is also an important contributor to the

aroma of surface mold-ripened cheese, and P. camem-

berti, G. candidum,andBr. linens play major roles in

its production. Nonvolatile amines (i.e., tyramine,

histamine, tryptamine, and putrescine) have also

been identified in this cheese type.

0033The lactones, g-decalactone, d-decalactone, g-

dodecalactone and d-dodecalactone, are present in

Camembert cheese; they are characterized by very

pronounced fruity notes (peach, apricot, and

coconut).

0034Many esters are present in surface mold-ripened

cheeses; they are characterized by fruity, floral

notes (e.g., pineapple, banana, apricot, pear, floral

rose, honey, and wine). 2-Phenylethyl acetate and

2-phenylethyl propanoate are quantitatively import-

ant in Camembert.

0035The main aldehydes in Brie and Camembert

cheeses are hexanal, heptanal, nonanal, 2-

methylbutanal, 3-methylbutanal, and benzaldehyde,

and they appear in trace amounts as early as the first

week of ripening. Hexanal gives the green note of

immature fruit, nonanal is described as having an

aromatic note resembling orange, while benzalde-

hyde is described as having an aromatic note of bitter

almond.

0036Compounds like styrene, which have a very strong

plastic odor, have been found in trace amounts in

Camembert, when the degradation of linoleic and

linolenic acids by P. camemberti is higher than

usual. Pyrazines (e.g., 2,5-dimethylpyrazine and 2-

methoxy-3-isopropylpyrazine) are also present in

Camembert. The former imparts a toasted hazelnut

note, whereas the latter is responsible for the rotten

soil, raw potato aroma note, which is regarded as a

defect.

0037Bitterness in surface mold-ripened cheese has been

correlated with the concentration of pH 4.6-soluble

nitrogen and thus with the formation of peptides.

Bitterness could be eliminated by ripening cheese in

an atmosphere containing NH

, which results in

slower growth of P. camemberti on the cheese surface

1128 CHEESES/Surface Mold-ripened Cheese Varieties

and therefore less proteolysis and a lower level of

bitter peptides, or by inoculating with secondary

microorganisms (P. camemberti, G. candidum, and

Br. linens) with a higher aminopeptidase activity.

0038 The characteristic appearance of surface mold-

ripened cheese is due to the presence of mold (e.g.,

P. camemberti), which produces enzymes with high

lipolytic and proteolytic activities, which play a major

role during ripening. These molds also lead to more

complex ripening patterns than in other varieties of

cheese with simpler flora. Much progress has been

made during the last 15 years in elucidating the mech-

anisms of ripening in surface mold-ripened cheeses.

However, further work is required to understand the

enzyme systems and the mechanisms involved in the

conversion of the primary products to volatile flavor

compounds.

Acknowledgments

0039 The author would like to thank Prof. P.F. Fox and

Dr. P.L.H. McSweeney for useful comments on the

manuscript.

See also: Cheeses: Chemistry and Microbiology of

Maturation; Manufacture of Extra-hard Cheeses;

Manufacture of Hard and Semi-hard Varieties of Cheese;

Mold-ripened Cheeses: Stilton and Related Varieties

Further Reading

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

Fundamentals of Cheese Science. Gaithersburg, MD:

Aspen.

Gripon JC (1993) Mould-ripened cheeses. In: Fox PF (ed.)

Cheese: Chemistry, Physics and Microbiology, 2nd edn,

vol. 2, pp. 111–136. London: Chapman & Hall.

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.

Molimard P and Spinnler HE (1996) Review: compounds

involved in the flavour of surface mould-ripened cheeses:

origins and properties. Journal of Dairy Science 79:

169–184.

Schlesser JE, Schmidt SJ and Speckman R (1992) Charac-

terization of chemical and physical changes in Camem-

bert cheese during ripening. Journal of Dairy Science 75:

1753–1760.

Sousa MJ and McSweeney PLH (2001) Studies on the

ripening of Cooleeney, an Irish farmhouse Camembert-

type cheese. Irish Journal of Agricultural and Food

Research 40: 83–95.

Robinson RK (1995) Cheese ripened with moulds. In:

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

Fermented Milks, pp. 11–127. London: Chapman &

Hall.

Dutch-type Cheeses

G van den Berg, NIZO Food Research, Ede, The

Netherlands

Introduction

0001Dutch-type cheeses represent the most important

kinds of semihard cheese. They are manufactured

from bovine milk, although small amounts of similar

cheeses are made from ovine or caprine milk. Other

semihard cheese types are also manufactured

according to a largely similar technology but their

characteristics are different. For this reason, Jarlsberg

or Maasdam and Tilsiter or Havarti cheese will not be

treated here.

0002Gouda and Edam cheese are the primary Dutch-

type cheese varieties and they are made all over the

world. However, in many countries a similar tech-

nology is used for related cheese types manufactured

under various names. The majority of all these cheese

varieties contain 40–52% fat in dry matter, and the

water content in the (unripened) fat-free cheese

ranges from 55 to 63%. They are made in sizes

between 0.2 and 20 kg. Their shape can be a flat

cylinder, often with somewhat bulging sides, a sphere,

a rectangular block, or a loaf. The latter are often

used for foil ripening (rindless cheese). The standard

cheeses are naturally ripened under drying condi-

tions.

0003Dutch-type cheeses are ripened for some weeks or

longer, sometimes for more than a year, and are often

covered with a plastic coating. The consistency varies

from rather firm and smooth to semisoft and changes

during natural ripening to a firmer and more brittle

structure. The flavor also changes from mild to strong

during such long ripening times. The interior of the

main cheese types shows some round eyes about the

size of a pea. Substances like cumin seeds or other

spices may be added. There is essentially no surface

flora.

Production Statistics

0004The worldwide production volume of Dutch-type

cheeses can only be estimated because from many

countries there are no official figures for individual

cheese types. Moreover, all related cheese types are

not always well described in different countries. So a

worldwide picture can only be estimated.

0005World cheese production in 1998, excluding pro-

cessed cheese but including fresh cheese and quark, is

estimated as 12 800 10

t. The share of the Dutch-

type varieties is estimated to be approximately 15%

CHEESES/Dutch-type Cheeses 1129

of this volume, which is based on a mix of real figures

for various European countries and estimates for

others. The production of these cheese types in The

Netherlands in 1999 was 535 10

t and in Germany

415 10

t as the two countries with the highest pro-

duction, while the whole European Union produced

approximately 1300 10

t. Dutch-type cheese is

usually made from pasteurized milk; only 10 10

mainly Gouda cheese, is farm-made from raw milk in

the Netherlands and will not be considered further.

Technology

0006 A typical manufacturing scheme for Gouda cheese is

given in Figure 1.

0007 The milk is thermized and standardized for its

fat : protein ratio in order to control the fat content

in the dry matter of the cheese. It is cold-stored until

cheese-making can take place. Then, the milk is pas-

teurized and pumped into the cheese vat. During one

of these heat treatments, the milk is often bactofu-

gated to reduce the number of spores of butyric acid

bacteria. The total heat load must be sufficient to

inhibit pathogenic microorganisms and some spoilage

organisms but not xanthine oxidase (EC no. 1.2.3.2).

The denaturation of whey proteins should be limited.

0008 For the manufacture of Dutch-type cheeses, the

milk is coagulated at approximately 30



C by the

action of renneting enzymes, usually a chymosin

(EC 3.4.23.4) preparation (calf rennet). This is

added together with the mesophilic starter and cal-

cium chloride to control the renneting process. Other

additives, such as nitrate and coloring agents, like

anatto (E160b) or carotene (EE160a), are often

used. The resulting coagulum consists of a continuous

network of strands of (para)casein micelles that

extends throughout the milk volume. (See Cheeses:

Starter Cultures Employed in Cheese-making.) In

general, this gel is not as firm when cut as is the case

for soft cheese-making. It is divided into fairly small

particles but not so fine as is the case for hard cooked

cheese.

0009After cutting, a part of the (first) whey already

liberated from the curd particles by syneresis (shrink-

age and expulsion of whey) is removed and warm

water is added. This scalding of the curd serves to

reduce the lactose content and to enhance syneresis of

the curd during further stirring. The amount of this

curd wash water is related to the desired pH of the

final cheese. This parameter is a result of the ratio

between the amount of lactose that is fermented to

lactic acid and the amount of the (para)caseinate–

phosphate complex (the acid buffering substance).

So in this respect, the lactose content of the milk

and the water content of the nonfat matter after

pressing/before brining are important. This water

content is important because it is equal to that of

the center of the cheese when all lactose has been

fermented. The higher these parameters, the more

lactose remains in the curd and the more water that

has to be added to maintain a constant pH.

0010The scalding temperature is primarily used to influ-

ence the dry-matter content of the cheese because it

affects syneresis. This is an intrinsic property of the

(para)casein gel that leads to the protein strands,

breaking whereupon new bonds will be easily formed

because the whole surface of the casein micelle can

be considered as reactive. The network is rearranged

when the moisture with dissolved components (whey)

is expelled. Increasing the surface of the coagulum

(cutting), acidification, temperature increase, and

stress (by stirring the curd or, during a successive

stage, by taking the curd out of the whey) all enhance

syneresis. The increase of the scalding temperature is

limited because of the use of a mesophilic starter.

0011After making curd, the curd particles are collected

under the whey to exclude air. Subsequently, the free

whey between the curd particles must be expelled by

drainage in order to obtain a closed texture in the

final cheese. However, even after pressing, some whey

still remains in the small interstices between the curd

particles, but during later stages, the temperature

drops and this whey is readsorbed by the curd so

Milk

Thermization

Standardization

Bactofugation

Storage 4 ⬚C

Pasteurization

Mixing

Cutting 20 min

Draining 45%

first whey

Renneting

30.5 ⬚C; 25 min

Whey

Scalding 35 ⬚C

Washing

water

Starter

nitrate

CaCl

Color

rennet

Ripening

Drying/coating

Brining 4 days

Acidification 1 h

Pressing

75 min

Draining/

molding

Storage tank

34 ⬚C

Stirring 25 min

fig0001 Figure 1 Main process steps of a modern manufacturing

scheme for 12-kg Gouda cheese.

1130 CHEESES/Dutch-type Cheeses

that fusion can be completed. In fact, a section of the

cheese will show a closed texture only after some

days.

0012 The blocks of curd are pressed in perforated molds

covered with a lid, allowing whey drainage. A rind of

a few millimeters thick is created by deformation of

the curd around threads of the liner or edges of per-

forations in the mold. This rind formation is due to

strong local syneresis and further fusion of the curd

particles, and more bonds between the casein strands

are created than elsewhere in the cheese. In essence,

syneresis, fusion, and rind formation are similar

processes.

0013 A closed rind is necessary, for the natural ripening

cheese in particular, to withstand the tension caused

by brining and to protect the cheese from penetration

of undesired microorganisms during brining and from

molds during ripening. (See Cheeses: White Brined

Varieties.)

0014 During curing the integrity of the rind has to be

maintained. Coating the cheese makes it much easier

to maintain the rind and gives a smooth and glossy

appearance when the optimal climatic conditions, air

flow, and cheese treatment scheme in the ripening

room are applied. The polyvinylacetate-based coating

layer reduces water evaporation from the cheese sur-

face to some extent. However, too strong drying will

make this hydrophilic coating layer too brittle and

mold will penetrate into cracks. On the other hand,

too little drying will easily allow undesired develop-

ment of bacteria that make the surface sticky, and the

presence of natamycin will not be sufficient to pre-

vent the growth of yeasts and molds. The normal

ripening temperature is rather moderate, approxi-

mately 13



C. In the case of ripening in foil, or in

wax, this temperature is normally lower and the

moisture content is often somewhat lower to keep

the cheese in better shape and to prevent it from

being too soft after curing.

0015 It is obvious that cheese composition has to be

controlled carefully. During the manufacture of

Gouda cheese, the casein is concentrated at the end

of curd preparation by a factor of approximately 4.5

and in the final cheese by approximately 10. In paral-

lel with this, the dry-matter content of the curd mass

increases to approximately 32% at the end of curd

preparation, to 42% after drainage, to 53% after

pressing, and to 57% after brining. The composition

of the cheese directly influences the product yield.

However, milk composition is the primary factor to

reckon with. Of the components to be concentrated,

casein is the most expensive one. The fat in the whey

can be recovered in the cheese by adding the whey

cream to the cheese milk whereas the casein (curd

fines) cannot when making quality products. So it is

good to express yield as kg per kg casein of the milk.

However, in a quantitative sense, water is the most

important cheese component but cheese quality

demands optimal water content, before brining in

particular, which depends on the cheese type in-

volved. This is important for the desired consistency

of the young cheese and for the conditioning of the

ripening processes.

0016Nowadays, the cheese-making process is carried

out in factories manufacturing 3–5 tonnes of cheese

per hour, and mechanization and automation based

on a good understanding of the technology are well

developed.

Starters and Lactose Fermentation

0017The role of starter bacteria is discussed elsewhere (See

Starter Cultures). The starters for Dutch-type cheese

have always been mesophilic lactic acid bacteria

(LAB). The commonly used starters consist of com-

binations of acid-producing Lactococcus lactis subsp.

lactis and cremoris strains and citrate-fermenting

(and carbon dioxide-producing) Leuconostoc lactis

and/or L. mesenteroides subsp. cremoris (L-starters)

or Lactococcus lactis var. lactis biovar diacetylactis

and Leuconostoc strains (DL-starters). DL-starters

are normally used when stronger eye formation is

desired because they ferment citrate faster and to a

greater extent than do L-starters. When in particular

cases no eye formation must occur, then a starter

without citrate-fermenting bacteria is often used

(O-starter). Mixed-strain starters are mainly used in

Europe for Dutch-type cheese. This is also true in the

case of an O-starter. Manufacturers, especially the

bigger factories, prefer to use their own bulk starter,

to realize lower starter costs and a better yield in

comparison with the use of a DVS (direct to the vat)

system. Such a bulk starter system is provided with

the means to avoid bacteriophage contamination,

such as a bacteriophage-free mother starter concen-

trate and a starter propagation tank with an over-

pressure of bacteriophage-free air. Such starters have

to be well selected because of their major influence on

cheese quality.

0018The amount of bulk starter of normal activity used

to inoculate cheese milk is 0.5–1.0%. During cheese-

making, starter LAB grow until a level of 10

colony-

forming units (cfu) g

1

has been reached. In Gouda

and Edam cheese, the pH at that time is approxi-

mately 5.7 and the cheese has already been pressed.

A picture of the usual pH course during cheese-

making is given in Figure 2.

0019During curd preparation, the pH remains rather

high until most of the whey is separated by drainage

in order to obtain the desired cheese consistency and

CHEESES/Dutch-type Cheeses 1131

yield. Moreover, less chymosin is bound to the casein

and the danger of bitterness after ripening is dimin-

ished. Before lactose fermentation has finished, the

cheese has already been put into the brine. The mois-

ture diffusing out of the cheese still contains lactose

and so does the brine, which is used for a long time.

As a result, after brining, the rind of the cheese still

contains some lactose, which disappears within the

first few weeks of ripening. For foil-ripened block

cheese, in particular, the time between pressing and

brining is often still shorter after pressing and these

effects are stronger.

0020 There is a strong interest in acceleration of ripening

and product differentiation, not only from differences

in packaging and shape, but also in flavor. To this

end, attenuated LAB starters are introduced as an

extra means of enhancing flavor development. They

are often thermophilic and propagated or treated in

such a way that they practically do not grow or

contribute to acidification, so that normal manufac-

turing procedures can be maintained. In the case of

low-fat cheese, the ability to enhance protein degrad-

ation is of special interest in order to achieve a more

acceptable consistency and a stronger flavor of the

final product.

Ripening Patterns

0021 After fermentation of lactose and citric acid, prote-

olysis is the main phenomenon in the manufacture of

Dutch-type cheese, followed by amino acid degrad-

ation. Within 24 h the pH of the cheese is 5.1–5.2,

increasing during the first 2 weeks by approximately

0.15, and thereafter only slightly during maturation.

The redox potential in the cheese has been reduced

by the lactic acid fermentation to approximately

140 mV. In the center of Gouda cheese the original

water content in the fat-free cheese is approximately

65%, but this decreases gradually by salt diffusion

and water evaporation. Under these conditions,

casein is degraded by chymosin (not inactivated by

high scalding temperatures), and to a lesser extent by

plasmin, into larger peptides. These are further de-

graded, finally into amino acids, by peptidases of the

starter LAB that also provide amino acid-converting

enzymes (AACEs) for the production of various vola-

tile (flavor) components.

0022Under the gradually changing conditions in normal

Gouda cheese, only a very global quantitative picture

can be given of how degradation of the (total) casein

proceeds during ripening. To this end, the nitrogen-

containing fraction of the cheese is separated into a

fraction which is soluble under cheese conditions

(SN) and a fraction which is still soluble in 12%

trichloroacetic acid (AN). The latter fraction of

< 1400 molecular weight contains only very small

peptides, amino acids, and further converted com-

ponents.

0023Figure 3 gives the average increase of these frac-

tions (expressed as a percentage of total nitrogen) in

normal Gouda cheese during ripening at 13



Generally, the SN fraction is mainly dependent on

chymosin activity and the AN fraction on activities

of enzymes associated with the starter bacteria. How-

ever, the production of peptides by the former stimu-

lates activity by the latter.

0024The use of attenuated thermophilic starters in add-

ition to the normal culture causes a greater increase of

the AN fraction while hardly affecting the SN frac-

tion. In fact, the peptidase and AACE activity is

primarily increased.

4.6

2468101214

5.0

5.4

5.8

6.2

6.6

Wash water In brine

Pressing

Time after adding starter (h)

Lactic acid

Lactose

g lactose or

g lactic acid

per 100 g H

fig0002 Figure 2 Lactose fermentation, acid production, and the pH of

curd and cheese during the manufacture of Gouda cheese after

starter addition.

024681012

Age of cheese (months)

Total nitrogen (%)

fig0003Figure 3 Increase of the soluble nitrogen-containing fraction

(SN) and the amino acid-containing fraction (AN) during ripening

of normal Gouda cheese as a percentage of total nitrogen fraction

in the cheese.

1132 CHEESES/Dutch-type Cheeses

0025 As noted, Figure 3 gives an overall picture of the

cheese. The center shows a greater degradation be-

cause of the higher moisture content and the (initially)

lower salt content. In the rind, proteolysis stops

within 3 months because of the low water content.

It will be obvious that when water evaporation is

prevented by packaging in foil or wax one may

speak of rindless cheese, because then the internal

ripening processes also continue in the rind zone.

However, such cheese is usually ripened at a low

temperature.

0026 Lipolysis is very limited in Dutch-type cheese.

Textural Characteristics

0027 Figure 4 gives an impression of the desired eye forma-

tion in normal Gouda cheese.

0028 For eye formation, a certain gas pressure in the very

young cheese is necessary when the consistency of the

cheese is still very elastic. To this end, saturation of

the milk with air, in particular with nitrogen – be-

cause oxygen disappears due to the activity of

the starter bacteria – and citrate fermentation by the

starter bacteria during the first weeks after manufac-

ture are crucial. The partial pressure of nitrogen in the

young cheese is approximately 0.9 bar and that of

carbon dioxide 0.4 bar, which together are sufficient

for eye development in Gouda cheese. Without the

nitrogen, the cheese would be ‘blind.’ However, with-

out ‘nuclei,’ eye formation does not take place either,

because then the pressure necessary to start the devel-

opment of an eye can never be reached. Various devi-

ations in the structure of a curd block may serve as

such ‘nuclei,’ like tiny air bubbles or remaining whey

pockets, but also foreign particles with certain apolar

surface properties. Faster citrate fermentation by DL-

starters can give more or bigger eyes, dependent on

the ‘nuclei’ available, because of the increased gas

pressure before the carbon dioxide can diffuse

through the rind. A sufficiently elastic texture is

necessary because too low a fracture stress will result

in cracks instead of eyes.

0029Such a short consistency is to be expected at low

pH. However, the desired consistency also depends

on the correct moisture and fat content and the pres-

ence of sufficient calcium phosphate. Therefore the

pH before pressing must be high. Proteolysis turns the

consistency during ripening from rather elastic to

smooth within 1–2 months and later to short. In the

meantime, the water content has considerably de-

creased and the consistency will also be rather hard

after a year. The rind zone increases in thickness

during ripening; it is tougher and harder than the

interior and becomes somewhat translucent. The in-

crease in ‘shortness’ of Gouda cheese during ripening

is illustrated in Figure 5 by the shift in the stress–

strain curves.

0030In Gouda cheeses ripened for more than 1 year,

tyrosine crystals are often visible as a result of the

progress of proteolysis. If attenuated thermophilic

starters are added, these crystals will be present after

a shorter period.

Flavor Characteristics

0031Primary products produced during cheese-making,

like lactic acid, diacetyl, and carbon dioxide and

related fermentation products, are essential for the

basic flavor of the young cheese. The same holds for

the very small amount of free fatty acids but the

desired flavor is based on the right balance of all

components. However, ripening starts immediately

after manufacture and causes development of a strong

flavor in the matured cheese. In this process, all com-

ponents are probably involved in numerous conver-

sions. So it is understandable that the flavor of the

young cheese depends more directly on the type of

fig0004 Figure 4 Section through a normal Gouda cheese.

100

200

Strain (−)

Stress (kPa)

fig0005Figure 5 Stress–strain curves obtained for Gouda cheese in a

compression test at 2 (

), 6 ( ), 13 ( ), and 26

(

) weeks. From Zoon P, NIZO Food Research.

CHEESES/Dutch-type Cheeses 1133

starter. Cheeses made using an O-starter have a less

creamy flavor than do those with an L-starter and

certainly those with a DL-starter. For the more

mature cheese, these differences disappear but other

starter-related differences are then observed, such as

more or less sweetness or fruitiness.

0032 During ripening, the effect of proteolysis becomes

more dominant, including amino acid conversion into

a great number of volatile flavor compounds. Path-

ways from protein to these compounds are becoming

better known. In good cheese, made with a mixed-

strain starter, they are quantitatively well balanced.

Some are more characteristic for a particular cheese

type than others. This is illustrated in Figure 6, which

shows the gas chromatogram area with the most

important differences between a Gouda cheese and a

similar cheese with an extra attenuated thermophilic

starter APS (Proosdij cheese).

0033 All volatile flavor components are already present

in small amounts in a 6-week-old cheese but the diff-

erent flavor is due to the difference in concentration

of the key components. Proosdij cheese has larger

amounts of peak 8 (butanone), 12 (3-methylbutanal),

14 (2-pentanone), and 22 (2-heptanone), while

Gouda cheese shows more of peak 7 (diacetyl), 11

(2-methylpropanol), 13 (1-butanol), 16 (3-methylbu-

tanol), and 21 (ethyl butyrate). The taste of Proosdij

cheese has more sweet, caramel, bouillon, and fruity

notes than the taste of Gouda cheese.

Defects

0034Process control is necessary to avoid a number of

defects in the cheese. The most important ones are

listed, with the main measures required to avoid

them.

Butyric Acid Fermentation

0035This ‘late blowing’ (large eyes and/or cracks with a

sweet and butyric off-flavor) is caused by the growth

of the anaerobic bacterium, Clostridium tyrobutyri-

cum, originating from spores in the milk, in the 1–5-

month-old cheese. The use of nitrate and bactofuga-

tion of the milk mainly prevent it.

Mesophilic Lactobacilli

0036Various strains of Lactobacillis plantarum, L. casei,

or L. brevis are able to grow in cheese and to produce

various off-flavors (gassy, putrid, fruity, etc.) and/or

carbon dioxide, causing cracks in the mature cheese.

Contamination and growth during cheese-making

must be avoided as much as possible. Some of these

bacteria are salt-tolerant and may contaminate the

cheese during brining. So the rind has to be closed

during pressing and the bacterial counts of the brine

must be controlled.

Thermoresistant Streptococci

0037In particular, strains of Streptococcus salivarius

subsp. thermophilus may be responsible for excessive

carbon dioxide production and some sweet off-flavor

in 1–2-month-old cheese. Counts of this organism in

the cheese milk have to be controlled, especially by

regularly cleaning the plate heat exchangers, because

the streptococci grow on the surface of the plates in

the regenerator section.

Slimy Rind

0038Growth of coryneform bacteria on the surface of the

cheese should be avoided by good acidification

during cheese-making and good curing conditions.

Otherwise they may cause gas production under the

wax layer which is applied before selling the cheese. A

slimy rind without bacterial growth is possible when

the calcium content of the brine is too low.

8 1012141618

Retention time (min)

(b)

(a)

20 22 24 26

fig0006 Figure 6 Gas chromatograms (relevant parts) of (a) Gouda

cheese (positive) and (b) Proosdij (negative), both after 6 months’

ripening. IS, internal standard; x, contaminant. Intensities of

peaks have been normalized upon the first IS. From Neeter R,

De Jong C, Teisman HGJ and Ellen G (1996) Determination of

volatile components in cheese using dynamic headspace tech-

niques. In: Taylor AJ and Mottram DS (eds) Flavour Science,

Recent Developments. Special publication no. 197, pp. 293–296.

Cambridge, UK: Royal Society of Chemistry, with permission.

1134 CHEESES/Dutch-type Cheeses

Mold Growth

0039 Mold growth on the surface of the cheese must be

avoided by the right curing conditions and turning

and coating program. Under normal conditions, the

use of natamycin in the coating inhibits mold growth.

Bitterness

0040 This is a ripening defect that can be caused by using

too much rennet or a low pH before pressing so that

more rennet is entrapped in the cheese, but mainly by

using the wrong starter with insufficient peptidase

activity to break down bitter peptides.

Texture Defects

0041 Besides the formation of cracks or over-large holes, it

is also possible to have too many small eyes or even

pinholes. The renneting milk should not contain

many very fine air bubbles and air inclusion during

drainage of the curd must be avoided. Curd lumps

that do not lose their whey properly during drainage

mainly cause nesty holes.

See also: Cheeses: Starter Cultures Employed in Cheese-

making; White Brined Varieties; Mold-ripened Cheeses:

Stilton and Related Varieties; Surface Mold-ripened

Cheese Varieties; Starter Cultures