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

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0017 The possibility of using ultrafiltration (UF) to con-

centrate milk to ‘precheese’ for Cheddar cheese has

been investigated, but the texture and flavor of the

product are unsatisfactory. However, UF retentate is

used to standardize the fat and protein content of

cheese-milk.

Other Hard Cheeses

0018 British Territorial varieties are a group of cheeses

which originated in various parts of Great Britain.

The most important of these is Cheshire, which has

a crumbly, hard texture and several mechanical open-

ings. The milk is inoculated with * 4% of a meso-

philic starter, and the curds are cooked at 32–35



which results in a lower pH, a shorter manufacturing

time, a higher moisture content, a lower calcium

content (due to the lower pH at whey drainage),

and a more crumbly texture than for Cheddar. The

curds are held on the bottom of the vat after whey

drainage, and the bed is broken occasionally to

prevent the development of an extensive structure.

Cheshire curds are dry-salted at * 3%, placed in

molds, drained overnight, pressed, packaged, and

matured at 6–8



0019Leicester is similar to Cheshire but is normally

colored with annatto. The curds are cooked at

* 37



C and pressed after whey drainage; blocks of

curd are placed on draining racks, turned, and cut to

promote whey drainage. The cheeses are dry-salted

and matured for 4–8 months at 10–15



C. Derby is a

little-known English variety with properties generally

similar to those of Leicester; it contains 48% FDM

and about 42% moisture.

0020Gloucester is manufactured by a process similar

to that for Cheddar and is colored with annatto. The

curds are cooked to 35–38



C, textured, milled twice,

dry-salted and pressed into cylinders about 40 cm in

diameter and 6–8 cm high for ‘Single’ Gloucester and

15–20 cm high for ‘Double’ Gloucester. The cheeses

are matured for 4–6 months at 10–13



0021Cantal, a hard cheese from the Auvergne region of

France, is manufactured by a process somewhat simi-

lar to that used for British Territorial varieties. The

milk is coagulated using calf rennet and acidified by a

mesophilic lactic starter. The curds/whey mixture is

not cooked, but the drained curds are cheddared and

pressed to promote whey drainage. The blocks of

curd are milled, dry salted, molded, pressed, and

matured at 8–10



C for 3–6 months.

0022Kefalotiri is a Greek cheese made from pasteurized

sheep’s or goats’ milk standardized to c. 6.0% fat. The

milk is inoculated with a thermophilic culture (usually

Sc. thermophilus and Lactobacillus delbrueckii ssp.

bulgaricus) and coagulated by calf rennet. The curds

are cooked to 43–45



C, transferred to molds lined

with cheesecloth, and pressed at an increasing pres-

sure. The pressed cheeses are brine-salted initially and

then rubbed with dry salt for a few days to give a final

salt content of c. 4%. The cheeses are washed occa-

sionally with a brine-soaked cloth to control micro-

bial growth on the surface and ripened for c. 3 months

at * 15



C. Kefalotiri has a hard texture and a strong,

salty flavor.

0023Graviera is also produced in Greece, principally

from ewes’ milk, which is acidified by a mixed culture

[pH ~ 5.4]

Dry Salt

Ripen

Mill

Cheddar

[Raise temperature:

30⬚C to 37−39⬚C

over ~ 30 min;

hold for ~ 1 h]

Cook

Cut

Starter (1−2%, v/v):

Lactococcus lactis ssp. cremoris

and/or Lc. lactis ssp. lactis

Drain

Mould, Press and Package

CaCl

, 0.02%, w/v

Rennet (1:15,000)

[3−24 months; 4−12⬚C]

[NaCl, ~2%, w/w]

[~ 1 cm cubes]

Standardize casein:fat to 0.7:1.0

Pasteurize (HTST)

Cool to 31⬚C

Cows' Milk

Coagulum

Curds and Whey

Whey

Curds

Fresh Cheese

Mature Cheddar Cheese

fig0001 Figure 1 Protocol for the manufacture of Cheddar cheese.

1076 CHEESES/Manufacture of Hard and Semi-hard Varieties of Cheese

of mesophilic (1%; Lc. lactis ssp. lactis or Lc. lactis

ssp. cremoris) and thermophilic (0.1%; Sc. thermo-

philus and Lb. helveticus) organisms. The curds are

cooked to * 50



C and, after whey drainage, molded

and pressed at an increasing pressure. The cheeses are

salted by frequent application of dry salt to the sur-

face for 2–3 weeks and ripened for 3–4 months.

0024 Ras, the principal hard Egyptian cheese, is pro-

duced from cows’ milk, standardized to 3% fat, by

a process generally similar to that for Kefalotiri. The

curds are cooked to 45



C, salted at a level of 1%

after whey drainage, molded and pressed as for Kefa-

lotiri. The cheeses are brined for 24 h, rubbed with

dry salt daily for several weeks, and washed with

brine.

0025 Manchego, a cheese with appellation d’origine

contro

e (AOC) status, is probably the most import-

ant Spanish variety. It is made from ewes’ milk, al-

though generally similar cheeses (but without AOC

status) are manufactured from goats’ or cows’ or

mixed milk. Manchego is produced on an artisanal

scale from raw milk, without culture addition, or

commercially from pasteurized milk, inoculated

with a mesophilic starter. The milk is coagulated

with standard calf rennet. The curds are cooked to

* 38



C, molded, pressed for 12–16 h, brine-salted

and matured for at least 2, and up to 12, months,

depending on the maturity required, at 10–15



C and

85% equilibrium relative humidity (ERH).

0026Idiaza

bal, an AOC cheese, is produced in the

Basque region of northern Spain from raw ewes’

milk coagulated at 38



C. The coagulum is allowed

to cool to 25



C, then broken and the curds ladled

into molds. The cheeses are salted by brining or by the

application of dry salt and matured in caves for 2

months at * 9



C. The cheeses may be smoked in

beechwood kilns and matured further for up to a

year.

fig0002 Figure 2 Large-scale Cheddar cheese-making factory incorporating the CheddarMaster 3 system with a Cheddaring tower. 1,

Pasteurization and fat standardization; 2, protein standardization using UF; 3, cheese-making; 4, draining conveyor; 5, cheddaring

tower; 6, salting/mellowing conveyor; 7, block former; 8, vacuum packaging; 9, cheese block packing; 10, main process control panel.

Courtesy of APV Nordic Cheese, Denmark.

CHEESES/Manufacture of Hard and Semi-hard Varieties of Cheese 1077

0027 Roncal is another AOC cheese made in northern

Spain from raw ewes’ milk acidified by the adventi-

tious microflora. The curds/whey mixture is cooked

to * 37–40



C and the curds then allowed to settle to

the bottom of the vat. The whey isremoved slowly and

the curds pressed against the sides of the vat, molded,

pressed, and dry-salted. Roncal is smoked and ripened

at 6–8



C and 100% ERH for 45–50 days.

0028 La Serena is a hard cheese made in western Spain

from ewes’ milk. Traditionally, raw milk is used, but

pasteurized milk is now used for large-scale produc-

tion. The milk is coagulated at * 30



C with rennet

extracted from the thistle, Cynara cardunculus. The

flat cylindrical cheeses are dry-salted for * 24 h and

ripened for about 2 months at ambient temperature

(10–18



C).

0029 Sa

o Jorge is an AOC cheese produced on a small

scale from raw cows’ milk on the island, Sa

o Jorge, in

the Azores. The milk is coagulated using calf rennet,

and acidification of the curd depends on the activity

of the indigenous adventitious microflora. The

pressed cheeses are ripened at 10–12



C for up to 12

months and, being made from raw milk, develop a

strong, piquant flavor. The cheese, which is con-

sidered to resemble Cheddar, has been the subject of

very little study.

0030 Leyden and Friesian are hard cheeses produced in

The Netherlands. Leiden is made from partially

skimmed milk, has a flat cylindrical shape, weighs

8–12 kg, and is matured for 6–12 months. Its texture

is dry and hard (artisanal, * 30% FDM; commercial,

40% FDM), and it is flavored with cumin seeds.

Traditional Friesian cheese is similar to Leiden and

is made from partially skimmed raw milk. It has a

very hard texture and * 20% FDM. It may be made

without spices, with cumin, or with cumin and cloves.

Today, most Friesian cheese is made from fresh,

pasteurized, partly skimmed milk, acidified using a

mesophilic culture.

Semihard Varieties

0031 The ‘semihard’ group of cheeses is rather arbitary

and heterogeneous, and the distinction between it

and other groups, e.g., hard cheeses, smear-ripened

varieties or pasta filata cheeses, is not clear-cut. Semi-

hard cheeses include Colby and Monterey (stirred-

curd Cheddar-type cheeses), some British Territorial

varieties (Caerphilly, Lancashire, and Wensleydale),

Bryndza (Slovakia), and Mahon and Majorero

(Spain).

0032 Caerphilly, which originated in Wales, is a crumbly,

acidic cheese made from pasteurized cows’ milk using

calf rennet and a mesophilic starter. The curds are

cooked to 32–34



C and held at this temperature for

about 1 h. The whey is drawn off and the curds held

in the vat where rapid acidification occurs. Salt (1%)

is added to the curds before molding and pressing

overnight. The pressed curds are brine-salted for

24 h, packaged, and ripened at 10–13



C for 10–14

days.

0033Lancashire is made from cows’ milk using calf

rennet and a mesophilic starter. The curds and whey

are not cooked, but the drained curds are cheddared

and held overnight for acidification. The next day,

fresh curds are mixed with the acidified curds and

the mixture milled to promote uniformity, dry-salted,

molded, pressed, and ripened at 13–18



C for 3–12

weeks.

0034Wensleydale cheese, which originated in Yorkshire,

England, is made from cows’ milk, inoculated with a

mesophilic starter; the curds are cooked at 32–34



The bed of drained curds is broken to assist whey

drainage, dry-salted, molded, and pressed lightly.

Wensleydale, which is matured for c. 1 month at

*12



C, has mechanical openings and a mild, acidic

taste. A blue variant is produced also.

0035Two stirred-curd variants of Cheddar cheese are

recognized: Colby and Monterey. The manufacture

of Colby, which originated in the USA, follows a

protocol similar to Cheddar until after cooking,

when some whey is removed and replaced by cold

water, which reduces the lactose content and pH, and

increases the moisture content of the cheese. The

curds/whey mixture is stirred and most of the whey

removed; the curds and remaining whey are stirred

vigorously and the remaining whey drained off. The

drained curds are stirred until the pH reaches * 5.4,

when they are dry-salted, molded, pressed, and

ripened for 2–3 months at 3–4



C. Colby contains

less than 40% moisture and 50% FDM.

0036Monterey (Monterey Jack) cheese was first made in

California and is similar to Colby. The cheese, which

contains < 44% moisture and 50% FDM, is allowed

to form a rind before waxing or packaging in a plastic

film. Monterey, which is ripened for 5–7 weeks at

* 4



C, has many mechanical openings.

0037Bryndza is made from sheep’s milk coagulated with

rennet (with significant lipase activity) and acidified

by the adventitious microflora of the milk or by a

mesophilic starter. The curds are allowed to settle to

the bottom of the vat, most of the whey is removed,

and the curds are consolidated manually into lumps,

which are placed into cloth bags and stored until

sufficient acidity develops (about 3 days). The fresh

cheese is known as Hrudka and may be sold locally.

However, most Hrudka is transferred to a central

factory, where it is broken up, salted, passed between

granite rollers to a smooth paste, packed in poly-

thene-lined wooden tubs, and matured.

1078 CHEESES/Manufacture of Hard and Semi-hard Varieties of Cheese

0038 Mahon is produced in the Balearic Island of Min-

orca from raw cows’ milk acidified by its adventitious

microflora. Mahon is brine-salted and ripened at



C for c. 2 months. Although the texture of

Mahon is semihard, its moisture content is reported

to be about 32%. Majorejo is made from goats’ milk

on the Canary Island, Fuerteventura. Milk is acidified

by a mesophilic starter and coagulated using rennet

extract, although artisanal cheesemakers rely on the

indigenous microflora of the milk and use rennet

paste as coagulant. The curds are molded in braided

palm leaves (which give its surface a characteristic

pattern), pressed lightly, and dry-salted. Majorejo

develops a strong flavor during ripening.

Ripening

0039 Although rennet-coagulated cheese curd may be con-

sumed at the end of manufacture, it is usually ripened

(cured, matured) for a period ranging from * 3

weeks to > 2 years; generally, the duration of ripening

is inversely related to the moisture content of the

cheese. Many varieties may be consumed at any of

several stages of maturity, depending on the flavor

preferences of consumers and economic factors.

0040 The unique characteristics of the individual cheeses

develop during ripening as a result of a complex set

of biochemical reactions, which are largely pre-

determined by the manufacturing process, i.e., by

composition, especially moisture, NaCl, pH, level of

coagulant activity in the curd, type of starter, and an

intentional or adventitious secondary microflora. The

ripening agents in cheese are derived from one or

more of the following:

0041 coagulant;

0042 indigenous milk enzymes, especially proteinase and

lipase;

0043 starter bacteria and their enzymes;

0044 secondary microorganisms, both intentional and

adventitious, and their enzymes.

0045 The characteristics of many cheeses are dominated

by the metabolic activity of the secondary microflora,

but traditionally, Cheddar and the other varieties dis-

cussed here were not inoculated with a secondary

culture, although an adventitious secondary micro-

flora of nonstarter LAB (NSLAB), mainly mesophilic

lactobacilli, grows to 10

–10

CFU g

1

. The NSLAB

are more heterogeneous in cheese made from raw

milk than in that made from pasteurized milk,

which probably explains the more intense, but more

variable, flavor development in the former. The inter-

ior of Cheddar cheese is a rather selective envir-

onment: it has a low pH (* 5) and a relatively high

salt content, is anaerobic, lacks a fermentable

carbohydrate, and may contain bacteriocins pro-

duced by the starter bacteria; hence, the rather limited

diversity of NSLAB.

0046The primary biochemical changes in ripening

cheese are the metabolism of residual lactose and the

catabolism of lactate and citrate (often referred to

collectively, but erroneously, as glycolysis), lipolysis

and proteolysis, which are followed and overlapped

by secondary catabolic changes to the products of

these primary pathways, including deamination, dec-

arboxylation, and desulfurylation of amino acids and

b-oxidation of fatty acids. Considerable progress has

been made on elucidating the primary reactions in

Cheddar. Unfortunately, only limited information is

currently available on the ripening of the other hard

and semihard cheeses discussed here, but since the

ripening agents and the composition of all these

cheeses are generally similar, the overall features of

ripening are probably similar. However, differences in

flavor and texture between members of this group are

readily apparent, due partially to the degree of matur-

ity of the cheeses, but also reflect the effect of small

differences in composition and manufacturing tech-

nology, which affects the microflora of the cheese.

Glycolysis and Related Events

0047Most (* 98%) of the lactose in milk is removed in the

whey as lactose or lactic acid but fresh curd for hard

and semihard cheese contains 1–2% lactose. The

catabolism of lactose and resulting lactic acid is under-

stood at the molecular level. For most cheese varieties,

the residual lactose is metabolized by the starter bac-

teria within about 12 h. However, owing to the low

pH (* 5.4) of curd for Cheddar and similar cheeses at

molding and the practise of dry-salting the curd for

these cheeses, which rapidly gives an inhibitory level

of NaCl throughout the cheese, residual lactose is

metabolized slowly, normally by residual starter ac-

tivity to l(þ)-lactic acid; young Cheddar cheese con-

tains * 1.5% lactic acid. The curds for Colby and

Monterey are washed to reduce the lactose content

of the curd (and also to increase its moisture content).

0048In Cheddar and probably in related varieties, l(þ )-

lactate is racemized to dl-lactate. Racemization has

no significant effect on cheese flavor, but if the con-

centration of d-lactate is too high, it may form un-

desirable crystals on the cheese surface. Oxidation of

lactic acid to acetic acid occurs to an extent depend-

ent on the concentration of O

in the curd, which is

strongly affected by the gas permeability of the pack-

aging material.

0049The pH of most cheeses increases during ripening,

but the pH of Cheddar changes little. Cheese has

a strong buffering peak at pH * 5.2, and if the pH

of cheese falls below this value, as for Cheddar,

CHEESES/Manufacture of Hard and Semi-hard Varieties of Cheese 1079

insufficient NH

and amines may be produced to

cause an increase in pH. However, if the lactose con-

tent of Cheddar curd is reduced by washing or whey

replacement, residual lactose in the cheese is metab-

olized rapidly, and the pH increases during ripening.

Low-lactose cheese has a clean, mild flavor, whereas

lactose-supplemented cheese develops a strong, harsh

flavor, probably due to the low pH.

0050 Cheddar-type cheese contains * 2 g of citrate per

kilogram, which is fermented slowly by NSLAB, prin-

cipally to formic acid and CO

; the latter may cause

an undesirable open texture.

Lipolysis

0051 Lipolysis is quite limited in most cheese varieties,

including Cheddar and related types. A low concen-

tration of fatty acids is important, probably essential,

for cheese flavor, but even slightly excessive lipolysis

causes rancidity or unbalanced flavor in hard and

semihard cheeses. Considerably more lipolysis occurs

in raw milk than in pasteurized milk Cheddar, sug-

gesting that the indigenous lipoprotein lipase in milk

and/or NSLAB is significant. Although LAB are

weakly lipolytic, they do possess esterases/lipases,

which release a low level of fatty acids during a long

ripening period. Fatty acids contribute directly to

cheese flavor and also serve as substrates for several

flavor-generating reactions (Figure 3). These second-

ary reactions are quite limited in hard and semihard,

internal bacterially ripened cheese but probably do

contribute to overall flavor intensity and balance, es-

pecially the lactones and thioesters. Esters, especially

ethyl butyrate, ethyl hexanoate, and ethyl octanoate,

are responsible for a fruity flavor, which is usually

regarded as a defect in Cheddar-type cheese. The oxi-

dation of fatty acids to alkan-2-ones (n-methyl

ketones) is a key flavor-generating reaction in mold-

ripened cheese, especially blue cheeses, but is very

OHC

Triglyceride

Fatty acids

Lipase

Partial glycerides

OCH

Ethyl esters

Ethanol

S-RC

Thioesters

R-SH

Thiols

Alkan-2-ones

Alkan-2-ols

β-Oxidation

γ- or δ-lactones

γ- or δ-hydroxy fatty acids

fig0003 Figure 3 General pathway for the production and catabolism of fatty acids in cheese during ripening.

1080 CHEESES/Manufacture of Hard and Semi-hard Varieties of Cheese

limited in hard and semihard bacterially ripened

cheeses.

Proteolysis

0052 Proteolysis is the most complex and perhaps the most

important of the three primary ripening events, espe-

cially in internal bacterially ripened cheese. It is pri-

marily responsible for changes in cheese texture and

makes a significant contribution to flavor, especially

background flavor via the formation of amino acids

and small peptides. Catabolism of amino acids leads

to many sapid and aromatic compounds, which are

probably major contributors to cheese flavor and may

be rate-limiting in flavor development in hard and

semihard cheese. Owing to its perceived importance

to the rate of ripening and to the quality of the mature

cheese, proteolysis and related events have been the

subject of intense research in recent years.

0053 Cheddar-type cheese contains a broad range of

proteinases and peptidases which originate from the

coagulant, milk, starter, and NSLAB. The proteinases

and peptidases from most of these sources have been

isolated and characterized, and their contribution to

cheese ripening established.

0054 The sequence of proteolysis in Cheddar and similar

varieties is summarized in Figure 4. Primary proteoly-

sis is catalyzed mainly by the coagulant and is princi-

pally responsible for the hydrolysis of a

-casein

which, in mature Cheddar cheese, is completely

hydrolyzed at Phe

–Phe

, at least 50% at Leu

101

–

Lys

102

, and, to a lesser extent, at other bonds. In

cheese, b-casein is hydrolyzed only slightly by most

coagulants, but about 50% is hydrolyzed by plasmin

to g-caseins and proteose peptones. Primary proteoly-

sis contributes little or nothing to the flavor of cheese

but is mainly responsible for the changes in cheese

texture which occur during the early stages of

ripening.

0055The large C-terminal peptides produced from

- and b-caseins by the coagulant and plasmin,

respectively, and para-k-casein produced during

milk coagulation, accumulate during ripening and

are present even in extra-mature cheese. However,

the complimentary N-terminal peptides from a

and b-caseins are hydrolyzed by lactococcal protei-

nases and peptidases to smaller peptides and amino

acids. The NSLAB contribute mainly at the level of

amino acid production. About 200 peptides have

been isolated from Cheddar cheese and characterized.

0056Small peptides and amino acids contribute to the

background flavor of cheese, but an excessive concen-

tration of small hydrophobic peptides may cause bit-

terness, which is probably the most common flavor

defect in cheese. More importantly, amino acids can

be converted to a range of flavor compounds, includ-

ing amines, acids, carbonyls, NH

, sulfur com-

pounds, and hydrocarbons by enzymes derived from

the starter or NSLAB or through chemical reactions.

The enzymatic catabolism of amino acids is summar-

ized in Figure 4 and elaborated in Figures 5–7. These

reactions and the enzymes involved have attracted

considerable attention during the past few years.

The principal amino acid-derived flavor compounds

in cheese are listed in Table 1.

Casein

coagulant

plasmin

Large and small polypeptides

Starter proteinases

Small peptides

Starter and non-starter

peptidases

Small peptides +

amino acids

deaminases

Acids

lyases

Sulphur

compounds

decarboxylases

Amines

Carbonyls

transaminases

α-Keto acid 2

α-Amino acid

α-Keto acid 1

fig0004 Figure 4 Summary of proteolysis and amino acid catabolism in cheese during ripening.

CHEESES/Manufacture of Hard and Semi-hard Varieties of Cheese 1081

tbl0001 Table 1 Major aroma compounds derived from branched chain and aromatic amino acids and methionine in cheese during ripening

Amino acid Carboxylic acids

Amines Aldehydes Alcohols Thiols/others

Valine 2-Methyl propionic acid 2-Methyl propylamine 2-Methyl propanal 2-Methyl propanol

Leucine 3-Methylbutanoic acid 3-Methyl butylamine 3-Methyl butanal 3-Methyl butanol

Isoleucine 2-Methylbutanoic acid 2-Methyl butylamine 2-Methyl butanal 3-Methyl butanol

Phenylalanine Phenylacetic acid Phenylethyl amine Phenylacetaldehyde, benzaldehyde Phenylethanol

Tyrosine p-Hydroxyphenylacetic acid p-Hydroxyphenylethyl amine

(tyramine)

p-Hydroxyphenylacetaldehyde,

p-hydroxybenzaldehyde

p-Hydroxyphenylethanol p-Cresol, phenol

Tryptophan Indole-3-acetic acid Indole-3-ethyl amine (tryptamine) Indole-3-acetaldehyde

Indole-3-aldehyde

Indole-3-ethanol

(tryptophol)

Skatole, indole

Methionine 3-Methylthiopropionic acid 3-Methylthiopropylamine 3-Methylthiopropanal (methional) 3-Methylthiopropanol Methanethiol

Further carboxylic acids can be produced from amino acids by deamination.

From Yvon M and Rijnen L (2001) Cheese flavour formation by amino acid catabolism. International Dairy Journal 11: 185–201.

0057 The Strecker reaction between an amino acid and a

dicarbonyl (Figure 8) is an important chemical flavor-

generating reaction involving amino acids in

cheese, but the Maillard reaction between an amine

(e.g., amino acid) and a monocarbonyl (e.g., a reducing

sugar) may be significant to cheese flavor (and color)

under certain circumstances, e.g., low-moisture

grated cheese or cooked cheese.

Adjunct Cultures

0058 The use of pasteurized milk for cheese-making dates

from the beginning of the twentieth century but did

not become widespread until about 1950. The princi-

pal objective of pasteurizing milk is to kill pathogenic

bacteria, but most other microorganisms, including

desirable NSLAB, are killed also, and many indi-

genous enzymes are inactivated. For public-health

reasons and because the quality of cheese made

from pasteurized milk is more consistent and uniform

than that made from raw milk, it is very unlikely that

raw milk will be used for the manufacture of Cheddar

cheese in the very large, highly mechanized factories

which are now common. However, there is a general

perception that the flavor of modern Cheddar has

become too mild, possibly owing to the use of very

high microbiological quality cheese milk (pasteuriza-

tion of which renders it essentially free of NSLAB),

the use of highly active starters containing only a

few strains of Lactococcus, and the manufacture of

cheese in enclosed equipment which reduces contam-

ination from the environment. While most consumers

today prefer mild Cheddar, there are niche markets

for more mature, intensely flavored cheese. Also,

some retailers and cheese manufacturers wish to

offer for sale cheese with a flavor identifiable with

that company. The use of adjunct cultures (which

are not required for acid production) is considered

to be the most effective way of achieving this; essen-

tially, these cultures diversify the microflora of the

cheese and are an attempt to reproduce the microflora

of raw milk cheese in a controlled way. Since the

NCHC

CH CH

Leucine

CH CH

2-Keto-4-methylpentanoic acid

α-Ketoglutarate

Glutamic acid

CH CH

3-Methylbutanal

CH CH

3-Methylbutanol

CH CH

3-Methylbutanoic acid

TRANSAMINASE DECARBOXYLASE

CH CH

3-Methylbutylamine

DECARBOXYLASE

CH CH

4-Methylpentanoic acid

DEAMINASE

fig0005 Figure 5 Catabolism of leucine. Similar pathways apply for the other branched-chain amino acids, isoleucine, and valine.

CHEESES/Manufacture of Hard and Semi-hard Varieties of Cheese 1083

Reduction

Homoalanine

2-aminobutyric acid

Methionine

4-Methylthio-2-aminobutyrate

4-Methylthio-2-ketobutyrate

Glutamic Acid

2-aminopentanedioic acid

Aminotransferase

Methanethiol

Dimethyldisulphide

α-Ketoglutaric acid

2-oxopentanedioic acid

Dimethyltrisulphide

Pyridoxal

phosphate

Decarboxylase

Thiamine

pyrophosphate

Methional

3-Methylthiopropionaldehyde

2-Oxo-butyrate

Pyridoxal

phosphate

Cystathionine b-lyase

CSH

α, γ -elimination

Methionine-g -demthiolase

(non-deaminating)

Homoalanine

Deaminase

NH3

Homocysteine

2-amino-4-mercaptobutyric acid

2-Oxo-4-thiomethyl butyrate

a -Keto-g -thiomethylbutyrate

demethiolase

Methionine-a -deaminase

Methionine-a -transaminase

-S-CO-R

Methylthioesters

Methylthioacetate

Methylthiopropanoate

Dimethylsulphide

Methionol

3-Methylthio-1-propanol

3-Methylthiopropan-1-oic acid

Oxidation

Hydrogen sulphide

Ethyl-3-Methylthio-1-propanoate

CS CH

fig0006 Figure 6 Suggested pathways for the catabolism of methionine in cheese during ripening.

NSLAB in Cheddar cheese are mainly mesophilic

lactobacilli, especially Lb. casei and Lb. paracasei,

most studies on the use of adjunct cultures for Ched-

dar cheese have concentrated on mesophilic lactoba-

cilli; most investigators report positive results.

Thermophilic lactobacilli are more effective than

mesophilic lactobacilli, possibly because the former

die rapidly in cheese, releasing their intracellular

enzymes, while the latter do not. However, the

number of thermophilic lactobacilli added must be

controlled carefully – if too numerous, a Swiss

cheese-type flavor will develop.

Acceleration of Cheese Ripening

0059Some high-moisture cheeses develop an intense flavor

through a very active secondary microflora, e.g.,

internal blue mold, external white mold, or a bacter-

ial surface smear; these cheeses ripen rapidly. High-

moisture internal bacterially ripened cheeses also

mature rapidly but develop a low flavor intensity; if

−

COO

−

COO

−

COO

−

COO

−

CHOH

Transaminase

amino acid

Benzaldehyde

Phenyl pyruvate

Phenyl acetate

Phenylethanol

Phenyl lactate

α-ketoacid

Phenyl ethyl amine

Decarboxylase

Phenyl propionate

Deaminase

Phenylalanine

CHO

(a)

(c)

−

COO

−

CHO

COO

−

CHOH

Tryptamine

Indole pyruvate

Indole aldehyde

Indole acetate

Skatole

Indole lactate

Indole pyruvate

dehydrogenase

non-enzymatic or decarboxylase

Decarboxylase

α-ketoacid

Transaminase

amino acid

COO

−

COO

−

Indole propionate

Deaminase

Tryptophan

(b)

−

COO

−

COO

−

COO

−

CHOH

amino acid

p-OH-Phenyl pyruvate

p-Cresol

p-OH-Phenyl

aldehyde

p-OH-Phenyl acetate

Dehydrogenase

p-OH-Phenyl lactate

non-enzymatic or

decarboxylase

Decarboxylase

Tyramine

Transaminase

α-ketoacid

Tyrosine

CHO

COO

−

p-OH-Phenyl propionate

Deaminase

fig0007 Figure 7 Suggested pathways for the catabolism of (a) phenylalanine, (b) tyrosine, and (c) tryptophan in cheese during ripening.

CHEESES/Manufacture of Hard and Semi-hard Varieties of Cheese 1085