| Cheese
is a fresh or ripened product made from coagulated milk. Cheese
can be differentiated both by the type of milk - raw, skimmed
or pasteurised, and by animal - cow, goat, sheep, buffalo, horse
or camel. For all of them however, there are four major stages
in the basic process:
The
Basic Components of Cheese
Curdling
or coagulation of the milk
The first step in cheesemaking is to coagulate the milk solids
into a curd. It can be done either by acid coagulation or rennet
coagulation. Acid coagulation is caused by adding an acid substance
(lemon juice, vinegar) or by adding a bacterial culture that
turns the lactose into lactic acid. Renneting consists in adding
the rennet to the heated milk. Coagulation, which cannot take
place under 10 C, is activated at temperatures between 20 and
40 C. The coagulation period depends on the type of cheese and
varies from 30 minutes to 36 hours.
Shaping of the curds
The curds are broken down in a vat to separate the curds from
the whey. As larger cheese curds contain more water than small
ones, a large curd is prepared for soft cheeses, a medium-sized
curd for firmer cheeses and a small curd for hard cheeses. The
curds are cut up into lumps. The curd mass is constantly stirred
to prevent it from agglomerating again. The duration of this
cutting up (de-curding) period also varies according to the
cheese. For many cheeses, a medium- sized curd is prepared first.
It than gives off more whey when it is stirred and warmed. There
are several methods for removing the curds from the vat for
draining. A draining-board in long grooves is used and the entire
vat poured onto it for goat's cheeses. Ladles may also be used
to transfer the curds directly into moulds containing holes
through which the whey can run off. With pressed cheeses, strong
cloth which allows the whey to filter through the holes and
retains the curds, is used.
Salting, washing and seeding
Salt plays a substantial role in cheesemaking. Salting serves
a number of functions, it speeds up the drying process, heightens
the cheese's flavour, helps the rind to form and slows down
the proliferation of micro-organisms. Each type of cheese has
a specified salt content. The most common method is an immersion
in a brine bath. Depending on the cheese, the brine will contain
between 250 and 350g salt per litre. Dry-salting is done by
rubbing the cheese with salt on repeated occasions after it
has been removed from the mould.
Washed-rind
cheeses are brushed or washed with salt at regular intervals
during their maturation, preventing the formation of mould and
keeping the rind soft. Cheeses may be washed in spirits (wine
or bear).
Cheeses can be seeded with fungus to produce the soft white
down of their "bloomy" rind, or the blue-green veining of "blue"
cheeses.
Maturing
The environment in which the majority of cheeses are ripened
is usually a ripening cellar or a special storage room. Cheese-makers
are often putting their cheeses in drying-rooms to speed up
the maturation.
The
ripening cellar may be humid and warm, or relatively cool. The
climate of the cellar is determined by the ambient temperature
and relative humidity, as well as by the natural movement of
air in the space.
The
temperature can range from 32 to 77 F, but the majority of cheeses
are ripened at between 46 and 60 F. During the maturation period
there is a constant exchange between ripening gases, such as
carbon dioxide and ammonia, from the cheese and oxygen in the
air, which is essencial for the growth of both aerobic surface
flora and interior flora.
The
Basic Components of Cheese
Milk
Fat
Fat
exists in milk as small globules that can vary in size depending
on the breed of cow. The fat in the milk helps to produce flavour,
aroma and body in mature cheese. Cheese made from skimmed milk
is hard in body and texture, and lacks flavour. However, only
a small amount of fat (as low as 1%) can produce a background
flavour, and today's makers exploit this with their 'low-fat
cheese' for which there is a growing demand.
Protein
Protein
exists in two forms in milk as a suspension/colloidal (casein)
and in a soluble form (whey proteins). As an analogy, however,
consider the first type of protein as a densely woven mesh rather
like a string vest suspended freely in the aqueous phase of
milk. As long as the milk remains sweet, this structure is unaffected
and the milk remains totally fluid. However, if the milk acidifies
(i.e. goes sour) without the presence of coagulating enzymes
the structure changes quite suddenly at the 'iso-electric point',
and a fragile curd is formed that collapses with the slightest
agitation into tiny fragments. A typical example is the fine
mass we see when milk sours naturally. By adding rennet, at
just the right time before the milk would go completely sour,
the structure of the casein is changed radically to form a solid
curd called para-casein. This can then be cut with knives and
saved to be collected as grains of curd for subsequent processing.
The
second fraction of protein is called albumen (alpha-lactalbumin
and beta-lactoglobulin). This as described above passes out
with the whey and is usually lost, though it can be recovered
by specialised and expensive filtration methods. When hot milk
is allowed to stand still for any time, whey proteins appear
as a 'skin' on the surface.
Enzymes
In
milk different enzymes may arise from the cow herself, from
bacteria present in the teat canals or from organisms that gain
entry to the milk at a later stage. As we shall see shortly
these enzymes have a profound effect on the quality of raw milk,
and the ripening of cheese in the store. For example, lipases,
proteases and lactase enzymes hydrolyse the fat, protein and
lactose respectively into different components. In this case,
these enzymes, which occur naturally in the milk or which are
sometimes supplied by the indigenous bacteria in the milk and
the added starter culture, can change the milk fats and proteins
in the process of ripening the cheese to produce the delicate
flavours and aromas that make mature cheese so enjoyable. Later
we shall see just how a cheese grader can assess these vital
elements.
Vitamins
These
are organic substances in milk which help to promote growth.
Milk fat holds the fat soluble vitamins (A, D, E and K) and
the water soluble vitamins are the B complex and C which are
in the whey. They also play an important part in encouraging
bacteria to grow in the cheese ripening process.
Lactose
This
is the main sugar in the milk. It provides the energy source
for the starter cultures to produce lactic acid, and so helps
to modify the milk for cheesemaking. About 10% of the lactose
is used by the starter bacteria to make lactic acid, and the
rest is drawn off with the whey. It was used in the past to
feed to pigs for fattening up, but with the massive increase
in cheese production this no longer became practical.
Surprisingly
enough, whey was generally considered by practical cheesemakers
of the day to be little more than a confounded nuisance and
where sewage facilities were not available large quantities
were simply dumped surreptitiously into ditches, down old quarries,
sprayed over land or piped straight out to sea.
Ash
Those
substances are present in milk and consist of metallic components
(sodium, potassium, calcium, magnesium, manganese, iron, copper)
and non-metallic elements such as sulphur, chlorine, phosphorous.
Calcium is probably the most important mineral for the coagulation
of milk, and together with the protein is an excellent source
of food, especially for children who can absorb it quickly into
their growth system.
Starter
Cultures
Cheese
is really a form of fermented milk, and acid production is carried
out by starter cultures. Milk being sourced from a living animal
has bacteria in it when fed to the calf. Some bacteria produce
acid, others help to digest the protein in the milk; some use
milk as a base for their own development which, in the case
of disease-producing bacteria, can infect those who drink it.
Tuberculosis, brucellosis and undulant fever are three examples
of diseases that can affect those who may drink unpasteurised
milk.
Happily,
the acid producing bacteria can in some cases directly suppress
disease-producing bacteria under normal conditions. This is
why fermented milk products are among the safest foods to take
in their natural state particularly in areas where food hygiene
may be suspect. Down through the centuries until around 1860,
the existence of bacteria and how they worked was not known.
A few countries in Europe including Scotland played an important
role in the early days of cheesemaking when little was known
of how to use bacterial cultures effectively. The first breakthrough
came when a French scientist called Louis Pasteur was able to
show their harmful effect in wine and later in milk. Lister
in 1873 isolated a mesophilic bacterium which he named Bacterium
lactis and later known as Streptococcus lactis (the
present designation is Lactococcus lactis subsp. lactis)
for use as a cheese starter culture.
The
first practical use of bacterial cultures for the dairy industry
was in fact for butter. In 1890, the Danish scientist Storch
developed a selected strain of bacteria which he called Streptococcus
cremoris (the present designation Lactococcus lactis
subsp. cremoris), and this knowledge was soon applied
to cheesemaking. At that time discoloration in cheese was a
problem caused by contamination of the raw milk. A committee
of interested parties decided that this should be checked by
thorough cooling of the evening milk and by the addition of
a vigorous pure culture to start the fermentation in the mixed
evening and morning's milk when cheesemaking started. The success,
which followed extensive trials in the south west of Scotland,
did much to establish the practice of using pure starter cultures.
In the period from 1895 to around 1910, there was growing interest
in the use of pure starter cultures for cheesemaking. During
the same period, Lloyd in England developed a test to determine
acidity in milk. Workers on the continent selected pure bacterial
cultures just for making cheese to which the name was given
as starters.
Until
the middle of the 19th century, cheesemakers on croft and farm
simply held over a portion of soured milk or whey in a small
jug or churn and used it the following day to make cheese. This
worked perfectly well as long as the amount of cheese being
made was relatively small, but cheesemaking was never consistent
and results varied greatly. Cheesemaking was carried out only
in the summer months and at the end of the season starter had
somehow to be kept for the next year. This was in fact done
in many rural areas by filling up a clean bottle with starter,
corking it securely and burying it in the back garden. The following
Spring it was dug up and, after one or two sub-cultures, used
again for cheesemaking.
Moulds
play their part in cheesemaking. The white mould seen on Camembert
helps to hydrolyse the protein in the final cheese by working
from the outside in. Blue moulds can be added with the starter,
and help to breakdown the curd produced from the inside of the
cheese outwards. Sometimes, to help the growth of blue mould,
the cheese is pierced with a skewer which lets in air and helps
the mould to spread and carry on the good work of protein/fat
hydrolysis. This explains the blue streaks seen sometimes in
Danish Blue cheese.
Over
the last sixty years much work has been done to develop starters
that would work consistently under creamery conditions. In effect
we have moved from the forties where starter was made up fresh
each day in liquid form to the situation now where starter is
kept as freeze-dried or in deep freeze cabinets and added as
a powder or granules, respectively, to the vat before cheesemaking
begins. These starter culture systems are known as direct-to-vat
inoculation (DVI).
Coagulants/Rennet
The
need to coagulate milk has been well recognised since Roman
times, and this can be achieved by the selective use of certain
plants or by extracting the enzyme rennet (chymosin and pepsin)
from the fourth stomach of the milk-fed calf. Plants are widely
used in some European countries and the far East. In Britain,
the butterworts, artichokes, teasel, spearwort and thistles
are said to have been used, but are usually too mild for general
use. Up to the 19th century, Ladies' Bedstraw (Galium verum)
was said to have been used for making Cheshire cheese.
Records
for the making of rennet go back to the 16th century. The farmer
or small-holder cheesemaker would select and slaughter a milk-fed
calf, remove and wash the fourth stomach carefully. He would
then hang this out to air-dry in which case it would become
known as a 'vell'. There was a regular market for dried vells.
It is difficult to ascertain how these vells were first used
in traditional farmhouse cheesemaking in Scotland or elsewhere.
However, it is most likely that dried pieces of vells were added
directly to the milk, and at later times vell extracts in salt
solution were used. Basically, sliced or mascerated vells were
soaked in salty water to provide a solution of enzymes. Filtration
may have been used for the purification of the final rennet
solution. Storing the rennet in a salt solution keeps it in
good condition and suppresses any bacteria that might cause
a deterioration in quality. Such rennets are known as 'calf
rennets'.
Rennet
is very strong in action (1 part of commercial rennet can coagulate
5000 parts of milk) and today rennet supplies are meticulously
monitored. The main suppliers are Chr. Hansen's of Denmark and
Rh™ne Poulenc of France. The British firm of R.J. Fullwood &
Bland Limited of Ellesmere in Shropshire (who manufactured non
synthetic annatto and rennet for over 200 years) no longer supply
it, as their core business is now the manufacture and installation
of milking machines and associated products.
Another
form of rennet is called 'vegetable' rennet which is derived
from certain strains of fungi and bacteria. Today, this type
of rennet is very popular, reflecting a move towards 'vegetarian cheese'. Substantial
amounts are now used at farmhouse and creamery level. Recently,
due to world shortage of calf rennet, recombinant or genetically
engineered pure chymosin derived from different microorganisms
is available on the market, and is currently used by many cheesemakers
in different countries.
Salt
By
this term we mean sodium chloride, the common salt used at home
for cooking and seasoning food. Four main methods are used depending
on the type of cheese that is being made.
1.
Hard-pressed cheese
These
are called textured cheese, such as Cheddar, Cheshire and the
English regional cheeses including Caerphilly, which undergo
pressing for a period from 18 hours up to 2-3 days after being
put into the cheese moulds. Throughout the cheesemaking process
we have described for Cheddar, the starter is steadily making
acid, its speed in so doing reduced somewhat in the heating
process used in the final stages. To stop further acid development,
and also to provide an element of flavour and help preserve
the final cheese, salt is added after the curd blocks are milled.
The amount varies with the type of cheese made, but is usually
around 1.5 - 3% (w/w). Salting provokes a further small rush
of whey, cools the curd slightly and controls further acid development.
In traditional cheese vats, the salt was added by hand after
milling either in the vat or in the 'cooler' (a trolley-like
vehicle on which curd blocks were cheddared and made ready for
milling). However, in modern automated plants, the salt can
be blown from a salt-silo directly on to the milled curd laid
out on a moving bed. Mechanical probes assess the curd depth
and adjust the amount of salt needed electronically.
2.
Brine-salted cheese
These
are also hard- and semi-hard pressed cheese, but usually salted
for a much shorter time and relatively large and small in size,
respectively. A typical example would be the Edam (Dutch) and
Emmental (Swiss). In this case, the cheese are removed from
their mould and tumbled straight into a bath of salt solution
strong enough to float the cheese. By holding these cheese in
huge shallow tanks, they start absorbing salt, and after a period
they are floated along to similar tanks with an even stronger
salt solution during which the salt continues to be absorbed.
They are then removed by elevator from the brine bath, allowed
to dry out by which time the degree of salt needed has spread
through the cheese.
3.
Soft cheese salting
Soft
cheese types, which tend to be small, can be rubbed with salt
on the outer surface at least once, and sometimes twice. The
salt can then migrate across the cheese in about 24 hours. This
method of salting assists in the formation of rind on the cheese.
4.
Blue-veined cheese salting
Salt
is usually applied on the curd before moulding, sometimes on
the curd while in its mould or indeed after the cheese has been
removed from the cheese mould.
Moulding
and Pressing
Moulding
has nothing to do with the blue green mass sometimes seen on
traditional cheese, or stale bread, but is the term used for
containing and pressing salted curd into a certain shape in
which it can be matured before finally being sold. In Scotland,
traditionally they referred to such containers as 'chissets'.
The
'chissets' were made of oak wood and banded with iron for strength.
They came in various sizes based on the width of the final cheese.
Cheddar cheese were usually 60 to 80 lb in weight on the larger
farms down to relatively small moulds used in Highland crofts
that made a cheese of some 3-5 lb in weight. The first stage
was to line the mould with a coarse cheesecloth called 'scrim'
that would help to drain the initial flow of whey. The salted
curd was then shovelled or hand filled into the 'chisset', and
the final few handfuls being placed centrally to pack the 'chisset'
completely. The ends of the 'scrim' were folded over neatly
then the so-called 'follower' was placed on top. Being of slightly
less diameter than the 'chisset', it would sink down into it
slightly and so apply pressure to the curd within.
Having
filled the 'chisset', be it on the croft or farmhouse, the next
step was to consolidate the curd into a firm mass. Many and
varied were the methods for doing this. It is essential to apply
pressure progressively so that the whey can be uniformly expressed
and not locked into the curd permanently. On the croft with
a shortage of space and capital, recourse was made to that abundant
local material - stone. The need was to secure a stone that
would exert just the right amount of pressure relative to the
size of the 'chisset', and experience was the best guide. However,
a stone was a dead weight in itself as a single unit, and early
trials were made using a stone with a screwed shaft sunk through
it on an iron or wooden frame. This allowed the dead weight
of the stone to be progressively applied and so improve the
overall drainage and firming up of the curd.
Moving
up the scale from croft or farm level was the two or four 'chisset'
cast-iron press which was very common throughout the late 18th
and 19th centuries. Here the 'chisset' was slid on to a circular
table, another 'chisset' placed on top and the press head lowered
down by a hand wheel.
A
big advance as it allowed pressure on the cheese to be easily
adjusted by placing a series of different weights on the counter-balanced
pressure levers. This was of particular value where cheese such
as Cheshire were being made. It is necessary to apply pressure
progressively over two or three days due to the much wetter
curd involved in traditional Cheshire cheesemaking, and also
allowed the relatively rich (salted) cheese whey to be collected.
Pressure was applied to the cheese for two or three hours then
it was released. The 'chissets' were up-ended, the 'scrim' was
then pulled up tight to ensure that no folds that may have been
driven onto the top or into the sides remained. The followers
were replaced and the cheese repressed at full overnight pressure.
This could also mean a return late in the evening to tighten
up the presses, a chore not always welcomed after a hard days
work.
Traditionally
made cheese often had to face a period of storage under conditions
far from ideal. Accordingly, a Cheddar would be made with up
to 36% moisture in the final curd to allow for a loss in store
of 3-6% before it was finally sold. A firm coating was, therefore,
essential to prevent damage of the cheese and mould penetration.
The following day the cheese in their 'chissets' would be removed
from the press and taken over to the scalding benches. Here
the 'chisset' would be inverted, and the rim tapped against
a block of wood or rubber so that the cheese and cloth slid
out freely on to the knock-out stool. It would then be reversed,
and very hot water poured over the cheese. This was the first
stage in forming the rind by hardening of the protein on the
surface of the cheese. It was then returned to the mould in
the same 'scrim' and re-pressed for some two hours to cool and
firm up. The cheese were then removed after being reversed and
a fine cloth would be placed over the cheese. Then the cheese
and cloth together would be knocked down into the 'chisset'
before returning to press for a second night. The following
morning after being knocked out, the fine cloth was removed
and the cheese were then transferred to the loft or cheese store.
At this stage it would be still 'tender' and require some final
support.
Cheese
Bandaging
The
first step was to coat the surface of the cheese with a form
of grease that would provide a fixative and close up any surface
deficiencies. Pig fat was in common use and a colleague of the
author recalls full well as late as 1940, before turning up
for school each morning, calling in to collect a bucket of lard
and 'larding the cheese' at Stewarton. After larding the cheese
would then be secured with a roller bandage wound round from
bottom to top. Stitched in position it would then be stamped
for identification, and placed carefully on the cheese shelf.
A drying-out period of one or two days would then ensue.
"Conventional
cheese lofts did not have any heating or cooling as we know
it today. Some enlightened farmers had a cooling system of
a kind which consisted of mains water being pumped up along
pipes sited on either side of the roof crown and running the
full length. In warm weather, in spring and summer, these
were turned on and the mains water ran down the slates to
cool the roof on either side. The majority of conventional
lofts had only wooden shelves, some had what were called 'turning
dales' (Plate 3). These held 10 or 12 traditional Cheddars
(70 lb) which could be turned all at once. This reduced the
time taken each day to turn the cheese. Flavour and quality
depended to a large extent on hygiene at milking, equipment,
cheese cultures and the cheesemaker's ability to make good
cheese (about 35-36% moisture). If he had slow cheese, which
generally tended to hold moisture, the flavour would go bad
fairly quickly (4-5 months). If the acid in the cheese developed
very rapidly, a lot of the cheese in store would run whey
and would have to be sold at a lower price, as would the ones
that had gone off flavour, resulting in a loss to the farmer.
The body of cheese in conventional lofts could be affected
by the rise in temperature during spring and summer. This
gave rise to problems with the shape of the cheese which as
usual led to a loss of money when selling the product. In
conventional stores humidity was fairly critical, if too high
or too dry this resulted in a lot of mould or cracked rinds,
respectively.
Cold
storage enables cheese to be stored at a constant temperature
which means control of the maturation of the cheese. Even
high moisture cheese can be stored at a temperature which
if properly controlled, allows the cheese to be stored for
another 2-3 months without unduly affecting the flavour".
Farmhouse
Cheese Ripening
The
traditional cheese, placed in the store immediately out of press,
was basically a rubbery and elastic mass of curd, still warm
from the cheesemaking operation, and largely without flavour
or aroma. The milled particles still retained their identity
in spite of the pressing over the previous two days. There may
well have been some mechanical openness and free moisture. For
the first few days it needed careful handling. Eventually the
curd cooled and became more solid, and a firm bodied structure
ready for the changes that would turn it into the type of cheese
aimed at by the maker. The actual ripening process - then and
now - is brought about through the agency of enzyme systems
produced by bacteria which have grown or are growing in the
curd.
Cheese
made from raw milk will always have a subtler and richer flavour
at the end of its ripening period as the raw milk bacteria and
their enzymes are carried forward into the final making process.
Pasteurising the milk can destroy the indigenous bacteria and
also the lipolytic enzymes that both contribute to flavour and
aroma. However, the pathogenic (or 'illness-causing') bacteria
are destroyed by pasteurisation, and where close control of
the milk cannot be exercised ultimately by the cheesemaker (as
it may arrive in bulk from several farms) pasteurisation is
regarded as obligatory for such supplies.
At
the time under review, however, farmers had complete control
of their own supplies and the cheese was made on the spot. Indeed,
raw milk cheese making was the norm on farms almost until the
outbreak of World War II. This still applies today to the small
number of dedicated 'raw milk' farmhouse cheesemakers in Scotland
who operate under an "Agreed Code of Conduct" in the making
of cheese from raw milk. However, in 1964-65 a "Code of Practice
for Cheesemaking" was introduced and accepted by all the major
cheesemaking organisations in the UK under which the milk was
and is subjected to heat treatment.
The
ripening process could be briefly described as follows:-
"Although
the breakdown of the main constituents of curd, i.e. protein,
fats and sugars, is responsible for the changes in body, flavour
and aroma, they are not necessarily degraded step by step.
The amount of cross-linking of degraded products and the multiplicity
of enzymes in the curd give rise to a multitude of substances
which, individually affect the body, flavour and aroma of
cheese. However, it is the combinationof
these individual flavours and aromas against the background
of the intact fats and proteins which
constitute those characteristics appreciated by the customer".
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