Cheese Making in General
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 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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The Specialist Cheesemakers Association


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H.S. Bourne
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