There are thousands of varieties of cheese made each day across the world. A cheesemaker will start with a vat of milk and by the end of the cheesemaking process a cheese has been made. But why are there so many different cheeses when they are all coming from the one ingredient; milk. What does the cheesemaker do that makes one cheese different to another?
The cheesemaker has at least 17 variables under their control, each of which will slightly or significantly influence the type of cheese being produced. When combined, they produce cheese that are sometimes close and sometimes vastly different. The variables include:
Variables in manufacture of cheese varieties
- Type of milk
- Standardisation of fat levels
- Raw or Pasteurised milk
- Degree of souring allowed (priming)
- Starter Cultures
- Ripening and Flavouring Cultures
- Amount of rennet used
- Size of cut
- Temperatures used in cooking (or no cooking)
- Amount and speed of stirring
- Degree of whey drainage
- Pressing or not pressing the curd
- Method of salting
- Conditions and length of curing
- Use of special bacteria or mould in curing; and
- Use of additives
Type of milk
Milk from different animals will impart different characteristics to a cheese. Some varieties are only considered genuine when made from the milk of a particular animal (for example, Roquefort from ewes’ milk, Chabichou from goat milk). Cow’s milk tends to impart a yellow colour to cheese.
Difficulty may be experienced in manufacturing a cheese variety from milk other than that traditionally used for that variety (for example, Mozzarella from goat milk).
Standardisation of fat
In setting out to make any particular cheese variety the resultant cheese will be different depending on the balance of fat to protein in the milk. The fat content can be adjusted by adding or removing cream. Lower cream levels will tend toward increased hardness of a variety eg Parmesan and Comte. Increased cream levels will tend towards higher fat and higher moisture cheese such as a Brie or Triple Cream.
Heat treatment of milk
The use or raw or pasteurised milk often divides the cheesemaking community. Raw milk can only be used to produce certain varieties of cheese, mostly those with protected designations of origin (PDO). Outside of those rules the cheesemaker has a make a significant decision about the safety of the cheese based partly on using either raw or pasteurised milk.
Curd from pasteurised milk may tend to be softer, due to precipitation of some of the soluble calcium and it may be necessary to compensate by the addition of calcium chloride before renneting.
The disruption of fat globules caused by homogenising exposes a much greater surface area of fat to the action of the enzyme lipase, thereby accelerating the fat breakdown process during cheese maturing. Homogenising also makes milk and cheese feel much smoother, and produces a slightly paler curd. These factors, and the extra fat breakdown, are all desirable in Blue Vein cheese, where the cream in removed from the milk, homogenised and then returned to the milk.
Homogenising is also used for Cream cheese and some soft cheese types.
Degree of souring of milk
This may be controlled by varying the amount of starter added or by varying the time between addition of starter and rennet. Some cheese such as Cheddar require only a small amount of souring before the rennet is added and some cheese such as certain blue vein varieties require more than one hour. Lactic curd such as Persian Feta requires several hours. High acidities will favour increased moisture expulsion and firmer curd.
Starters are selected for different cheese varieties for two basic reasons: they must be able to produce, as appropriate, acid, gas and desirable flavours, and they must be able to withstand some of the temperatures which are themselves integral parts of the manufacture methods. In large eye type cheesemaking (for example, Emmental), the starter comprises several different cultures because of the various stages of manufacture, to produce acid slowly during the early stage of manufacture, and then to withstand the high cooking temperature later in the process.
Some cheese varieties such as Ricotta require no starter. The curd is formed by heating to near boiling and adding an organic acid to complete the precipitation. The curd rises to the top and is ladled into perforated moulds for draining. It is the eaten fresh.
Amount of rennet
Increased quantities of rennet will tend to produce a firmer curd, with an increased rate of protein breakdown during maturing. Excess rennet may cause ‘bitterness’. Some cheese such as Halloumi do not usually require a starter culture but rennet is essential. Some cheese such as Lactic Acid varieties require very minimal rennet, relying on the developed acidity to form the curd.
Size of cut
Fine cutting of the curd will favour increased moisture expulsion, resulting in a firmer cheese. Softer varieties, for example, Blue Vein and Camembert, frequently employ a larger cut to retain moisture.
Temperature used in cooking
High cooking temperatures favour increased curd shrinkage to produce firm curd in the whey and in some cases to reduce the levels of undesirable bacteria. Use of heat tolerant starters ensures that acid production resumes later, and usually continues during early maturing until the lactose is used up.
In some fresh, soft, or semi‑hard types where high moisture content is desired (for example Blue Vein, Feta and Camembert) the curds and whey are not cooked.
Near boiling temperature is used for non‑cultured cheese where the curd is formed by heat precipitation of the albumin followed by sudden acidification to induce coagulation and flocculation of all the protein (for example, Ricotta).
In the manufacture of Gouda and Raclette styles, part of the whey is removed during or immediately after cooking, and replaced by water, either at the same temperature as the vat contents or slightly hotter, in order to reach the final cooking temperature. The amounts of whey removed and water added can be varied and are used to vary the pH and body of the cheese.
The more water is added, the longer the curd remains in the diluted whey, the higher will be the cheese pH, and the weaker the body. The extra water in the whey surrounding the curd particles causes more lactic acid and lactose, to diffuse out of the curd. This results in less residual lactose in the curd after whey removal, thereby limiting the extent of subsequent acid development.
Degree of whey drainage
The stage and method of whey removal have important effects on the cheese produced. Early drainage of a soft curd is usually used in making soft cheese types. Some traditional Camembert only requires the ladling of coagulated curd directly into the moulds, with no cutting, stirring or cooking. Some feta styles are placed in drainage hoops or trays as soon as the curd has been cut. Blue Vein requires a short period of agitation and curd firming before it is placed in perforated hoops for draining and matting.
Late draining after prolonged agitation, cooking and acid development characterises the making of most firm and hard cheese (for example, Cheddar, Parmesan).
For eye‑type cheese, whey drainage is completed only after the curd has been compressed under the whey. This is necessary to achieve a close textured cheese with no mechanical openings due to inclusion of air during drainage and pressing. Any mechanical openings in eye‑type cheese will cause uneven and irregular eye formation, a serious appearance defect.
Bag draining without hooping and little or no pressing is applied to cheese with no real fused curd structure or shape. Cheese of this type includes Quark and Cream cheese.
Methods used to compact curd
Curd may be salted and pressed without any time allowed for matting (stirred‑curd type such as Romano) or allowed prolonged periods of matting (for example, Cheddar). Some varieties such as Edam and Gouda employ matting by pressure under the whey to give close textured cheese due to complete exclusion of air.
Varieties such as Mozzarella and Pizza incorporate vigorous dry or wet stretching of the matted curd (pasta‑filata process) to impart a smooth velvety character to the curd.
Firm cheese varieties employ mechanical pressure to finally mould the finished cheese, while softer varieties frequently rely on no application of pressure.
Method of salting
Salt, except in low concentrations, retards or stops bacterial growth, including that of starters, so it is always applied when acid production is sufficient and needs to be moderated. Salting from the outside, either by brining or dry salting, after the cheese has been pressed, allows acid production, regulated by storage temperature, to continue inside the cheese for some time, as the salt only penetrates slowly.
Brine or dry salting aids in forming a rind, by producing a dry salty zone around the outside.
The salt content of cheese is controlled by the amount added, when it is added and the time of exposure during brining and by rubbing salt into the cheese. Some cheese (for example, Feta) are packed, stored, and marketed in brine.
Conditions and length of curing
Curing conditions are not means of producing varietal characteristics in cheese. The object of curing is to allow the cheese to mature at a rate which results in the properly balanced development of flavour and other properties such as mould development and softening. Cost considerations generally mean that the fastest rate of maturing, which does not affect quality, is used.
Generally speaking, cheese of high moisture content and a delicate flavour requires the shortest ripening period. Fresh cheese such as Cottage and Quark are not ripened at all. Cheese like Camembert reaches and passes its peak of maturity very quickly.
Curing times lengthen as moisture contents decrease. Romano cheese at six months of age is a moderately flavoured table cheese, but can be cured for 12 months or more and used for grating and cooking.
Curing conditions for most varieties vary between 7‑15°C at 75‑80% relative humidity. These conditions ensure the desired flavour development and prevent mould growth and drying out of cheese. Mould ripened varieties require high humidity (95%).
Use of special bacteria or mould in curing
Under this heading there are several treatments which are peculiar to certain types of cheese, and contribute to their characteristics.
Internal mould ripening: In the various ‘blue’ cheese varieties the growth of Penicillium roqueforti, inside the cheese produces a characteristic spicy, peppery flavour, as well as a distinctive marbled colour. The flavour is a combination of the mould itself and various fat and protein breakdown products resulting from the actions of enzymes, produced either by the mould and the starter, or present in the milk. The mould may be added either to the milk before setting or to the curd after whey removal, before hooping.
During storage, the cheese is usually pierced with thick stainless steel wires to admit air which is essential for mould growth. The cheese should also have considerable mechanical openness to allow even mould growth throughout.
Surface ripening: The ripening of many types of soft or semi‑hard cheese is aided by enzymes and flavouring substances produced by microorganisms growing on the surfaces.
The ways in which these surface growths are induced and controlled are varied, ranging from strictly controlled use of pure cultures to rather ‘haphazard’ arrangements in which many organisms grow either together or in succession during storage. The use of a high humidity ripening container with even temperatures, often with little or no air circulation is usually necessary to obtain good surface growths.
Eye formation: Although Gruyere and Emmental are the best-known examples of eye type cheese, there are many others, having smaller or fewer eyes; these include Tilsit, Havarti, Samsoe, Gouda and Edam.
Successful eye formation depends on the inclusion of organisms in the starter such as propionic acid bacteria or Streptococcus diacetylactis strains. Correct temperatures of storage are also essential. Large eye types such as Gruyere are usually stored at a temperature around 20°C for several weeks, during which time eye formation occurs, causing the cheese to swell. When the eyes are the right size, the temperature must be reduced to around 10°C to stop further enlargement of the eyes.
Use of additives
A number of herbs and spices are used in traditional cheese varieties. These are usually mixed with the curd just before hooping. Whole peppercorns are added to stirred Romano type curd to make Pepato cheese. Leiden cheese is flavoured with added cumin seeds. Sage Derby cheese has ground sage mixed in with the milled curd. This not only flavours the cheese but also produces a pleasing green veining as each milled curd particle is outlined with a green edge. It is important to ensure any herbs or spice added to cheese has low bacterial numbers as failure to do so may result in cheese defects.
Enzymes such as lipase are added to varieties such as Feta, Parmesan, and Romano to accelerate the breakdown of fat and produce the required flavour.