There are hundreds of different types of cheese, but each is made using similar principles of
coagulating the proteins in milk to form curds, and then separating the curds from the liquid
whey. The coagulation of milk proteins can be done as follows:
Using rennet (or ‘chymosin’) - an enzyme extracted from calves’ stomachs that coagulates
the proteins in milk. Rennet produced by micro-organisms is available for vegetarian
Fermenting to form lactic acid.
Adding acid (e.g. lemon juice, lime juice or vinegar).
Using plant extracts (e.g. papaya sap (papain enzyme), fig bark (ficin enzyme), stems of
Bryophylum species or leaves of Calotropis procera.
The different cheese flavours and textures arise from variations in the type of milk, the amount of
fat in the milk, bacteria that are used to ferment the milk, and variations in the processing
conditions. Cheeses may be broadly grouped into ‘soft’, ‘semi-hard’ and ‘hard’ cheeses (Table 1).
Soft cheeses are easier to make than hard cheeses and are traditional foods that are popular in
many countries. They are made using lactic acid bacteria (see Technical Brief: Soured milk and
yoghurt) or an acid, such as lemon or lime juice or vinegar. These cheeses are soft, moist, creamy
cheeses and include curd cheese, paneer, and small-curd cottage cheese. Those made from
buffalo milk are white and those made from cows’ milk are pale creamy yellow. They have a shelf
life of around 3 days when refrigerated, or 5 days if covered with brine and refrigerated.
Hard cheeses (e.g. ‘Cheddar’ cheese) and large-curd cottage cheese are produced using lactic
acid bacteria and rennet. Hard cheese requires greater investment in equipment and greater skill
to produce than soft cheeses. Cheddar cheese for example, is a firm solid compressed curd that
has a pale yellow colour, a texture that varies from rubbery to flaky, a mildly acidic taste and a
characteristic flavour/aroma. It is matured for different periods of time, and the flavour gradually
changes from a mellow creamy taste after 2-8 months, to a tangy flavour of mature cheese after
8-12 months, and then to a strong, more bitter flavour of vintage cheese after more than 12
months. Hard cheeses may also be made with a variety of flavourings, including caraway seed,
chilli pepper, garlic, rosemary or sage, or they may be smoked. It is recommended that market
research be undertaken to find which types of cheese are popular before contemplating
production, because the demand for hard cheeses may be more limited in some countries and a
careful market analysis is needed before starting their production. Training in production should
then be obtained from an experienced cheese-maker.
Cheese is preserved by a number of different mechanisms: the raw milk is pasteurised to destroy
most enzymes and contaminating bacteria; fermentation by lactic acid bacteria increases the
acidity which inhibits growth of food poisoning and spoilage bacteria; the moisture content is
reduced and salt is added, both of which inhibit bacterial contamination (see also Technical
Brief: Dairy processing - an overview, which is intended to be read alongside this Technical Brief).
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