Making Cheese at Home

Cheese is made from the milk of goats, sheep, buffalo, reindeer, camel, llama, and yak but is usually made from cow's milk. Cow's milk is about 88% water and the remainder is fat, protein, sugar, minerals and vitamins. In the process of cheese-making, most of the protein, fat and some minerals and vitamins are concentrated and separated as a solid. The remaining liquid, called 'whey', contains most of the sugar and water and some protein, minerals and vitamins. Whey is utilized in foods and feeds or disposed of as waste.There are two principal agents which bring about the concentration and separation of protein and fat to make cheese, namely, bacterial culture and coagulating enzyme.

Bacterial culture

Bacteria are often responsible for food spoilage but there are also many useful types. During the manufacture of cheese and other cultured dairy products lactic acid bacteria change the milk sugar to lactic acid. The acid acts as a preservative by inhibiting undesirable types of bacteria, helps remove water from the curd (formation of curd is described in the next section) and is important to the development of cheese texture. The lactic acid bacteria and other microorganisms which happen to be present in the cheese contribute enzymes which break down fats, proteins and sugar during aging to produce flavours characteristic of particular cheese varieties. Lactic acid bacteria are naturally present in milk, and cheese can be made by holding fresh milk in a warm environment. However, this process is slow and cheese quality tends to be inconsistent. It is recommended that the milk be pasteurized by heating at 60-62C (140-144F) for 30 min . This heat treatment will destroy most lactic acid bacteria in the milk and will also destroy pathogenic bacteria which may cause food illness. Note that over pasteurization will prevent proper coagulation. Most store bought milk is unsuitable for cheese making because it has received too much heat treatment.

After pasteurization the milk is cooled to 32-37C (89.6-98.6F) and lactic acid bacteria are added to the milk. The suspension of bacteria is called a 'culture' and the process of adding the culture to the milk is called 'inoculation'. The culture may be a frozen or freeze-dried concentrate of bacterial cells or it could be cultured milk (milk in which lactic acid bacteria have been allowed to grow). Different bacterial cultures are recommended for specific types of cheese but most types can be made using fresh, plain yoghurt or buttermilk as a culture. If yoghurt is used, the milk should be inoculated at 37C. Buttermilk contains gas forming bacteria and may cause the development of small eyes in some cheese. In addition to bacteria, some types of cheese such as 'blue' and 'camembert' are inoculated with mould to develop characteristic appearance and flavour.

Coagulating enzymes

Proteins can be thought of as long microscopic chains. Various food products such as jello, jams and cheese depend on the ability of protein chains to intertwine and form a mesh-like network. The formation of this network is called 'coagulation'. When proteins coagulate in water, they trap water in the network and change the liquid to a semisolid gel. In cheese-making gelation is caused by an enzyme, 'rennet'. When rennet is added to warm milk, the liquid milk is transformed into a soft gel. When the gel is firm enough, it is cut into small pieces, 0.5-1.0 cm square (1/4-3/8 inch) called 'curds'.

Exceptions

Certain types of cheese such as some types of Queso Blanco (Latin American countries) and Paneer (India) are made without bacterial cultures and without rennet. In these types, curd is formed by adding vinegar (or other acid juices) to hot milk. A procedure for heat-acid precipitated Queso Blanco is included in this booklet because it is one of the most simple varieties to make and has the advantage that all the milk proteins including proteins normally lost in the whey are included in the cheese. Some fresh cheese (i.e. cheese which are eaten immediately after manufacture) such as Cottage cheese and quark are made with little or no rennet. In these cheese, coagulation is caused by high acid development by the bacterial culture. A procedure for fresh cheese or European style Cottage cheese is included.

For the home cheese maker, a start up set of supplies should include: a pasteuriser, cheese mould, cheese press, dairy thermometer or any food grade thermometer for the range of 0 to 100C, and cheese cloth. Bacterial cultures and rennet can sometimes be purchased in natural food stores.

Small scale cheese making equipment and other supplies, including literature, can be obtained from New England Cheese Making Supply Company, 85 Main St., Ashfield, MA 01330 (413-628-3808; Fax: 413-628-4061).