Today, there are a variety of cheese made from the milk of different animals such as cow, goat, sheep, buffalo, mare, llama and yak. There are over 240 different kinds of French cheese because the French are the greatest cheese-eaters. They eat more than 18 kg cheese per person every year. The different varieties of cheese can be clubbed under two groups – hard and soft.
Hard cheese is made from pasteurized whole milk ripened with a culture of lactic acid bacteria that converts some of the lactose into lactic acid. The milk proteins are then coagulated into a sort of ‘curd’ by the addition of rennet. Rennet contains the enzymes, rennin and pepsin, obtained from the stomach of young calves. This is useful to transform curdling milk to junket (junket is a custard like pudding made of milk). The junket is then cut into cubes to allow the liquid residue (whey) to separate. It is then heated to 38°C to drain off whatever whey might be left. It is then cut into blocks and pressed to remove the last traces of whey. These blocks of dry ‘curd’ are cut into small pieces and then salt is added to act as a preservative and to improve its flavour. Finally the cheese is produced by pressing the salted curd in moulds for about 48 hours and then ripening it under controlled temperature and humidity for three to six months. The ripening occurs on account of bacterial and enzyme action.
Soft cheese is made in a similar way but with a major difference: the whey is left to drain off from the curd by gravity without applying any pressure or heat. The resulting cheese has high moisture content, between 50 to 70 percent, and they have mould cultures that excrete enzymes to give them the characteristic flavour.
Lactic acid cheese is produced by the action of lactic acid on the milk protein. The acid coagulates the protein into a soft curd, from which whey is drained off and then salted. Cottage cheese is made from pasteurized fat-free milk and the curd is washed with skimmed milk. This often contains skimmed milk powder to give it its characteristic texture.
The process of making cheese reduces milk to one-tenth of its volume. The curd or soft gel is formed by casein which is the chief protein in milk. This occurs when enough lactic acid is developed from lactose by the micro-organism present in the milk, or when it is acted upon by rennin. At the moment of coagulation, all the milk constituents, including most of the fat, casein and other water insoluble substances, are present in the curd. In the modern factories, mass production of cheese according to standardized recipes and techniques has resulted in the products of a much more uniform quality.
The cheese industry has been of primary economic importance for hundreds of years in many European countries such as the Netherlands, France, Italy and Switzerland.