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How is Butter Made?
Butter is the fat from milk of cows and other mammals (e.g. goats or sheep). An average composition is 81.5 per cent milkfat, 15.9 per cent water, up to 2.5 per cent salt, and up to 2.0 per cent milk protein and other residues. Butter supplies approximately 6 per cent of natural energy food requirements, and a proportion of the vitamin requirements. Records show that butter has been used as a cosmetic for skin and hair, a medical tonic, a salve for burns, an oil for lamps, an axle grease, and has played a part in ritual ceremonies (e.g. the Hindu marriage feast). Bog butters found in Ireland show that butter has been stored for long periods. The earliest biblical reference to butter occurs in Genesis 8:18.
Milk fat consists of a glycerol base combined with fatty acids. The following are amongst those normally found, given in order of quantitative importance: oleic, palmitic, stearic, myristic, butyric, lauric, capric, caproic, caprylic, decenoic, linoleic, arachnidic. Milk fat exists as minute globules, .0001 mm to .001 mm in size, suspended in the aqueous milk serum. The specific gravities of serum and fat are 1.036 and 0.95 respectively and so the fat globules will rise as a creamy layer on the surface of milk on standing. This cream can be skimmed from the surface of milk for churning into butter, as in farmhouse practice. The factory method uses centrifugal force in a mechanical separator to divide the milk into cream and the serum, called skimmed milk. The skimmed milk is often dried into powder for future food use.
The technology of butter manufacture has developed slowly over the years. In biblical times, milk in a skin bag was agitated until butter grains formed; later barrels, or suspended boxes, were used to produce the agitation. If the cream or milk was sour the butter grains were produced more quickly and had more flavour. In Wales sour milk was churned into butter and in this case the serum or buttermilk resulting was prized as a beverage. The souring, or 'ripening', of milk or cream with lactic organisms became common practice as a result of the researches of Dr Orla Jensen in Denmark. The presence of the wrong types of organisms in cream or butter produces severe spoilage—hence it is essential to keep all machines and utensils scrupulously clean. The cream is then heated to about 93°C to destroy bacteria and enzymes, after which it is cooled to 4°C for some hours before churning into butter. Alternatively, the cream may be ripened at about 20°C by growing in it pure cultures of lactic streptococci to produce flavoring substances to enhance the flavor of the butter. The cream (either sweet or ripened) is poured into large wooden barrel churns which are revolved for about 40 minutes to produce the agitation necessary to cause the fat globules to coalesce into butter grains, which float in the serum or buttermilk. Since bacteria and milk solids produce deterioration in butter, it is necessary to drain off the buttermilk and wash the grains thoroughly with cold water. After washing, the grains are salted as necessary and then 'worked' or pressed together to produce blocks of butter. The working process is important to remove surplus moisture and air pockets before the butter is packed for sale. The legal maximum water content is 16 per cent.
Although many butter manufacturing centers (such as the world's largest at Chard in Somerset) still use wooden barrel-shaped churns, newer stainless steel churns in cubical or conical shapes are being used. Continuous butter-making machines have been developed in which high speed beaters produce butter in a few seconds. When the cream is produced with the same chemical composition as butter, it is possible to cause coalescence of the fat globules into a continuous phase by progressive cooling and application of pressure, as in the Alfa Laval process, first developed in Sweden and modified in the USA, but more in use for margarine production.
It is illegal to use preservatives in butter. Chemical methods are used to discover illegally added preservatives like borax and formalin. Adulteration of butter with cheaper animal or vegetable fats can be determined by the use of chromatographic techniques.