When milk is allowed to stand for some time the fat globules in the milk rise to the top, forming cream. The thickness of this layer of cream varies. The normal average quantity of cream is over 8 to 9 per cent, of the volume of the milk, but there may be over 20 per cent. If the cream falls below 5 per cent, of the volume of milk, the milk has been watered. The proportion of cream in milk is dependent on various factors, such as the breed, age, and food of the cows. Alderneys and Guernsey cows give a milk very rich in cream. The milk which comes towards the end of milking contains more fat than that which is first drawn. Afternoon milk is richer than morning milk, both in protein and fat. The rise of the cream is favoured by a cool temperature; the addition of a little warm water added to the milk hastens the rising of the cream by altering the specific gravity of the milk.
The percentage of fat in cream may be 10 to 20 per cent., as in cream obtained by skimming milk; cream produced by centrifuge may contain from 40 to 60 per cent.; and the clotted Devonshire cream may contain as much as 70 per cent, or more. A legal standard for cream would be advantageous.
Tea cream as sold in the dairy is generally a thin cream produced by skimming milk in the ordinary way.
Double cream, or separator cream, is obtained from the milk by centrifugal force. A small and large drum are placed one within the other, leaving a space of a few inches between. The inner drum is made of porous material. It is filled with milk and set in rapid revolution. The lighter portion, the cream, remains in the inner drum, while the other ingredients are forced through it into the outer drum.
This method of obtaining cream is far more rapid than when it is allowed to rise by standing, and also it obtains almost all the fat from the milk. Cream procured in this manner does not remain fresh so long as ordinary cream, for it is separated at a temperature favourable to the growth of bacteria.
Condensed or evaporated cream consists of one-fourth cream and three-fourths other ingredients of milk, the whole milk having been evaporated. It is, therefore, a natural product and is not artificially sweetened.
Clotted or Devonshire cream is a special variety prepared by heating the milk in deep pans over a slow fire not above 150° F. This causes a rapid and complete separation of fat. The proportion of fat in such cream is about 60 to 70 per cent. Devonshire cream contains only about half as much sugar as ordinary cream, and it is peculiarly suited to be a source of fat in the dietary of diabetics. Fothergill wrote:"Devonshire cream is delicious with preserved ginger, while cream and maraschino form a nutritive drink for the affluent consumptive".
Cream is one of the most wholesome and agreeable forms of fat. It is often eaten too rich and may disagree on that account, whereas diluted with an equal bulk of water or of lime-water it can be easily digested.
Where there is difficulty in digesting milk, 3 or 4 table-spoonfuls of cream in a tumblerful of Vichy makes a nourishing and digestible beverage. The nutritive value may be increased, if desired, by the addition of half an ounce of sugar of milk. It may be used along with or to replace cod-liver oil in pulmonary tuberculosis, and it is an admirable food in any case of long-continued suppurative disease, e.g., hip joint, empyema. It must be avoided in cases of flatulent indigestion, in most forms of gastric disorder, in obesity, and in gall-stones.
In the feeding of infants who cannot readily take diluted milk, and in infants suffering from diarrhoea, marasmus, and the like, cream given in well-diluted form is of great value.
The addition of strong liquors to cream lessens its digestibility: the alcohol coagulates and toughens the envelopes of the fat globules.
Ice cream is a frozen mixture of cream, sugar, and flavouring agent. When very simply made it is nutritious, and may be allowed to many patients. It is soothing to inflamed throats, and is enjoyed by convalescents from fevers. It should be eaten very slowly, so that it may get warmer in its passage to the stomach, and not retard digestion by a cold mass being suddenly introduced. The nutritional value of ice cream can be increased by the addition of egg or plasmon.