[Fig. 17], is a number of glass tubes of equal size, set in a frame called a lactometer or cream guage. If milk from different cows be set in these, the depth of the cream will indicate their comparative richness.
Cream.
If milk be immediately set away in shallow vessels, after being taken from the cow, the cream rises to the surface, carrying with it most of the butter contained in the milk, and much of its casein also. Hence, the great nutritive properties of buttermilk, which retains the casein in very large proportions, much of it being rejected by the butter in its separation from the cream.
A temperature below 34°, will prevent the cream from rising in any considerable quantity, and preserve the milk unaltered for some weeks. Coagulating the milk from any cause, will equally prevent the separation of the cream. The elevation of temperature within certain limits, hastens the separation. Thus, at 50°, the cream will mostly have risen in 36 hours; at 55°, in 24; at 68°, in 18 or 20; and at 77°, in 10 or 12 hours.
Heating the milk near the boiling point, and then setting it away and allowing it to remain undisturbed, will soon cause the cream to rise. In the celebrated Orange dairy, near Baltimore, Md., this system was practised, by which, not only most of the cream was secured for butter, but in consequence of its rapid separation, the skimmed milk was sent to market within a few hours after being drawn; and the scalding imparted to it an agreeable flavor and apparent richness, which it did not really possess.
The celebrated clouted cream of Devonshire, England, and the butter made from it, contains an unusual quantity of
casein, the consequence of heating the milk. "It is prepared by straining the warm milk into large shallow pans into which a little water has previously been put, allowing these to stand from six to twelve hours, and then carefully heating them over a slow fire, or on a hot plate, till the milk approaches the boiling point. The milk, however, must not actually boil, nor must the skin of the cream be broken. The dishes are now removed into the dairy, and allowed to cool. In summer the cream should be churned on the following day; in winter it may stand over two days. The quantity of cream obtained is said to be one-fourth greater by this method, and the milk which is left is proportionably poor."—[Johnston.]