To obtain the greatest amount of cream from a given quantity of milk, the depth in the pan should, it seems to me, never exceed two inches. A high temperature and shallow depth, as they liquefy the milk and facilitate the rising of the particles, tend to secure a cream free from the cheesy matter, and such cream will make a quality of butter both more delicate to the taste, and less likely to become rancid, than any other.
It has already been intimated, in another connection, that neither the largest quantity nor the best quality of milk is given by the cow till after she has had two or three calves, or has arrived at the age of five or six years. It may also be said, what cannot fail to have attracted the attention of observing dairymen, that in very dry seasons the quantity of milk yielded will generally be less, though the quality will be richer, than in moist and mild seasons.
Hence it may be inferred that moist climates are much more favorable to the production of milk than dry ones; and this also has been frequently observed and admitted to be a well-known fact. From these facts it may be stated that dry and warm weather increases the quantity of butter, but it is also true that cooler weather produces a greater amount of cheese. A state of pregnancy, it is obvious, must reduce the quality of the milk, and cause it to yield less cream than before.
In the treatment of milk the utmost cleanliness is especially requisite. The pails, the strainers, the pans, the milk-room, and, in short, everything connected with the dairy, must be kept neat and clean to an extent which few but the very best dairy-women can appreciate. The smallest portion of old milk left to sour in the strainers or pans will be sure to taint them, and impart their bad flavor to the new milk put into them. Every one is familiar with the fact that an exceedingly small quantity of yeast causes an active fermentation. The process is a chemical one, and another familiar instance of it is in the distillation of liquors and the brewing of beer, where the malt creates a very active fermentation. In a similar manner the smallest particle of sour milk will taint a large quantity of sweet.
The milk-room should be removed from dampness, and all gases which might be injurious to the milk by infecting the atmosphere. If the state of the atmosphere and the temperature, as has been stated, affect it, all contact with foreign substances to which it is liable in careless and slovenly milking, and all air rendered impure by vegetables and innumerable other things kept in a house-cellar, will be much more liable to taint and injure it. Milk appears to absorb odors from objects near it, to such an extent that a piece of catnip lying near the pan has been known to impart its flavor to it.
Milk, as sold in most large cities, is often adulterated to a great extent, but most frequently with water. Not unfrequently, too, a part of the cream is first taken off, and water afterwards added; in which case the use of burnt sugar is very common for coloring the milk, the blueness of which would otherwise lead to detection. The adulteration of pure milk from the healthy cow by water, though dishonest, and objectionable in the highest degree, is far less iniquitous in its consequences than the nefarious traffic in “swill-milk,” or milk produced from cows fed entirely on “still-slops,” from which they soon become diseased, after which the milk contains a subtle poison, which is as difficult of detection by any known process of chemistry as the miasma of an atmosphere tainted with yellow fever or the cholera. The simple fact is sufficiently palpable, that no pure and healthy milk can be produced by an unhealthy and diseased animal; and that no animal can long remain healthy that is fed on an unnatural food, and treated in the manner too common around the distilleries of many large cities.
Fig. 71.
It is evident, from the well-known influence which “still-slops” and other exceedingly succulent food have in increasing the amount of water in the milk, that adulteration may be effected by means of the food, as well as by addition of water to the milk itself. It is evident, too, on a moment’s reflection, that the specific gravity of pure milk must vary exceedingly, as it comes from different cows, or from the same cow at different times. This variation reached to the extent of twenty-three degrees in the milk of forty-two different cows, or from one thousand and eight to one thousand and thirty-one; but so great a variation is very rare, and not to be expected.
No reliable conclusion, as to whether a particular specimen of milk has been adulterated or not, can therefore be drawn from the differences in specific gravity alone. A radical difficulty attending this test arises from the fact that the specific gravity both of water and cream is less than that of pure milk. If, therefore, the hydrometer sinks deeper into the fluid than would be expected in ordinary pure milk, how is it possible, unless the variation is very large, to tell whether it is due to the richness of the milk in cream, or to the water? I have, for instance, two instruments, each labelled “Lactometer,” but both of which are simple hydrometers ([Fig. 71]), or specific gravity testers, one of which is graduated with the water-mark 0 and that of pure milk 20°; the water-mark of the other being 0, like the first, and that of pure milk 100°. Both are the same in principle, the only difference being in the graduation. On the former, graduated for pure milk at 20°, it is difficult to tell with accuracy the small variations in the percentage of water or cream, the divisions on the scale are so minute, while the latter marks them so that they can be read off with greater ease and precision.