A large part of the milk that is shipped goes to dairies, where it is either simply strained, cooled, and poured into bottles or cans, or under goes a more extensive process.
The contents of the cans is tested by taste. or with alcohol, and is then poured through sieves into large reservoirs. (A sieve covering the entire reservoir is most effective.) The milk. usually warmed to 30° C. (80° F.), then passes through filters of cotton-wool or of gravel.
though these last need careful cleaning and ore not very efficient. It is often still further purified by centrifugation. (These indeed, remove the milk slime, but the number of bacteria is apparently increased by uniform distribution.) Finally. it is cooled, and sometimes pasteurized, and then flows into the cans or bottles in which it is sold. hill: kept over night is stored in well cooled reser voirs ('.; 11° F.), which is favorohle to the destruction of bacteria.
It is a precarious task to prepare milk for children in such dairies, because of the promiscuous mixing of large quantities which cannot he traced backward and regulated from the start. It could be better accomplished by the separate treat ment of milk from the different stables. If this is attempted the indiscriminate pasteurization of the milk does not seem expedient. In cases Whore the mothers have sufficient time and intelligence it would be better to have pure milk or cream, of the proper quality. delivered in its natural state and prepared at Inwne under direction of the physician. On the other hand, there is a demand for small dairies, or separate departments of large ones, which shall devote themselves to the prtparation of milk for infants, furnished in portions ready to drink. and made up, as by an apothecary. from prescriptions by a physician for each individual case. For such establishments the name of Milk Laboratories has been coined in America. Attempts at this are already found in the dairies of all large cities for commercial reasons, because children's milk opens the door of the consumer.
.\.n ideal arrangement would be to supply the special department of the large dairy with selected milk from their own stables or from stables under their supervision. From this, and from ordinary milk for those of smaller means, the necessary mixtures could be made and put up in portions proper for a single feeding. This would require bot
tles much smaller than those used heretofore (50, 75. 100 c.c.). Finally, the preparations prescribed for infants could he compounded.
Preparations of cream may be specified as such. These have be come practicable only since the introduction of separators, since the cream obtained by gravity was more or less sour and often bitter, and even now the cream produced by centrifugation contains ninny more germs than does the milk. Usually the dairies give, for use with coffee, a cream with 14 to 15 per cent. of fat, 3 per cent. of albumin, 4 per cent. of sugar, and 0.6 per cent. of ash, so that by a mixture of 100 cream and 300 water and 2 Gm. milk-sugar a food is obtained similar to human milk. but this mixture cannot stand rough carriage by wagon, because butter forms easily on account of its slight viscosity. For this reason, preparations of cream in the dairies are formed with skimmed milk. A change will be effected by the machine for homogenization, in which milk or cream warmed to 5.0° (170° F.) will be forced under a high pressure (2:30 atmospheres) through minute channels (machines by Condin, Paris. Julien, Petersburg), or, under somewhat lower pressure (150 atmospheres), will be drawn between rapidly rotating disks (the Berberick system of the Dentschen Homogenisierungsmachinen-Ge.sell schaft at Liibeck). The milk globules are thus made so small that under the microscope they look like fine dust. They are not entirely changed to butter, even by centrifugation, but on the other hand, they are easily affected by the bacteria that decompose fat.
Modified Milk by Gartner's at cow heat, or 36° C., is diluted with an equal quantity of warm water that has been boiled, and is passed through a separator which is so adjusted that the tubes for the cream and for skim milk each carry off the same amount. The cream so obtained contains about 1.7 per cent. albumin, 3 per cent. fat, 2.5 per cent. sugar, and 0.:35 per cent, ash, and consequently requires an addition of 5 per cent. of sugar. The proportion of fat varies with that of the natural milk.