See also:young . The milk of various domesticated animals is more or less used by man for
See also:food . The milk of the cow, which may be taken as typical of all others, and is indeed by far the most important and valuable of all (see
See also:DAIRY AND DAIRY FARMING), is, when newly
See also:drawn, an opaque
See also:white fluid, with a yellowish tinge, soft, bland and sweetish to the taste, and possessed of a faintly animal odour . This odour, according to Schreiner, is due to the presence of sulphuretted hydrogen, and disappears after a
See also:short exposure . The specific gravity of milk ordinarily ranges from 1.029 to 1.033, very seldom reaching 1.035 or falling so low as 1.027 . In chemical constitution it consists of an emulsion of fatty globules (cream) in a watery alkaline solution of casein, and a variety of
See also:peculiar to milk, called lactose . The
See also:fat (which when separated we know as
See also:butter) and the lactose constitute the carbonaceous portion of the milk regarded as food . The casein, which forms the
See also:principal constituent of
See also:cheese, and a certain proportion of albumen which is
See also:form the nitrogenous, while the complex saline substances and
See also:water are the
See also:mineral constituents . These various substances are present in the proportions which render milk a perfect and typical food suitable to the wants of the young of the various animals for whom it is provided by nature . The milk of animals, so far as is known, contains them, although they are present in somewhat different proportions . It is probable that the milk of ruminants possesses certain
See also:physical and physiological distinctions from that of non-ruminant animals, which will account for the virtues attributed to the milk of the ass and
See also:mare . The following table exhibits the chemical constitution of the kinds of milk most frequently used by man:- Cow .
See also:Goat .
See also:Ewe.' Mare . Ass . Human . C o 1 8 O • (1 C .~
See also:cam) 0 V t, m~ a 8 E U Water . 86.87 87.00 84.48 83.70 90.310 91.65 88.02 3'50 4.00 6.11 4.45 1.055 0.11 2.90 Fat . .i 4.75 4 .10 3.94 5.16 1.953 P82 1.6o n an. d Casein and Sugar . . 4.00 4.28 4.68 5'73 6.285 6•o8 7.03 Ash . . 0.70 0'62 0.79 0.96 0.369 0'34 0.31 In addition to these constituents milk contains small proportions of the gases carbonic acid, sulphuretted hydrogen, nitrogen and
See also:oxygen, and minute quantities of other principles, the
See also:constant presence and essential conditions of which have not been determined . These consist of galactin and lactochrome, substances peculiar to milk, discovered by Winter
See also:Blyth, with certain animal principles such as leucin, pepton, kreatin, tyrosin, &c . The salts in milk consist, according to the
See also:average of numerous analyses by Fleischmann, of the following constituents:- . . 28.31 Potash ..
. 17'34 Phosphoric acidChlorine . 16.34
See also:Magnesia . 4.07 Lime . . 27.00 Ferric
See also:oxide o•62 Soda . . . IO•oo Milk thus is not to be regarded as a definite chemical compound nor even as a mixture of bodies in fixed and invariable proportions . Not only does the milk of different races and breeds of cows vary within comparatively wide limits; the milk of the same animal is subject to extensive fluctuation . The principal causes of variation in the individual are age,
See also:period of lactation, nature and amount of food, state of
See also:health, and treatment, such as frequency of milking, &c . The following table indicates the range of normal variations: 90•00.t0 83.65 Water . Fat . . 2.8o ,, 4.50 Casein and albumin 3'30 ,, 5.55 Sugar . . • 3'00 ,, 5.50 Ash .
. 0'70 „ o•8o The average quantity of milk yielded by cows is also highly variable, both in individuals and breeds . Milk and Disease.-Although the milk of a perfectly healthy cow may be absolutely sterile, it is difficult to obtain it in that
See also:condition . In the
See also:report of the joint
See also:committee appointed for the purpose by the
See also:county boroughs of
See also:Hull, Leeds, Rotherham and Sheffield in 1908, the following conclusions were drawn: (i) Cows' milk freshly drawn from the udder by ordinary methods contains bacteria . They are more numerous in the first flow of the milk . (2) There is a
See also:great increase in contamination in the milk at each stage before it reaches the customer . This is due to (a) the dirty condition of the cows' udders, (b) the imperfect cleansing of the cans and of the hands of the milkers . The committee recommend: ' Ewe's milk is exceedingly variable, especially in its percentage of fat . The above analysis is one of nine by Dr Arthur Voelcker, in which the fat was found to range from about 2 to 121%." (I) The washing of the udder and flanks with
See also:soap and water, and similar
See also:attention to the hands of the milker . (2) Efficient sterilization of all vessels by steam if possible, or by abundance of boiling water . (3) Rejection of the first draw of the milk from each teat . (4) Avoidance of any
See also:work raising dust immediately before or during milking . (5) Removal of the milk of each cow immediately from the
See also:shed .
(6)Ventilation and cleanliness of the cowsheds.' This provides for the reduction as far as possible of contamination during the milking
See also:process itself . As any bacteria present in the milk tend to multiply rapidly on the way to the consumer, it is mainly a question of the
See also:time which elapses before
See also:consumption . It is, there-fore, further recommended (a) that the milk be rapidly cooled or chilled, as the
See also:lower the temperature the less do the bacteria multiply, (b) that contamination during railway transit be avoided by dust-
See also:proof locked milk cans . By treating milk at a temperature of 6o° C. for one
See also:hour, 7o° C. for ten minutes, and 950 C. for one minute, tubercle bacilli, if present, will certainly be killed . Cholera and typhoid organisms are less resistant, and are killed more quickly than tubercle bacilli at the above temperatures . Only a single pathogenic
See also:species can with-stand the short boiling to which milk is ordinarily treated in domestic management, and this is the
See also:anthrax bacillus containing spores . The danger from this source is remote, as the microbe does not form spores within the animal
See also:body . Even in the worst cases, therefore, only
See also:vegetable forms, easily destroyed by boiling, can find their way into the milk from the body of the cow . The lactic acid bacillus, always present in unboiled milk (to which the souring of milk is due), is easily destroyed by
See also:heat; but the bacillus mesentericus, often found in it, forms spores, which are not destroyed by ordinary boiling, and germinate when the milk is kept at a moderately warm temperature, producing a brisk
See also:fermentation whereby a large
See also:volume of
See also:gas is liberated . The ,fundamental idea of Soxhlet's method for sterilizing milk is to
See also:boil it for
See also:forty minutes in small bottles holding just enough for one
See also:meal, and closing the same with an impervious stopper, which is only re-moved just before use . Milk so treated will keep at the ordinary
See also:room temperature, as the spores of the B. mesentericus do not develop below 15° C.; but if it be introduced into the alimentary canal of a
See also:child the spores will rapidly multiply, and in such cases large quantities of gas, giving rise to flatulency, will be formed, and possibly also poisonous decomposition products of albuminoid
See also:matter . To render milk sterile in the strict sense of the word it is necessary to raise it to a temperature of about 120° C. for twenty minutes .
Under these conditions the lactose decomposes into dark-
See also:brown fission products, the fat loses its emulsified condition and separates out as cream which cannot be made to diffuse again even by shaking, and the albuminoids are converted into a form very difficult of digestion . In short, there is the greatest difficulty in freeing milk on a large scale from germs without at the same time seriously prejudicing its flavour and nutritive value . Since, then, the destruction of the
See also:hardy germs is so difficult, the greater care should be taken, by washing the udder, hands and milk vessels, to secure extreme cleanliness in the preparation of milk intended for
See also:infant consumption . Sterilization then becomes an easier task, the milk drawn under these conditions being very poor in spore-forming bacteria . It is imperative that cream destined for butter-making should be
See also:free from pathogenic organisms . The organisms of cholera, typhoid fever and
See also:tuberculosis present in butter retain their vitality for a long time . As butter is consumed in the raw state, a trustworthy preliminary treatment of the cream is in the highest degree desirable . Schuppan has shown that it is possible to produce
See also:good butter from Pasteurized or even sterilized cream, and Weigmann introduced the plan of artificially souring cream by means of pure cultures of B. acidi lactici . Since Metchnikoff's introduction (see
See also:LONGEVITY) of the use of soured milk for dietetic purposes-the lactic acid bacillus destroying pathogenic bacteria in the
See also:intestine-a great impetus has been given to the multiplication of laboratory preparations containing cultures of the bacillus; and in
See also:recent years much benefit to health has, in certain cases, been derived from the
See also:discovery . See also the articles ADULTERATION; DAIRY AND DAIRY FARMING;
See also:DIETETICS; FOOD and
See also:Foot) PRESERVATION; in the last of which the preparation of condensed milk is described .
MILITIA OF TIIE UNITED
MILK AND BUTTER
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